1

Renewable Energy Sources II Alternatives Part I

Lecture 10HNRT 228 Spring 2013Energy and the Environment

2

Chapter 5 Summary

bull Hydroelectric Powerbull Wind Powerbull Ocean Thermal Energy Conversionbull Biomass as Energybull Geothermal Energybull Tidal Energybull Wave Energybull Todayrsquos Focus

ndash Hydroelectric Powerndash Wind Power

3

iClicker Question

bull What is the definition of insolationbull A The effective solar insulation factorbull B The amount of light received by a

horizontal surface averaged over the yearbull C The amount of light received by a unit

area of the atmosphere averaged over the year

bull D There is none it is a mis-spelling of insulation

bull E The amount of insulation that is received from the Sun

4

iClicker Question

bull What is the definition of insolationbull A The effective solar insulation factorbull B The amount of light received by a

horizontal surface averaged over the yearbull C The amount of light received by a unit

area of the atmosphere averaged over the year

bull D There is none it is a mis-spelling of insulation

bull E The amount of insulation that is received from the Sun

5

iClicker Question

bull Roughly what percentage of light from the Sun reaches the groundndash A 10ndash B 20ndash C 30ndash D 40ndash E 50

6

iClicker Question

bull Roughly what percentage of light from the Sun reaches the groundndash A 10ndash B 20ndash C 30ndash D 40ndash E 50

7

iClicker Question

bull What is roughly the maximum efficiency for a photovoltaic cellndash A 10ndash B 15ndash C 30ndash D 40ndash E 50

8

iClicker Question

bull What is roughly the maximum efficiency for a photovoltaic cellndash A 10ndash B 15ndash C 30ndash D 40ndash E 50

9

iClicker Question

bull How much energy does the largest photovoltaic system producendash A 10 MWndash B 20 MWndash C 60 MWndash D 100 MWndash E 200 MW

10

iClicker Question

bull How much energy does the largest photovoltaic system producendash A 10 MWndash B 20 MWndash C 60 MWndash D 100 MWndash E 200 MW

11

iClicker Question

bull What must be done to overcome the setting of the Sun in a solar energy systemndash A Store energy in batteriesndash B Get electrical power from elsewherendash C Donrsquot use electrical power at nightndash D All of the above are alternative

approaches for energy after sunset

12

iClicker Question

bull What must be done to overcome the setting of the Sun in a solar energy systemndash A Store energy in batteriesndash B Get electrical power from elsewherendash C Donrsquot use electrical power at nightndash D All of the above are alternative

approaches for energy after sunset

13

iClicker Question

bull Based upon the discussion of the glass in a flat plate collector how would you define the greenhouse gas effect

bull A An effect caused by a gas that is transparent to visible light and opaque to infrared radiation

bull B An effect caused by a gas that is transparent to infrared radiation and opaque to ultraviolet radiation

bull C An effect caused by a gas that is transparent to ultraviolet radiation and opaque to infrared radiation

bull D An effect caused by a gas that is transparent to infrared radiation and opaque to visible light

bull E An effect caused by the sun emitting more infrared radiation than ultraviolet radiation

14

iClicker Question

bull Based upon the discussion of the glass in a flat plate collector how would you define the greenhouse gas effect

bull A An effect caused by a gas that is transparent to visible light and opaque to infrared radiation

bull B An effect caused by a gas that is transparent to infrared radiation and opaque to ultraviolet radiation

bull C An effect caused by a gas that is transparent to ultraviolet radiation and opaque to infrared radiation

bull D An effect caused by a gas that is transparent to infrared radiation and opaque to visible light

bull E An effect caused by the sun emitting more infrared radiation than ultraviolet radiation

15

Renewable Resources Discussed in Book

bull Renewable means anything that wonrsquot be permanently destroyed by using itndash sunlight (the sun will rise again tomorrow)ndash biomass (grows again)ndash hydrological cycle (will rain again)ndash wind (sunlight on Earth makes more)ndash ocean currents (driven by Sun)ndash tidal motion (MoonSun keep on producing it)ndash geothermal (heat sources inside Earth not

used up fast)

16

Renewable Energy Consumption

Energy Source

QBtu (1994)

Percent (1994)

QBtu (2003)

Percent (2003)

Hydroelectric 3037 343 2779 283

Geothermal 0357 040 0314 032

Biomass 2852 322 2884 294

Solar Energy 0069 0077 0063 006

Wind 0036 0040 0108 011

Total 6351 718 615 63

17

Another look at available energy flow

bull The flow of radiation (solar and thermal) was covered previouslyndash earth is in an energy balance energy in =

energy outndash 30 reflected 70 thermally re-radiated

bull Some of the incident energy is absorbed but what exactly does this dondash much goes into heating the airlandndash much goes into driving weather (rain wind)ndash some goes into ocean currentsndash some goes into photosynthesis

18

The Renewable Budget

19

Outstanding Points from Fig 51

bull Incident radiation is 1741015 Wndash this is 1370 Wm2 times area facing sun

(R2)bull 30 directly reflected back to space

ndash off clouds air landbull 47 goes into heating air land waterbull 23 goes into evaporating water

precipitation etc (part of weather)bull Adds to 100 so wersquore done

ndash but wait therersquos morehellip

20

Energy Flow continued

bull 021 goes into wind waves convection currentsndash note this is 100 times less than driving the water

cyclendash but this is the ldquootherrdquo aspect of weather

bull 0023 is stored as chemical energy in plants via photosynthesis

ndash total is 401012 W half in ocean (plankton)ndash humans are 6 billion times 100 W = 061012 Wndash this is 15 of bio-energy 000034 of incident

powerbull All of this (bio-activity wind weather etc) ends up

creating heat and re-radiating to spacendash except some small amount of storage in fossil fuels

21

The Hydrologic Cycle

Lots of energy associated with evaporationboth mgh (4 for 10 km lift) and latent heat (96) of water

22

Energetics of the hydrologic cycle

bull It takes energy to evaporate water 2444 J per gramndash this is why ldquoswamp coolersrdquo work evaporation

pulls heat out of environment making it feel cooler

ndash 23 of sunrsquos incident energy goes into evaporation

bull By contrast raising one gram of water to the top of the troposphere (10000 m or 33000 ft) takes

mgh = (0001 kg)(10 ms2)(10000 m) = 100 J

bull So gt 96 of the energy associated with forming clouds is the evaporation lt 4 in lifting against gravity

23

Let it Rain

bull When water condenses in clouds it re-releases this ldquolatent heatrdquo

ndash but this is re-radiated and is of no consequence to hydro-power

bull When it rains the gravitational potential energy is released mostly as kinetic energy and ultimately heat

bull Some tiny bit of gravitational potential energy remains IF the rain falls on terrain (eg higher than sea level where it originated)

ndash hydroelectric plants use this tiny left-over energy itrsquos the energy that drives the flow of streams and rivers

ndash damming up a river concentrates the potential energy in one location for easy exploitation

24

How much of the process do we get to keep

bull According to Figure 51 401015 W of solar power goes into evaporation

ndash this corresponds to 161010 kg per second of evaporated water

ndash this is 35 mm per day off the ocean surface (replenished by rain)

bull The gravitational potential energy given to water vapor (mostly in clouds) in the atmosphere (per second) is thenmgh = (161010 kg)(10 ms2)(2000 m) = 321014 J

bull One can calculate that we gain access to only 25 of the total amount (and use only 125)

ndash based on the 18 land area of the US and the maximum potential of 1477 GW as presented in Table 52

25

iClicker Question

bull With respects to energy hydroelectric power representsndash A remnant electric power from stormsndash B remnant water energy from chemical

bondsndash C remnant energy of chemical bondingndash D remnant gravitational potential

energy of precipitationndash E a form of fictitious energy

26

iClicker Question

bull With respects to energy hydroelectric power representsndash A remnant electric power from stormsndash B remnant water energy from chemical

bondsndash C remnant energy of chemical bondingndash D remnant gravitational potential

energy of precipitationndash E a form of fictitious energy

27

Power of a hydroelectric dam

bull Most impressive is Grand Coulee in Washington on Columbia River

ndash 350 feet = 107 m of ldquoheadrdquondash gt 6000 m3s flow rate (Pacific Northwest gets

rain)ndash each cubic meter of water (1000 kg) has potential

energy mgh = (1000 kg)(10 ms2)(110 m) = 11 MJ

ndash At 6000 m3s get over 6 GW of powerbull Large nuclear plants are usually 1ndash2 GWbull 11 other dams in US in 1ndash2 GW rangebull 74 GW total hydroelectric capacity presently

28

Importance of Hydroelectricity

29

Hydroelectric potential by region in GW

Region Potential

Developed

Undeveloped

Developed

New England 63 19 44 301

Middle Atlantic 98 49 49 500

East North Central 29 12 17 413

West North Central

62 31 31 500

South Atlantic 139 67 72 482

East South Central 83 59 24 711

West South Central

73 27 46 369

Mountain 286 95 191 332

Pacific 644 382 262 593

Total 1477 741 736 502

30

iClicker Question

bull What is true about hydroelectric power generation since 1950ndash A It has always increased in MW producedndash B It has always decreased in MW producedndash C It has increased and decreased in total

MW produced but is now at a peakndash D It has both increased and decreased in

total MW producedndash E The percentage of electric power

produced by hydroelectric plants has generally increased over time

31

iClicker Question

bull What is true about hydroelectric power generation since 1950ndash A It has always increased in MW producedndash B It has always decreased in MW producedndash C It has increased and decreased in total

MW produced but is now at a peakndash D It has both increased and decreased in

total MW producedndash E The percentage of electric power

produced by hydroelectric plants has generally increased over time

32

Hydroelectricity in the future

bull Wersquore almost tapped-outndash 50 of potential is developedndash remaining potential in large number of small-scale

unitsbull Problems with dams

ndash silt limits lifetime to 50ndash200 years after which dam is useless and in fact a potential disaster and nagging maintenance site

ndash habitat loss for fish (salmon) etc wrecks otherwise stunning landscapes (Glenn Canyon in UT)

ndash Disasters waiting to happen 1680 deaths in US alone from 1918ndash1958 often upstream from major population centers

33

Sorry try againhellip

bull So hydroelectricity is a nice ldquofreebeerdquo handed to us by nature but itrsquos not enough to cover our appetite for energy

bull Though very efficient and seemingly environmentally friendly dams do have their problems

bull This isnrsquot the answer to all our energy problems though it is likely to maintain a role well into our future

34

Wind Energy

35

The Power of Wind

bull Wersquove talked about the kinetic energy in wind beforendash a wind traveling at speed v covers v meters

every second (if v is expressed in ms)ndash the kinetic energy hitting a square meter is

then the kinetic energy the mass of air defined by a rectangular tube

ndash tube is one square meter by v meters or v m3

ndash density of air is = 13 kgm3 at sea levelndash mass is v kgndash KE = frac12(v)v2 = frac12v3 (per square meter)

065v3 at sea level

36

Wind Energy proportional to cube of velocity

bull The book (p 134) says power per square meter is 061v3 which is a more-or-less identical resultndash might account for average density in

continental US (above sea level so air slightly less dense)

bull So if the wind speed doubles the power available in the wind increases by 23 = 222 = 8 times

bull A wind of 10 ms (22 mph) has a power density of 610 Wm2

bull A wind of 20 ms (44 mph) has a power density of 4880 Wm2

37

Canrsquot get it all

bull A windmill canrsquot extract all of the kinetic energy available in the wind because this would mean stopping the wind entirely

bull Stopped wind would divert oncoming wind around it and the windmill would stop spinning

bull On the other hand if you donrsquot slow the wind down much at all you wonrsquot get much energy

bull Theoretical maximum performance is 59 of energy extractedndash corresponds to reducing velocity by 36

38

Practical Efficiencies

bull Modern windmills attain maybe 50ndash70 of the theoretical maximumndash 05ndash07 times 059 is 030ndash041 or

about 30ndash40ndash this figure is the mechanical energy

extracted from the windbull Conversion from mechanical to

electrical is 90 efficientndash 09 times 030ndash041 is 27ndash37

39

iClicker Question

bull What is about the maximum efficiency of energy generation using the windndash A 20ndash B 40ndash C 60ndash D 80ndash E 100

40

iClicker Question

bull What is about the maximum efficiency of energy generation using the windndash A 20ndash B 40ndash C 60ndash D 80ndash E 100

41

Achievable efficiencies

42

Typical Windmillsbull A typical windmill might be 15 m in diameter

ndash 176 m2

bull At 10 ms wind 40 efficiency this delivers about 100 kW of power

ndash this would be 800 kW at 20 msndash typical windmills are rated at 50 to 600 kW

bull How much energy per yearndash 10 ms 610 Wm2 40 240 Wm2 8760 hours per

year 2000 kWh per year per square meterndash but wind is intermittent real range from 100ndash500 kWhm2

ndash corresponds to 11ndash57 Wm2 average available power density

bull Note the really high tip speeds bird killers

43

Average available wind powerrecall that average solar insolation is about 150ndash250 Wm2

44

Comparable to solar

bull These numbers are similar to solar if not a little biggerndash Letrsquos go to wind

bull BUT the ldquoper square meterrdquo is not land areamdashitrsquos rotor area

bull Doesnrsquot pay to space windmills too closelymdashone robs the other of energy

bull Typical arrangements have rotors 10 diameters apart in direction of prevailing wind 5 diameters apart in the cross-wind directionndash works out to 16 ldquofill factorrdquo

45

Current implementations

bull Rapidly developing resourcendash 1400 MW in 1989 up to 6400 MW in 2003ndash but still insignificant total (compare to large

dams)ndash cost (at 5ndash7cent per kWh) is competitivendash growing at 25 per yearndash expect to triple over next ten years

bull Current capacity 116 GW (April 2007)ndash Texas 2768 MW (recently took lead over

California)ndash California 2361 MWndash Iowa 936 MWndash Minnesota 895 MWndash Washington 818 MW

46

Flies in the Ointment

bull Find that only 20 of rated capacity is achievedndash design for high wind but seldom get it

bull Only 12 of electrical capacity in US is now windndash total electrical capacity in US is 948 GWndash tripling in ten years means 36ndash but achieving only 20 of capacity reduces

substantiallybull If fully developed we could generate an average

power almost equal to our current electrical capacity (764 GW)

ndash but highly variable resource and problematic if more than 20 comes from the intermittent wind

47

iClicker Question

bull Which state generates the most amount of electricity derived from wind powerndash A Virginiandash B Alaskandash C Montanandash D Californiandash E Texas

48

iClicker Question

bull Which state generates the most amount of electricity derived from wind powerndash A Virginiandash B Alaskandash C Montanandash D Californiandash E Texas

• Renewable Energy Sources II Alternatives Part I
• Chapter 5 Summary
• Slide 3
• Slide 4
• Slide 5
• Slide 6
• Slide 7
• Slide 8
• Slide 9
• Slide 10
• Slide 11
• Slide 12
• Slide 13
• Slide 14
• Renewable Resources Discussed in Book
• Renewable Energy Consumption
• Another look at available energy flow
• The Renewable Budget
• Outstanding Points from Fig 51
• Energy Flow continued
• The Hydrologic Cycle
• Energetics of the hydrologic cycle
• Let it Rain
• How much of the process do we get to keep
• iClicker Question
• Slide 26
• Power of a hydroelectric dam
• Importance of Hydroelectricity
• Hydroelectric potential by region in GW
• Slide 30
• Slide 31
• Hydroelectricity in the future
• Sorry try againhellip
• Wind Energy
• The Power of Wind
• Wind Energy proportional to cube of velocity
• Canrsquot get it all
• Practical Efficiencies
• Slide 39
• Slide 40
• Achievable efficiencies
• Typical Windmills
• Average available wind power
• Comparable to solar
• Current implementations
• Flies in the Ointment
• Slide 47
• Slide 48

2

Chapter 5 Summary

bull Hydroelectric Powerbull Wind Powerbull Ocean Thermal Energy Conversionbull Biomass as Energybull Geothermal Energybull Tidal Energybull Wave Energybull Todayrsquos Focus

ndash Hydroelectric Powerndash Wind Power

3

iClicker Question

bull What is the definition of insolationbull A The effective solar insulation factorbull B The amount of light received by a

horizontal surface averaged over the yearbull C The amount of light received by a unit

area of the atmosphere averaged over the year

bull D There is none it is a mis-spelling of insulation

bull E The amount of insulation that is received from the Sun

4

iClicker Question

bull What is the definition of insolationbull A The effective solar insulation factorbull B The amount of light received by a

horizontal surface averaged over the yearbull C The amount of light received by a unit

area of the atmosphere averaged over the year

bull D There is none it is a mis-spelling of insulation

bull E The amount of insulation that is received from the Sun

5

iClicker Question

bull Roughly what percentage of light from the Sun reaches the groundndash A 10ndash B 20ndash C 30ndash D 40ndash E 50

6

iClicker Question

bull Roughly what percentage of light from the Sun reaches the groundndash A 10ndash B 20ndash C 30ndash D 40ndash E 50

7

iClicker Question

bull What is roughly the maximum efficiency for a photovoltaic cellndash A 10ndash B 15ndash C 30ndash D 40ndash E 50

8

iClicker Question

bull What is roughly the maximum efficiency for a photovoltaic cellndash A 10ndash B 15ndash C 30ndash D 40ndash E 50

9

iClicker Question

bull How much energy does the largest photovoltaic system producendash A 10 MWndash B 20 MWndash C 60 MWndash D 100 MWndash E 200 MW

10

iClicker Question

bull How much energy does the largest photovoltaic system producendash A 10 MWndash B 20 MWndash C 60 MWndash D 100 MWndash E 200 MW

11

iClicker Question

bull What must be done to overcome the setting of the Sun in a solar energy systemndash A Store energy in batteriesndash B Get electrical power from elsewherendash C Donrsquot use electrical power at nightndash D All of the above are alternative

approaches for energy after sunset

12

iClicker Question

bull What must be done to overcome the setting of the Sun in a solar energy systemndash A Store energy in batteriesndash B Get electrical power from elsewherendash C Donrsquot use electrical power at nightndash D All of the above are alternative

approaches for energy after sunset

13

iClicker Question

bull Based upon the discussion of the glass in a flat plate collector how would you define the greenhouse gas effect

bull A An effect caused by a gas that is transparent to visible light and opaque to infrared radiation

bull B An effect caused by a gas that is transparent to infrared radiation and opaque to ultraviolet radiation

bull C An effect caused by a gas that is transparent to ultraviolet radiation and opaque to infrared radiation

bull D An effect caused by a gas that is transparent to infrared radiation and opaque to visible light

bull E An effect caused by the sun emitting more infrared radiation than ultraviolet radiation

14

iClicker Question

bull Based upon the discussion of the glass in a flat plate collector how would you define the greenhouse gas effect

bull A An effect caused by a gas that is transparent to visible light and opaque to infrared radiation

bull B An effect caused by a gas that is transparent to infrared radiation and opaque to ultraviolet radiation

bull C An effect caused by a gas that is transparent to ultraviolet radiation and opaque to infrared radiation

bull D An effect caused by a gas that is transparent to infrared radiation and opaque to visible light

bull E An effect caused by the sun emitting more infrared radiation than ultraviolet radiation

15

Renewable Resources Discussed in Book

bull Renewable means anything that wonrsquot be permanently destroyed by using itndash sunlight (the sun will rise again tomorrow)ndash biomass (grows again)ndash hydrological cycle (will rain again)ndash wind (sunlight on Earth makes more)ndash ocean currents (driven by Sun)ndash tidal motion (MoonSun keep on producing it)ndash geothermal (heat sources inside Earth not

used up fast)

16

Renewable Energy Consumption

Energy Source

QBtu (1994)

Percent (1994)

QBtu (2003)

Percent (2003)

Hydroelectric 3037 343 2779 283

Geothermal 0357 040 0314 032

Biomass 2852 322 2884 294

Solar Energy 0069 0077 0063 006

Wind 0036 0040 0108 011

Total 6351 718 615 63

17

Another look at available energy flow

bull The flow of radiation (solar and thermal) was covered previouslyndash earth is in an energy balance energy in =

energy outndash 30 reflected 70 thermally re-radiated

bull Some of the incident energy is absorbed but what exactly does this dondash much goes into heating the airlandndash much goes into driving weather (rain wind)ndash some goes into ocean currentsndash some goes into photosynthesis

18

The Renewable Budget

19

Outstanding Points from Fig 51

bull Incident radiation is 1741015 Wndash this is 1370 Wm2 times area facing sun

(R2)bull 30 directly reflected back to space

ndash off clouds air landbull 47 goes into heating air land waterbull 23 goes into evaporating water

precipitation etc (part of weather)bull Adds to 100 so wersquore done

ndash but wait therersquos morehellip

20

Energy Flow continued

bull 021 goes into wind waves convection currentsndash note this is 100 times less than driving the water

cyclendash but this is the ldquootherrdquo aspect of weather

bull 0023 is stored as chemical energy in plants via photosynthesis

ndash total is 401012 W half in ocean (plankton)ndash humans are 6 billion times 100 W = 061012 Wndash this is 15 of bio-energy 000034 of incident

powerbull All of this (bio-activity wind weather etc) ends up

creating heat and re-radiating to spacendash except some small amount of storage in fossil fuels

21

The Hydrologic Cycle

Lots of energy associated with evaporationboth mgh (4 for 10 km lift) and latent heat (96) of water

22

Energetics of the hydrologic cycle

bull It takes energy to evaporate water 2444 J per gramndash this is why ldquoswamp coolersrdquo work evaporation

pulls heat out of environment making it feel cooler

ndash 23 of sunrsquos incident energy goes into evaporation

bull By contrast raising one gram of water to the top of the troposphere (10000 m or 33000 ft) takes

mgh = (0001 kg)(10 ms2)(10000 m) = 100 J

bull So gt 96 of the energy associated with forming clouds is the evaporation lt 4 in lifting against gravity

23

Let it Rain

bull When water condenses in clouds it re-releases this ldquolatent heatrdquo

ndash but this is re-radiated and is of no consequence to hydro-power

bull When it rains the gravitational potential energy is released mostly as kinetic energy and ultimately heat

bull Some tiny bit of gravitational potential energy remains IF the rain falls on terrain (eg higher than sea level where it originated)

ndash hydroelectric plants use this tiny left-over energy itrsquos the energy that drives the flow of streams and rivers

ndash damming up a river concentrates the potential energy in one location for easy exploitation

24

How much of the process do we get to keep

bull According to Figure 51 401015 W of solar power goes into evaporation

ndash this corresponds to 161010 kg per second of evaporated water

ndash this is 35 mm per day off the ocean surface (replenished by rain)

bull The gravitational potential energy given to water vapor (mostly in clouds) in the atmosphere (per second) is thenmgh = (161010 kg)(10 ms2)(2000 m) = 321014 J

bull One can calculate that we gain access to only 25 of the total amount (and use only 125)

ndash based on the 18 land area of the US and the maximum potential of 1477 GW as presented in Table 52

25

iClicker Question

bull With respects to energy hydroelectric power representsndash A remnant electric power from stormsndash B remnant water energy from chemical

bondsndash C remnant energy of chemical bondingndash D remnant gravitational potential

energy of precipitationndash E a form of fictitious energy

26

iClicker Question

bull With respects to energy hydroelectric power representsndash A remnant electric power from stormsndash B remnant water energy from chemical

bondsndash C remnant energy of chemical bondingndash D remnant gravitational potential

energy of precipitationndash E a form of fictitious energy

27

Power of a hydroelectric dam

bull Most impressive is Grand Coulee in Washington on Columbia River

ndash 350 feet = 107 m of ldquoheadrdquondash gt 6000 m3s flow rate (Pacific Northwest gets

rain)ndash each cubic meter of water (1000 kg) has potential

energy mgh = (1000 kg)(10 ms2)(110 m) = 11 MJ

ndash At 6000 m3s get over 6 GW of powerbull Large nuclear plants are usually 1ndash2 GWbull 11 other dams in US in 1ndash2 GW rangebull 74 GW total hydroelectric capacity presently

28

Importance of Hydroelectricity

29

Hydroelectric potential by region in GW

Region Potential

Developed

Undeveloped

Developed

New England 63 19 44 301

Middle Atlantic 98 49 49 500

East North Central 29 12 17 413

West North Central

62 31 31 500

South Atlantic 139 67 72 482

East South Central 83 59 24 711

West South Central

73 27 46 369

Mountain 286 95 191 332

Pacific 644 382 262 593

Total 1477 741 736 502

30

iClicker Question

bull What is true about hydroelectric power generation since 1950ndash A It has always increased in MW producedndash B It has always decreased in MW producedndash C It has increased and decreased in total

MW produced but is now at a peakndash D It has both increased and decreased in

total MW producedndash E The percentage of electric power

produced by hydroelectric plants has generally increased over time

31

iClicker Question

bull What is true about hydroelectric power generation since 1950ndash A It has always increased in MW producedndash B It has always decreased in MW producedndash C It has increased and decreased in total

MW produced but is now at a peakndash D It has both increased and decreased in

total MW producedndash E The percentage of electric power

produced by hydroelectric plants has generally increased over time

32

Hydroelectricity in the future

bull Wersquore almost tapped-outndash 50 of potential is developedndash remaining potential in large number of small-scale

unitsbull Problems with dams

ndash silt limits lifetime to 50ndash200 years after which dam is useless and in fact a potential disaster and nagging maintenance site

ndash habitat loss for fish (salmon) etc wrecks otherwise stunning landscapes (Glenn Canyon in UT)

ndash Disasters waiting to happen 1680 deaths in US alone from 1918ndash1958 often upstream from major population centers

33

Sorry try againhellip

bull So hydroelectricity is a nice ldquofreebeerdquo handed to us by nature but itrsquos not enough to cover our appetite for energy

bull Though very efficient and seemingly environmentally friendly dams do have their problems

bull This isnrsquot the answer to all our energy problems though it is likely to maintain a role well into our future

34

Wind Energy

35

The Power of Wind

bull Wersquove talked about the kinetic energy in wind beforendash a wind traveling at speed v covers v meters

every second (if v is expressed in ms)ndash the kinetic energy hitting a square meter is

then the kinetic energy the mass of air defined by a rectangular tube

ndash tube is one square meter by v meters or v m3

ndash density of air is = 13 kgm3 at sea levelndash mass is v kgndash KE = frac12(v)v2 = frac12v3 (per square meter)

065v3 at sea level

36

Wind Energy proportional to cube of velocity

bull The book (p 134) says power per square meter is 061v3 which is a more-or-less identical resultndash might account for average density in

continental US (above sea level so air slightly less dense)

bull So if the wind speed doubles the power available in the wind increases by 23 = 222 = 8 times

bull A wind of 10 ms (22 mph) has a power density of 610 Wm2

bull A wind of 20 ms (44 mph) has a power density of 4880 Wm2

37

Canrsquot get it all

bull A windmill canrsquot extract all of the kinetic energy available in the wind because this would mean stopping the wind entirely

bull Stopped wind would divert oncoming wind around it and the windmill would stop spinning

bull On the other hand if you donrsquot slow the wind down much at all you wonrsquot get much energy

bull Theoretical maximum performance is 59 of energy extractedndash corresponds to reducing velocity by 36

38

Practical Efficiencies

bull Modern windmills attain maybe 50ndash70 of the theoretical maximumndash 05ndash07 times 059 is 030ndash041 or

about 30ndash40ndash this figure is the mechanical energy

extracted from the windbull Conversion from mechanical to

electrical is 90 efficientndash 09 times 030ndash041 is 27ndash37

39

iClicker Question

bull What is about the maximum efficiency of energy generation using the windndash A 20ndash B 40ndash C 60ndash D 80ndash E 100

40

iClicker Question

bull What is about the maximum efficiency of energy generation using the windndash A 20ndash B 40ndash C 60ndash D 80ndash E 100

41

Achievable efficiencies

42

Typical Windmillsbull A typical windmill might be 15 m in diameter

ndash 176 m2

bull At 10 ms wind 40 efficiency this delivers about 100 kW of power

ndash this would be 800 kW at 20 msndash typical windmills are rated at 50 to 600 kW

bull How much energy per yearndash 10 ms 610 Wm2 40 240 Wm2 8760 hours per

year 2000 kWh per year per square meterndash but wind is intermittent real range from 100ndash500 kWhm2

ndash corresponds to 11ndash57 Wm2 average available power density

bull Note the really high tip speeds bird killers

43

Average available wind powerrecall that average solar insolation is about 150ndash250 Wm2

44

Comparable to solar

bull These numbers are similar to solar if not a little biggerndash Letrsquos go to wind

bull BUT the ldquoper square meterrdquo is not land areamdashitrsquos rotor area

bull Doesnrsquot pay to space windmills too closelymdashone robs the other of energy

bull Typical arrangements have rotors 10 diameters apart in direction of prevailing wind 5 diameters apart in the cross-wind directionndash works out to 16 ldquofill factorrdquo

45

Current implementations

bull Rapidly developing resourcendash 1400 MW in 1989 up to 6400 MW in 2003ndash but still insignificant total (compare to large

dams)ndash cost (at 5ndash7cent per kWh) is competitivendash growing at 25 per yearndash expect to triple over next ten years

bull Current capacity 116 GW (April 2007)ndash Texas 2768 MW (recently took lead over

California)ndash California 2361 MWndash Iowa 936 MWndash Minnesota 895 MWndash Washington 818 MW

46

Flies in the Ointment

bull Find that only 20 of rated capacity is achievedndash design for high wind but seldom get it

bull Only 12 of electrical capacity in US is now windndash total electrical capacity in US is 948 GWndash tripling in ten years means 36ndash but achieving only 20 of capacity reduces

substantiallybull If fully developed we could generate an average

power almost equal to our current electrical capacity (764 GW)

ndash but highly variable resource and problematic if more than 20 comes from the intermittent wind

47

iClicker Question

bull Which state generates the most amount of electricity derived from wind powerndash A Virginiandash B Alaskandash C Montanandash D Californiandash E Texas

48

iClicker Question

bull Which state generates the most amount of electricity derived from wind powerndash A Virginiandash B Alaskandash C Montanandash D Californiandash E Texas

• Renewable Energy Sources II Alternatives Part I
• Chapter 5 Summary
• Slide 3
• Slide 4
• Slide 5
• Slide 6
• Slide 7
• Slide 8
• Slide 9
• Slide 10
• Slide 11
• Slide 12
• Slide 13
• Slide 14
• Renewable Resources Discussed in Book
• Renewable Energy Consumption
• Another look at available energy flow
• The Renewable Budget
• Outstanding Points from Fig 51
• Energy Flow continued
• The Hydrologic Cycle
• Energetics of the hydrologic cycle
• Let it Rain
• How much of the process do we get to keep
• iClicker Question
• Slide 26
• Power of a hydroelectric dam
• Importance of Hydroelectricity
• Hydroelectric potential by region in GW
• Slide 30
• Slide 31
• Hydroelectricity in the future
• Sorry try againhellip
• Wind Energy
• The Power of Wind
• Wind Energy proportional to cube of velocity
• Canrsquot get it all
• Practical Efficiencies
• Slide 39
• Slide 40
• Achievable efficiencies
• Typical Windmills
• Average available wind power
• Comparable to solar
• Current implementations
• Flies in the Ointment
• Slide 47
• Slide 48

3

iClicker Question

bull What is the definition of insolationbull A The effective solar insulation factorbull B The amount of light received by a

horizontal surface averaged over the yearbull C The amount of light received by a unit

area of the atmosphere averaged over the year

bull D There is none it is a mis-spelling of insulation

bull E The amount of insulation that is received from the Sun

4

iClicker Question

bull What is the definition of insolationbull A The effective solar insulation factorbull B The amount of light received by a

horizontal surface averaged over the yearbull C The amount of light received by a unit

area of the atmosphere averaged over the year

bull D There is none it is a mis-spelling of insulation

bull E The amount of insulation that is received from the Sun

5

iClicker Question

bull Roughly what percentage of light from the Sun reaches the groundndash A 10ndash B 20ndash C 30ndash D 40ndash E 50

6

iClicker Question

bull Roughly what percentage of light from the Sun reaches the groundndash A 10ndash B 20ndash C 30ndash D 40ndash E 50

7

iClicker Question

bull What is roughly the maximum efficiency for a photovoltaic cellndash A 10ndash B 15ndash C 30ndash D 40ndash E 50

8

iClicker Question

bull What is roughly the maximum efficiency for a photovoltaic cellndash A 10ndash B 15ndash C 30ndash D 40ndash E 50

9

iClicker Question

bull How much energy does the largest photovoltaic system producendash A 10 MWndash B 20 MWndash C 60 MWndash D 100 MWndash E 200 MW

10

iClicker Question

bull How much energy does the largest photovoltaic system producendash A 10 MWndash B 20 MWndash C 60 MWndash D 100 MWndash E 200 MW

11

iClicker Question

bull What must be done to overcome the setting of the Sun in a solar energy systemndash A Store energy in batteriesndash B Get electrical power from elsewherendash C Donrsquot use electrical power at nightndash D All of the above are alternative

approaches for energy after sunset

12

iClicker Question

bull What must be done to overcome the setting of the Sun in a solar energy systemndash A Store energy in batteriesndash B Get electrical power from elsewherendash C Donrsquot use electrical power at nightndash D All of the above are alternative

approaches for energy after sunset

13

iClicker Question

bull Based upon the discussion of the glass in a flat plate collector how would you define the greenhouse gas effect

bull A An effect caused by a gas that is transparent to visible light and opaque to infrared radiation

bull B An effect caused by a gas that is transparent to infrared radiation and opaque to ultraviolet radiation

bull C An effect caused by a gas that is transparent to ultraviolet radiation and opaque to infrared radiation

bull D An effect caused by a gas that is transparent to infrared radiation and opaque to visible light

bull E An effect caused by the sun emitting more infrared radiation than ultraviolet radiation

14

iClicker Question

bull Based upon the discussion of the glass in a flat plate collector how would you define the greenhouse gas effect

bull A An effect caused by a gas that is transparent to visible light and opaque to infrared radiation

bull B An effect caused by a gas that is transparent to infrared radiation and opaque to ultraviolet radiation

bull C An effect caused by a gas that is transparent to ultraviolet radiation and opaque to infrared radiation

bull D An effect caused by a gas that is transparent to infrared radiation and opaque to visible light

bull E An effect caused by the sun emitting more infrared radiation than ultraviolet radiation

15

Renewable Resources Discussed in Book

bull Renewable means anything that wonrsquot be permanently destroyed by using itndash sunlight (the sun will rise again tomorrow)ndash biomass (grows again)ndash hydrological cycle (will rain again)ndash wind (sunlight on Earth makes more)ndash ocean currents (driven by Sun)ndash tidal motion (MoonSun keep on producing it)ndash geothermal (heat sources inside Earth not

used up fast)

16

Renewable Energy Consumption

Energy Source

QBtu (1994)

Percent (1994)

QBtu (2003)

Percent (2003)

Hydroelectric 3037 343 2779 283

Geothermal 0357 040 0314 032

Biomass 2852 322 2884 294

Solar Energy 0069 0077 0063 006

Wind 0036 0040 0108 011

Total 6351 718 615 63

17

Another look at available energy flow

bull The flow of radiation (solar and thermal) was covered previouslyndash earth is in an energy balance energy in =

energy outndash 30 reflected 70 thermally re-radiated

bull Some of the incident energy is absorbed but what exactly does this dondash much goes into heating the airlandndash much goes into driving weather (rain wind)ndash some goes into ocean currentsndash some goes into photosynthesis

18

The Renewable Budget

19

Outstanding Points from Fig 51

bull Incident radiation is 1741015 Wndash this is 1370 Wm2 times area facing sun

(R2)bull 30 directly reflected back to space

ndash off clouds air landbull 47 goes into heating air land waterbull 23 goes into evaporating water

precipitation etc (part of weather)bull Adds to 100 so wersquore done

ndash but wait therersquos morehellip

20

Energy Flow continued

bull 021 goes into wind waves convection currentsndash note this is 100 times less than driving the water

cyclendash but this is the ldquootherrdquo aspect of weather

bull 0023 is stored as chemical energy in plants via photosynthesis

ndash total is 401012 W half in ocean (plankton)ndash humans are 6 billion times 100 W = 061012 Wndash this is 15 of bio-energy 000034 of incident

powerbull All of this (bio-activity wind weather etc) ends up

creating heat and re-radiating to spacendash except some small amount of storage in fossil fuels

21

The Hydrologic Cycle

Lots of energy associated with evaporationboth mgh (4 for 10 km lift) and latent heat (96) of water

22

Energetics of the hydrologic cycle

bull It takes energy to evaporate water 2444 J per gramndash this is why ldquoswamp coolersrdquo work evaporation

pulls heat out of environment making it feel cooler

ndash 23 of sunrsquos incident energy goes into evaporation

bull By contrast raising one gram of water to the top of the troposphere (10000 m or 33000 ft) takes

mgh = (0001 kg)(10 ms2)(10000 m) = 100 J

bull So gt 96 of the energy associated with forming clouds is the evaporation lt 4 in lifting against gravity

23

Let it Rain

bull When water condenses in clouds it re-releases this ldquolatent heatrdquo

ndash but this is re-radiated and is of no consequence to hydro-power

bull When it rains the gravitational potential energy is released mostly as kinetic energy and ultimately heat

bull Some tiny bit of gravitational potential energy remains IF the rain falls on terrain (eg higher than sea level where it originated)

ndash hydroelectric plants use this tiny left-over energy itrsquos the energy that drives the flow of streams and rivers

ndash damming up a river concentrates the potential energy in one location for easy exploitation

24

How much of the process do we get to keep

bull According to Figure 51 401015 W of solar power goes into evaporation

ndash this corresponds to 161010 kg per second of evaporated water

ndash this is 35 mm per day off the ocean surface (replenished by rain)

bull The gravitational potential energy given to water vapor (mostly in clouds) in the atmosphere (per second) is thenmgh = (161010 kg)(10 ms2)(2000 m) = 321014 J

bull One can calculate that we gain access to only 25 of the total amount (and use only 125)

ndash based on the 18 land area of the US and the maximum potential of 1477 GW as presented in Table 52

25

iClicker Question

bull With respects to energy hydroelectric power representsndash A remnant electric power from stormsndash B remnant water energy from chemical

bondsndash C remnant energy of chemical bondingndash D remnant gravitational potential

energy of precipitationndash E a form of fictitious energy

26

iClicker Question

bull With respects to energy hydroelectric power representsndash A remnant electric power from stormsndash B remnant water energy from chemical

bondsndash C remnant energy of chemical bondingndash D remnant gravitational potential

energy of precipitationndash E a form of fictitious energy

27

Power of a hydroelectric dam

bull Most impressive is Grand Coulee in Washington on Columbia River

ndash 350 feet = 107 m of ldquoheadrdquondash gt 6000 m3s flow rate (Pacific Northwest gets

rain)ndash each cubic meter of water (1000 kg) has potential

energy mgh = (1000 kg)(10 ms2)(110 m) = 11 MJ

ndash At 6000 m3s get over 6 GW of powerbull Large nuclear plants are usually 1ndash2 GWbull 11 other dams in US in 1ndash2 GW rangebull 74 GW total hydroelectric capacity presently

28

Importance of Hydroelectricity

29

Hydroelectric potential by region in GW

Region Potential

Developed

Undeveloped

Developed

New England 63 19 44 301

Middle Atlantic 98 49 49 500

East North Central 29 12 17 413

West North Central

62 31 31 500

South Atlantic 139 67 72 482

East South Central 83 59 24 711

West South Central

73 27 46 369

Mountain 286 95 191 332

Pacific 644 382 262 593

Total 1477 741 736 502

30

iClicker Question

bull What is true about hydroelectric power generation since 1950ndash A It has always increased in MW producedndash B It has always decreased in MW producedndash C It has increased and decreased in total

MW produced but is now at a peakndash D It has both increased and decreased in

total MW producedndash E The percentage of electric power

produced by hydroelectric plants has generally increased over time

31

iClicker Question

bull What is true about hydroelectric power generation since 1950ndash A It has always increased in MW producedndash B It has always decreased in MW producedndash C It has increased and decreased in total

MW produced but is now at a peakndash D It has both increased and decreased in

total MW producedndash E The percentage of electric power

produced by hydroelectric plants has generally increased over time

32

Hydroelectricity in the future

bull Wersquore almost tapped-outndash 50 of potential is developedndash remaining potential in large number of small-scale

unitsbull Problems with dams

ndash silt limits lifetime to 50ndash200 years after which dam is useless and in fact a potential disaster and nagging maintenance site

ndash habitat loss for fish (salmon) etc wrecks otherwise stunning landscapes (Glenn Canyon in UT)

ndash Disasters waiting to happen 1680 deaths in US alone from 1918ndash1958 often upstream from major population centers

33

Sorry try againhellip

bull So hydroelectricity is a nice ldquofreebeerdquo handed to us by nature but itrsquos not enough to cover our appetite for energy

bull Though very efficient and seemingly environmentally friendly dams do have their problems

bull This isnrsquot the answer to all our energy problems though it is likely to maintain a role well into our future

34

Wind Energy

35

The Power of Wind

bull Wersquove talked about the kinetic energy in wind beforendash a wind traveling at speed v covers v meters

every second (if v is expressed in ms)ndash the kinetic energy hitting a square meter is

then the kinetic energy the mass of air defined by a rectangular tube

ndash tube is one square meter by v meters or v m3

ndash density of air is = 13 kgm3 at sea levelndash mass is v kgndash KE = frac12(v)v2 = frac12v3 (per square meter)

065v3 at sea level

36

Wind Energy proportional to cube of velocity

bull The book (p 134) says power per square meter is 061v3 which is a more-or-less identical resultndash might account for average density in

continental US (above sea level so air slightly less dense)

bull So if the wind speed doubles the power available in the wind increases by 23 = 222 = 8 times

bull A wind of 10 ms (22 mph) has a power density of 610 Wm2

bull A wind of 20 ms (44 mph) has a power density of 4880 Wm2

37

Canrsquot get it all

bull A windmill canrsquot extract all of the kinetic energy available in the wind because this would mean stopping the wind entirely

bull Stopped wind would divert oncoming wind around it and the windmill would stop spinning

bull On the other hand if you donrsquot slow the wind down much at all you wonrsquot get much energy

bull Theoretical maximum performance is 59 of energy extractedndash corresponds to reducing velocity by 36

38

Practical Efficiencies

bull Modern windmills attain maybe 50ndash70 of the theoretical maximumndash 05ndash07 times 059 is 030ndash041 or

about 30ndash40ndash this figure is the mechanical energy

extracted from the windbull Conversion from mechanical to

electrical is 90 efficientndash 09 times 030ndash041 is 27ndash37

39

iClicker Question

bull What is about the maximum efficiency of energy generation using the windndash A 20ndash B 40ndash C 60ndash D 80ndash E 100

40

iClicker Question

bull What is about the maximum efficiency of energy generation using the windndash A 20ndash B 40ndash C 60ndash D 80ndash E 100

41

Achievable efficiencies

42

Typical Windmillsbull A typical windmill might be 15 m in diameter

ndash 176 m2

bull At 10 ms wind 40 efficiency this delivers about 100 kW of power

ndash this would be 800 kW at 20 msndash typical windmills are rated at 50 to 600 kW

bull How much energy per yearndash 10 ms 610 Wm2 40 240 Wm2 8760 hours per

year 2000 kWh per year per square meterndash but wind is intermittent real range from 100ndash500 kWhm2

ndash corresponds to 11ndash57 Wm2 average available power density

bull Note the really high tip speeds bird killers

43

Average available wind powerrecall that average solar insolation is about 150ndash250 Wm2

44

Comparable to solar

bull These numbers are similar to solar if not a little biggerndash Letrsquos go to wind

bull BUT the ldquoper square meterrdquo is not land areamdashitrsquos rotor area

bull Doesnrsquot pay to space windmills too closelymdashone robs the other of energy

bull Typical arrangements have rotors 10 diameters apart in direction of prevailing wind 5 diameters apart in the cross-wind directionndash works out to 16 ldquofill factorrdquo

45

Current implementations

bull Rapidly developing resourcendash 1400 MW in 1989 up to 6400 MW in 2003ndash but still insignificant total (compare to large

dams)ndash cost (at 5ndash7cent per kWh) is competitivendash growing at 25 per yearndash expect to triple over next ten years

bull Current capacity 116 GW (April 2007)ndash Texas 2768 MW (recently took lead over

California)ndash California 2361 MWndash Iowa 936 MWndash Minnesota 895 MWndash Washington 818 MW

46

Flies in the Ointment

bull Find that only 20 of rated capacity is achievedndash design for high wind but seldom get it

bull Only 12 of electrical capacity in US is now windndash total electrical capacity in US is 948 GWndash tripling in ten years means 36ndash but achieving only 20 of capacity reduces

substantiallybull If fully developed we could generate an average

power almost equal to our current electrical capacity (764 GW)

ndash but highly variable resource and problematic if more than 20 comes from the intermittent wind

47

iClicker Question

bull Which state generates the most amount of electricity derived from wind powerndash A Virginiandash B Alaskandash C Montanandash D Californiandash E Texas

48

iClicker Question

bull Which state generates the most amount of electricity derived from wind powerndash A Virginiandash B Alaskandash C Montanandash D Californiandash E Texas

• Renewable Energy Sources II Alternatives Part I
• Chapter 5 Summary
• Slide 3
• Slide 4
• Slide 5
• Slide 6
• Slide 7
• Slide 8
• Slide 9
• Slide 10
• Slide 11
• Slide 12
• Slide 13
• Slide 14
• Renewable Resources Discussed in Book
• Renewable Energy Consumption
• Another look at available energy flow
• The Renewable Budget
• Outstanding Points from Fig 51
• Energy Flow continued
• The Hydrologic Cycle
• Energetics of the hydrologic cycle
• Let it Rain
• How much of the process do we get to keep
• iClicker Question
• Slide 26
• Power of a hydroelectric dam
• Importance of Hydroelectricity
• Hydroelectric potential by region in GW
• Slide 30
• Slide 31
• Hydroelectricity in the future
• Sorry try againhellip
• Wind Energy
• The Power of Wind
• Wind Energy proportional to cube of velocity
• Canrsquot get it all
• Practical Efficiencies
• Slide 39
• Slide 40
• Achievable efficiencies
• Typical Windmills
• Average available wind power
• Comparable to solar
• Current implementations
• Flies in the Ointment
• Slide 47
• Slide 48

4

iClicker Question

bull What is the definition of insolationbull A The effective solar insulation factorbull B The amount of light received by a

horizontal surface averaged over the yearbull C The amount of light received by a unit

area of the atmosphere averaged over the year

bull D There is none it is a mis-spelling of insulation

bull E The amount of insulation that is received from the Sun

5

iClicker Question

bull Roughly what percentage of light from the Sun reaches the groundndash A 10ndash B 20ndash C 30ndash D 40ndash E 50

6

iClicker Question

bull Roughly what percentage of light from the Sun reaches the groundndash A 10ndash B 20ndash C 30ndash D 40ndash E 50

7

iClicker Question

bull What is roughly the maximum efficiency for a photovoltaic cellndash A 10ndash B 15ndash C 30ndash D 40ndash E 50

8

iClicker Question

bull What is roughly the maximum efficiency for a photovoltaic cellndash A 10ndash B 15ndash C 30ndash D 40ndash E 50

9

iClicker Question

bull How much energy does the largest photovoltaic system producendash A 10 MWndash B 20 MWndash C 60 MWndash D 100 MWndash E 200 MW

10

iClicker Question

bull How much energy does the largest photovoltaic system producendash A 10 MWndash B 20 MWndash C 60 MWndash D 100 MWndash E 200 MW

11

iClicker Question

bull What must be done to overcome the setting of the Sun in a solar energy systemndash A Store energy in batteriesndash B Get electrical power from elsewherendash C Donrsquot use electrical power at nightndash D All of the above are alternative

approaches for energy after sunset

12

iClicker Question

bull What must be done to overcome the setting of the Sun in a solar energy systemndash A Store energy in batteriesndash B Get electrical power from elsewherendash C Donrsquot use electrical power at nightndash D All of the above are alternative

approaches for energy after sunset

13

iClicker Question

bull Based upon the discussion of the glass in a flat plate collector how would you define the greenhouse gas effect

bull A An effect caused by a gas that is transparent to visible light and opaque to infrared radiation

bull B An effect caused by a gas that is transparent to infrared radiation and opaque to ultraviolet radiation

bull C An effect caused by a gas that is transparent to ultraviolet radiation and opaque to infrared radiation

bull D An effect caused by a gas that is transparent to infrared radiation and opaque to visible light

bull E An effect caused by the sun emitting more infrared radiation than ultraviolet radiation

14

iClicker Question

bull Based upon the discussion of the glass in a flat plate collector how would you define the greenhouse gas effect

bull A An effect caused by a gas that is transparent to visible light and opaque to infrared radiation

bull B An effect caused by a gas that is transparent to infrared radiation and opaque to ultraviolet radiation

bull C An effect caused by a gas that is transparent to ultraviolet radiation and opaque to infrared radiation

bull D An effect caused by a gas that is transparent to infrared radiation and opaque to visible light

bull E An effect caused by the sun emitting more infrared radiation than ultraviolet radiation

15

Renewable Resources Discussed in Book

bull Renewable means anything that wonrsquot be permanently destroyed by using itndash sunlight (the sun will rise again tomorrow)ndash biomass (grows again)ndash hydrological cycle (will rain again)ndash wind (sunlight on Earth makes more)ndash ocean currents (driven by Sun)ndash tidal motion (MoonSun keep on producing it)ndash geothermal (heat sources inside Earth not

used up fast)

16

Renewable Energy Consumption

Energy Source

QBtu (1994)

Percent (1994)

QBtu (2003)

Percent (2003)

Hydroelectric 3037 343 2779 283

Geothermal 0357 040 0314 032

Biomass 2852 322 2884 294

Solar Energy 0069 0077 0063 006

Wind 0036 0040 0108 011

Total 6351 718 615 63

17

Another look at available energy flow

bull The flow of radiation (solar and thermal) was covered previouslyndash earth is in an energy balance energy in =

energy outndash 30 reflected 70 thermally re-radiated

bull Some of the incident energy is absorbed but what exactly does this dondash much goes into heating the airlandndash much goes into driving weather (rain wind)ndash some goes into ocean currentsndash some goes into photosynthesis

18

The Renewable Budget

19

Outstanding Points from Fig 51

bull Incident radiation is 1741015 Wndash this is 1370 Wm2 times area facing sun

(R2)bull 30 directly reflected back to space

ndash off clouds air landbull 47 goes into heating air land waterbull 23 goes into evaporating water

precipitation etc (part of weather)bull Adds to 100 so wersquore done

ndash but wait therersquos morehellip

20

Energy Flow continued

bull 021 goes into wind waves convection currentsndash note this is 100 times less than driving the water

cyclendash but this is the ldquootherrdquo aspect of weather

bull 0023 is stored as chemical energy in plants via photosynthesis

ndash total is 401012 W half in ocean (plankton)ndash humans are 6 billion times 100 W = 061012 Wndash this is 15 of bio-energy 000034 of incident

powerbull All of this (bio-activity wind weather etc) ends up

creating heat and re-radiating to spacendash except some small amount of storage in fossil fuels

21

The Hydrologic Cycle

Lots of energy associated with evaporationboth mgh (4 for 10 km lift) and latent heat (96) of water

22

Energetics of the hydrologic cycle

bull It takes energy to evaporate water 2444 J per gramndash this is why ldquoswamp coolersrdquo work evaporation

pulls heat out of environment making it feel cooler

ndash 23 of sunrsquos incident energy goes into evaporation

bull By contrast raising one gram of water to the top of the troposphere (10000 m or 33000 ft) takes

mgh = (0001 kg)(10 ms2)(10000 m) = 100 J

bull So gt 96 of the energy associated with forming clouds is the evaporation lt 4 in lifting against gravity

23

Let it Rain

bull When water condenses in clouds it re-releases this ldquolatent heatrdquo

ndash but this is re-radiated and is of no consequence to hydro-power

bull When it rains the gravitational potential energy is released mostly as kinetic energy and ultimately heat

bull Some tiny bit of gravitational potential energy remains IF the rain falls on terrain (eg higher than sea level where it originated)

ndash hydroelectric plants use this tiny left-over energy itrsquos the energy that drives the flow of streams and rivers

ndash damming up a river concentrates the potential energy in one location for easy exploitation

24

How much of the process do we get to keep

bull According to Figure 51 401015 W of solar power goes into evaporation

ndash this corresponds to 161010 kg per second of evaporated water

ndash this is 35 mm per day off the ocean surface (replenished by rain)

bull The gravitational potential energy given to water vapor (mostly in clouds) in the atmosphere (per second) is thenmgh = (161010 kg)(10 ms2)(2000 m) = 321014 J

bull One can calculate that we gain access to only 25 of the total amount (and use only 125)

ndash based on the 18 land area of the US and the maximum potential of 1477 GW as presented in Table 52

25

iClicker Question

bull With respects to energy hydroelectric power representsndash A remnant electric power from stormsndash B remnant water energy from chemical

bondsndash C remnant energy of chemical bondingndash D remnant gravitational potential

energy of precipitationndash E a form of fictitious energy

26

iClicker Question

bull With respects to energy hydroelectric power representsndash A remnant electric power from stormsndash B remnant water energy from chemical

bondsndash C remnant energy of chemical bondingndash D remnant gravitational potential

energy of precipitationndash E a form of fictitious energy

27

Power of a hydroelectric dam

bull Most impressive is Grand Coulee in Washington on Columbia River

ndash 350 feet = 107 m of ldquoheadrdquondash gt 6000 m3s flow rate (Pacific Northwest gets

rain)ndash each cubic meter of water (1000 kg) has potential

energy mgh = (1000 kg)(10 ms2)(110 m) = 11 MJ

ndash At 6000 m3s get over 6 GW of powerbull Large nuclear plants are usually 1ndash2 GWbull 11 other dams in US in 1ndash2 GW rangebull 74 GW total hydroelectric capacity presently

28

Importance of Hydroelectricity

29

Hydroelectric potential by region in GW

Region Potential

Developed

Undeveloped

Developed

New England 63 19 44 301

Middle Atlantic 98 49 49 500

East North Central 29 12 17 413

West North Central

62 31 31 500

South Atlantic 139 67 72 482

East South Central 83 59 24 711

West South Central

73 27 46 369

Mountain 286 95 191 332

Pacific 644 382 262 593

Total 1477 741 736 502

30

iClicker Question

bull What is true about hydroelectric power generation since 1950ndash A It has always increased in MW producedndash B It has always decreased in MW producedndash C It has increased and decreased in total

MW produced but is now at a peakndash D It has both increased and decreased in

total MW producedndash E The percentage of electric power

produced by hydroelectric plants has generally increased over time

31

iClicker Question

bull What is true about hydroelectric power generation since 1950ndash A It has always increased in MW producedndash B It has always decreased in MW producedndash C It has increased and decreased in total

MW produced but is now at a peakndash D It has both increased and decreased in

total MW producedndash E The percentage of electric power

produced by hydroelectric plants has generally increased over time

32

Hydroelectricity in the future

bull Wersquore almost tapped-outndash 50 of potential is developedndash remaining potential in large number of small-scale

unitsbull Problems with dams

ndash silt limits lifetime to 50ndash200 years after which dam is useless and in fact a potential disaster and nagging maintenance site

ndash habitat loss for fish (salmon) etc wrecks otherwise stunning landscapes (Glenn Canyon in UT)

ndash Disasters waiting to happen 1680 deaths in US alone from 1918ndash1958 often upstream from major population centers

33

Sorry try againhellip

bull So hydroelectricity is a nice ldquofreebeerdquo handed to us by nature but itrsquos not enough to cover our appetite for energy

bull Though very efficient and seemingly environmentally friendly dams do have their problems

bull This isnrsquot the answer to all our energy problems though it is likely to maintain a role well into our future

34

Wind Energy

35

The Power of Wind

bull Wersquove talked about the kinetic energy in wind beforendash a wind traveling at speed v covers v meters

every second (if v is expressed in ms)ndash the kinetic energy hitting a square meter is

then the kinetic energy the mass of air defined by a rectangular tube

ndash tube is one square meter by v meters or v m3

ndash density of air is = 13 kgm3 at sea levelndash mass is v kgndash KE = frac12(v)v2 = frac12v3 (per square meter)

065v3 at sea level

36

Wind Energy proportional to cube of velocity

bull The book (p 134) says power per square meter is 061v3 which is a more-or-less identical resultndash might account for average density in

continental US (above sea level so air slightly less dense)

bull So if the wind speed doubles the power available in the wind increases by 23 = 222 = 8 times

bull A wind of 10 ms (22 mph) has a power density of 610 Wm2

bull A wind of 20 ms (44 mph) has a power density of 4880 Wm2

37

Canrsquot get it all

bull A windmill canrsquot extract all of the kinetic energy available in the wind because this would mean stopping the wind entirely

bull Stopped wind would divert oncoming wind around it and the windmill would stop spinning

bull On the other hand if you donrsquot slow the wind down much at all you wonrsquot get much energy

bull Theoretical maximum performance is 59 of energy extractedndash corresponds to reducing velocity by 36

38

Practical Efficiencies

bull Modern windmills attain maybe 50ndash70 of the theoretical maximumndash 05ndash07 times 059 is 030ndash041 or

about 30ndash40ndash this figure is the mechanical energy

extracted from the windbull Conversion from mechanical to

electrical is 90 efficientndash 09 times 030ndash041 is 27ndash37

39

iClicker Question

bull What is about the maximum efficiency of energy generation using the windndash A 20ndash B 40ndash C 60ndash D 80ndash E 100

40

iClicker Question

bull What is about the maximum efficiency of energy generation using the windndash A 20ndash B 40ndash C 60ndash D 80ndash E 100

41

Achievable efficiencies

42

Typical Windmillsbull A typical windmill might be 15 m in diameter

ndash 176 m2

bull At 10 ms wind 40 efficiency this delivers about 100 kW of power

ndash this would be 800 kW at 20 msndash typical windmills are rated at 50 to 600 kW

bull How much energy per yearndash 10 ms 610 Wm2 40 240 Wm2 8760 hours per

year 2000 kWh per year per square meterndash but wind is intermittent real range from 100ndash500 kWhm2

ndash corresponds to 11ndash57 Wm2 average available power density

bull Note the really high tip speeds bird killers

43

Average available wind powerrecall that average solar insolation is about 150ndash250 Wm2

44

Comparable to solar

bull These numbers are similar to solar if not a little biggerndash Letrsquos go to wind

bull BUT the ldquoper square meterrdquo is not land areamdashitrsquos rotor area

bull Doesnrsquot pay to space windmills too closelymdashone robs the other of energy

bull Typical arrangements have rotors 10 diameters apart in direction of prevailing wind 5 diameters apart in the cross-wind directionndash works out to 16 ldquofill factorrdquo

45

Current implementations

bull Rapidly developing resourcendash 1400 MW in 1989 up to 6400 MW in 2003ndash but still insignificant total (compare to large

dams)ndash cost (at 5ndash7cent per kWh) is competitivendash growing at 25 per yearndash expect to triple over next ten years

bull Current capacity 116 GW (April 2007)ndash Texas 2768 MW (recently took lead over

California)ndash California 2361 MWndash Iowa 936 MWndash Minnesota 895 MWndash Washington 818 MW

46

Flies in the Ointment

bull Find that only 20 of rated capacity is achievedndash design for high wind but seldom get it

bull Only 12 of electrical capacity in US is now windndash total electrical capacity in US is 948 GWndash tripling in ten years means 36ndash but achieving only 20 of capacity reduces

substantiallybull If fully developed we could generate an average

power almost equal to our current electrical capacity (764 GW)

ndash but highly variable resource and problematic if more than 20 comes from the intermittent wind

47

iClicker Question

bull Which state generates the most amount of electricity derived from wind powerndash A Virginiandash B Alaskandash C Montanandash D Californiandash E Texas

48

iClicker Question

bull Which state generates the most amount of electricity derived from wind powerndash A Virginiandash B Alaskandash C Montanandash D Californiandash E Texas

• Renewable Energy Sources II Alternatives Part I
• Chapter 5 Summary
• Slide 3
• Slide 4
• Slide 5
• Slide 6
• Slide 7
• Slide 8
• Slide 9
• Slide 10
• Slide 11
• Slide 12
• Slide 13
• Slide 14
• Renewable Resources Discussed in Book
• Renewable Energy Consumption
• Another look at available energy flow
• The Renewable Budget
• Outstanding Points from Fig 51
• Energy Flow continued
• The Hydrologic Cycle
• Energetics of the hydrologic cycle
• Let it Rain
• How much of the process do we get to keep
• iClicker Question
• Slide 26
• Power of a hydroelectric dam
• Importance of Hydroelectricity
• Hydroelectric potential by region in GW
• Slide 30
• Slide 31
• Hydroelectricity in the future
• Sorry try againhellip
• Wind Energy
• The Power of Wind
• Wind Energy proportional to cube of velocity
• Canrsquot get it all
• Practical Efficiencies
• Slide 39
• Slide 40
• Achievable efficiencies
• Typical Windmills
• Average available wind power
• Comparable to solar
• Current implementations
• Flies in the Ointment
• Slide 47
• Slide 48

5

iClicker Question

bull Roughly what percentage of light from the Sun reaches the groundndash A 10ndash B 20ndash C 30ndash D 40ndash E 50

6

iClicker Question

bull Roughly what percentage of light from the Sun reaches the groundndash A 10ndash B 20ndash C 30ndash D 40ndash E 50

7

iClicker Question

bull What is roughly the maximum efficiency for a photovoltaic cellndash A 10ndash B 15ndash C 30ndash D 40ndash E 50

8

iClicker Question

bull What is roughly the maximum efficiency for a photovoltaic cellndash A 10ndash B 15ndash C 30ndash D 40ndash E 50

9

iClicker Question

bull How much energy does the largest photovoltaic system producendash A 10 MWndash B 20 MWndash C 60 MWndash D 100 MWndash E 200 MW

10

iClicker Question

bull How much energy does the largest photovoltaic system producendash A 10 MWndash B 20 MWndash C 60 MWndash D 100 MWndash E 200 MW

11

iClicker Question

bull What must be done to overcome the setting of the Sun in a solar energy systemndash A Store energy in batteriesndash B Get electrical power from elsewherendash C Donrsquot use electrical power at nightndash D All of the above are alternative

approaches for energy after sunset

12

iClicker Question

bull What must be done to overcome the setting of the Sun in a solar energy systemndash A Store energy in batteriesndash B Get electrical power from elsewherendash C Donrsquot use electrical power at nightndash D All of the above are alternative

approaches for energy after sunset

13

iClicker Question

bull Based upon the discussion of the glass in a flat plate collector how would you define the greenhouse gas effect

bull A An effect caused by a gas that is transparent to visible light and opaque to infrared radiation

bull B An effect caused by a gas that is transparent to infrared radiation and opaque to ultraviolet radiation

bull C An effect caused by a gas that is transparent to ultraviolet radiation and opaque to infrared radiation

bull D An effect caused by a gas that is transparent to infrared radiation and opaque to visible light

bull E An effect caused by the sun emitting more infrared radiation than ultraviolet radiation

14

iClicker Question

bull Based upon the discussion of the glass in a flat plate collector how would you define the greenhouse gas effect

bull A An effect caused by a gas that is transparent to visible light and opaque to infrared radiation

bull B An effect caused by a gas that is transparent to infrared radiation and opaque to ultraviolet radiation

bull C An effect caused by a gas that is transparent to ultraviolet radiation and opaque to infrared radiation

bull D An effect caused by a gas that is transparent to infrared radiation and opaque to visible light

bull E An effect caused by the sun emitting more infrared radiation than ultraviolet radiation

15

Renewable Resources Discussed in Book

bull Renewable means anything that wonrsquot be permanently destroyed by using itndash sunlight (the sun will rise again tomorrow)ndash biomass (grows again)ndash hydrological cycle (will rain again)ndash wind (sunlight on Earth makes more)ndash ocean currents (driven by Sun)ndash tidal motion (MoonSun keep on producing it)ndash geothermal (heat sources inside Earth not

used up fast)

16

Renewable Energy Consumption

Energy Source

QBtu (1994)

Percent (1994)

QBtu (2003)

Percent (2003)

Hydroelectric 3037 343 2779 283

Geothermal 0357 040 0314 032

Biomass 2852 322 2884 294

Solar Energy 0069 0077 0063 006

Wind 0036 0040 0108 011

Total 6351 718 615 63

17

Another look at available energy flow

bull The flow of radiation (solar and thermal) was covered previouslyndash earth is in an energy balance energy in =

energy outndash 30 reflected 70 thermally re-radiated

bull Some of the incident energy is absorbed but what exactly does this dondash much goes into heating the airlandndash much goes into driving weather (rain wind)ndash some goes into ocean currentsndash some goes into photosynthesis

18

The Renewable Budget

19

Outstanding Points from Fig 51

bull Incident radiation is 1741015 Wndash this is 1370 Wm2 times area facing sun

(R2)bull 30 directly reflected back to space

ndash off clouds air landbull 47 goes into heating air land waterbull 23 goes into evaporating water

precipitation etc (part of weather)bull Adds to 100 so wersquore done

ndash but wait therersquos morehellip

20

Energy Flow continued

bull 021 goes into wind waves convection currentsndash note this is 100 times less than driving the water

cyclendash but this is the ldquootherrdquo aspect of weather

bull 0023 is stored as chemical energy in plants via photosynthesis

ndash total is 401012 W half in ocean (plankton)ndash humans are 6 billion times 100 W = 061012 Wndash this is 15 of bio-energy 000034 of incident

powerbull All of this (bio-activity wind weather etc) ends up

creating heat and re-radiating to spacendash except some small amount of storage in fossil fuels

21

The Hydrologic Cycle

Lots of energy associated with evaporationboth mgh (4 for 10 km lift) and latent heat (96) of water

22

Energetics of the hydrologic cycle

bull It takes energy to evaporate water 2444 J per gramndash this is why ldquoswamp coolersrdquo work evaporation

pulls heat out of environment making it feel cooler

ndash 23 of sunrsquos incident energy goes into evaporation

bull By contrast raising one gram of water to the top of the troposphere (10000 m or 33000 ft) takes

mgh = (0001 kg)(10 ms2)(10000 m) = 100 J

bull So gt 96 of the energy associated with forming clouds is the evaporation lt 4 in lifting against gravity

23

Let it Rain

bull When water condenses in clouds it re-releases this ldquolatent heatrdquo

ndash but this is re-radiated and is of no consequence to hydro-power

bull When it rains the gravitational potential energy is released mostly as kinetic energy and ultimately heat

bull Some tiny bit of gravitational potential energy remains IF the rain falls on terrain (eg higher than sea level where it originated)

ndash hydroelectric plants use this tiny left-over energy itrsquos the energy that drives the flow of streams and rivers

ndash damming up a river concentrates the potential energy in one location for easy exploitation

24

How much of the process do we get to keep

bull According to Figure 51 401015 W of solar power goes into evaporation

ndash this corresponds to 161010 kg per second of evaporated water

ndash this is 35 mm per day off the ocean surface (replenished by rain)

bull The gravitational potential energy given to water vapor (mostly in clouds) in the atmosphere (per second) is thenmgh = (161010 kg)(10 ms2)(2000 m) = 321014 J

bull One can calculate that we gain access to only 25 of the total amount (and use only 125)

ndash based on the 18 land area of the US and the maximum potential of 1477 GW as presented in Table 52

25

iClicker Question

bull With respects to energy hydroelectric power representsndash A remnant electric power from stormsndash B remnant water energy from chemical

bondsndash C remnant energy of chemical bondingndash D remnant gravitational potential

energy of precipitationndash E a form of fictitious energy

26

iClicker Question

bull With respects to energy hydroelectric power representsndash A remnant electric power from stormsndash B remnant water energy from chemical

bondsndash C remnant energy of chemical bondingndash D remnant gravitational potential

energy of precipitationndash E a form of fictitious energy

27

Power of a hydroelectric dam

bull Most impressive is Grand Coulee in Washington on Columbia River

ndash 350 feet = 107 m of ldquoheadrdquondash gt 6000 m3s flow rate (Pacific Northwest gets

rain)ndash each cubic meter of water (1000 kg) has potential

energy mgh = (1000 kg)(10 ms2)(110 m) = 11 MJ

ndash At 6000 m3s get over 6 GW of powerbull Large nuclear plants are usually 1ndash2 GWbull 11 other dams in US in 1ndash2 GW rangebull 74 GW total hydroelectric capacity presently

28

Importance of Hydroelectricity

29

Hydroelectric potential by region in GW

Region Potential

Developed

Undeveloped

Developed

New England 63 19 44 301

Middle Atlantic 98 49 49 500

East North Central 29 12 17 413

West North Central

62 31 31 500

South Atlantic 139 67 72 482

East South Central 83 59 24 711

West South Central

73 27 46 369

Mountain 286 95 191 332

Pacific 644 382 262 593

Total 1477 741 736 502

30

iClicker Question

bull What is true about hydroelectric power generation since 1950ndash A It has always increased in MW producedndash B It has always decreased in MW producedndash C It has increased and decreased in total

MW produced but is now at a peakndash D It has both increased and decreased in

total MW producedndash E The percentage of electric power

produced by hydroelectric plants has generally increased over time

31

iClicker Question

bull What is true about hydroelectric power generation since 1950ndash A It has always increased in MW producedndash B It has always decreased in MW producedndash C It has increased and decreased in total

MW produced but is now at a peakndash D It has both increased and decreased in

total MW producedndash E The percentage of electric power

produced by hydroelectric plants has generally increased over time

32

Hydroelectricity in the future

bull Wersquore almost tapped-outndash 50 of potential is developedndash remaining potential in large number of small-scale

unitsbull Problems with dams

ndash silt limits lifetime to 50ndash200 years after which dam is useless and in fact a potential disaster and nagging maintenance site

ndash habitat loss for fish (salmon) etc wrecks otherwise stunning landscapes (Glenn Canyon in UT)

ndash Disasters waiting to happen 1680 deaths in US alone from 1918ndash1958 often upstream from major population centers

33

Sorry try againhellip

bull So hydroelectricity is a nice ldquofreebeerdquo handed to us by nature but itrsquos not enough to cover our appetite for energy

bull Though very efficient and seemingly environmentally friendly dams do have their problems

bull This isnrsquot the answer to all our energy problems though it is likely to maintain a role well into our future

34

Wind Energy

35

The Power of Wind

bull Wersquove talked about the kinetic energy in wind beforendash a wind traveling at speed v covers v meters

every second (if v is expressed in ms)ndash the kinetic energy hitting a square meter is

then the kinetic energy the mass of air defined by a rectangular tube

ndash tube is one square meter by v meters or v m3

ndash density of air is = 13 kgm3 at sea levelndash mass is v kgndash KE = frac12(v)v2 = frac12v3 (per square meter)

065v3 at sea level

36

Wind Energy proportional to cube of velocity

bull The book (p 134) says power per square meter is 061v3 which is a more-or-less identical resultndash might account for average density in

continental US (above sea level so air slightly less dense)

bull So if the wind speed doubles the power available in the wind increases by 23 = 222 = 8 times

bull A wind of 10 ms (22 mph) has a power density of 610 Wm2

bull A wind of 20 ms (44 mph) has a power density of 4880 Wm2

37

Canrsquot get it all

bull A windmill canrsquot extract all of the kinetic energy available in the wind because this would mean stopping the wind entirely

bull Stopped wind would divert oncoming wind around it and the windmill would stop spinning

bull On the other hand if you donrsquot slow the wind down much at all you wonrsquot get much energy

bull Theoretical maximum performance is 59 of energy extractedndash corresponds to reducing velocity by 36

38

Practical Efficiencies

bull Modern windmills attain maybe 50ndash70 of the theoretical maximumndash 05ndash07 times 059 is 030ndash041 or

about 30ndash40ndash this figure is the mechanical energy

extracted from the windbull Conversion from mechanical to

electrical is 90 efficientndash 09 times 030ndash041 is 27ndash37

39

iClicker Question

bull What is about the maximum efficiency of energy generation using the windndash A 20ndash B 40ndash C 60ndash D 80ndash E 100

40

iClicker Question

bull What is about the maximum efficiency of energy generation using the windndash A 20ndash B 40ndash C 60ndash D 80ndash E 100

41

Achievable efficiencies

42

Typical Windmillsbull A typical windmill might be 15 m in diameter

ndash 176 m2

bull At 10 ms wind 40 efficiency this delivers about 100 kW of power

ndash this would be 800 kW at 20 msndash typical windmills are rated at 50 to 600 kW

bull How much energy per yearndash 10 ms 610 Wm2 40 240 Wm2 8760 hours per

year 2000 kWh per year per square meterndash but wind is intermittent real range from 100ndash500 kWhm2

ndash corresponds to 11ndash57 Wm2 average available power density

bull Note the really high tip speeds bird killers

43

Average available wind powerrecall that average solar insolation is about 150ndash250 Wm2

44

Comparable to solar

bull These numbers are similar to solar if not a little biggerndash Letrsquos go to wind

bull BUT the ldquoper square meterrdquo is not land areamdashitrsquos rotor area

bull Doesnrsquot pay to space windmills too closelymdashone robs the other of energy

bull Typical arrangements have rotors 10 diameters apart in direction of prevailing wind 5 diameters apart in the cross-wind directionndash works out to 16 ldquofill factorrdquo

45

Current implementations

bull Rapidly developing resourcendash 1400 MW in 1989 up to 6400 MW in 2003ndash but still insignificant total (compare to large

dams)ndash cost (at 5ndash7cent per kWh) is competitivendash growing at 25 per yearndash expect to triple over next ten years

bull Current capacity 116 GW (April 2007)ndash Texas 2768 MW (recently took lead over

California)ndash California 2361 MWndash Iowa 936 MWndash Minnesota 895 MWndash Washington 818 MW

46

Flies in the Ointment

bull Find that only 20 of rated capacity is achievedndash design for high wind but seldom get it

bull Only 12 of electrical capacity in US is now windndash total electrical capacity in US is 948 GWndash tripling in ten years means 36ndash but achieving only 20 of capacity reduces

substantiallybull If fully developed we could generate an average

power almost equal to our current electrical capacity (764 GW)

ndash but highly variable resource and problematic if more than 20 comes from the intermittent wind

47

iClicker Question

bull Which state generates the most amount of electricity derived from wind powerndash A Virginiandash B Alaskandash C Montanandash D Californiandash E Texas

48

iClicker Question

bull Which state generates the most amount of electricity derived from wind powerndash A Virginiandash B Alaskandash C Montanandash D Californiandash E Texas

• Renewable Energy Sources II Alternatives Part I
• Chapter 5 Summary
• Slide 3
• Slide 4
• Slide 5
• Slide 6
• Slide 7
• Slide 8
• Slide 9
• Slide 10
• Slide 11
• Slide 12
• Slide 13
• Slide 14
• Renewable Resources Discussed in Book
• Renewable Energy Consumption
• Another look at available energy flow
• The Renewable Budget
• Outstanding Points from Fig 51
• Energy Flow continued
• The Hydrologic Cycle
• Energetics of the hydrologic cycle
• Let it Rain
• How much of the process do we get to keep
• iClicker Question
• Slide 26
• Power of a hydroelectric dam
• Importance of Hydroelectricity
• Hydroelectric potential by region in GW
• Slide 30
• Slide 31
• Hydroelectricity in the future
• Sorry try againhellip
• Wind Energy
• The Power of Wind
• Wind Energy proportional to cube of velocity
• Canrsquot get it all
• Practical Efficiencies
• Slide 39
• Slide 40
• Achievable efficiencies
• Typical Windmills
• Average available wind power
• Comparable to solar
• Current implementations
• Flies in the Ointment
• Slide 47
• Slide 48

6

iClicker Question

bull Roughly what percentage of light from the Sun reaches the groundndash A 10ndash B 20ndash C 30ndash D 40ndash E 50

7

iClicker Question

bull What is roughly the maximum efficiency for a photovoltaic cellndash A 10ndash B 15ndash C 30ndash D 40ndash E 50

8

iClicker Question

bull What is roughly the maximum efficiency for a photovoltaic cellndash A 10ndash B 15ndash C 30ndash D 40ndash E 50

9

iClicker Question

bull How much energy does the largest photovoltaic system producendash A 10 MWndash B 20 MWndash C 60 MWndash D 100 MWndash E 200 MW

10

iClicker Question

bull How much energy does the largest photovoltaic system producendash A 10 MWndash B 20 MWndash C 60 MWndash D 100 MWndash E 200 MW

11

iClicker Question

bull What must be done to overcome the setting of the Sun in a solar energy systemndash A Store energy in batteriesndash B Get electrical power from elsewherendash C Donrsquot use electrical power at nightndash D All of the above are alternative

approaches for energy after sunset

12

iClicker Question

bull What must be done to overcome the setting of the Sun in a solar energy systemndash A Store energy in batteriesndash B Get electrical power from elsewherendash C Donrsquot use electrical power at nightndash D All of the above are alternative

approaches for energy after sunset

13

iClicker Question

bull Based upon the discussion of the glass in a flat plate collector how would you define the greenhouse gas effect

bull A An effect caused by a gas that is transparent to visible light and opaque to infrared radiation

bull B An effect caused by a gas that is transparent to infrared radiation and opaque to ultraviolet radiation

bull C An effect caused by a gas that is transparent to ultraviolet radiation and opaque to infrared radiation

bull D An effect caused by a gas that is transparent to infrared radiation and opaque to visible light

bull E An effect caused by the sun emitting more infrared radiation than ultraviolet radiation

14

iClicker Question

bull Based upon the discussion of the glass in a flat plate collector how would you define the greenhouse gas effect

bull A An effect caused by a gas that is transparent to visible light and opaque to infrared radiation

bull B An effect caused by a gas that is transparent to infrared radiation and opaque to ultraviolet radiation

bull C An effect caused by a gas that is transparent to ultraviolet radiation and opaque to infrared radiation

bull D An effect caused by a gas that is transparent to infrared radiation and opaque to visible light

bull E An effect caused by the sun emitting more infrared radiation than ultraviolet radiation

15

Renewable Resources Discussed in Book

bull Renewable means anything that wonrsquot be permanently destroyed by using itndash sunlight (the sun will rise again tomorrow)ndash biomass (grows again)ndash hydrological cycle (will rain again)ndash wind (sunlight on Earth makes more)ndash ocean currents (driven by Sun)ndash tidal motion (MoonSun keep on producing it)ndash geothermal (heat sources inside Earth not

used up fast)

16

Renewable Energy Consumption

Energy Source

QBtu (1994)

Percent (1994)

QBtu (2003)

Percent (2003)

Hydroelectric 3037 343 2779 283

Geothermal 0357 040 0314 032

Biomass 2852 322 2884 294

Solar Energy 0069 0077 0063 006

Wind 0036 0040 0108 011

Total 6351 718 615 63

17

Another look at available energy flow

bull The flow of radiation (solar and thermal) was covered previouslyndash earth is in an energy balance energy in =

energy outndash 30 reflected 70 thermally re-radiated

bull Some of the incident energy is absorbed but what exactly does this dondash much goes into heating the airlandndash much goes into driving weather (rain wind)ndash some goes into ocean currentsndash some goes into photosynthesis

18

The Renewable Budget

19

Outstanding Points from Fig 51

bull Incident radiation is 1741015 Wndash this is 1370 Wm2 times area facing sun

(R2)bull 30 directly reflected back to space

ndash off clouds air landbull 47 goes into heating air land waterbull 23 goes into evaporating water

precipitation etc (part of weather)bull Adds to 100 so wersquore done

ndash but wait therersquos morehellip

20

Energy Flow continued

bull 021 goes into wind waves convection currentsndash note this is 100 times less than driving the water

cyclendash but this is the ldquootherrdquo aspect of weather

bull 0023 is stored as chemical energy in plants via photosynthesis

ndash total is 401012 W half in ocean (plankton)ndash humans are 6 billion times 100 W = 061012 Wndash this is 15 of bio-energy 000034 of incident

powerbull All of this (bio-activity wind weather etc) ends up

creating heat and re-radiating to spacendash except some small amount of storage in fossil fuels

21

The Hydrologic Cycle

Lots of energy associated with evaporationboth mgh (4 for 10 km lift) and latent heat (96) of water

22

Energetics of the hydrologic cycle

bull It takes energy to evaporate water 2444 J per gramndash this is why ldquoswamp coolersrdquo work evaporation

pulls heat out of environment making it feel cooler

ndash 23 of sunrsquos incident energy goes into evaporation

bull By contrast raising one gram of water to the top of the troposphere (10000 m or 33000 ft) takes

mgh = (0001 kg)(10 ms2)(10000 m) = 100 J

bull So gt 96 of the energy associated with forming clouds is the evaporation lt 4 in lifting against gravity

23

Let it Rain

bull When water condenses in clouds it re-releases this ldquolatent heatrdquo

ndash but this is re-radiated and is of no consequence to hydro-power

bull When it rains the gravitational potential energy is released mostly as kinetic energy and ultimately heat

bull Some tiny bit of gravitational potential energy remains IF the rain falls on terrain (eg higher than sea level where it originated)

ndash hydroelectric plants use this tiny left-over energy itrsquos the energy that drives the flow of streams and rivers

ndash damming up a river concentrates the potential energy in one location for easy exploitation

24

How much of the process do we get to keep

bull According to Figure 51 401015 W of solar power goes into evaporation

ndash this corresponds to 161010 kg per second of evaporated water

ndash this is 35 mm per day off the ocean surface (replenished by rain)

bull The gravitational potential energy given to water vapor (mostly in clouds) in the atmosphere (per second) is thenmgh = (161010 kg)(10 ms2)(2000 m) = 321014 J

bull One can calculate that we gain access to only 25 of the total amount (and use only 125)

ndash based on the 18 land area of the US and the maximum potential of 1477 GW as presented in Table 52

25

iClicker Question

bull With respects to energy hydroelectric power representsndash A remnant electric power from stormsndash B remnant water energy from chemical

bondsndash C remnant energy of chemical bondingndash D remnant gravitational potential

energy of precipitationndash E a form of fictitious energy

26

iClicker Question

bull With respects to energy hydroelectric power representsndash A remnant electric power from stormsndash B remnant water energy from chemical

bondsndash C remnant energy of chemical bondingndash D remnant gravitational potential

energy of precipitationndash E a form of fictitious energy

27

Power of a hydroelectric dam

bull Most impressive is Grand Coulee in Washington on Columbia River

ndash 350 feet = 107 m of ldquoheadrdquondash gt 6000 m3s flow rate (Pacific Northwest gets

rain)ndash each cubic meter of water (1000 kg) has potential

energy mgh = (1000 kg)(10 ms2)(110 m) = 11 MJ

ndash At 6000 m3s get over 6 GW of powerbull Large nuclear plants are usually 1ndash2 GWbull 11 other dams in US in 1ndash2 GW rangebull 74 GW total hydroelectric capacity presently

28

Importance of Hydroelectricity

29

Hydroelectric potential by region in GW

Region Potential

Developed

Undeveloped

Developed

New England 63 19 44 301

Middle Atlantic 98 49 49 500

East North Central 29 12 17 413

West North Central

62 31 31 500

South Atlantic 139 67 72 482

East South Central 83 59 24 711

West South Central

73 27 46 369

Mountain 286 95 191 332

Pacific 644 382 262 593

Total 1477 741 736 502

30

iClicker Question

bull What is true about hydroelectric power generation since 1950ndash A It has always increased in MW producedndash B It has always decreased in MW producedndash C It has increased and decreased in total

MW produced but is now at a peakndash D It has both increased and decreased in

total MW producedndash E The percentage of electric power

produced by hydroelectric plants has generally increased over time

31

iClicker Question

bull What is true about hydroelectric power generation since 1950ndash A It has always increased in MW producedndash B It has always decreased in MW producedndash C It has increased and decreased in total

MW produced but is now at a peakndash D It has both increased and decreased in

total MW producedndash E The percentage of electric power

produced by hydroelectric plants has generally increased over time

32

Hydroelectricity in the future

bull Wersquore almost tapped-outndash 50 of potential is developedndash remaining potential in large number of small-scale

unitsbull Problems with dams

ndash silt limits lifetime to 50ndash200 years after which dam is useless and in fact a potential disaster and nagging maintenance site

ndash habitat loss for fish (salmon) etc wrecks otherwise stunning landscapes (Glenn Canyon in UT)

ndash Disasters waiting to happen 1680 deaths in US alone from 1918ndash1958 often upstream from major population centers

33

Sorry try againhellip

bull So hydroelectricity is a nice ldquofreebeerdquo handed to us by nature but itrsquos not enough to cover our appetite for energy

bull Though very efficient and seemingly environmentally friendly dams do have their problems

bull This isnrsquot the answer to all our energy problems though it is likely to maintain a role well into our future

34

Wind Energy

35

The Power of Wind

bull Wersquove talked about the kinetic energy in wind beforendash a wind traveling at speed v covers v meters

every second (if v is expressed in ms)ndash the kinetic energy hitting a square meter is

then the kinetic energy the mass of air defined by a rectangular tube

ndash tube is one square meter by v meters or v m3

ndash density of air is = 13 kgm3 at sea levelndash mass is v kgndash KE = frac12(v)v2 = frac12v3 (per square meter)

065v3 at sea level

36

Wind Energy proportional to cube of velocity

bull The book (p 134) says power per square meter is 061v3 which is a more-or-less identical resultndash might account for average density in

continental US (above sea level so air slightly less dense)

bull So if the wind speed doubles the power available in the wind increases by 23 = 222 = 8 times

bull A wind of 10 ms (22 mph) has a power density of 610 Wm2

bull A wind of 20 ms (44 mph) has a power density of 4880 Wm2

37

Canrsquot get it all

bull A windmill canrsquot extract all of the kinetic energy available in the wind because this would mean stopping the wind entirely

bull Stopped wind would divert oncoming wind around it and the windmill would stop spinning

bull On the other hand if you donrsquot slow the wind down much at all you wonrsquot get much energy

bull Theoretical maximum performance is 59 of energy extractedndash corresponds to reducing velocity by 36

38

Practical Efficiencies

bull Modern windmills attain maybe 50ndash70 of the theoretical maximumndash 05ndash07 times 059 is 030ndash041 or

about 30ndash40ndash this figure is the mechanical energy

extracted from the windbull Conversion from mechanical to

electrical is 90 efficientndash 09 times 030ndash041 is 27ndash37

39

iClicker Question

bull What is about the maximum efficiency of energy generation using the windndash A 20ndash B 40ndash C 60ndash D 80ndash E 100

40

iClicker Question

bull What is about the maximum efficiency of energy generation using the windndash A 20ndash B 40ndash C 60ndash D 80ndash E 100

41

Achievable efficiencies

42

Typical Windmillsbull A typical windmill might be 15 m in diameter

ndash 176 m2

bull At 10 ms wind 40 efficiency this delivers about 100 kW of power

ndash this would be 800 kW at 20 msndash typical windmills are rated at 50 to 600 kW

bull How much energy per yearndash 10 ms 610 Wm2 40 240 Wm2 8760 hours per

year 2000 kWh per year per square meterndash but wind is intermittent real range from 100ndash500 kWhm2

ndash corresponds to 11ndash57 Wm2 average available power density

bull Note the really high tip speeds bird killers

43

Average available wind powerrecall that average solar insolation is about 150ndash250 Wm2

44

Comparable to solar

bull These numbers are similar to solar if not a little biggerndash Letrsquos go to wind

bull BUT the ldquoper square meterrdquo is not land areamdashitrsquos rotor area

bull Doesnrsquot pay to space windmills too closelymdashone robs the other of energy

bull Typical arrangements have rotors 10 diameters apart in direction of prevailing wind 5 diameters apart in the cross-wind directionndash works out to 16 ldquofill factorrdquo

45

Current implementations

bull Rapidly developing resourcendash 1400 MW in 1989 up to 6400 MW in 2003ndash but still insignificant total (compare to large

dams)ndash cost (at 5ndash7cent per kWh) is competitivendash growing at 25 per yearndash expect to triple over next ten years

bull Current capacity 116 GW (April 2007)ndash Texas 2768 MW (recently took lead over

California)ndash California 2361 MWndash Iowa 936 MWndash Minnesota 895 MWndash Washington 818 MW

46

Flies in the Ointment

bull Find that only 20 of rated capacity is achievedndash design for high wind but seldom get it

bull Only 12 of electrical capacity in US is now windndash total electrical capacity in US is 948 GWndash tripling in ten years means 36ndash but achieving only 20 of capacity reduces

substantiallybull If fully developed we could generate an average

power almost equal to our current electrical capacity (764 GW)

ndash but highly variable resource and problematic if more than 20 comes from the intermittent wind

47

iClicker Question

bull Which state generates the most amount of electricity derived from wind powerndash A Virginiandash B Alaskandash C Montanandash D Californiandash E Texas

48

iClicker Question

bull Which state generates the most amount of electricity derived from wind powerndash A Virginiandash B Alaskandash C Montanandash D Californiandash E Texas

• Renewable Energy Sources II Alternatives Part I
• Chapter 5 Summary
• Slide 3
• Slide 4
• Slide 5
• Slide 6
• Slide 7
• Slide 8
• Slide 9
• Slide 10
• Slide 11
• Slide 12
• Slide 13
• Slide 14
• Renewable Resources Discussed in Book
• Renewable Energy Consumption
• Another look at available energy flow
• The Renewable Budget
• Outstanding Points from Fig 51
• Energy Flow continued
• The Hydrologic Cycle
• Energetics of the hydrologic cycle
• Let it Rain
• How much of the process do we get to keep
• iClicker Question
• Slide 26
• Power of a hydroelectric dam
• Importance of Hydroelectricity
• Hydroelectric potential by region in GW
• Slide 30
• Slide 31
• Hydroelectricity in the future
• Sorry try againhellip
• Wind Energy
• The Power of Wind
• Wind Energy proportional to cube of velocity
• Canrsquot get it all
• Practical Efficiencies
• Slide 39
• Slide 40
• Achievable efficiencies
• Typical Windmills
• Average available wind power
• Comparable to solar
• Current implementations
• Flies in the Ointment
• Slide 47
• Slide 48

7

iClicker Question

bull What is roughly the maximum efficiency for a photovoltaic cellndash A 10ndash B 15ndash C 30ndash D 40ndash E 50

8

iClicker Question

bull What is roughly the maximum efficiency for a photovoltaic cellndash A 10ndash B 15ndash C 30ndash D 40ndash E 50

9

iClicker Question

bull How much energy does the largest photovoltaic system producendash A 10 MWndash B 20 MWndash C 60 MWndash D 100 MWndash E 200 MW

10

iClicker Question

bull How much energy does the largest photovoltaic system producendash A 10 MWndash B 20 MWndash C 60 MWndash D 100 MWndash E 200 MW

11

iClicker Question

bull What must be done to overcome the setting of the Sun in a solar energy systemndash A Store energy in batteriesndash B Get electrical power from elsewherendash C Donrsquot use electrical power at nightndash D All of the above are alternative

approaches for energy after sunset

12

iClicker Question

bull What must be done to overcome the setting of the Sun in a solar energy systemndash A Store energy in batteriesndash B Get electrical power from elsewherendash C Donrsquot use electrical power at nightndash D All of the above are alternative

approaches for energy after sunset

13

iClicker Question

bull Based upon the discussion of the glass in a flat plate collector how would you define the greenhouse gas effect

bull A An effect caused by a gas that is transparent to visible light and opaque to infrared radiation

bull B An effect caused by a gas that is transparent to infrared radiation and opaque to ultraviolet radiation

bull C An effect caused by a gas that is transparent to ultraviolet radiation and opaque to infrared radiation

bull D An effect caused by a gas that is transparent to infrared radiation and opaque to visible light

bull E An effect caused by the sun emitting more infrared radiation than ultraviolet radiation

14

iClicker Question

bull Based upon the discussion of the glass in a flat plate collector how would you define the greenhouse gas effect

bull A An effect caused by a gas that is transparent to visible light and opaque to infrared radiation

bull B An effect caused by a gas that is transparent to infrared radiation and opaque to ultraviolet radiation

bull C An effect caused by a gas that is transparent to ultraviolet radiation and opaque to infrared radiation

bull D An effect caused by a gas that is transparent to infrared radiation and opaque to visible light

bull E An effect caused by the sun emitting more infrared radiation than ultraviolet radiation

15

Renewable Resources Discussed in Book

bull Renewable means anything that wonrsquot be permanently destroyed by using itndash sunlight (the sun will rise again tomorrow)ndash biomass (grows again)ndash hydrological cycle (will rain again)ndash wind (sunlight on Earth makes more)ndash ocean currents (driven by Sun)ndash tidal motion (MoonSun keep on producing it)ndash geothermal (heat sources inside Earth not

used up fast)

16

Renewable Energy Consumption

Energy Source

QBtu (1994)

Percent (1994)

QBtu (2003)

Percent (2003)

Hydroelectric 3037 343 2779 283

Geothermal 0357 040 0314 032

Biomass 2852 322 2884 294

Solar Energy 0069 0077 0063 006

Wind 0036 0040 0108 011

Total 6351 718 615 63

17

Another look at available energy flow

bull The flow of radiation (solar and thermal) was covered previouslyndash earth is in an energy balance energy in =

energy outndash 30 reflected 70 thermally re-radiated

bull Some of the incident energy is absorbed but what exactly does this dondash much goes into heating the airlandndash much goes into driving weather (rain wind)ndash some goes into ocean currentsndash some goes into photosynthesis

18

The Renewable Budget

19

Outstanding Points from Fig 51

bull Incident radiation is 1741015 Wndash this is 1370 Wm2 times area facing sun

(R2)bull 30 directly reflected back to space

ndash off clouds air landbull 47 goes into heating air land waterbull 23 goes into evaporating water

precipitation etc (part of weather)bull Adds to 100 so wersquore done

ndash but wait therersquos morehellip

20

Energy Flow continued

bull 021 goes into wind waves convection currentsndash note this is 100 times less than driving the water

cyclendash but this is the ldquootherrdquo aspect of weather

bull 0023 is stored as chemical energy in plants via photosynthesis

ndash total is 401012 W half in ocean (plankton)ndash humans are 6 billion times 100 W = 061012 Wndash this is 15 of bio-energy 000034 of incident

powerbull All of this (bio-activity wind weather etc) ends up

creating heat and re-radiating to spacendash except some small amount of storage in fossil fuels

21

The Hydrologic Cycle

Lots of energy associated with evaporationboth mgh (4 for 10 km lift) and latent heat (96) of water

22

Energetics of the hydrologic cycle

bull It takes energy to evaporate water 2444 J per gramndash this is why ldquoswamp coolersrdquo work evaporation

pulls heat out of environment making it feel cooler

ndash 23 of sunrsquos incident energy goes into evaporation

bull By contrast raising one gram of water to the top of the troposphere (10000 m or 33000 ft) takes

mgh = (0001 kg)(10 ms2)(10000 m) = 100 J

bull So gt 96 of the energy associated with forming clouds is the evaporation lt 4 in lifting against gravity

23

Let it Rain

bull When water condenses in clouds it re-releases this ldquolatent heatrdquo

ndash but this is re-radiated and is of no consequence to hydro-power

bull When it rains the gravitational potential energy is released mostly as kinetic energy and ultimately heat

bull Some tiny bit of gravitational potential energy remains IF the rain falls on terrain (eg higher than sea level where it originated)

ndash hydroelectric plants use this tiny left-over energy itrsquos the energy that drives the flow of streams and rivers

ndash damming up a river concentrates the potential energy in one location for easy exploitation

24

How much of the process do we get to keep

bull According to Figure 51 401015 W of solar power goes into evaporation

ndash this corresponds to 161010 kg per second of evaporated water

ndash this is 35 mm per day off the ocean surface (replenished by rain)

bull The gravitational potential energy given to water vapor (mostly in clouds) in the atmosphere (per second) is thenmgh = (161010 kg)(10 ms2)(2000 m) = 321014 J

bull One can calculate that we gain access to only 25 of the total amount (and use only 125)

ndash based on the 18 land area of the US and the maximum potential of 1477 GW as presented in Table 52

25

iClicker Question

bull With respects to energy hydroelectric power representsndash A remnant electric power from stormsndash B remnant water energy from chemical

bondsndash C remnant energy of chemical bondingndash D remnant gravitational potential

energy of precipitationndash E a form of fictitious energy

26

iClicker Question

bull With respects to energy hydroelectric power representsndash A remnant electric power from stormsndash B remnant water energy from chemical

bondsndash C remnant energy of chemical bondingndash D remnant gravitational potential

energy of precipitationndash E a form of fictitious energy

27

Power of a hydroelectric dam

bull Most impressive is Grand Coulee in Washington on Columbia River

ndash 350 feet = 107 m of ldquoheadrdquondash gt 6000 m3s flow rate (Pacific Northwest gets

rain)ndash each cubic meter of water (1000 kg) has potential

energy mgh = (1000 kg)(10 ms2)(110 m) = 11 MJ

ndash At 6000 m3s get over 6 GW of powerbull Large nuclear plants are usually 1ndash2 GWbull 11 other dams in US in 1ndash2 GW rangebull 74 GW total hydroelectric capacity presently

28

Importance of Hydroelectricity

29

Hydroelectric potential by region in GW

Region Potential

Developed

Undeveloped

Developed

New England 63 19 44 301

Middle Atlantic 98 49 49 500

East North Central 29 12 17 413

West North Central

62 31 31 500

South Atlantic 139 67 72 482

East South Central 83 59 24 711

West South Central

73 27 46 369

Mountain 286 95 191 332

Pacific 644 382 262 593

Total 1477 741 736 502

30

iClicker Question

bull What is true about hydroelectric power generation since 1950ndash A It has always increased in MW producedndash B It has always decreased in MW producedndash C It has increased and decreased in total

MW produced but is now at a peakndash D It has both increased and decreased in

total MW producedndash E The percentage of electric power

produced by hydroelectric plants has generally increased over time

31

iClicker Question

bull What is true about hydroelectric power generation since 1950ndash A It has always increased in MW producedndash B It has always decreased in MW producedndash C It has increased and decreased in total

MW produced but is now at a peakndash D It has both increased and decreased in

total MW producedndash E The percentage of electric power

produced by hydroelectric plants has generally increased over time

32

Hydroelectricity in the future

bull Wersquore almost tapped-outndash 50 of potential is developedndash remaining potential in large number of small-scale

unitsbull Problems with dams

ndash silt limits lifetime to 50ndash200 years after which dam is useless and in fact a potential disaster and nagging maintenance site

ndash habitat loss for fish (salmon) etc wrecks otherwise stunning landscapes (Glenn Canyon in UT)

ndash Disasters waiting to happen 1680 deaths in US alone from 1918ndash1958 often upstream from major population centers

33

Sorry try againhellip

bull So hydroelectricity is a nice ldquofreebeerdquo handed to us by nature but itrsquos not enough to cover our appetite for energy

bull Though very efficient and seemingly environmentally friendly dams do have their problems

bull This isnrsquot the answer to all our energy problems though it is likely to maintain a role well into our future

34

Wind Energy

35

The Power of Wind

bull Wersquove talked about the kinetic energy in wind beforendash a wind traveling at speed v covers v meters

every second (if v is expressed in ms)ndash the kinetic energy hitting a square meter is

then the kinetic energy the mass of air defined by a rectangular tube

ndash tube is one square meter by v meters or v m3

ndash density of air is = 13 kgm3 at sea levelndash mass is v kgndash KE = frac12(v)v2 = frac12v3 (per square meter)

065v3 at sea level

36

Wind Energy proportional to cube of velocity

bull The book (p 134) says power per square meter is 061v3 which is a more-or-less identical resultndash might account for average density in

continental US (above sea level so air slightly less dense)

bull So if the wind speed doubles the power available in the wind increases by 23 = 222 = 8 times

bull A wind of 10 ms (22 mph) has a power density of 610 Wm2

bull A wind of 20 ms (44 mph) has a power density of 4880 Wm2

37

Canrsquot get it all

bull A windmill canrsquot extract all of the kinetic energy available in the wind because this would mean stopping the wind entirely

bull Stopped wind would divert oncoming wind around it and the windmill would stop spinning

bull On the other hand if you donrsquot slow the wind down much at all you wonrsquot get much energy

bull Theoretical maximum performance is 59 of energy extractedndash corresponds to reducing velocity by 36

38

Practical Efficiencies

bull Modern windmills attain maybe 50ndash70 of the theoretical maximumndash 05ndash07 times 059 is 030ndash041 or

about 30ndash40ndash this figure is the mechanical energy

extracted from the windbull Conversion from mechanical to

electrical is 90 efficientndash 09 times 030ndash041 is 27ndash37

39

iClicker Question

bull What is about the maximum efficiency of energy generation using the windndash A 20ndash B 40ndash C 60ndash D 80ndash E 100

40

iClicker Question

bull What is about the maximum efficiency of energy generation using the windndash A 20ndash B 40ndash C 60ndash D 80ndash E 100

41

Achievable efficiencies

42

Typical Windmillsbull A typical windmill might be 15 m in diameter

ndash 176 m2

bull At 10 ms wind 40 efficiency this delivers about 100 kW of power

ndash this would be 800 kW at 20 msndash typical windmills are rated at 50 to 600 kW

bull How much energy per yearndash 10 ms 610 Wm2 40 240 Wm2 8760 hours per

year 2000 kWh per year per square meterndash but wind is intermittent real range from 100ndash500 kWhm2

ndash corresponds to 11ndash57 Wm2 average available power density

bull Note the really high tip speeds bird killers

43

Average available wind powerrecall that average solar insolation is about 150ndash250 Wm2

44

Comparable to solar

bull These numbers are similar to solar if not a little biggerndash Letrsquos go to wind

bull BUT the ldquoper square meterrdquo is not land areamdashitrsquos rotor area

bull Doesnrsquot pay to space windmills too closelymdashone robs the other of energy

bull Typical arrangements have rotors 10 diameters apart in direction of prevailing wind 5 diameters apart in the cross-wind directionndash works out to 16 ldquofill factorrdquo

45

Current implementations

bull Rapidly developing resourcendash 1400 MW in 1989 up to 6400 MW in 2003ndash but still insignificant total (compare to large

dams)ndash cost (at 5ndash7cent per kWh) is competitivendash growing at 25 per yearndash expect to triple over next ten years

bull Current capacity 116 GW (April 2007)ndash Texas 2768 MW (recently took lead over

California)ndash California 2361 MWndash Iowa 936 MWndash Minnesota 895 MWndash Washington 818 MW

46

Flies in the Ointment

bull Find that only 20 of rated capacity is achievedndash design for high wind but seldom get it

bull Only 12 of electrical capacity in US is now windndash total electrical capacity in US is 948 GWndash tripling in ten years means 36ndash but achieving only 20 of capacity reduces

substantiallybull If fully developed we could generate an average

power almost equal to our current electrical capacity (764 GW)

ndash but highly variable resource and problematic if more than 20 comes from the intermittent wind

47

iClicker Question

bull Which state generates the most amount of electricity derived from wind powerndash A Virginiandash B Alaskandash C Montanandash D Californiandash E Texas

48

iClicker Question

bull Which state generates the most amount of electricity derived from wind powerndash A Virginiandash B Alaskandash C Montanandash D Californiandash E Texas

• Renewable Energy Sources II Alternatives Part I
• Chapter 5 Summary
• Slide 3
• Slide 4
• Slide 5
• Slide 6
• Slide 7
• Slide 8
• Slide 9
• Slide 10
• Slide 11
• Slide 12
• Slide 13
• Slide 14
• Renewable Resources Discussed in Book
• Renewable Energy Consumption
• Another look at available energy flow
• The Renewable Budget
• Outstanding Points from Fig 51
• Energy Flow continued
• The Hydrologic Cycle
• Energetics of the hydrologic cycle
• Let it Rain
• How much of the process do we get to keep
• iClicker Question
• Slide 26
• Power of a hydroelectric dam
• Importance of Hydroelectricity
• Hydroelectric potential by region in GW
• Slide 30
• Slide 31
• Hydroelectricity in the future
• Sorry try againhellip
• Wind Energy
• The Power of Wind
• Wind Energy proportional to cube of velocity
• Canrsquot get it all
• Practical Efficiencies
• Slide 39
• Slide 40
• Achievable efficiencies
• Typical Windmills
• Average available wind power
• Comparable to solar
• Current implementations
• Flies in the Ointment
• Slide 47
• Slide 48

8

iClicker Question

bull What is roughly the maximum efficiency for a photovoltaic cellndash A 10ndash B 15ndash C 30ndash D 40ndash E 50

9

iClicker Question

bull How much energy does the largest photovoltaic system producendash A 10 MWndash B 20 MWndash C 60 MWndash D 100 MWndash E 200 MW

10

iClicker Question

bull How much energy does the largest photovoltaic system producendash A 10 MWndash B 20 MWndash C 60 MWndash D 100 MWndash E 200 MW

11

iClicker Question

bull What must be done to overcome the setting of the Sun in a solar energy systemndash A Store energy in batteriesndash B Get electrical power from elsewherendash C Donrsquot use electrical power at nightndash D All of the above are alternative

approaches for energy after sunset

12

iClicker Question

bull What must be done to overcome the setting of the Sun in a solar energy systemndash A Store energy in batteriesndash B Get electrical power from elsewherendash C Donrsquot use electrical power at nightndash D All of the above are alternative

approaches for energy after sunset

13

iClicker Question

bull Based upon the discussion of the glass in a flat plate collector how would you define the greenhouse gas effect

bull A An effect caused by a gas that is transparent to visible light and opaque to infrared radiation

bull B An effect caused by a gas that is transparent to infrared radiation and opaque to ultraviolet radiation

bull C An effect caused by a gas that is transparent to ultraviolet radiation and opaque to infrared radiation

bull D An effect caused by a gas that is transparent to infrared radiation and opaque to visible light

bull E An effect caused by the sun emitting more infrared radiation than ultraviolet radiation

14

iClicker Question

bull Based upon the discussion of the glass in a flat plate collector how would you define the greenhouse gas effect

bull A An effect caused by a gas that is transparent to visible light and opaque to infrared radiation

bull B An effect caused by a gas that is transparent to infrared radiation and opaque to ultraviolet radiation

bull C An effect caused by a gas that is transparent to ultraviolet radiation and opaque to infrared radiation

bull D An effect caused by a gas that is transparent to infrared radiation and opaque to visible light

bull E An effect caused by the sun emitting more infrared radiation than ultraviolet radiation

15

Renewable Resources Discussed in Book

bull Renewable means anything that wonrsquot be permanently destroyed by using itndash sunlight (the sun will rise again tomorrow)ndash biomass (grows again)ndash hydrological cycle (will rain again)ndash wind (sunlight on Earth makes more)ndash ocean currents (driven by Sun)ndash tidal motion (MoonSun keep on producing it)ndash geothermal (heat sources inside Earth not

used up fast)

16

Renewable Energy Consumption

Energy Source

QBtu (1994)

Percent (1994)

QBtu (2003)

Percent (2003)

Hydroelectric 3037 343 2779 283

Geothermal 0357 040 0314 032

Biomass 2852 322 2884 294

Solar Energy 0069 0077 0063 006

Wind 0036 0040 0108 011

Total 6351 718 615 63

17

Another look at available energy flow

bull The flow of radiation (solar and thermal) was covered previouslyndash earth is in an energy balance energy in =

energy outndash 30 reflected 70 thermally re-radiated

bull Some of the incident energy is absorbed but what exactly does this dondash much goes into heating the airlandndash much goes into driving weather (rain wind)ndash some goes into ocean currentsndash some goes into photosynthesis

18

The Renewable Budget

19

Outstanding Points from Fig 51

bull Incident radiation is 1741015 Wndash this is 1370 Wm2 times area facing sun

(R2)bull 30 directly reflected back to space

ndash off clouds air landbull 47 goes into heating air land waterbull 23 goes into evaporating water

precipitation etc (part of weather)bull Adds to 100 so wersquore done

ndash but wait therersquos morehellip

20

Energy Flow continued

bull 021 goes into wind waves convection currentsndash note this is 100 times less than driving the water

cyclendash but this is the ldquootherrdquo aspect of weather

bull 0023 is stored as chemical energy in plants via photosynthesis

ndash total is 401012 W half in ocean (plankton)ndash humans are 6 billion times 100 W = 061012 Wndash this is 15 of bio-energy 000034 of incident

powerbull All of this (bio-activity wind weather etc) ends up

creating heat and re-radiating to spacendash except some small amount of storage in fossil fuels

21

The Hydrologic Cycle

Lots of energy associated with evaporationboth mgh (4 for 10 km lift) and latent heat (96) of water

22

Energetics of the hydrologic cycle

bull It takes energy to evaporate water 2444 J per gramndash this is why ldquoswamp coolersrdquo work evaporation

pulls heat out of environment making it feel cooler

ndash 23 of sunrsquos incident energy goes into evaporation

bull By contrast raising one gram of water to the top of the troposphere (10000 m or 33000 ft) takes

mgh = (0001 kg)(10 ms2)(10000 m) = 100 J

bull So gt 96 of the energy associated with forming clouds is the evaporation lt 4 in lifting against gravity

23

Let it Rain

bull When water condenses in clouds it re-releases this ldquolatent heatrdquo

ndash but this is re-radiated and is of no consequence to hydro-power

bull When it rains the gravitational potential energy is released mostly as kinetic energy and ultimately heat

bull Some tiny bit of gravitational potential energy remains IF the rain falls on terrain (eg higher than sea level where it originated)

ndash hydroelectric plants use this tiny left-over energy itrsquos the energy that drives the flow of streams and rivers

ndash damming up a river concentrates the potential energy in one location for easy exploitation

24

How much of the process do we get to keep

bull According to Figure 51 401015 W of solar power goes into evaporation

ndash this corresponds to 161010 kg per second of evaporated water

ndash this is 35 mm per day off the ocean surface (replenished by rain)

bull The gravitational potential energy given to water vapor (mostly in clouds) in the atmosphere (per second) is thenmgh = (161010 kg)(10 ms2)(2000 m) = 321014 J

bull One can calculate that we gain access to only 25 of the total amount (and use only 125)

ndash based on the 18 land area of the US and the maximum potential of 1477 GW as presented in Table 52

25

iClicker Question

bull With respects to energy hydroelectric power representsndash A remnant electric power from stormsndash B remnant water energy from chemical

bondsndash C remnant energy of chemical bondingndash D remnant gravitational potential

energy of precipitationndash E a form of fictitious energy

26

iClicker Question

bull With respects to energy hydroelectric power representsndash A remnant electric power from stormsndash B remnant water energy from chemical

bondsndash C remnant energy of chemical bondingndash D remnant gravitational potential

energy of precipitationndash E a form of fictitious energy

27

Power of a hydroelectric dam

bull Most impressive is Grand Coulee in Washington on Columbia River

ndash 350 feet = 107 m of ldquoheadrdquondash gt 6000 m3s flow rate (Pacific Northwest gets

rain)ndash each cubic meter of water (1000 kg) has potential

energy mgh = (1000 kg)(10 ms2)(110 m) = 11 MJ

ndash At 6000 m3s get over 6 GW of powerbull Large nuclear plants are usually 1ndash2 GWbull 11 other dams in US in 1ndash2 GW rangebull 74 GW total hydroelectric capacity presently

28

Importance of Hydroelectricity

29

Hydroelectric potential by region in GW

Region Potential

Developed

Undeveloped

Developed

New England 63 19 44 301

Middle Atlantic 98 49 49 500

East North Central 29 12 17 413

West North Central

62 31 31 500

South Atlantic 139 67 72 482

East South Central 83 59 24 711

West South Central

73 27 46 369

Mountain 286 95 191 332

Pacific 644 382 262 593

Total 1477 741 736 502

30

iClicker Question

bull What is true about hydroelectric power generation since 1950ndash A It has always increased in MW producedndash B It has always decreased in MW producedndash C It has increased and decreased in total

MW produced but is now at a peakndash D It has both increased and decreased in

total MW producedndash E The percentage of electric power

produced by hydroelectric plants has generally increased over time

31

iClicker Question

bull What is true about hydroelectric power generation since 1950ndash A It has always increased in MW producedndash B It has always decreased in MW producedndash C It has increased and decreased in total

MW produced but is now at a peakndash D It has both increased and decreased in

total MW producedndash E The percentage of electric power

produced by hydroelectric plants has generally increased over time

32

Hydroelectricity in the future

bull Wersquore almost tapped-outndash 50 of potential is developedndash remaining potential in large number of small-scale

unitsbull Problems with dams

ndash silt limits lifetime to 50ndash200 years after which dam is useless and in fact a potential disaster and nagging maintenance site

ndash habitat loss for fish (salmon) etc wrecks otherwise stunning landscapes (Glenn Canyon in UT)

ndash Disasters waiting to happen 1680 deaths in US alone from 1918ndash1958 often upstream from major population centers

33

Sorry try againhellip

bull So hydroelectricity is a nice ldquofreebeerdquo handed to us by nature but itrsquos not enough to cover our appetite for energy

bull Though very efficient and seemingly environmentally friendly dams do have their problems

bull This isnrsquot the answer to all our energy problems though it is likely to maintain a role well into our future

34

Wind Energy

35

The Power of Wind

bull Wersquove talked about the kinetic energy in wind beforendash a wind traveling at speed v covers v meters

every second (if v is expressed in ms)ndash the kinetic energy hitting a square meter is

then the kinetic energy the mass of air defined by a rectangular tube

ndash tube is one square meter by v meters or v m3

ndash density of air is = 13 kgm3 at sea levelndash mass is v kgndash KE = frac12(v)v2 = frac12v3 (per square meter)

065v3 at sea level

36

Wind Energy proportional to cube of velocity

bull The book (p 134) says power per square meter is 061v3 which is a more-or-less identical resultndash might account for average density in

continental US (above sea level so air slightly less dense)

bull So if the wind speed doubles the power available in the wind increases by 23 = 222 = 8 times

bull A wind of 10 ms (22 mph) has a power density of 610 Wm2

bull A wind of 20 ms (44 mph) has a power density of 4880 Wm2

37

Canrsquot get it all

bull A windmill canrsquot extract all of the kinetic energy available in the wind because this would mean stopping the wind entirely

bull Stopped wind would divert oncoming wind around it and the windmill would stop spinning

bull On the other hand if you donrsquot slow the wind down much at all you wonrsquot get much energy

bull Theoretical maximum performance is 59 of energy extractedndash corresponds to reducing velocity by 36

38

Practical Efficiencies

bull Modern windmills attain maybe 50ndash70 of the theoretical maximumndash 05ndash07 times 059 is 030ndash041 or

about 30ndash40ndash this figure is the mechanical energy

extracted from the windbull Conversion from mechanical to

electrical is 90 efficientndash 09 times 030ndash041 is 27ndash37

39

iClicker Question

bull What is about the maximum efficiency of energy generation using the windndash A 20ndash B 40ndash C 60ndash D 80ndash E 100

40

iClicker Question

bull What is about the maximum efficiency of energy generation using the windndash A 20ndash B 40ndash C 60ndash D 80ndash E 100

41

Achievable efficiencies

42

Typical Windmillsbull A typical windmill might be 15 m in diameter

ndash 176 m2

bull At 10 ms wind 40 efficiency this delivers about 100 kW of power

ndash this would be 800 kW at 20 msndash typical windmills are rated at 50 to 600 kW

bull How much energy per yearndash 10 ms 610 Wm2 40 240 Wm2 8760 hours per

year 2000 kWh per year per square meterndash but wind is intermittent real range from 100ndash500 kWhm2

ndash corresponds to 11ndash57 Wm2 average available power density

bull Note the really high tip speeds bird killers

43

Average available wind powerrecall that average solar insolation is about 150ndash250 Wm2

44

Comparable to solar

bull These numbers are similar to solar if not a little biggerndash Letrsquos go to wind

bull BUT the ldquoper square meterrdquo is not land areamdashitrsquos rotor area

bull Doesnrsquot pay to space windmills too closelymdashone robs the other of energy

bull Typical arrangements have rotors 10 diameters apart in direction of prevailing wind 5 diameters apart in the cross-wind directionndash works out to 16 ldquofill factorrdquo

45

Current implementations

bull Rapidly developing resourcendash 1400 MW in 1989 up to 6400 MW in 2003ndash but still insignificant total (compare to large

dams)ndash cost (at 5ndash7cent per kWh) is competitivendash growing at 25 per yearndash expect to triple over next ten years

bull Current capacity 116 GW (April 2007)ndash Texas 2768 MW (recently took lead over

California)ndash California 2361 MWndash Iowa 936 MWndash Minnesota 895 MWndash Washington 818 MW

46

Flies in the Ointment

bull Find that only 20 of rated capacity is achievedndash design for high wind but seldom get it

bull Only 12 of electrical capacity in US is now windndash total electrical capacity in US is 948 GWndash tripling in ten years means 36ndash but achieving only 20 of capacity reduces

substantiallybull If fully developed we could generate an average

power almost equal to our current electrical capacity (764 GW)

ndash but highly variable resource and problematic if more than 20 comes from the intermittent wind

47

iClicker Question

bull Which state generates the most amount of electricity derived from wind powerndash A Virginiandash B Alaskandash C Montanandash D Californiandash E Texas

48

iClicker Question

bull Which state generates the most amount of electricity derived from wind powerndash A Virginiandash B Alaskandash C Montanandash D Californiandash E Texas

• Renewable Energy Sources II Alternatives Part I
• Chapter 5 Summary
• Slide 3
• Slide 4
• Slide 5
• Slide 6
• Slide 7
• Slide 8
• Slide 9
• Slide 10
• Slide 11
• Slide 12
• Slide 13
• Slide 14
• Renewable Resources Discussed in Book
• Renewable Energy Consumption
• Another look at available energy flow
• The Renewable Budget
• Outstanding Points from Fig 51
• Energy Flow continued
• The Hydrologic Cycle
• Energetics of the hydrologic cycle
• Let it Rain
• How much of the process do we get to keep
• iClicker Question
• Slide 26
• Power of a hydroelectric dam
• Importance of Hydroelectricity
• Hydroelectric potential by region in GW
• Slide 30
• Slide 31
• Hydroelectricity in the future
• Sorry try againhellip
• Wind Energy
• The Power of Wind
• Wind Energy proportional to cube of velocity
• Canrsquot get it all
• Practical Efficiencies
• Slide 39
• Slide 40
• Achievable efficiencies
• Typical Windmills
• Average available wind power
• Comparable to solar
• Current implementations
• Flies in the Ointment
• Slide 47
• Slide 48

9

iClicker Question

bull How much energy does the largest photovoltaic system producendash A 10 MWndash B 20 MWndash C 60 MWndash D 100 MWndash E 200 MW

10

iClicker Question

bull How much energy does the largest photovoltaic system producendash A 10 MWndash B 20 MWndash C 60 MWndash D 100 MWndash E 200 MW

11

iClicker Question

bull What must be done to overcome the setting of the Sun in a solar energy systemndash A Store energy in batteriesndash B Get electrical power from elsewherendash C Donrsquot use electrical power at nightndash D All of the above are alternative

approaches for energy after sunset

12

iClicker Question

bull What must be done to overcome the setting of the Sun in a solar energy systemndash A Store energy in batteriesndash B Get electrical power from elsewherendash C Donrsquot use electrical power at nightndash D All of the above are alternative

approaches for energy after sunset

13

iClicker Question

bull Based upon the discussion of the glass in a flat plate collector how would you define the greenhouse gas effect

bull A An effect caused by a gas that is transparent to visible light and opaque to infrared radiation

bull B An effect caused by a gas that is transparent to infrared radiation and opaque to ultraviolet radiation

bull C An effect caused by a gas that is transparent to ultraviolet radiation and opaque to infrared radiation

bull D An effect caused by a gas that is transparent to infrared radiation and opaque to visible light

bull E An effect caused by the sun emitting more infrared radiation than ultraviolet radiation

14

iClicker Question

bull Based upon the discussion of the glass in a flat plate collector how would you define the greenhouse gas effect

bull A An effect caused by a gas that is transparent to visible light and opaque to infrared radiation

bull B An effect caused by a gas that is transparent to infrared radiation and opaque to ultraviolet radiation

bull C An effect caused by a gas that is transparent to ultraviolet radiation and opaque to infrared radiation

bull D An effect caused by a gas that is transparent to infrared radiation and opaque to visible light

bull E An effect caused by the sun emitting more infrared radiation than ultraviolet radiation

15

Renewable Resources Discussed in Book

bull Renewable means anything that wonrsquot be permanently destroyed by using itndash sunlight (the sun will rise again tomorrow)ndash biomass (grows again)ndash hydrological cycle (will rain again)ndash wind (sunlight on Earth makes more)ndash ocean currents (driven by Sun)ndash tidal motion (MoonSun keep on producing it)ndash geothermal (heat sources inside Earth not

used up fast)

16

Renewable Energy Consumption

Energy Source

QBtu (1994)

Percent (1994)

QBtu (2003)

Percent (2003)

Hydroelectric 3037 343 2779 283

Geothermal 0357 040 0314 032

Biomass 2852 322 2884 294

Solar Energy 0069 0077 0063 006

Wind 0036 0040 0108 011

Total 6351 718 615 63

17

Another look at available energy flow

bull The flow of radiation (solar and thermal) was covered previouslyndash earth is in an energy balance energy in =

energy outndash 30 reflected 70 thermally re-radiated

bull Some of the incident energy is absorbed but what exactly does this dondash much goes into heating the airlandndash much goes into driving weather (rain wind)ndash some goes into ocean currentsndash some goes into photosynthesis

18

The Renewable Budget

19

Outstanding Points from Fig 51

bull Incident radiation is 1741015 Wndash this is 1370 Wm2 times area facing sun

(R2)bull 30 directly reflected back to space

ndash off clouds air landbull 47 goes into heating air land waterbull 23 goes into evaporating water

precipitation etc (part of weather)bull Adds to 100 so wersquore done

ndash but wait therersquos morehellip

20

Energy Flow continued

bull 021 goes into wind waves convection currentsndash note this is 100 times less than driving the water

cyclendash but this is the ldquootherrdquo aspect of weather

bull 0023 is stored as chemical energy in plants via photosynthesis

ndash total is 401012 W half in ocean (plankton)ndash humans are 6 billion times 100 W = 061012 Wndash this is 15 of bio-energy 000034 of incident

powerbull All of this (bio-activity wind weather etc) ends up

creating heat and re-radiating to spacendash except some small amount of storage in fossil fuels

21

The Hydrologic Cycle

Lots of energy associated with evaporationboth mgh (4 for 10 km lift) and latent heat (96) of water

22

Energetics of the hydrologic cycle

bull It takes energy to evaporate water 2444 J per gramndash this is why ldquoswamp coolersrdquo work evaporation

pulls heat out of environment making it feel cooler

ndash 23 of sunrsquos incident energy goes into evaporation

bull By contrast raising one gram of water to the top of the troposphere (10000 m or 33000 ft) takes

mgh = (0001 kg)(10 ms2)(10000 m) = 100 J

bull So gt 96 of the energy associated with forming clouds is the evaporation lt 4 in lifting against gravity

23

Let it Rain

bull When water condenses in clouds it re-releases this ldquolatent heatrdquo

ndash but this is re-radiated and is of no consequence to hydro-power

bull When it rains the gravitational potential energy is released mostly as kinetic energy and ultimately heat

bull Some tiny bit of gravitational potential energy remains IF the rain falls on terrain (eg higher than sea level where it originated)

ndash hydroelectric plants use this tiny left-over energy itrsquos the energy that drives the flow of streams and rivers

ndash damming up a river concentrates the potential energy in one location for easy exploitation

24

How much of the process do we get to keep

bull According to Figure 51 401015 W of solar power goes into evaporation

ndash this corresponds to 161010 kg per second of evaporated water

ndash this is 35 mm per day off the ocean surface (replenished by rain)

bull The gravitational potential energy given to water vapor (mostly in clouds) in the atmosphere (per second) is thenmgh = (161010 kg)(10 ms2)(2000 m) = 321014 J

bull One can calculate that we gain access to only 25 of the total amount (and use only 125)

ndash based on the 18 land area of the US and the maximum potential of 1477 GW as presented in Table 52

25

iClicker Question

bull With respects to energy hydroelectric power representsndash A remnant electric power from stormsndash B remnant water energy from chemical

bondsndash C remnant energy of chemical bondingndash D remnant gravitational potential

energy of precipitationndash E a form of fictitious energy

26

iClicker Question

bull With respects to energy hydroelectric power representsndash A remnant electric power from stormsndash B remnant water energy from chemical

bondsndash C remnant energy of chemical bondingndash D remnant gravitational potential

energy of precipitationndash E a form of fictitious energy

27

Power of a hydroelectric dam

bull Most impressive is Grand Coulee in Washington on Columbia River

ndash 350 feet = 107 m of ldquoheadrdquondash gt 6000 m3s flow rate (Pacific Northwest gets

rain)ndash each cubic meter of water (1000 kg) has potential

energy mgh = (1000 kg)(10 ms2)(110 m) = 11 MJ

ndash At 6000 m3s get over 6 GW of powerbull Large nuclear plants are usually 1ndash2 GWbull 11 other dams in US in 1ndash2 GW rangebull 74 GW total hydroelectric capacity presently

28

Importance of Hydroelectricity

29

Hydroelectric potential by region in GW

Region Potential

Developed

Undeveloped

Developed

New England 63 19 44 301

Middle Atlantic 98 49 49 500

East North Central 29 12 17 413

West North Central

62 31 31 500

South Atlantic 139 67 72 482

East South Central 83 59 24 711

West South Central

73 27 46 369

Mountain 286 95 191 332

Pacific 644 382 262 593

Total 1477 741 736 502

30

iClicker Question

bull What is true about hydroelectric power generation since 1950ndash A It has always increased in MW producedndash B It has always decreased in MW producedndash C It has increased and decreased in total

MW produced but is now at a peakndash D It has both increased and decreased in

total MW producedndash E The percentage of electric power

produced by hydroelectric plants has generally increased over time

31

iClicker Question

bull What is true about hydroelectric power generation since 1950ndash A It has always increased in MW producedndash B It has always decreased in MW producedndash C It has increased and decreased in total

MW produced but is now at a peakndash D It has both increased and decreased in

total MW producedndash E The percentage of electric power

produced by hydroelectric plants has generally increased over time

32

Hydroelectricity in the future

bull Wersquore almost tapped-outndash 50 of potential is developedndash remaining potential in large number of small-scale

unitsbull Problems with dams

ndash silt limits lifetime to 50ndash200 years after which dam is useless and in fact a potential disaster and nagging maintenance site

ndash habitat loss for fish (salmon) etc wrecks otherwise stunning landscapes (Glenn Canyon in UT)

ndash Disasters waiting to happen 1680 deaths in US alone from 1918ndash1958 often upstream from major population centers

33

Sorry try againhellip

bull So hydroelectricity is a nice ldquofreebeerdquo handed to us by nature but itrsquos not enough to cover our appetite for energy

bull Though very efficient and seemingly environmentally friendly dams do have their problems

bull This isnrsquot the answer to all our energy problems though it is likely to maintain a role well into our future

34

Wind Energy

35

The Power of Wind

bull Wersquove talked about the kinetic energy in wind beforendash a wind traveling at speed v covers v meters

every second (if v is expressed in ms)ndash the kinetic energy hitting a square meter is

then the kinetic energy the mass of air defined by a rectangular tube

ndash tube is one square meter by v meters or v m3

ndash density of air is = 13 kgm3 at sea levelndash mass is v kgndash KE = frac12(v)v2 = frac12v3 (per square meter)

065v3 at sea level

36

Wind Energy proportional to cube of velocity

bull The book (p 134) says power per square meter is 061v3 which is a more-or-less identical resultndash might account for average density in

continental US (above sea level so air slightly less dense)

bull So if the wind speed doubles the power available in the wind increases by 23 = 222 = 8 times

bull A wind of 10 ms (22 mph) has a power density of 610 Wm2

bull A wind of 20 ms (44 mph) has a power density of 4880 Wm2

37

Canrsquot get it all

bull A windmill canrsquot extract all of the kinetic energy available in the wind because this would mean stopping the wind entirely

bull Stopped wind would divert oncoming wind around it and the windmill would stop spinning

bull On the other hand if you donrsquot slow the wind down much at all you wonrsquot get much energy

bull Theoretical maximum performance is 59 of energy extractedndash corresponds to reducing velocity by 36

38

Practical Efficiencies

bull Modern windmills attain maybe 50ndash70 of the theoretical maximumndash 05ndash07 times 059 is 030ndash041 or

about 30ndash40ndash this figure is the mechanical energy

extracted from the windbull Conversion from mechanical to

electrical is 90 efficientndash 09 times 030ndash041 is 27ndash37

39

iClicker Question

bull What is about the maximum efficiency of energy generation using the windndash A 20ndash B 40ndash C 60ndash D 80ndash E 100

40

iClicker Question

bull What is about the maximum efficiency of energy generation using the windndash A 20ndash B 40ndash C 60ndash D 80ndash E 100

41

Achievable efficiencies

42

Typical Windmillsbull A typical windmill might be 15 m in diameter

ndash 176 m2

bull At 10 ms wind 40 efficiency this delivers about 100 kW of power

ndash this would be 800 kW at 20 msndash typical windmills are rated at 50 to 600 kW

bull How much energy per yearndash 10 ms 610 Wm2 40 240 Wm2 8760 hours per

year 2000 kWh per year per square meterndash but wind is intermittent real range from 100ndash500 kWhm2

ndash corresponds to 11ndash57 Wm2 average available power density

bull Note the really high tip speeds bird killers

43

Average available wind powerrecall that average solar insolation is about 150ndash250 Wm2

44

Comparable to solar

bull These numbers are similar to solar if not a little biggerndash Letrsquos go to wind

bull BUT the ldquoper square meterrdquo is not land areamdashitrsquos rotor area

bull Doesnrsquot pay to space windmills too closelymdashone robs the other of energy

bull Typical arrangements have rotors 10 diameters apart in direction of prevailing wind 5 diameters apart in the cross-wind directionndash works out to 16 ldquofill factorrdquo

45

Current implementations

bull Rapidly developing resourcendash 1400 MW in 1989 up to 6400 MW in 2003ndash but still insignificant total (compare to large

dams)ndash cost (at 5ndash7cent per kWh) is competitivendash growing at 25 per yearndash expect to triple over next ten years

bull Current capacity 116 GW (April 2007)ndash Texas 2768 MW (recently took lead over

California)ndash California 2361 MWndash Iowa 936 MWndash Minnesota 895 MWndash Washington 818 MW

46

Flies in the Ointment

bull Find that only 20 of rated capacity is achievedndash design for high wind but seldom get it

bull Only 12 of electrical capacity in US is now windndash total electrical capacity in US is 948 GWndash tripling in ten years means 36ndash but achieving only 20 of capacity reduces

substantiallybull If fully developed we could generate an average

power almost equal to our current electrical capacity (764 GW)

ndash but highly variable resource and problematic if more than 20 comes from the intermittent wind

47

iClicker Question

bull Which state generates the most amount of electricity derived from wind powerndash A Virginiandash B Alaskandash C Montanandash D Californiandash E Texas

48

iClicker Question

bull Which state generates the most amount of electricity derived from wind powerndash A Virginiandash B Alaskandash C Montanandash D Californiandash E Texas

• Renewable Energy Sources II Alternatives Part I
• Chapter 5 Summary
• Slide 3
• Slide 4
• Slide 5
• Slide 6
• Slide 7
• Slide 8
• Slide 9
• Slide 10
• Slide 11
• Slide 12
• Slide 13
• Slide 14
• Renewable Resources Discussed in Book
• Renewable Energy Consumption
• Another look at available energy flow
• The Renewable Budget
• Outstanding Points from Fig 51
• Energy Flow continued
• The Hydrologic Cycle
• Energetics of the hydrologic cycle
• Let it Rain
• How much of the process do we get to keep
• iClicker Question
• Slide 26
• Power of a hydroelectric dam
• Importance of Hydroelectricity
• Hydroelectric potential by region in GW
• Slide 30
• Slide 31
• Hydroelectricity in the future
• Sorry try againhellip
• Wind Energy
• The Power of Wind
• Wind Energy proportional to cube of velocity
• Canrsquot get it all
• Practical Efficiencies
• Slide 39
• Slide 40
• Achievable efficiencies
• Typical Windmills
• Average available wind power
• Comparable to solar
• Current implementations
• Flies in the Ointment
• Slide 47
• Slide 48

10

iClicker Question

bull How much energy does the largest photovoltaic system producendash A 10 MWndash B 20 MWndash C 60 MWndash D 100 MWndash E 200 MW

11

iClicker Question

bull What must be done to overcome the setting of the Sun in a solar energy systemndash A Store energy in batteriesndash B Get electrical power from elsewherendash C Donrsquot use electrical power at nightndash D All of the above are alternative

approaches for energy after sunset

12

iClicker Question

bull What must be done to overcome the setting of the Sun in a solar energy systemndash A Store energy in batteriesndash B Get electrical power from elsewherendash C Donrsquot use electrical power at nightndash D All of the above are alternative

approaches for energy after sunset

13

iClicker Question

bull Based upon the discussion of the glass in a flat plate collector how would you define the greenhouse gas effect

bull A An effect caused by a gas that is transparent to visible light and opaque to infrared radiation

bull B An effect caused by a gas that is transparent to infrared radiation and opaque to ultraviolet radiation

bull C An effect caused by a gas that is transparent to ultraviolet radiation and opaque to infrared radiation

bull D An effect caused by a gas that is transparent to infrared radiation and opaque to visible light

bull E An effect caused by the sun emitting more infrared radiation than ultraviolet radiation

14

iClicker Question

bull Based upon the discussion of the glass in a flat plate collector how would you define the greenhouse gas effect

bull A An effect caused by a gas that is transparent to visible light and opaque to infrared radiation

bull B An effect caused by a gas that is transparent to infrared radiation and opaque to ultraviolet radiation

bull C An effect caused by a gas that is transparent to ultraviolet radiation and opaque to infrared radiation

bull D An effect caused by a gas that is transparent to infrared radiation and opaque to visible light

bull E An effect caused by the sun emitting more infrared radiation than ultraviolet radiation

15

Renewable Resources Discussed in Book

bull Renewable means anything that wonrsquot be permanently destroyed by using itndash sunlight (the sun will rise again tomorrow)ndash biomass (grows again)ndash hydrological cycle (will rain again)ndash wind (sunlight on Earth makes more)ndash ocean currents (driven by Sun)ndash tidal motion (MoonSun keep on producing it)ndash geothermal (heat sources inside Earth not

used up fast)

16

Renewable Energy Consumption

Energy Source

QBtu (1994)

Percent (1994)

QBtu (2003)

Percent (2003)

Hydroelectric 3037 343 2779 283

Geothermal 0357 040 0314 032

Biomass 2852 322 2884 294

Solar Energy 0069 0077 0063 006

Wind 0036 0040 0108 011

Total 6351 718 615 63

17

Another look at available energy flow

bull The flow of radiation (solar and thermal) was covered previouslyndash earth is in an energy balance energy in =

energy outndash 30 reflected 70 thermally re-radiated

bull Some of the incident energy is absorbed but what exactly does this dondash much goes into heating the airlandndash much goes into driving weather (rain wind)ndash some goes into ocean currentsndash some goes into photosynthesis

18

The Renewable Budget

19

Outstanding Points from Fig 51

bull Incident radiation is 1741015 Wndash this is 1370 Wm2 times area facing sun

(R2)bull 30 directly reflected back to space

ndash off clouds air landbull 47 goes into heating air land waterbull 23 goes into evaporating water

precipitation etc (part of weather)bull Adds to 100 so wersquore done

ndash but wait therersquos morehellip

20

Energy Flow continued

bull 021 goes into wind waves convection currentsndash note this is 100 times less than driving the water

cyclendash but this is the ldquootherrdquo aspect of weather

bull 0023 is stored as chemical energy in plants via photosynthesis

ndash total is 401012 W half in ocean (plankton)ndash humans are 6 billion times 100 W = 061012 Wndash this is 15 of bio-energy 000034 of incident

powerbull All of this (bio-activity wind weather etc) ends up

creating heat and re-radiating to spacendash except some small amount of storage in fossil fuels

21

The Hydrologic Cycle

Lots of energy associated with evaporationboth mgh (4 for 10 km lift) and latent heat (96) of water

22

Energetics of the hydrologic cycle

bull It takes energy to evaporate water 2444 J per gramndash this is why ldquoswamp coolersrdquo work evaporation

pulls heat out of environment making it feel cooler

ndash 23 of sunrsquos incident energy goes into evaporation

bull By contrast raising one gram of water to the top of the troposphere (10000 m or 33000 ft) takes

mgh = (0001 kg)(10 ms2)(10000 m) = 100 J

bull So gt 96 of the energy associated with forming clouds is the evaporation lt 4 in lifting against gravity

23

Let it Rain

bull When water condenses in clouds it re-releases this ldquolatent heatrdquo

ndash but this is re-radiated and is of no consequence to hydro-power

bull When it rains the gravitational potential energy is released mostly as kinetic energy and ultimately heat

bull Some tiny bit of gravitational potential energy remains IF the rain falls on terrain (eg higher than sea level where it originated)

ndash hydroelectric plants use this tiny left-over energy itrsquos the energy that drives the flow of streams and rivers

ndash damming up a river concentrates the potential energy in one location for easy exploitation

24

How much of the process do we get to keep

bull According to Figure 51 401015 W of solar power goes into evaporation

ndash this corresponds to 161010 kg per second of evaporated water

ndash this is 35 mm per day off the ocean surface (replenished by rain)

bull The gravitational potential energy given to water vapor (mostly in clouds) in the atmosphere (per second) is thenmgh = (161010 kg)(10 ms2)(2000 m) = 321014 J

bull One can calculate that we gain access to only 25 of the total amount (and use only 125)

ndash based on the 18 land area of the US and the maximum potential of 1477 GW as presented in Table 52

25

iClicker Question

bull With respects to energy hydroelectric power representsndash A remnant electric power from stormsndash B remnant water energy from chemical

bondsndash C remnant energy of chemical bondingndash D remnant gravitational potential

energy of precipitationndash E a form of fictitious energy

26

iClicker Question

bull With respects to energy hydroelectric power representsndash A remnant electric power from stormsndash B remnant water energy from chemical

bondsndash C remnant energy of chemical bondingndash D remnant gravitational potential

energy of precipitationndash E a form of fictitious energy

27

Power of a hydroelectric dam

bull Most impressive is Grand Coulee in Washington on Columbia River

ndash 350 feet = 107 m of ldquoheadrdquondash gt 6000 m3s flow rate (Pacific Northwest gets

rain)ndash each cubic meter of water (1000 kg) has potential

energy mgh = (1000 kg)(10 ms2)(110 m) = 11 MJ

ndash At 6000 m3s get over 6 GW of powerbull Large nuclear plants are usually 1ndash2 GWbull 11 other dams in US in 1ndash2 GW rangebull 74 GW total hydroelectric capacity presently

28

Importance of Hydroelectricity

29

Hydroelectric potential by region in GW

Region Potential

Developed

Undeveloped

Developed

New England 63 19 44 301

Middle Atlantic 98 49 49 500

East North Central 29 12 17 413

West North Central

62 31 31 500

South Atlantic 139 67 72 482

East South Central 83 59 24 711

West South Central

73 27 46 369

Mountain 286 95 191 332

Pacific 644 382 262 593

Total 1477 741 736 502

30

iClicker Question

bull What is true about hydroelectric power generation since 1950ndash A It has always increased in MW producedndash B It has always decreased in MW producedndash C It has increased and decreased in total

MW produced but is now at a peakndash D It has both increased and decreased in

total MW producedndash E The percentage of electric power

produced by hydroelectric plants has generally increased over time

31

iClicker Question

bull What is true about hydroelectric power generation since 1950ndash A It has always increased in MW producedndash B It has always decreased in MW producedndash C It has increased and decreased in total

MW produced but is now at a peakndash D It has both increased and decreased in

total MW producedndash E The percentage of electric power

produced by hydroelectric plants has generally increased over time

32

Hydroelectricity in the future

bull Wersquore almost tapped-outndash 50 of potential is developedndash remaining potential in large number of small-scale

unitsbull Problems with dams

ndash silt limits lifetime to 50ndash200 years after which dam is useless and in fact a potential disaster and nagging maintenance site

ndash habitat loss for fish (salmon) etc wrecks otherwise stunning landscapes (Glenn Canyon in UT)

ndash Disasters waiting to happen 1680 deaths in US alone from 1918ndash1958 often upstream from major population centers

33

Sorry try againhellip

bull So hydroelectricity is a nice ldquofreebeerdquo handed to us by nature but itrsquos not enough to cover our appetite for energy

bull Though very efficient and seemingly environmentally friendly dams do have their problems

bull This isnrsquot the answer to all our energy problems though it is likely to maintain a role well into our future

34

Wind Energy

35

The Power of Wind

bull Wersquove talked about the kinetic energy in wind beforendash a wind traveling at speed v covers v meters

every second (if v is expressed in ms)ndash the kinetic energy hitting a square meter is

then the kinetic energy the mass of air defined by a rectangular tube

ndash tube is one square meter by v meters or v m3

ndash density of air is = 13 kgm3 at sea levelndash mass is v kgndash KE = frac12(v)v2 = frac12v3 (per square meter)

065v3 at sea level

36

Wind Energy proportional to cube of velocity

bull The book (p 134) says power per square meter is 061v3 which is a more-or-less identical resultndash might account for average density in

continental US (above sea level so air slightly less dense)

bull So if the wind speed doubles the power available in the wind increases by 23 = 222 = 8 times

bull A wind of 10 ms (22 mph) has a power density of 610 Wm2

bull A wind of 20 ms (44 mph) has a power density of 4880 Wm2

37

Canrsquot get it all

bull A windmill canrsquot extract all of the kinetic energy available in the wind because this would mean stopping the wind entirely

bull Stopped wind would divert oncoming wind around it and the windmill would stop spinning

bull On the other hand if you donrsquot slow the wind down much at all you wonrsquot get much energy

bull Theoretical maximum performance is 59 of energy extractedndash corresponds to reducing velocity by 36

38

Practical Efficiencies

bull Modern windmills attain maybe 50ndash70 of the theoretical maximumndash 05ndash07 times 059 is 030ndash041 or

about 30ndash40ndash this figure is the mechanical energy

extracted from the windbull Conversion from mechanical to

electrical is 90 efficientndash 09 times 030ndash041 is 27ndash37

39

iClicker Question

bull What is about the maximum efficiency of energy generation using the windndash A 20ndash B 40ndash C 60ndash D 80ndash E 100

40

iClicker Question

bull What is about the maximum efficiency of energy generation using the windndash A 20ndash B 40ndash C 60ndash D 80ndash E 100

41

Achievable efficiencies

42

Typical Windmillsbull A typical windmill might be 15 m in diameter

ndash 176 m2

bull At 10 ms wind 40 efficiency this delivers about 100 kW of power

ndash this would be 800 kW at 20 msndash typical windmills are rated at 50 to 600 kW

bull How much energy per yearndash 10 ms 610 Wm2 40 240 Wm2 8760 hours per

year 2000 kWh per year per square meterndash but wind is intermittent real range from 100ndash500 kWhm2

ndash corresponds to 11ndash57 Wm2 average available power density

bull Note the really high tip speeds bird killers

43

Average available wind powerrecall that average solar insolation is about 150ndash250 Wm2

44

Comparable to solar

bull These numbers are similar to solar if not a little biggerndash Letrsquos go to wind

bull BUT the ldquoper square meterrdquo is not land areamdashitrsquos rotor area

bull Doesnrsquot pay to space windmills too closelymdashone robs the other of energy

bull Typical arrangements have rotors 10 diameters apart in direction of prevailing wind 5 diameters apart in the cross-wind directionndash works out to 16 ldquofill factorrdquo

45

Current implementations

bull Rapidly developing resourcendash 1400 MW in 1989 up to 6400 MW in 2003ndash but still insignificant total (compare to large

dams)ndash cost (at 5ndash7cent per kWh) is competitivendash growing at 25 per yearndash expect to triple over next ten years

bull Current capacity 116 GW (April 2007)ndash Texas 2768 MW (recently took lead over

California)ndash California 2361 MWndash Iowa 936 MWndash Minnesota 895 MWndash Washington 818 MW

46

Flies in the Ointment

bull Find that only 20 of rated capacity is achievedndash design for high wind but seldom get it

bull Only 12 of electrical capacity in US is now windndash total electrical capacity in US is 948 GWndash tripling in ten years means 36ndash but achieving only 20 of capacity reduces

substantiallybull If fully developed we could generate an average

power almost equal to our current electrical capacity (764 GW)

ndash but highly variable resource and problematic if more than 20 comes from the intermittent wind

47

iClicker Question

bull Which state generates the most amount of electricity derived from wind powerndash A Virginiandash B Alaskandash C Montanandash D Californiandash E Texas

48

iClicker Question

bull Which state generates the most amount of electricity derived from wind powerndash A Virginiandash B Alaskandash C Montanandash D Californiandash E Texas

• Renewable Energy Sources II Alternatives Part I
• Chapter 5 Summary
• Slide 3
• Slide 4
• Slide 5
• Slide 6
• Slide 7
• Slide 8
• Slide 9
• Slide 10
• Slide 11
• Slide 12
• Slide 13
• Slide 14
• Renewable Resources Discussed in Book
• Renewable Energy Consumption
• Another look at available energy flow
• The Renewable Budget
• Outstanding Points from Fig 51
• Energy Flow continued
• The Hydrologic Cycle
• Energetics of the hydrologic cycle
• Let it Rain
• How much of the process do we get to keep
• iClicker Question
• Slide 26
• Power of a hydroelectric dam
• Importance of Hydroelectricity
• Hydroelectric potential by region in GW
• Slide 30
• Slide 31
• Hydroelectricity in the future
• Sorry try againhellip
• Wind Energy
• The Power of Wind
• Wind Energy proportional to cube of velocity
• Canrsquot get it all
• Practical Efficiencies
• Slide 39
• Slide 40
• Achievable efficiencies
• Typical Windmills
• Average available wind power
• Comparable to solar
• Current implementations
• Flies in the Ointment
• Slide 47
• Slide 48

11

iClicker Question

bull What must be done to overcome the setting of the Sun in a solar energy systemndash A Store energy in batteriesndash B Get electrical power from elsewherendash C Donrsquot use electrical power at nightndash D All of the above are alternative

approaches for energy after sunset

12

iClicker Question

bull What must be done to overcome the setting of the Sun in a solar energy systemndash A Store energy in batteriesndash B Get electrical power from elsewherendash C Donrsquot use electrical power at nightndash D All of the above are alternative

approaches for energy after sunset

13

iClicker Question

bull Based upon the discussion of the glass in a flat plate collector how would you define the greenhouse gas effect

bull A An effect caused by a gas that is transparent to visible light and opaque to infrared radiation

bull B An effect caused by a gas that is transparent to infrared radiation and opaque to ultraviolet radiation

bull C An effect caused by a gas that is transparent to ultraviolet radiation and opaque to infrared radiation

bull D An effect caused by a gas that is transparent to infrared radiation and opaque to visible light

bull E An effect caused by the sun emitting more infrared radiation than ultraviolet radiation

14

iClicker Question

bull Based upon the discussion of the glass in a flat plate collector how would you define the greenhouse gas effect

bull A An effect caused by a gas that is transparent to visible light and opaque to infrared radiation

bull B An effect caused by a gas that is transparent to infrared radiation and opaque to ultraviolet radiation

bull C An effect caused by a gas that is transparent to ultraviolet radiation and opaque to infrared radiation

bull D An effect caused by a gas that is transparent to infrared radiation and opaque to visible light

bull E An effect caused by the sun emitting more infrared radiation than ultraviolet radiation

15

Renewable Resources Discussed in Book

bull Renewable means anything that wonrsquot be permanently destroyed by using itndash sunlight (the sun will rise again tomorrow)ndash biomass (grows again)ndash hydrological cycle (will rain again)ndash wind (sunlight on Earth makes more)ndash ocean currents (driven by Sun)ndash tidal motion (MoonSun keep on producing it)ndash geothermal (heat sources inside Earth not

used up fast)

16

Renewable Energy Consumption

Energy Source

QBtu (1994)

Percent (1994)

QBtu (2003)

Percent (2003)

Hydroelectric 3037 343 2779 283

Geothermal 0357 040 0314 032

Biomass 2852 322 2884 294

Solar Energy 0069 0077 0063 006

Wind 0036 0040 0108 011

Total 6351 718 615 63

17

Another look at available energy flow

bull The flow of radiation (solar and thermal) was covered previouslyndash earth is in an energy balance energy in =

energy outndash 30 reflected 70 thermally re-radiated

bull Some of the incident energy is absorbed but what exactly does this dondash much goes into heating the airlandndash much goes into driving weather (rain wind)ndash some goes into ocean currentsndash some goes into photosynthesis

18

The Renewable Budget

19

Outstanding Points from Fig 51

bull Incident radiation is 1741015 Wndash this is 1370 Wm2 times area facing sun

(R2)bull 30 directly reflected back to space

ndash off clouds air landbull 47 goes into heating air land waterbull 23 goes into evaporating water

precipitation etc (part of weather)bull Adds to 100 so wersquore done

ndash but wait therersquos morehellip

20

Energy Flow continued

bull 021 goes into wind waves convection currentsndash note this is 100 times less than driving the water

cyclendash but this is the ldquootherrdquo aspect of weather

bull 0023 is stored as chemical energy in plants via photosynthesis

ndash total is 401012 W half in ocean (plankton)ndash humans are 6 billion times 100 W = 061012 Wndash this is 15 of bio-energy 000034 of incident

powerbull All of this (bio-activity wind weather etc) ends up

creating heat and re-radiating to spacendash except some small amount of storage in fossil fuels

21

The Hydrologic Cycle

Lots of energy associated with evaporationboth mgh (4 for 10 km lift) and latent heat (96) of water

22

Energetics of the hydrologic cycle

bull It takes energy to evaporate water 2444 J per gramndash this is why ldquoswamp coolersrdquo work evaporation

pulls heat out of environment making it feel cooler

ndash 23 of sunrsquos incident energy goes into evaporation

bull By contrast raising one gram of water to the top of the troposphere (10000 m or 33000 ft) takes

mgh = (0001 kg)(10 ms2)(10000 m) = 100 J

bull So gt 96 of the energy associated with forming clouds is the evaporation lt 4 in lifting against gravity

23

Let it Rain

bull When water condenses in clouds it re-releases this ldquolatent heatrdquo

ndash but this is re-radiated and is of no consequence to hydro-power

bull When it rains the gravitational potential energy is released mostly as kinetic energy and ultimately heat

bull Some tiny bit of gravitational potential energy remains IF the rain falls on terrain (eg higher than sea level where it originated)

ndash hydroelectric plants use this tiny left-over energy itrsquos the energy that drives the flow of streams and rivers

ndash damming up a river concentrates the potential energy in one location for easy exploitation

24

How much of the process do we get to keep

bull According to Figure 51 401015 W of solar power goes into evaporation

ndash this corresponds to 161010 kg per second of evaporated water

ndash this is 35 mm per day off the ocean surface (replenished by rain)

bull The gravitational potential energy given to water vapor (mostly in clouds) in the atmosphere (per second) is thenmgh = (161010 kg)(10 ms2)(2000 m) = 321014 J

bull One can calculate that we gain access to only 25 of the total amount (and use only 125)

ndash based on the 18 land area of the US and the maximum potential of 1477 GW as presented in Table 52

25

iClicker Question

bull With respects to energy hydroelectric power representsndash A remnant electric power from stormsndash B remnant water energy from chemical

bondsndash C remnant energy of chemical bondingndash D remnant gravitational potential

energy of precipitationndash E a form of fictitious energy

26

iClicker Question

bull With respects to energy hydroelectric power representsndash A remnant electric power from stormsndash B remnant water energy from chemical

bondsndash C remnant energy of chemical bondingndash D remnant gravitational potential

energy of precipitationndash E a form of fictitious energy

27

Power of a hydroelectric dam

bull Most impressive is Grand Coulee in Washington on Columbia River

ndash 350 feet = 107 m of ldquoheadrdquondash gt 6000 m3s flow rate (Pacific Northwest gets

rain)ndash each cubic meter of water (1000 kg) has potential

energy mgh = (1000 kg)(10 ms2)(110 m) = 11 MJ

ndash At 6000 m3s get over 6 GW of powerbull Large nuclear plants are usually 1ndash2 GWbull 11 other dams in US in 1ndash2 GW rangebull 74 GW total hydroelectric capacity presently

28

Importance of Hydroelectricity

29

Hydroelectric potential by region in GW

Region Potential

Developed

Undeveloped

Developed

New England 63 19 44 301

Middle Atlantic 98 49 49 500

East North Central 29 12 17 413

West North Central

62 31 31 500

South Atlantic 139 67 72 482

East South Central 83 59 24 711

West South Central

73 27 46 369

Mountain 286 95 191 332

Pacific 644 382 262 593

Total 1477 741 736 502

30

iClicker Question

bull What is true about hydroelectric power generation since 1950ndash A It has always increased in MW producedndash B It has always decreased in MW producedndash C It has increased and decreased in total

MW produced but is now at a peakndash D It has both increased and decreased in

total MW producedndash E The percentage of electric power

produced by hydroelectric plants has generally increased over time

31

iClicker Question

bull What is true about hydroelectric power generation since 1950ndash A It has always increased in MW producedndash B It has always decreased in MW producedndash C It has increased and decreased in total

MW produced but is now at a peakndash D It has both increased and decreased in

total MW producedndash E The percentage of electric power

produced by hydroelectric plants has generally increased over time

32

Hydroelectricity in the future

bull Wersquore almost tapped-outndash 50 of potential is developedndash remaining potential in large number of small-scale

unitsbull Problems with dams

ndash silt limits lifetime to 50ndash200 years after which dam is useless and in fact a potential disaster and nagging maintenance site

ndash habitat loss for fish (salmon) etc wrecks otherwise stunning landscapes (Glenn Canyon in UT)

ndash Disasters waiting to happen 1680 deaths in US alone from 1918ndash1958 often upstream from major population centers

33

Sorry try againhellip

bull So hydroelectricity is a nice ldquofreebeerdquo handed to us by nature but itrsquos not enough to cover our appetite for energy

bull Though very efficient and seemingly environmentally friendly dams do have their problems

bull This isnrsquot the answer to all our energy problems though it is likely to maintain a role well into our future

34

Wind Energy

35

The Power of Wind

bull Wersquove talked about the kinetic energy in wind beforendash a wind traveling at speed v covers v meters

every second (if v is expressed in ms)ndash the kinetic energy hitting a square meter is

then the kinetic energy the mass of air defined by a rectangular tube

ndash tube is one square meter by v meters or v m3

ndash density of air is = 13 kgm3 at sea levelndash mass is v kgndash KE = frac12(v)v2 = frac12v3 (per square meter)

065v3 at sea level

36

Wind Energy proportional to cube of velocity

bull The book (p 134) says power per square meter is 061v3 which is a more-or-less identical resultndash might account for average density in

continental US (above sea level so air slightly less dense)

bull So if the wind speed doubles the power available in the wind increases by 23 = 222 = 8 times

bull A wind of 10 ms (22 mph) has a power density of 610 Wm2

bull A wind of 20 ms (44 mph) has a power density of 4880 Wm2

37

Canrsquot get it all

bull A windmill canrsquot extract all of the kinetic energy available in the wind because this would mean stopping the wind entirely

bull Stopped wind would divert oncoming wind around it and the windmill would stop spinning

bull On the other hand if you donrsquot slow the wind down much at all you wonrsquot get much energy

bull Theoretical maximum performance is 59 of energy extractedndash corresponds to reducing velocity by 36

38

Practical Efficiencies

bull Modern windmills attain maybe 50ndash70 of the theoretical maximumndash 05ndash07 times 059 is 030ndash041 or

about 30ndash40ndash this figure is the mechanical energy

extracted from the windbull Conversion from mechanical to

electrical is 90 efficientndash 09 times 030ndash041 is 27ndash37

39

iClicker Question

bull What is about the maximum efficiency of energy generation using the windndash A 20ndash B 40ndash C 60ndash D 80ndash E 100

40

iClicker Question

bull What is about the maximum efficiency of energy generation using the windndash A 20ndash B 40ndash C 60ndash D 80ndash E 100

41

Achievable efficiencies

42

Typical Windmillsbull A typical windmill might be 15 m in diameter

ndash 176 m2

bull At 10 ms wind 40 efficiency this delivers about 100 kW of power

ndash this would be 800 kW at 20 msndash typical windmills are rated at 50 to 600 kW

bull How much energy per yearndash 10 ms 610 Wm2 40 240 Wm2 8760 hours per

year 2000 kWh per year per square meterndash but wind is intermittent real range from 100ndash500 kWhm2

ndash corresponds to 11ndash57 Wm2 average available power density

bull Note the really high tip speeds bird killers

43

Average available wind powerrecall that average solar insolation is about 150ndash250 Wm2

44

Comparable to solar

bull These numbers are similar to solar if not a little biggerndash Letrsquos go to wind

bull BUT the ldquoper square meterrdquo is not land areamdashitrsquos rotor area

bull Doesnrsquot pay to space windmills too closelymdashone robs the other of energy

bull Typical arrangements have rotors 10 diameters apart in direction of prevailing wind 5 diameters apart in the cross-wind directionndash works out to 16 ldquofill factorrdquo

45

Current implementations

bull Rapidly developing resourcendash 1400 MW in 1989 up to 6400 MW in 2003ndash but still insignificant total (compare to large

dams)ndash cost (at 5ndash7cent per kWh) is competitivendash growing at 25 per yearndash expect to triple over next ten years

bull Current capacity 116 GW (April 2007)ndash Texas 2768 MW (recently took lead over

California)ndash California 2361 MWndash Iowa 936 MWndash Minnesota 895 MWndash Washington 818 MW

46

Flies in the Ointment

bull Find that only 20 of rated capacity is achievedndash design for high wind but seldom get it

bull Only 12 of electrical capacity in US is now windndash total electrical capacity in US is 948 GWndash tripling in ten years means 36ndash but achieving only 20 of capacity reduces

substantiallybull If fully developed we could generate an average

power almost equal to our current electrical capacity (764 GW)

ndash but highly variable resource and problematic if more than 20 comes from the intermittent wind

47

iClicker Question

bull Which state generates the most amount of electricity derived from wind powerndash A Virginiandash B Alaskandash C Montanandash D Californiandash E Texas

48

iClicker Question

bull Which state generates the most amount of electricity derived from wind powerndash A Virginiandash B Alaskandash C Montanandash D Californiandash E Texas

• Renewable Energy Sources II Alternatives Part I
• Chapter 5 Summary
• Slide 3
• Slide 4
• Slide 5
• Slide 6
• Slide 7
• Slide 8
• Slide 9
• Slide 10
• Slide 11
• Slide 12
• Slide 13
• Slide 14
• Renewable Resources Discussed in Book
• Renewable Energy Consumption
• Another look at available energy flow
• The Renewable Budget
• Outstanding Points from Fig 51
• Energy Flow continued
• The Hydrologic Cycle
• Energetics of the hydrologic cycle
• Let it Rain
• How much of the process do we get to keep
• iClicker Question
• Slide 26
• Power of a hydroelectric dam
• Importance of Hydroelectricity
• Hydroelectric potential by region in GW
• Slide 30
• Slide 31
• Hydroelectricity in the future
• Sorry try againhellip
• Wind Energy
• The Power of Wind
• Wind Energy proportional to cube of velocity
• Canrsquot get it all
• Practical Efficiencies
• Slide 39
• Slide 40
• Achievable efficiencies
• Typical Windmills
• Average available wind power
• Comparable to solar
• Current implementations
• Flies in the Ointment
• Slide 47
• Slide 48

12

iClicker Question

bull What must be done to overcome the setting of the Sun in a solar energy systemndash A Store energy in batteriesndash B Get electrical power from elsewherendash C Donrsquot use electrical power at nightndash D All of the above are alternative

approaches for energy after sunset

13

iClicker Question

bull Based upon the discussion of the glass in a flat plate collector how would you define the greenhouse gas effect

bull A An effect caused by a gas that is transparent to visible light and opaque to infrared radiation

bull B An effect caused by a gas that is transparent to infrared radiation and opaque to ultraviolet radiation

bull C An effect caused by a gas that is transparent to ultraviolet radiation and opaque to infrared radiation

bull D An effect caused by a gas that is transparent to infrared radiation and opaque to visible light

bull E An effect caused by the sun emitting more infrared radiation than ultraviolet radiation

14

iClicker Question

bull Based upon the discussion of the glass in a flat plate collector how would you define the greenhouse gas effect

bull A An effect caused by a gas that is transparent to visible light and opaque to infrared radiation

bull B An effect caused by a gas that is transparent to infrared radiation and opaque to ultraviolet radiation

bull C An effect caused by a gas that is transparent to ultraviolet radiation and opaque to infrared radiation

bull D An effect caused by a gas that is transparent to infrared radiation and opaque to visible light

bull E An effect caused by the sun emitting more infrared radiation than ultraviolet radiation

15

Renewable Resources Discussed in Book

bull Renewable means anything that wonrsquot be permanently destroyed by using itndash sunlight (the sun will rise again tomorrow)ndash biomass (grows again)ndash hydrological cycle (will rain again)ndash wind (sunlight on Earth makes more)ndash ocean currents (driven by Sun)ndash tidal motion (MoonSun keep on producing it)ndash geothermal (heat sources inside Earth not

used up fast)

16

Renewable Energy Consumption

Energy Source

QBtu (1994)

Percent (1994)

QBtu (2003)

Percent (2003)

Hydroelectric 3037 343 2779 283

Geothermal 0357 040 0314 032

Biomass 2852 322 2884 294

Solar Energy 0069 0077 0063 006

Wind 0036 0040 0108 011

Total 6351 718 615 63

17

Another look at available energy flow

bull The flow of radiation (solar and thermal) was covered previouslyndash earth is in an energy balance energy in =

energy outndash 30 reflected 70 thermally re-radiated

bull Some of the incident energy is absorbed but what exactly does this dondash much goes into heating the airlandndash much goes into driving weather (rain wind)ndash some goes into ocean currentsndash some goes into photosynthesis

18

The Renewable Budget

19

Outstanding Points from Fig 51

bull Incident radiation is 1741015 Wndash this is 1370 Wm2 times area facing sun

(R2)bull 30 directly reflected back to space

ndash off clouds air landbull 47 goes into heating air land waterbull 23 goes into evaporating water

precipitation etc (part of weather)bull Adds to 100 so wersquore done

ndash but wait therersquos morehellip

20

Energy Flow continued

bull 021 goes into wind waves convection currentsndash note this is 100 times less than driving the water

cyclendash but this is the ldquootherrdquo aspect of weather

bull 0023 is stored as chemical energy in plants via photosynthesis

ndash total is 401012 W half in ocean (plankton)ndash humans are 6 billion times 100 W = 061012 Wndash this is 15 of bio-energy 000034 of incident

powerbull All of this (bio-activity wind weather etc) ends up

creating heat and re-radiating to spacendash except some small amount of storage in fossil fuels

21

The Hydrologic Cycle

Lots of energy associated with evaporationboth mgh (4 for 10 km lift) and latent heat (96) of water

22

Energetics of the hydrologic cycle

bull It takes energy to evaporate water 2444 J per gramndash this is why ldquoswamp coolersrdquo work evaporation

pulls heat out of environment making it feel cooler

ndash 23 of sunrsquos incident energy goes into evaporation

bull By contrast raising one gram of water to the top of the troposphere (10000 m or 33000 ft) takes

mgh = (0001 kg)(10 ms2)(10000 m) = 100 J

bull So gt 96 of the energy associated with forming clouds is the evaporation lt 4 in lifting against gravity

23

Let it Rain

bull When water condenses in clouds it re-releases this ldquolatent heatrdquo

ndash but this is re-radiated and is of no consequence to hydro-power

bull When it rains the gravitational potential energy is released mostly as kinetic energy and ultimately heat

bull Some tiny bit of gravitational potential energy remains IF the rain falls on terrain (eg higher than sea level where it originated)

ndash hydroelectric plants use this tiny left-over energy itrsquos the energy that drives the flow of streams and rivers

ndash damming up a river concentrates the potential energy in one location for easy exploitation

24

How much of the process do we get to keep

bull According to Figure 51 401015 W of solar power goes into evaporation

ndash this corresponds to 161010 kg per second of evaporated water

ndash this is 35 mm per day off the ocean surface (replenished by rain)

bull The gravitational potential energy given to water vapor (mostly in clouds) in the atmosphere (per second) is thenmgh = (161010 kg)(10 ms2)(2000 m) = 321014 J

bull One can calculate that we gain access to only 25 of the total amount (and use only 125)

ndash based on the 18 land area of the US and the maximum potential of 1477 GW as presented in Table 52

25

iClicker Question

bull With respects to energy hydroelectric power representsndash A remnant electric power from stormsndash B remnant water energy from chemical

bondsndash C remnant energy of chemical bondingndash D remnant gravitational potential

energy of precipitationndash E a form of fictitious energy

26

iClicker Question

bull With respects to energy hydroelectric power representsndash A remnant electric power from stormsndash B remnant water energy from chemical

bondsndash C remnant energy of chemical bondingndash D remnant gravitational potential

energy of precipitationndash E a form of fictitious energy

27

Power of a hydroelectric dam

bull Most impressive is Grand Coulee in Washington on Columbia River

ndash 350 feet = 107 m of ldquoheadrdquondash gt 6000 m3s flow rate (Pacific Northwest gets

rain)ndash each cubic meter of water (1000 kg) has potential

energy mgh = (1000 kg)(10 ms2)(110 m) = 11 MJ

ndash At 6000 m3s get over 6 GW of powerbull Large nuclear plants are usually 1ndash2 GWbull 11 other dams in US in 1ndash2 GW rangebull 74 GW total hydroelectric capacity presently

28

Importance of Hydroelectricity

29

Hydroelectric potential by region in GW

Region Potential

Developed

Undeveloped

Developed

New England 63 19 44 301

Middle Atlantic 98 49 49 500

East North Central 29 12 17 413

West North Central

62 31 31 500

South Atlantic 139 67 72 482

East South Central 83 59 24 711

West South Central

73 27 46 369

Mountain 286 95 191 332

Pacific 644 382 262 593

Total 1477 741 736 502

30

iClicker Question

bull What is true about hydroelectric power generation since 1950ndash A It has always increased in MW producedndash B It has always decreased in MW producedndash C It has increased and decreased in total

MW produced but is now at a peakndash D It has both increased and decreased in

total MW producedndash E The percentage of electric power

produced by hydroelectric plants has generally increased over time

31

iClicker Question

bull What is true about hydroelectric power generation since 1950ndash A It has always increased in MW producedndash B It has always decreased in MW producedndash C It has increased and decreased in total

MW produced but is now at a peakndash D It has both increased and decreased in

total MW producedndash E The percentage of electric power

produced by hydroelectric plants has generally increased over time

32

Hydroelectricity in the future

bull Wersquore almost tapped-outndash 50 of potential is developedndash remaining potential in large number of small-scale

unitsbull Problems with dams

ndash silt limits lifetime to 50ndash200 years after which dam is useless and in fact a potential disaster and nagging maintenance site

ndash habitat loss for fish (salmon) etc wrecks otherwise stunning landscapes (Glenn Canyon in UT)

ndash Disasters waiting to happen 1680 deaths in US alone from 1918ndash1958 often upstream from major population centers

33

Sorry try againhellip

bull So hydroelectricity is a nice ldquofreebeerdquo handed to us by nature but itrsquos not enough to cover our appetite for energy

bull Though very efficient and seemingly environmentally friendly dams do have their problems

bull This isnrsquot the answer to all our energy problems though it is likely to maintain a role well into our future

34

Wind Energy

35

The Power of Wind

bull Wersquove talked about the kinetic energy in wind beforendash a wind traveling at speed v covers v meters

every second (if v is expressed in ms)ndash the kinetic energy hitting a square meter is

then the kinetic energy the mass of air defined by a rectangular tube

ndash tube is one square meter by v meters or v m3

ndash density of air is = 13 kgm3 at sea levelndash mass is v kgndash KE = frac12(v)v2 = frac12v3 (per square meter)

065v3 at sea level

36

Wind Energy proportional to cube of velocity

bull The book (p 134) says power per square meter is 061v3 which is a more-or-less identical resultndash might account for average density in

continental US (above sea level so air slightly less dense)

bull So if the wind speed doubles the power available in the wind increases by 23 = 222 = 8 times

bull A wind of 10 ms (22 mph) has a power density of 610 Wm2

bull A wind of 20 ms (44 mph) has a power density of 4880 Wm2

37

Canrsquot get it all

bull A windmill canrsquot extract all of the kinetic energy available in the wind because this would mean stopping the wind entirely

bull Stopped wind would divert oncoming wind around it and the windmill would stop spinning

bull On the other hand if you donrsquot slow the wind down much at all you wonrsquot get much energy

bull Theoretical maximum performance is 59 of energy extractedndash corresponds to reducing velocity by 36

38

Practical Efficiencies

bull Modern windmills attain maybe 50ndash70 of the theoretical maximumndash 05ndash07 times 059 is 030ndash041 or

about 30ndash40ndash this figure is the mechanical energy

extracted from the windbull Conversion from mechanical to

electrical is 90 efficientndash 09 times 030ndash041 is 27ndash37

39

iClicker Question

bull What is about the maximum efficiency of energy generation using the windndash A 20ndash B 40ndash C 60ndash D 80ndash E 100

40

iClicker Question

bull What is about the maximum efficiency of energy generation using the windndash A 20ndash B 40ndash C 60ndash D 80ndash E 100

41

Achievable efficiencies

42

Typical Windmillsbull A typical windmill might be 15 m in diameter

ndash 176 m2

bull At 10 ms wind 40 efficiency this delivers about 100 kW of power

ndash this would be 800 kW at 20 msndash typical windmills are rated at 50 to 600 kW

bull How much energy per yearndash 10 ms 610 Wm2 40 240 Wm2 8760 hours per

year 2000 kWh per year per square meterndash but wind is intermittent real range from 100ndash500 kWhm2

ndash corresponds to 11ndash57 Wm2 average available power density

bull Note the really high tip speeds bird killers

43

Average available wind powerrecall that average solar insolation is about 150ndash250 Wm2

44

Comparable to solar

bull These numbers are similar to solar if not a little biggerndash Letrsquos go to wind

bull BUT the ldquoper square meterrdquo is not land areamdashitrsquos rotor area

bull Doesnrsquot pay to space windmills too closelymdashone robs the other of energy

bull Typical arrangements have rotors 10 diameters apart in direction of prevailing wind 5 diameters apart in the cross-wind directionndash works out to 16 ldquofill factorrdquo

45

Current implementations

bull Rapidly developing resourcendash 1400 MW in 1989 up to 6400 MW in 2003ndash but still insignificant total (compare to large

dams)ndash cost (at 5ndash7cent per kWh) is competitivendash growing at 25 per yearndash expect to triple over next ten years

bull Current capacity 116 GW (April 2007)ndash Texas 2768 MW (recently took lead over

California)ndash California 2361 MWndash Iowa 936 MWndash Minnesota 895 MWndash Washington 818 MW

46

Flies in the Ointment

bull Find that only 20 of rated capacity is achievedndash design for high wind but seldom get it

bull Only 12 of electrical capacity in US is now windndash total electrical capacity in US is 948 GWndash tripling in ten years means 36ndash but achieving only 20 of capacity reduces

substantiallybull If fully developed we could generate an average

power almost equal to our current electrical capacity (764 GW)

ndash but highly variable resource and problematic if more than 20 comes from the intermittent wind

47

iClicker Question

bull Which state generates the most amount of electricity derived from wind powerndash A Virginiandash B Alaskandash C Montanandash D Californiandash E Texas

48

iClicker Question

bull Which state generates the most amount of electricity derived from wind powerndash A Virginiandash B Alaskandash C Montanandash D Californiandash E Texas

• Renewable Energy Sources II Alternatives Part I
• Chapter 5 Summary
• Slide 3
• Slide 4
• Slide 5
• Slide 6
• Slide 7
• Slide 8
• Slide 9
• Slide 10
• Slide 11
• Slide 12
• Slide 13
• Slide 14
• Renewable Resources Discussed in Book
• Renewable Energy Consumption
• Another look at available energy flow
• The Renewable Budget
• Outstanding Points from Fig 51
• Energy Flow continued
• The Hydrologic Cycle
• Energetics of the hydrologic cycle
• Let it Rain
• How much of the process do we get to keep
• iClicker Question
• Slide 26
• Power of a hydroelectric dam
• Importance of Hydroelectricity
• Hydroelectric potential by region in GW
• Slide 30
• Slide 31
• Hydroelectricity in the future
• Sorry try againhellip
• Wind Energy
• The Power of Wind
• Wind Energy proportional to cube of velocity
• Canrsquot get it all
• Practical Efficiencies
• Slide 39
• Slide 40
• Achievable efficiencies
• Typical Windmills
• Average available wind power
• Comparable to solar
• Current implementations
• Flies in the Ointment
• Slide 47
• Slide 48

13

iClicker Question

bull Based upon the discussion of the glass in a flat plate collector how would you define the greenhouse gas effect

bull A An effect caused by a gas that is transparent to visible light and opaque to infrared radiation

bull B An effect caused by a gas that is transparent to infrared radiation and opaque to ultraviolet radiation

bull C An effect caused by a gas that is transparent to ultraviolet radiation and opaque to infrared radiation

bull D An effect caused by a gas that is transparent to infrared radiation and opaque to visible light

bull E An effect caused by the sun emitting more infrared radiation than ultraviolet radiation

14

iClicker Question

bull Based upon the discussion of the glass in a flat plate collector how would you define the greenhouse gas effect

bull A An effect caused by a gas that is transparent to visible light and opaque to infrared radiation

bull B An effect caused by a gas that is transparent to infrared radiation and opaque to ultraviolet radiation

bull C An effect caused by a gas that is transparent to ultraviolet radiation and opaque to infrared radiation

bull D An effect caused by a gas that is transparent to infrared radiation and opaque to visible light

bull E An effect caused by the sun emitting more infrared radiation than ultraviolet radiation

15

Renewable Resources Discussed in Book

bull Renewable means anything that wonrsquot be permanently destroyed by using itndash sunlight (the sun will rise again tomorrow)ndash biomass (grows again)ndash hydrological cycle (will rain again)ndash wind (sunlight on Earth makes more)ndash ocean currents (driven by Sun)ndash tidal motion (MoonSun keep on producing it)ndash geothermal (heat sources inside Earth not

used up fast)

16

Renewable Energy Consumption

Energy Source

QBtu (1994)

Percent (1994)

QBtu (2003)

Percent (2003)

Hydroelectric 3037 343 2779 283

Geothermal 0357 040 0314 032

Biomass 2852 322 2884 294

Solar Energy 0069 0077 0063 006

Wind 0036 0040 0108 011

Total 6351 718 615 63

17

Another look at available energy flow

bull The flow of radiation (solar and thermal) was covered previouslyndash earth is in an energy balance energy in =

energy outndash 30 reflected 70 thermally re-radiated

bull Some of the incident energy is absorbed but what exactly does this dondash much goes into heating the airlandndash much goes into driving weather (rain wind)ndash some goes into ocean currentsndash some goes into photosynthesis

18

The Renewable Budget

19

Outstanding Points from Fig 51

bull Incident radiation is 1741015 Wndash this is 1370 Wm2 times area facing sun

(R2)bull 30 directly reflected back to space

ndash off clouds air landbull 47 goes into heating air land waterbull 23 goes into evaporating water

precipitation etc (part of weather)bull Adds to 100 so wersquore done

ndash but wait therersquos morehellip

20

Energy Flow continued

bull 021 goes into wind waves convection currentsndash note this is 100 times less than driving the water

cyclendash but this is the ldquootherrdquo aspect of weather

bull 0023 is stored as chemical energy in plants via photosynthesis

ndash total is 401012 W half in ocean (plankton)ndash humans are 6 billion times 100 W = 061012 Wndash this is 15 of bio-energy 000034 of incident

powerbull All of this (bio-activity wind weather etc) ends up

creating heat and re-radiating to spacendash except some small amount of storage in fossil fuels

21

The Hydrologic Cycle

Lots of energy associated with evaporationboth mgh (4 for 10 km lift) and latent heat (96) of water

22

Energetics of the hydrologic cycle

bull It takes energy to evaporate water 2444 J per gramndash this is why ldquoswamp coolersrdquo work evaporation

pulls heat out of environment making it feel cooler

ndash 23 of sunrsquos incident energy goes into evaporation

bull By contrast raising one gram of water to the top of the troposphere (10000 m or 33000 ft) takes

mgh = (0001 kg)(10 ms2)(10000 m) = 100 J

bull So gt 96 of the energy associated with forming clouds is the evaporation lt 4 in lifting against gravity

23

Let it Rain

bull When water condenses in clouds it re-releases this ldquolatent heatrdquo

ndash but this is re-radiated and is of no consequence to hydro-power

bull When it rains the gravitational potential energy is released mostly as kinetic energy and ultimately heat

bull Some tiny bit of gravitational potential energy remains IF the rain falls on terrain (eg higher than sea level where it originated)

ndash hydroelectric plants use this tiny left-over energy itrsquos the energy that drives the flow of streams and rivers

ndash damming up a river concentrates the potential energy in one location for easy exploitation

24

How much of the process do we get to keep

bull According to Figure 51 401015 W of solar power goes into evaporation

ndash this corresponds to 161010 kg per second of evaporated water

ndash this is 35 mm per day off the ocean surface (replenished by rain)

bull The gravitational potential energy given to water vapor (mostly in clouds) in the atmosphere (per second) is thenmgh = (161010 kg)(10 ms2)(2000 m) = 321014 J

bull One can calculate that we gain access to only 25 of the total amount (and use only 125)

ndash based on the 18 land area of the US and the maximum potential of 1477 GW as presented in Table 52

25

iClicker Question

bull With respects to energy hydroelectric power representsndash A remnant electric power from stormsndash B remnant water energy from chemical

bondsndash C remnant energy of chemical bondingndash D remnant gravitational potential

energy of precipitationndash E a form of fictitious energy

26

iClicker Question

bull With respects to energy hydroelectric power representsndash A remnant electric power from stormsndash B remnant water energy from chemical

bondsndash C remnant energy of chemical bondingndash D remnant gravitational potential

energy of precipitationndash E a form of fictitious energy

27

Power of a hydroelectric dam

bull Most impressive is Grand Coulee in Washington on Columbia River

ndash 350 feet = 107 m of ldquoheadrdquondash gt 6000 m3s flow rate (Pacific Northwest gets

rain)ndash each cubic meter of water (1000 kg) has potential

energy mgh = (1000 kg)(10 ms2)(110 m) = 11 MJ

ndash At 6000 m3s get over 6 GW of powerbull Large nuclear plants are usually 1ndash2 GWbull 11 other dams in US in 1ndash2 GW rangebull 74 GW total hydroelectric capacity presently

28

Importance of Hydroelectricity

29

Hydroelectric potential by region in GW

Region Potential

Developed

Undeveloped

Developed

New England 63 19 44 301

Middle Atlantic 98 49 49 500

East North Central 29 12 17 413

West North Central

62 31 31 500

South Atlantic 139 67 72 482

East South Central 83 59 24 711

West South Central

73 27 46 369

Mountain 286 95 191 332

Pacific 644 382 262 593

Total 1477 741 736 502

30

iClicker Question

bull What is true about hydroelectric power generation since 1950ndash A It has always increased in MW producedndash B It has always decreased in MW producedndash C It has increased and decreased in total

MW produced but is now at a peakndash D It has both increased and decreased in

total MW producedndash E The percentage of electric power

produced by hydroelectric plants has generally increased over time

31

iClicker Question

bull What is true about hydroelectric power generation since 1950ndash A It has always increased in MW producedndash B It has always decreased in MW producedndash C It has increased and decreased in total

MW produced but is now at a peakndash D It has both increased and decreased in

total MW producedndash E The percentage of electric power

produced by hydroelectric plants has generally increased over time

32

Hydroelectricity in the future

bull Wersquore almost tapped-outndash 50 of potential is developedndash remaining potential in large number of small-scale

unitsbull Problems with dams

ndash silt limits lifetime to 50ndash200 years after which dam is useless and in fact a potential disaster and nagging maintenance site

ndash habitat loss for fish (salmon) etc wrecks otherwise stunning landscapes (Glenn Canyon in UT)

ndash Disasters waiting to happen 1680 deaths in US alone from 1918ndash1958 often upstream from major population centers

33

Sorry try againhellip

bull So hydroelectricity is a nice ldquofreebeerdquo handed to us by nature but itrsquos not enough to cover our appetite for energy

bull Though very efficient and seemingly environmentally friendly dams do have their problems

bull This isnrsquot the answer to all our energy problems though it is likely to maintain a role well into our future

34

Wind Energy

35

The Power of Wind

bull Wersquove talked about the kinetic energy in wind beforendash a wind traveling at speed v covers v meters

every second (if v is expressed in ms)ndash the kinetic energy hitting a square meter is

then the kinetic energy the mass of air defined by a rectangular tube

ndash tube is one square meter by v meters or v m3

ndash density of air is = 13 kgm3 at sea levelndash mass is v kgndash KE = frac12(v)v2 = frac12v3 (per square meter)

065v3 at sea level

36

Wind Energy proportional to cube of velocity

bull The book (p 134) says power per square meter is 061v3 which is a more-or-less identical resultndash might account for average density in

continental US (above sea level so air slightly less dense)

bull So if the wind speed doubles the power available in the wind increases by 23 = 222 = 8 times

bull A wind of 10 ms (22 mph) has a power density of 610 Wm2

bull A wind of 20 ms (44 mph) has a power density of 4880 Wm2

37

Canrsquot get it all

bull A windmill canrsquot extract all of the kinetic energy available in the wind because this would mean stopping the wind entirely

bull Stopped wind would divert oncoming wind around it and the windmill would stop spinning

bull On the other hand if you donrsquot slow the wind down much at all you wonrsquot get much energy

bull Theoretical maximum performance is 59 of energy extractedndash corresponds to reducing velocity by 36

38

Practical Efficiencies

bull Modern windmills attain maybe 50ndash70 of the theoretical maximumndash 05ndash07 times 059 is 030ndash041 or

about 30ndash40ndash this figure is the mechanical energy

extracted from the windbull Conversion from mechanical to

electrical is 90 efficientndash 09 times 030ndash041 is 27ndash37

39

iClicker Question

bull What is about the maximum efficiency of energy generation using the windndash A 20ndash B 40ndash C 60ndash D 80ndash E 100

40

iClicker Question

bull What is about the maximum efficiency of energy generation using the windndash A 20ndash B 40ndash C 60ndash D 80ndash E 100

41

Achievable efficiencies

42

Typical Windmillsbull A typical windmill might be 15 m in diameter

ndash 176 m2

bull At 10 ms wind 40 efficiency this delivers about 100 kW of power

ndash this would be 800 kW at 20 msndash typical windmills are rated at 50 to 600 kW

bull How much energy per yearndash 10 ms 610 Wm2 40 240 Wm2 8760 hours per

year 2000 kWh per year per square meterndash but wind is intermittent real range from 100ndash500 kWhm2

ndash corresponds to 11ndash57 Wm2 average available power density

bull Note the really high tip speeds bird killers

43

Average available wind powerrecall that average solar insolation is about 150ndash250 Wm2

44

Comparable to solar

bull These numbers are similar to solar if not a little biggerndash Letrsquos go to wind

bull BUT the ldquoper square meterrdquo is not land areamdashitrsquos rotor area

bull Doesnrsquot pay to space windmills too closelymdashone robs the other of energy

bull Typical arrangements have rotors 10 diameters apart in direction of prevailing wind 5 diameters apart in the cross-wind directionndash works out to 16 ldquofill factorrdquo

45

Current implementations

bull Rapidly developing resourcendash 1400 MW in 1989 up to 6400 MW in 2003ndash but still insignificant total (compare to large

dams)ndash cost (at 5ndash7cent per kWh) is competitivendash growing at 25 per yearndash expect to triple over next ten years

bull Current capacity 116 GW (April 2007)ndash Texas 2768 MW (recently took lead over

California)ndash California 2361 MWndash Iowa 936 MWndash Minnesota 895 MWndash Washington 818 MW

46

Flies in the Ointment

bull Find that only 20 of rated capacity is achievedndash design for high wind but seldom get it

bull Only 12 of electrical capacity in US is now windndash total electrical capacity in US is 948 GWndash tripling in ten years means 36ndash but achieving only 20 of capacity reduces

substantiallybull If fully developed we could generate an average

power almost equal to our current electrical capacity (764 GW)

ndash but highly variable resource and problematic if more than 20 comes from the intermittent wind

47

iClicker Question

bull Which state generates the most amount of electricity derived from wind powerndash A Virginiandash B Alaskandash C Montanandash D Californiandash E Texas

48

iClicker Question

bull Which state generates the most amount of electricity derived from wind powerndash A Virginiandash B Alaskandash C Montanandash D Californiandash E Texas

• Renewable Energy Sources II Alternatives Part I
• Chapter 5 Summary
• Slide 3
• Slide 4
• Slide 5
• Slide 6
• Slide 7
• Slide 8
• Slide 9
• Slide 10
• Slide 11
• Slide 12
• Slide 13
• Slide 14
• Renewable Resources Discussed in Book
• Renewable Energy Consumption
• Another look at available energy flow
• The Renewable Budget
• Outstanding Points from Fig 51
• Energy Flow continued
• The Hydrologic Cycle
• Energetics of the hydrologic cycle
• Let it Rain
• How much of the process do we get to keep
• iClicker Question
• Slide 26
• Power of a hydroelectric dam
• Importance of Hydroelectricity
• Hydroelectric potential by region in GW
• Slide 30
• Slide 31
• Hydroelectricity in the future
• Sorry try againhellip
• Wind Energy
• The Power of Wind
• Wind Energy proportional to cube of velocity
• Canrsquot get it all
• Practical Efficiencies
• Slide 39
• Slide 40
• Achievable efficiencies
• Typical Windmills
• Average available wind power
• Comparable to solar
• Current implementations
• Flies in the Ointment
• Slide 47
• Slide 48

14

iClicker Question

bull Based upon the discussion of the glass in a flat plate collector how would you define the greenhouse gas effect

bull A An effect caused by a gas that is transparent to visible light and opaque to infrared radiation

bull B An effect caused by a gas that is transparent to infrared radiation and opaque to ultraviolet radiation

bull C An effect caused by a gas that is transparent to ultraviolet radiation and opaque to infrared radiation

bull D An effect caused by a gas that is transparent to infrared radiation and opaque to visible light

bull E An effect caused by the sun emitting more infrared radiation than ultraviolet radiation

15

Renewable Resources Discussed in Book

bull Renewable means anything that wonrsquot be permanently destroyed by using itndash sunlight (the sun will rise again tomorrow)ndash biomass (grows again)ndash hydrological cycle (will rain again)ndash wind (sunlight on Earth makes more)ndash ocean currents (driven by Sun)ndash tidal motion (MoonSun keep on producing it)ndash geothermal (heat sources inside Earth not

used up fast)

16

Renewable Energy Consumption

Energy Source

QBtu (1994)

Percent (1994)

QBtu (2003)

Percent (2003)

Hydroelectric 3037 343 2779 283

Geothermal 0357 040 0314 032

Biomass 2852 322 2884 294

Solar Energy 0069 0077 0063 006

Wind 0036 0040 0108 011

Total 6351 718 615 63

17

Another look at available energy flow

bull The flow of radiation (solar and thermal) was covered previouslyndash earth is in an energy balance energy in =

energy outndash 30 reflected 70 thermally re-radiated

bull Some of the incident energy is absorbed but what exactly does this dondash much goes into heating the airlandndash much goes into driving weather (rain wind)ndash some goes into ocean currentsndash some goes into photosynthesis

18

The Renewable Budget

19

Outstanding Points from Fig 51

bull Incident radiation is 1741015 Wndash this is 1370 Wm2 times area facing sun

(R2)bull 30 directly reflected back to space

ndash off clouds air landbull 47 goes into heating air land waterbull 23 goes into evaporating water

precipitation etc (part of weather)bull Adds to 100 so wersquore done

ndash but wait therersquos morehellip

20

Energy Flow continued

bull 021 goes into wind waves convection currentsndash note this is 100 times less than driving the water

cyclendash but this is the ldquootherrdquo aspect of weather

bull 0023 is stored as chemical energy in plants via photosynthesis

ndash total is 401012 W half in ocean (plankton)ndash humans are 6 billion times 100 W = 061012 Wndash this is 15 of bio-energy 000034 of incident

powerbull All of this (bio-activity wind weather etc) ends up

creating heat and re-radiating to spacendash except some small amount of storage in fossil fuels

21

The Hydrologic Cycle

Lots of energy associated with evaporationboth mgh (4 for 10 km lift) and latent heat (96) of water

22

Energetics of the hydrologic cycle

bull It takes energy to evaporate water 2444 J per gramndash this is why ldquoswamp coolersrdquo work evaporation

pulls heat out of environment making it feel cooler

ndash 23 of sunrsquos incident energy goes into evaporation

bull By contrast raising one gram of water to the top of the troposphere (10000 m or 33000 ft) takes

mgh = (0001 kg)(10 ms2)(10000 m) = 100 J

bull So gt 96 of the energy associated with forming clouds is the evaporation lt 4 in lifting against gravity

23

Let it Rain

bull When water condenses in clouds it re-releases this ldquolatent heatrdquo

ndash but this is re-radiated and is of no consequence to hydro-power

bull When it rains the gravitational potential energy is released mostly as kinetic energy and ultimately heat

bull Some tiny bit of gravitational potential energy remains IF the rain falls on terrain (eg higher than sea level where it originated)

ndash hydroelectric plants use this tiny left-over energy itrsquos the energy that drives the flow of streams and rivers

ndash damming up a river concentrates the potential energy in one location for easy exploitation

24

How much of the process do we get to keep

bull According to Figure 51 401015 W of solar power goes into evaporation

ndash this corresponds to 161010 kg per second of evaporated water

ndash this is 35 mm per day off the ocean surface (replenished by rain)

bull The gravitational potential energy given to water vapor (mostly in clouds) in the atmosphere (per second) is thenmgh = (161010 kg)(10 ms2)(2000 m) = 321014 J

bull One can calculate that we gain access to only 25 of the total amount (and use only 125)

ndash based on the 18 land area of the US and the maximum potential of 1477 GW as presented in Table 52

25

iClicker Question

bull With respects to energy hydroelectric power representsndash A remnant electric power from stormsndash B remnant water energy from chemical

bondsndash C remnant energy of chemical bondingndash D remnant gravitational potential

energy of precipitationndash E a form of fictitious energy

26

iClicker Question

bull With respects to energy hydroelectric power representsndash A remnant electric power from stormsndash B remnant water energy from chemical

bondsndash C remnant energy of chemical bondingndash D remnant gravitational potential

energy of precipitationndash E a form of fictitious energy

27

Power of a hydroelectric dam

bull Most impressive is Grand Coulee in Washington on Columbia River

ndash 350 feet = 107 m of ldquoheadrdquondash gt 6000 m3s flow rate (Pacific Northwest gets

rain)ndash each cubic meter of water (1000 kg) has potential

energy mgh = (1000 kg)(10 ms2)(110 m) = 11 MJ

ndash At 6000 m3s get over 6 GW of powerbull Large nuclear plants are usually 1ndash2 GWbull 11 other dams in US in 1ndash2 GW rangebull 74 GW total hydroelectric capacity presently

28

Importance of Hydroelectricity

29

Hydroelectric potential by region in GW

Region Potential

Developed

Undeveloped

Developed

New England 63 19 44 301

Middle Atlantic 98 49 49 500

East North Central 29 12 17 413

West North Central

62 31 31 500

South Atlantic 139 67 72 482

East South Central 83 59 24 711

West South Central

73 27 46 369

Mountain 286 95 191 332

Pacific 644 382 262 593

Total 1477 741 736 502

30

iClicker Question

bull What is true about hydroelectric power generation since 1950ndash A It has always increased in MW producedndash B It has always decreased in MW producedndash C It has increased and decreased in total

MW produced but is now at a peakndash D It has both increased and decreased in

total MW producedndash E The percentage of electric power

produced by hydroelectric plants has generally increased over time

31

iClicker Question

bull What is true about hydroelectric power generation since 1950ndash A It has always increased in MW producedndash B It has always decreased in MW producedndash C It has increased and decreased in total

MW produced but is now at a peakndash D It has both increased and decreased in

total MW producedndash E The percentage of electric power

produced by hydroelectric plants has generally increased over time

32

Hydroelectricity in the future

bull Wersquore almost tapped-outndash 50 of potential is developedndash remaining potential in large number of small-scale

unitsbull Problems with dams

ndash silt limits lifetime to 50ndash200 years after which dam is useless and in fact a potential disaster and nagging maintenance site

ndash habitat loss for fish (salmon) etc wrecks otherwise stunning landscapes (Glenn Canyon in UT)

ndash Disasters waiting to happen 1680 deaths in US alone from 1918ndash1958 often upstream from major population centers

33

Sorry try againhellip

bull So hydroelectricity is a nice ldquofreebeerdquo handed to us by nature but itrsquos not enough to cover our appetite for energy

bull Though very efficient and seemingly environmentally friendly dams do have their problems

bull This isnrsquot the answer to all our energy problems though it is likely to maintain a role well into our future

34

Wind Energy

35

The Power of Wind

bull Wersquove talked about the kinetic energy in wind beforendash a wind traveling at speed v covers v meters

every second (if v is expressed in ms)ndash the kinetic energy hitting a square meter is

then the kinetic energy the mass of air defined by a rectangular tube

ndash tube is one square meter by v meters or v m3

ndash density of air is = 13 kgm3 at sea levelndash mass is v kgndash KE = frac12(v)v2 = frac12v3 (per square meter)

065v3 at sea level

36

Wind Energy proportional to cube of velocity

bull The book (p 134) says power per square meter is 061v3 which is a more-or-less identical resultndash might account for average density in

continental US (above sea level so air slightly less dense)

bull So if the wind speed doubles the power available in the wind increases by 23 = 222 = 8 times

bull A wind of 10 ms (22 mph) has a power density of 610 Wm2

bull A wind of 20 ms (44 mph) has a power density of 4880 Wm2

37

Canrsquot get it all

bull A windmill canrsquot extract all of the kinetic energy available in the wind because this would mean stopping the wind entirely

bull Stopped wind would divert oncoming wind around it and the windmill would stop spinning

bull On the other hand if you donrsquot slow the wind down much at all you wonrsquot get much energy

bull Theoretical maximum performance is 59 of energy extractedndash corresponds to reducing velocity by 36

38

Practical Efficiencies

bull Modern windmills attain maybe 50ndash70 of the theoretical maximumndash 05ndash07 times 059 is 030ndash041 or

about 30ndash40ndash this figure is the mechanical energy

extracted from the windbull Conversion from mechanical to

electrical is 90 efficientndash 09 times 030ndash041 is 27ndash37

39

iClicker Question

bull What is about the maximum efficiency of energy generation using the windndash A 20ndash B 40ndash C 60ndash D 80ndash E 100

40

iClicker Question

bull What is about the maximum efficiency of energy generation using the windndash A 20ndash B 40ndash C 60ndash D 80ndash E 100

41

Achievable efficiencies

42

Typical Windmillsbull A typical windmill might be 15 m in diameter

ndash 176 m2

bull At 10 ms wind 40 efficiency this delivers about 100 kW of power

ndash this would be 800 kW at 20 msndash typical windmills are rated at 50 to 600 kW

bull How much energy per yearndash 10 ms 610 Wm2 40 240 Wm2 8760 hours per

year 2000 kWh per year per square meterndash but wind is intermittent real range from 100ndash500 kWhm2

ndash corresponds to 11ndash57 Wm2 average available power density

bull Note the really high tip speeds bird killers

43

Average available wind powerrecall that average solar insolation is about 150ndash250 Wm2

44

Comparable to solar

bull These numbers are similar to solar if not a little biggerndash Letrsquos go to wind

bull BUT the ldquoper square meterrdquo is not land areamdashitrsquos rotor area

bull Doesnrsquot pay to space windmills too closelymdashone robs the other of energy

bull Typical arrangements have rotors 10 diameters apart in direction of prevailing wind 5 diameters apart in the cross-wind directionndash works out to 16 ldquofill factorrdquo

45

Current implementations

bull Rapidly developing resourcendash 1400 MW in 1989 up to 6400 MW in 2003ndash but still insignificant total (compare to large

dams)ndash cost (at 5ndash7cent per kWh) is competitivendash growing at 25 per yearndash expect to triple over next ten years

bull Current capacity 116 GW (April 2007)ndash Texas 2768 MW (recently took lead over

California)ndash California 2361 MWndash Iowa 936 MWndash Minnesota 895 MWndash Washington 818 MW

46

Flies in the Ointment

bull Find that only 20 of rated capacity is achievedndash design for high wind but seldom get it

bull Only 12 of electrical capacity in US is now windndash total electrical capacity in US is 948 GWndash tripling in ten years means 36ndash but achieving only 20 of capacity reduces

substantiallybull If fully developed we could generate an average

power almost equal to our current electrical capacity (764 GW)

ndash but highly variable resource and problematic if more than 20 comes from the intermittent wind

47

iClicker Question

bull Which state generates the most amount of electricity derived from wind powerndash A Virginiandash B Alaskandash C Montanandash D Californiandash E Texas

48

iClicker Question

bull Which state generates the most amount of electricity derived from wind powerndash A Virginiandash B Alaskandash C Montanandash D Californiandash E Texas

• Renewable Energy Sources II Alternatives Part I
• Chapter 5 Summary
• Slide 3
• Slide 4
• Slide 5
• Slide 6
• Slide 7
• Slide 8
• Slide 9
• Slide 10
• Slide 11
• Slide 12
• Slide 13
• Slide 14
• Renewable Resources Discussed in Book
• Renewable Energy Consumption
• Another look at available energy flow
• The Renewable Budget
• Outstanding Points from Fig 51
• Energy Flow continued
• The Hydrologic Cycle
• Energetics of the hydrologic cycle
• Let it Rain
• How much of the process do we get to keep
• iClicker Question
• Slide 26
• Power of a hydroelectric dam
• Importance of Hydroelectricity
• Hydroelectric potential by region in GW
• Slide 30
• Slide 31
• Hydroelectricity in the future
• Sorry try againhellip
• Wind Energy
• The Power of Wind
• Wind Energy proportional to cube of velocity
• Canrsquot get it all
• Practical Efficiencies
• Slide 39
• Slide 40
• Achievable efficiencies
• Typical Windmills
• Average available wind power
• Comparable to solar
• Current implementations
• Flies in the Ointment
• Slide 47
• Slide 48

15

Renewable Resources Discussed in Book

bull Renewable means anything that wonrsquot be permanently destroyed by using itndash sunlight (the sun will rise again tomorrow)ndash biomass (grows again)ndash hydrological cycle (will rain again)ndash wind (sunlight on Earth makes more)ndash ocean currents (driven by Sun)ndash tidal motion (MoonSun keep on producing it)ndash geothermal (heat sources inside Earth not

used up fast)

16

Renewable Energy Consumption

Energy Source

QBtu (1994)

Percent (1994)

QBtu (2003)

Percent (2003)

Hydroelectric 3037 343 2779 283

Geothermal 0357 040 0314 032

Biomass 2852 322 2884 294

Solar Energy 0069 0077 0063 006

Wind 0036 0040 0108 011

Total 6351 718 615 63

17

Another look at available energy flow

bull The flow of radiation (solar and thermal) was covered previouslyndash earth is in an energy balance energy in =

energy outndash 30 reflected 70 thermally re-radiated

bull Some of the incident energy is absorbed but what exactly does this dondash much goes into heating the airlandndash much goes into driving weather (rain wind)ndash some goes into ocean currentsndash some goes into photosynthesis

18

The Renewable Budget

19

Outstanding Points from Fig 51

bull Incident radiation is 1741015 Wndash this is 1370 Wm2 times area facing sun

(R2)bull 30 directly reflected back to space

ndash off clouds air landbull 47 goes into heating air land waterbull 23 goes into evaporating water

precipitation etc (part of weather)bull Adds to 100 so wersquore done

ndash but wait therersquos morehellip

20

Energy Flow continued

bull 021 goes into wind waves convection currentsndash note this is 100 times less than driving the water

cyclendash but this is the ldquootherrdquo aspect of weather

bull 0023 is stored as chemical energy in plants via photosynthesis

ndash total is 401012 W half in ocean (plankton)ndash humans are 6 billion times 100 W = 061012 Wndash this is 15 of bio-energy 000034 of incident

powerbull All of this (bio-activity wind weather etc) ends up

creating heat and re-radiating to spacendash except some small amount of storage in fossil fuels

21

The Hydrologic Cycle

Lots of energy associated with evaporationboth mgh (4 for 10 km lift) and latent heat (96) of water

22

Energetics of the hydrologic cycle

bull It takes energy to evaporate water 2444 J per gramndash this is why ldquoswamp coolersrdquo work evaporation

pulls heat out of environment making it feel cooler

ndash 23 of sunrsquos incident energy goes into evaporation

bull By contrast raising one gram of water to the top of the troposphere (10000 m or 33000 ft) takes

mgh = (0001 kg)(10 ms2)(10000 m) = 100 J

bull So gt 96 of the energy associated with forming clouds is the evaporation lt 4 in lifting against gravity

23

Let it Rain

bull When water condenses in clouds it re-releases this ldquolatent heatrdquo

ndash but this is re-radiated and is of no consequence to hydro-power

bull When it rains the gravitational potential energy is released mostly as kinetic energy and ultimately heat

bull Some tiny bit of gravitational potential energy remains IF the rain falls on terrain (eg higher than sea level where it originated)

ndash hydroelectric plants use this tiny left-over energy itrsquos the energy that drives the flow of streams and rivers

ndash damming up a river concentrates the potential energy in one location for easy exploitation

24

How much of the process do we get to keep

bull According to Figure 51 401015 W of solar power goes into evaporation

ndash this corresponds to 161010 kg per second of evaporated water

ndash this is 35 mm per day off the ocean surface (replenished by rain)

bull The gravitational potential energy given to water vapor (mostly in clouds) in the atmosphere (per second) is thenmgh = (161010 kg)(10 ms2)(2000 m) = 321014 J

bull One can calculate that we gain access to only 25 of the total amount (and use only 125)

ndash based on the 18 land area of the US and the maximum potential of 1477 GW as presented in Table 52

25

iClicker Question

bull With respects to energy hydroelectric power representsndash A remnant electric power from stormsndash B remnant water energy from chemical

bondsndash C remnant energy of chemical bondingndash D remnant gravitational potential

energy of precipitationndash E a form of fictitious energy

26

iClicker Question

bull With respects to energy hydroelectric power representsndash A remnant electric power from stormsndash B remnant water energy from chemical

bondsndash C remnant energy of chemical bondingndash D remnant gravitational potential

energy of precipitationndash E a form of fictitious energy

27

Power of a hydroelectric dam

bull Most impressive is Grand Coulee in Washington on Columbia River

ndash 350 feet = 107 m of ldquoheadrdquondash gt 6000 m3s flow rate (Pacific Northwest gets

rain)ndash each cubic meter of water (1000 kg) has potential

energy mgh = (1000 kg)(10 ms2)(110 m) = 11 MJ

ndash At 6000 m3s get over 6 GW of powerbull Large nuclear plants are usually 1ndash2 GWbull 11 other dams in US in 1ndash2 GW rangebull 74 GW total hydroelectric capacity presently

28

Importance of Hydroelectricity

29

Hydroelectric potential by region in GW

Region Potential

Developed

Undeveloped

Developed

New England 63 19 44 301

Middle Atlantic 98 49 49 500

East North Central 29 12 17 413

West North Central

62 31 31 500

South Atlantic 139 67 72 482

East South Central 83 59 24 711

West South Central

73 27 46 369

Mountain 286 95 191 332

Pacific 644 382 262 593

Total 1477 741 736 502

30

iClicker Question

bull What is true about hydroelectric power generation since 1950ndash A It has always increased in MW producedndash B It has always decreased in MW producedndash C It has increased and decreased in total

MW produced but is now at a peakndash D It has both increased and decreased in

total MW producedndash E The percentage of electric power

produced by hydroelectric plants has generally increased over time

31

iClicker Question

bull What is true about hydroelectric power generation since 1950ndash A It has always increased in MW producedndash B It has always decreased in MW producedndash C It has increased and decreased in total

MW produced but is now at a peakndash D It has both increased and decreased in

total MW producedndash E The percentage of electric power

produced by hydroelectric plants has generally increased over time

32

Hydroelectricity in the future

bull Wersquore almost tapped-outndash 50 of potential is developedndash remaining potential in large number of small-scale

unitsbull Problems with dams

ndash silt limits lifetime to 50ndash200 years after which dam is useless and in fact a potential disaster and nagging maintenance site

ndash habitat loss for fish (salmon) etc wrecks otherwise stunning landscapes (Glenn Canyon in UT)

ndash Disasters waiting to happen 1680 deaths in US alone from 1918ndash1958 often upstream from major population centers

33

Sorry try againhellip

bull So hydroelectricity is a nice ldquofreebeerdquo handed to us by nature but itrsquos not enough to cover our appetite for energy

bull Though very efficient and seemingly environmentally friendly dams do have their problems

bull This isnrsquot the answer to all our energy problems though it is likely to maintain a role well into our future

34

Wind Energy

35

The Power of Wind

bull Wersquove talked about the kinetic energy in wind beforendash a wind traveling at speed v covers v meters

every second (if v is expressed in ms)ndash the kinetic energy hitting a square meter is

then the kinetic energy the mass of air defined by a rectangular tube

ndash tube is one square meter by v meters or v m3

ndash density of air is = 13 kgm3 at sea levelndash mass is v kgndash KE = frac12(v)v2 = frac12v3 (per square meter)

065v3 at sea level

36

Wind Energy proportional to cube of velocity

bull The book (p 134) says power per square meter is 061v3 which is a more-or-less identical resultndash might account for average density in

continental US (above sea level so air slightly less dense)

bull So if the wind speed doubles the power available in the wind increases by 23 = 222 = 8 times

bull A wind of 10 ms (22 mph) has a power density of 610 Wm2

bull A wind of 20 ms (44 mph) has a power density of 4880 Wm2

37

Canrsquot get it all

bull A windmill canrsquot extract all of the kinetic energy available in the wind because this would mean stopping the wind entirely

bull Stopped wind would divert oncoming wind around it and the windmill would stop spinning

bull On the other hand if you donrsquot slow the wind down much at all you wonrsquot get much energy

bull Theoretical maximum performance is 59 of energy extractedndash corresponds to reducing velocity by 36

38

Practical Efficiencies

bull Modern windmills attain maybe 50ndash70 of the theoretical maximumndash 05ndash07 times 059 is 030ndash041 or

about 30ndash40ndash this figure is the mechanical energy

extracted from the windbull Conversion from mechanical to

electrical is 90 efficientndash 09 times 030ndash041 is 27ndash37

39

iClicker Question

bull What is about the maximum efficiency of energy generation using the windndash A 20ndash B 40ndash C 60ndash D 80ndash E 100

40

iClicker Question

bull What is about the maximum efficiency of energy generation using the windndash A 20ndash B 40ndash C 60ndash D 80ndash E 100

41

Achievable efficiencies

42

Typical Windmillsbull A typical windmill might be 15 m in diameter

ndash 176 m2

bull At 10 ms wind 40 efficiency this delivers about 100 kW of power

ndash this would be 800 kW at 20 msndash typical windmills are rated at 50 to 600 kW

bull How much energy per yearndash 10 ms 610 Wm2 40 240 Wm2 8760 hours per

year 2000 kWh per year per square meterndash but wind is intermittent real range from 100ndash500 kWhm2

ndash corresponds to 11ndash57 Wm2 average available power density

bull Note the really high tip speeds bird killers

43

Average available wind powerrecall that average solar insolation is about 150ndash250 Wm2

44

Comparable to solar

bull These numbers are similar to solar if not a little biggerndash Letrsquos go to wind

bull BUT the ldquoper square meterrdquo is not land areamdashitrsquos rotor area

bull Doesnrsquot pay to space windmills too closelymdashone robs the other of energy

bull Typical arrangements have rotors 10 diameters apart in direction of prevailing wind 5 diameters apart in the cross-wind directionndash works out to 16 ldquofill factorrdquo

45

Current implementations

bull Rapidly developing resourcendash 1400 MW in 1989 up to 6400 MW in 2003ndash but still insignificant total (compare to large

dams)ndash cost (at 5ndash7cent per kWh) is competitivendash growing at 25 per yearndash expect to triple over next ten years

bull Current capacity 116 GW (April 2007)ndash Texas 2768 MW (recently took lead over

California)ndash California 2361 MWndash Iowa 936 MWndash Minnesota 895 MWndash Washington 818 MW

46

Flies in the Ointment

bull Find that only 20 of rated capacity is achievedndash design for high wind but seldom get it

bull Only 12 of electrical capacity in US is now windndash total electrical capacity in US is 948 GWndash tripling in ten years means 36ndash but achieving only 20 of capacity reduces

substantiallybull If fully developed we could generate an average

power almost equal to our current electrical capacity (764 GW)

ndash but highly variable resource and problematic if more than 20 comes from the intermittent wind

47

iClicker Question

bull Which state generates the most amount of electricity derived from wind powerndash A Virginiandash B Alaskandash C Montanandash D Californiandash E Texas

48

iClicker Question

bull Which state generates the most amount of electricity derived from wind powerndash A Virginiandash B Alaskandash C Montanandash D Californiandash E Texas

• Renewable Energy Sources II Alternatives Part I
• Chapter 5 Summary
• Slide 3
• Slide 4
• Slide 5
• Slide 6
• Slide 7
• Slide 8
• Slide 9
• Slide 10
• Slide 11
• Slide 12
• Slide 13
• Slide 14
• Renewable Resources Discussed in Book
• Renewable Energy Consumption
• Another look at available energy flow
• The Renewable Budget
• Outstanding Points from Fig 51
• Energy Flow continued
• The Hydrologic Cycle
• Energetics of the hydrologic cycle
• Let it Rain
• How much of the process do we get to keep
• iClicker Question
• Slide 26
• Power of a hydroelectric dam
• Importance of Hydroelectricity
• Hydroelectric potential by region in GW
• Slide 30
• Slide 31
• Hydroelectricity in the future
• Sorry try againhellip
• Wind Energy
• The Power of Wind
• Wind Energy proportional to cube of velocity
• Canrsquot get it all
• Practical Efficiencies
• Slide 39
• Slide 40
• Achievable efficiencies
• Typical Windmills
• Average available wind power
• Comparable to solar
• Current implementations
• Flies in the Ointment
• Slide 47
• Slide 48

16

Renewable Energy Consumption

Energy Source

QBtu (1994)

Percent (1994)

QBtu (2003)

Percent (2003)

Hydroelectric 3037 343 2779 283

Geothermal 0357 040 0314 032

Biomass 2852 322 2884 294

Solar Energy 0069 0077 0063 006

Wind 0036 0040 0108 011

Total 6351 718 615 63

17

Another look at available energy flow

bull The flow of radiation (solar and thermal) was covered previouslyndash earth is in an energy balance energy in =

energy outndash 30 reflected 70 thermally re-radiated

bull Some of the incident energy is absorbed but what exactly does this dondash much goes into heating the airlandndash much goes into driving weather (rain wind)ndash some goes into ocean currentsndash some goes into photosynthesis

18

The Renewable Budget

19

Outstanding Points from Fig 51

bull Incident radiation is 1741015 Wndash this is 1370 Wm2 times area facing sun

(R2)bull 30 directly reflected back to space

ndash off clouds air landbull 47 goes into heating air land waterbull 23 goes into evaporating water

precipitation etc (part of weather)bull Adds to 100 so wersquore done

ndash but wait therersquos morehellip

20

Energy Flow continued

bull 021 goes into wind waves convection currentsndash note this is 100 times less than driving the water

cyclendash but this is the ldquootherrdquo aspect of weather

bull 0023 is stored as chemical energy in plants via photosynthesis

ndash total is 401012 W half in ocean (plankton)ndash humans are 6 billion times 100 W = 061012 Wndash this is 15 of bio-energy 000034 of incident

powerbull All of this (bio-activity wind weather etc) ends up

creating heat and re-radiating to spacendash except some small amount of storage in fossil fuels

21

The Hydrologic Cycle

Lots of energy associated with evaporationboth mgh (4 for 10 km lift) and latent heat (96) of water

22

Energetics of the hydrologic cycle

bull It takes energy to evaporate water 2444 J per gramndash this is why ldquoswamp coolersrdquo work evaporation

pulls heat out of environment making it feel cooler

ndash 23 of sunrsquos incident energy goes into evaporation

bull By contrast raising one gram of water to the top of the troposphere (10000 m or 33000 ft) takes

mgh = (0001 kg)(10 ms2)(10000 m) = 100 J

bull So gt 96 of the energy associated with forming clouds is the evaporation lt 4 in lifting against gravity

23

Let it Rain

bull When water condenses in clouds it re-releases this ldquolatent heatrdquo

ndash but this is re-radiated and is of no consequence to hydro-power

bull When it rains the gravitational potential energy is released mostly as kinetic energy and ultimately heat

bull Some tiny bit of gravitational potential energy remains IF the rain falls on terrain (eg higher than sea level where it originated)

ndash hydroelectric plants use this tiny left-over energy itrsquos the energy that drives the flow of streams and rivers

ndash damming up a river concentrates the potential energy in one location for easy exploitation

24

How much of the process do we get to keep

bull According to Figure 51 401015 W of solar power goes into evaporation

ndash this corresponds to 161010 kg per second of evaporated water

ndash this is 35 mm per day off the ocean surface (replenished by rain)

bull The gravitational potential energy given to water vapor (mostly in clouds) in the atmosphere (per second) is thenmgh = (161010 kg)(10 ms2)(2000 m) = 321014 J

bull One can calculate that we gain access to only 25 of the total amount (and use only 125)

ndash based on the 18 land area of the US and the maximum potential of 1477 GW as presented in Table 52

25

iClicker Question

bull With respects to energy hydroelectric power representsndash A remnant electric power from stormsndash B remnant water energy from chemical

bondsndash C remnant energy of chemical bondingndash D remnant gravitational potential

energy of precipitationndash E a form of fictitious energy

26

iClicker Question

bull With respects to energy hydroelectric power representsndash A remnant electric power from stormsndash B remnant water energy from chemical

bondsndash C remnant energy of chemical bondingndash D remnant gravitational potential

energy of precipitationndash E a form of fictitious energy

27

Power of a hydroelectric dam

bull Most impressive is Grand Coulee in Washington on Columbia River

ndash 350 feet = 107 m of ldquoheadrdquondash gt 6000 m3s flow rate (Pacific Northwest gets

rain)ndash each cubic meter of water (1000 kg) has potential

energy mgh = (1000 kg)(10 ms2)(110 m) = 11 MJ

ndash At 6000 m3s get over 6 GW of powerbull Large nuclear plants are usually 1ndash2 GWbull 11 other dams in US in 1ndash2 GW rangebull 74 GW total hydroelectric capacity presently

28

Importance of Hydroelectricity

29

Hydroelectric potential by region in GW

Region Potential

Developed

Undeveloped

Developed

New England 63 19 44 301

Middle Atlantic 98 49 49 500

East North Central 29 12 17 413

West North Central

62 31 31 500

South Atlantic 139 67 72 482

East South Central 83 59 24 711

West South Central

73 27 46 369

Mountain 286 95 191 332

Pacific 644 382 262 593

Total 1477 741 736 502

30

iClicker Question

bull What is true about hydroelectric power generation since 1950ndash A It has always increased in MW producedndash B It has always decreased in MW producedndash C It has increased and decreased in total

MW produced but is now at a peakndash D It has both increased and decreased in

total MW producedndash E The percentage of electric power

produced by hydroelectric plants has generally increased over time

31

iClicker Question

bull What is true about hydroelectric power generation since 1950ndash A It has always increased in MW producedndash B It has always decreased in MW producedndash C It has increased and decreased in total

MW produced but is now at a peakndash D It has both increased and decreased in

total MW producedndash E The percentage of electric power

produced by hydroelectric plants has generally increased over time

32

Hydroelectricity in the future

bull Wersquore almost tapped-outndash 50 of potential is developedndash remaining potential in large number of small-scale

unitsbull Problems with dams

ndash silt limits lifetime to 50ndash200 years after which dam is useless and in fact a potential disaster and nagging maintenance site

ndash habitat loss for fish (salmon) etc wrecks otherwise stunning landscapes (Glenn Canyon in UT)

ndash Disasters waiting to happen 1680 deaths in US alone from 1918ndash1958 often upstream from major population centers

33

Sorry try againhellip

bull So hydroelectricity is a nice ldquofreebeerdquo handed to us by nature but itrsquos not enough to cover our appetite for energy

bull Though very efficient and seemingly environmentally friendly dams do have their problems

bull This isnrsquot the answer to all our energy problems though it is likely to maintain a role well into our future

34

Wind Energy

35

The Power of Wind

bull Wersquove talked about the kinetic energy in wind beforendash a wind traveling at speed v covers v meters

every second (if v is expressed in ms)ndash the kinetic energy hitting a square meter is

then the kinetic energy the mass of air defined by a rectangular tube

ndash tube is one square meter by v meters or v m3

ndash density of air is = 13 kgm3 at sea levelndash mass is v kgndash KE = frac12(v)v2 = frac12v3 (per square meter)

065v3 at sea level

36

Wind Energy proportional to cube of velocity

bull The book (p 134) says power per square meter is 061v3 which is a more-or-less identical resultndash might account for average density in

continental US (above sea level so air slightly less dense)

bull So if the wind speed doubles the power available in the wind increases by 23 = 222 = 8 times

bull A wind of 10 ms (22 mph) has a power density of 610 Wm2

bull A wind of 20 ms (44 mph) has a power density of 4880 Wm2

37

Canrsquot get it all

bull A windmill canrsquot extract all of the kinetic energy available in the wind because this would mean stopping the wind entirely

bull Stopped wind would divert oncoming wind around it and the windmill would stop spinning

bull On the other hand if you donrsquot slow the wind down much at all you wonrsquot get much energy

bull Theoretical maximum performance is 59 of energy extractedndash corresponds to reducing velocity by 36

38

Practical Efficiencies

bull Modern windmills attain maybe 50ndash70 of the theoretical maximumndash 05ndash07 times 059 is 030ndash041 or

about 30ndash40ndash this figure is the mechanical energy

extracted from the windbull Conversion from mechanical to

electrical is 90 efficientndash 09 times 030ndash041 is 27ndash37

39

iClicker Question

bull What is about the maximum efficiency of energy generation using the windndash A 20ndash B 40ndash C 60ndash D 80ndash E 100

40

iClicker Question

bull What is about the maximum efficiency of energy generation using the windndash A 20ndash B 40ndash C 60ndash D 80ndash E 100

41

Achievable efficiencies

42

Typical Windmillsbull A typical windmill might be 15 m in diameter

ndash 176 m2

bull At 10 ms wind 40 efficiency this delivers about 100 kW of power

ndash this would be 800 kW at 20 msndash typical windmills are rated at 50 to 600 kW

bull How much energy per yearndash 10 ms 610 Wm2 40 240 Wm2 8760 hours per

year 2000 kWh per year per square meterndash but wind is intermittent real range from 100ndash500 kWhm2

ndash corresponds to 11ndash57 Wm2 average available power density

bull Note the really high tip speeds bird killers

43

Average available wind powerrecall that average solar insolation is about 150ndash250 Wm2

44

Comparable to solar

bull These numbers are similar to solar if not a little biggerndash Letrsquos go to wind

bull BUT the ldquoper square meterrdquo is not land areamdashitrsquos rotor area

bull Doesnrsquot pay to space windmills too closelymdashone robs the other of energy

bull Typical arrangements have rotors 10 diameters apart in direction of prevailing wind 5 diameters apart in the cross-wind directionndash works out to 16 ldquofill factorrdquo

45

Current implementations

bull Rapidly developing resourcendash 1400 MW in 1989 up to 6400 MW in 2003ndash but still insignificant total (compare to large

dams)ndash cost (at 5ndash7cent per kWh) is competitivendash growing at 25 per yearndash expect to triple over next ten years

bull Current capacity 116 GW (April 2007)ndash Texas 2768 MW (recently took lead over

California)ndash California 2361 MWndash Iowa 936 MWndash Minnesota 895 MWndash Washington 818 MW

46

Flies in the Ointment

bull Find that only 20 of rated capacity is achievedndash design for high wind but seldom get it

bull Only 12 of electrical capacity in US is now windndash total electrical capacity in US is 948 GWndash tripling in ten years means 36ndash but achieving only 20 of capacity reduces

substantiallybull If fully developed we could generate an average

power almost equal to our current electrical capacity (764 GW)

ndash but highly variable resource and problematic if more than 20 comes from the intermittent wind

47

iClicker Question

bull Which state generates the most amount of electricity derived from wind powerndash A Virginiandash B Alaskandash C Montanandash D Californiandash E Texas

48

iClicker Question

bull Which state generates the most amount of electricity derived from wind powerndash A Virginiandash B Alaskandash C Montanandash D Californiandash E Texas

• Renewable Energy Sources II Alternatives Part I
• Chapter 5 Summary
• Slide 3
• Slide 4
• Slide 5
• Slide 6
• Slide 7
• Slide 8
• Slide 9
• Slide 10
• Slide 11
• Slide 12
• Slide 13
• Slide 14
• Renewable Resources Discussed in Book
• Renewable Energy Consumption
• Another look at available energy flow
• The Renewable Budget
• Outstanding Points from Fig 51
• Energy Flow continued
• The Hydrologic Cycle
• Energetics of the hydrologic cycle
• Let it Rain
• How much of the process do we get to keep
• iClicker Question
• Slide 26
• Power of a hydroelectric dam
• Importance of Hydroelectricity
• Hydroelectric potential by region in GW
• Slide 30
• Slide 31
• Hydroelectricity in the future
• Sorry try againhellip
• Wind Energy
• The Power of Wind
• Wind Energy proportional to cube of velocity
• Canrsquot get it all
• Practical Efficiencies
• Slide 39
• Slide 40
• Achievable efficiencies
• Typical Windmills
• Average available wind power
• Comparable to solar
• Current implementations
• Flies in the Ointment
• Slide 47
• Slide 48

17

Another look at available energy flow

bull The flow of radiation (solar and thermal) was covered previouslyndash earth is in an energy balance energy in =

energy outndash 30 reflected 70 thermally re-radiated

bull Some of the incident energy is absorbed but what exactly does this dondash much goes into heating the airlandndash much goes into driving weather (rain wind)ndash some goes into ocean currentsndash some goes into photosynthesis

18

The Renewable Budget

19

Outstanding Points from Fig 51

bull Incident radiation is 1741015 Wndash this is 1370 Wm2 times area facing sun

(R2)bull 30 directly reflected back to space

ndash off clouds air landbull 47 goes into heating air land waterbull 23 goes into evaporating water

precipitation etc (part of weather)bull Adds to 100 so wersquore done

ndash but wait therersquos morehellip

20

Energy Flow continued

bull 021 goes into wind waves convection currentsndash note this is 100 times less than driving the water

cyclendash but this is the ldquootherrdquo aspect of weather

bull 0023 is stored as chemical energy in plants via photosynthesis

ndash total is 401012 W half in ocean (plankton)ndash humans are 6 billion times 100 W = 061012 Wndash this is 15 of bio-energy 000034 of incident

powerbull All of this (bio-activity wind weather etc) ends up

creating heat and re-radiating to spacendash except some small amount of storage in fossil fuels

21

The Hydrologic Cycle

Lots of energy associated with evaporationboth mgh (4 for 10 km lift) and latent heat (96) of water

22

Energetics of the hydrologic cycle

bull It takes energy to evaporate water 2444 J per gramndash this is why ldquoswamp coolersrdquo work evaporation

pulls heat out of environment making it feel cooler

ndash 23 of sunrsquos incident energy goes into evaporation

bull By contrast raising one gram of water to the top of the troposphere (10000 m or 33000 ft) takes

mgh = (0001 kg)(10 ms2)(10000 m) = 100 J

bull So gt 96 of the energy associated with forming clouds is the evaporation lt 4 in lifting against gravity

23

Let it Rain

bull When water condenses in clouds it re-releases this ldquolatent heatrdquo

ndash but this is re-radiated and is of no consequence to hydro-power

bull When it rains the gravitational potential energy is released mostly as kinetic energy and ultimately heat

bull Some tiny bit of gravitational potential energy remains IF the rain falls on terrain (eg higher than sea level where it originated)

ndash hydroelectric plants use this tiny left-over energy itrsquos the energy that drives the flow of streams and rivers

ndash damming up a river concentrates the potential energy in one location for easy exploitation

24

How much of the process do we get to keep

bull According to Figure 51 401015 W of solar power goes into evaporation

ndash this corresponds to 161010 kg per second of evaporated water

ndash this is 35 mm per day off the ocean surface (replenished by rain)

bull The gravitational potential energy given to water vapor (mostly in clouds) in the atmosphere (per second) is thenmgh = (161010 kg)(10 ms2)(2000 m) = 321014 J

bull One can calculate that we gain access to only 25 of the total amount (and use only 125)

ndash based on the 18 land area of the US and the maximum potential of 1477 GW as presented in Table 52

25

iClicker Question

bull With respects to energy hydroelectric power representsndash A remnant electric power from stormsndash B remnant water energy from chemical

bondsndash C remnant energy of chemical bondingndash D remnant gravitational potential

energy of precipitationndash E a form of fictitious energy

26

iClicker Question

bull With respects to energy hydroelectric power representsndash A remnant electric power from stormsndash B remnant water energy from chemical

bondsndash C remnant energy of chemical bondingndash D remnant gravitational potential

energy of precipitationndash E a form of fictitious energy

27

Power of a hydroelectric dam

bull Most impressive is Grand Coulee in Washington on Columbia River

ndash 350 feet = 107 m of ldquoheadrdquondash gt 6000 m3s flow rate (Pacific Northwest gets

rain)ndash each cubic meter of water (1000 kg) has potential

energy mgh = (1000 kg)(10 ms2)(110 m) = 11 MJ

ndash At 6000 m3s get over 6 GW of powerbull Large nuclear plants are usually 1ndash2 GWbull 11 other dams in US in 1ndash2 GW rangebull 74 GW total hydroelectric capacity presently

28

Importance of Hydroelectricity

29

Hydroelectric potential by region in GW

Region Potential

Developed

Undeveloped

Developed

New England 63 19 44 301

Middle Atlantic 98 49 49 500

East North Central 29 12 17 413

West North Central

62 31 31 500

South Atlantic 139 67 72 482

East South Central 83 59 24 711

West South Central

73 27 46 369

Mountain 286 95 191 332

Pacific 644 382 262 593

Total 1477 741 736 502

30

iClicker Question

bull What is true about hydroelectric power generation since 1950ndash A It has always increased in MW producedndash B It has always decreased in MW producedndash C It has increased and decreased in total

MW produced but is now at a peakndash D It has both increased and decreased in

total MW producedndash E The percentage of electric power

produced by hydroelectric plants has generally increased over time

31

iClicker Question

bull What is true about hydroelectric power generation since 1950ndash A It has always increased in MW producedndash B It has always decreased in MW producedndash C It has increased and decreased in total

MW produced but is now at a peakndash D It has both increased and decreased in

total MW producedndash E The percentage of electric power

produced by hydroelectric plants has generally increased over time

32

Hydroelectricity in the future

bull Wersquore almost tapped-outndash 50 of potential is developedndash remaining potential in large number of small-scale

unitsbull Problems with dams

ndash silt limits lifetime to 50ndash200 years after which dam is useless and in fact a potential disaster and nagging maintenance site

ndash habitat loss for fish (salmon) etc wrecks otherwise stunning landscapes (Glenn Canyon in UT)

ndash Disasters waiting to happen 1680 deaths in US alone from 1918ndash1958 often upstream from major population centers

33

Sorry try againhellip

bull So hydroelectricity is a nice ldquofreebeerdquo handed to us by nature but itrsquos not enough to cover our appetite for energy

bull Though very efficient and seemingly environmentally friendly dams do have their problems

bull This isnrsquot the answer to all our energy problems though it is likely to maintain a role well into our future

34

Wind Energy

35

The Power of Wind

bull Wersquove talked about the kinetic energy in wind beforendash a wind traveling at speed v covers v meters

every second (if v is expressed in ms)ndash the kinetic energy hitting a square meter is

then the kinetic energy the mass of air defined by a rectangular tube

ndash tube is one square meter by v meters or v m3

ndash density of air is = 13 kgm3 at sea levelndash mass is v kgndash KE = frac12(v)v2 = frac12v3 (per square meter)

065v3 at sea level

36

Wind Energy proportional to cube of velocity

bull The book (p 134) says power per square meter is 061v3 which is a more-or-less identical resultndash might account for average density in

continental US (above sea level so air slightly less dense)

bull So if the wind speed doubles the power available in the wind increases by 23 = 222 = 8 times

bull A wind of 10 ms (22 mph) has a power density of 610 Wm2

bull A wind of 20 ms (44 mph) has a power density of 4880 Wm2

37

Canrsquot get it all

bull A windmill canrsquot extract all of the kinetic energy available in the wind because this would mean stopping the wind entirely

bull Stopped wind would divert oncoming wind around it and the windmill would stop spinning

bull On the other hand if you donrsquot slow the wind down much at all you wonrsquot get much energy

bull Theoretical maximum performance is 59 of energy extractedndash corresponds to reducing velocity by 36

38

Practical Efficiencies

bull Modern windmills attain maybe 50ndash70 of the theoretical maximumndash 05ndash07 times 059 is 030ndash041 or

about 30ndash40ndash this figure is the mechanical energy

extracted from the windbull Conversion from mechanical to

electrical is 90 efficientndash 09 times 030ndash041 is 27ndash37

39

iClicker Question

bull What is about the maximum efficiency of energy generation using the windndash A 20ndash B 40ndash C 60ndash D 80ndash E 100

40

iClicker Question

bull What is about the maximum efficiency of energy generation using the windndash A 20ndash B 40ndash C 60ndash D 80ndash E 100

41

Achievable efficiencies

42

Typical Windmillsbull A typical windmill might be 15 m in diameter

ndash 176 m2

bull At 10 ms wind 40 efficiency this delivers about 100 kW of power

ndash this would be 800 kW at 20 msndash typical windmills are rated at 50 to 600 kW

bull How much energy per yearndash 10 ms 610 Wm2 40 240 Wm2 8760 hours per

year 2000 kWh per year per square meterndash but wind is intermittent real range from 100ndash500 kWhm2

ndash corresponds to 11ndash57 Wm2 average available power density

bull Note the really high tip speeds bird killers

43

Average available wind powerrecall that average solar insolation is about 150ndash250 Wm2

44

Comparable to solar

bull These numbers are similar to solar if not a little biggerndash Letrsquos go to wind

bull BUT the ldquoper square meterrdquo is not land areamdashitrsquos rotor area

bull Doesnrsquot pay to space windmills too closelymdashone robs the other of energy

bull Typical arrangements have rotors 10 diameters apart in direction of prevailing wind 5 diameters apart in the cross-wind directionndash works out to 16 ldquofill factorrdquo

45

Current implementations

bull Rapidly developing resourcendash 1400 MW in 1989 up to 6400 MW in 2003ndash but still insignificant total (compare to large

dams)ndash cost (at 5ndash7cent per kWh) is competitivendash growing at 25 per yearndash expect to triple over next ten years

bull Current capacity 116 GW (April 2007)ndash Texas 2768 MW (recently took lead over

California)ndash California 2361 MWndash Iowa 936 MWndash Minnesota 895 MWndash Washington 818 MW

46

Flies in the Ointment

bull Find that only 20 of rated capacity is achievedndash design for high wind but seldom get it

bull Only 12 of electrical capacity in US is now windndash total electrical capacity in US is 948 GWndash tripling in ten years means 36ndash but achieving only 20 of capacity reduces

substantiallybull If fully developed we could generate an average

power almost equal to our current electrical capacity (764 GW)

ndash but highly variable resource and problematic if more than 20 comes from the intermittent wind

47

iClicker Question

bull Which state generates the most amount of electricity derived from wind powerndash A Virginiandash B Alaskandash C Montanandash D Californiandash E Texas

48

iClicker Question

bull Which state generates the most amount of electricity derived from wind powerndash A Virginiandash B Alaskandash C Montanandash D Californiandash E Texas

• Renewable Energy Sources II Alternatives Part I
• Chapter 5 Summary
• Slide 3
• Slide 4
• Slide 5
• Slide 6
• Slide 7
• Slide 8
• Slide 9
• Slide 10
• Slide 11
• Slide 12
• Slide 13
• Slide 14
• Renewable Resources Discussed in Book
• Renewable Energy Consumption
• Another look at available energy flow
• The Renewable Budget
• Outstanding Points from Fig 51
• Energy Flow continued
• The Hydrologic Cycle
• Energetics of the hydrologic cycle
• Let it Rain
• How much of the process do we get to keep
• iClicker Question
• Slide 26
• Power of a hydroelectric dam
• Importance of Hydroelectricity
• Hydroelectric potential by region in GW
• Slide 30
• Slide 31
• Hydroelectricity in the future
• Sorry try againhellip
• Wind Energy
• The Power of Wind
• Wind Energy proportional to cube of velocity
• Canrsquot get it all
• Practical Efficiencies
• Slide 39
• Slide 40
• Achievable efficiencies
• Typical Windmills
• Average available wind power
• Comparable to solar
• Current implementations
• Flies in the Ointment
• Slide 47
• Slide 48

18

The Renewable Budget

19

Outstanding Points from Fig 51

bull Incident radiation is 1741015 Wndash this is 1370 Wm2 times area facing sun

(R2)bull 30 directly reflected back to space

ndash off clouds air landbull 47 goes into heating air land waterbull 23 goes into evaporating water

precipitation etc (part of weather)bull Adds to 100 so wersquore done

ndash but wait therersquos morehellip

20

Energy Flow continued

bull 021 goes into wind waves convection currentsndash note this is 100 times less than driving the water

cyclendash but this is the ldquootherrdquo aspect of weather

bull 0023 is stored as chemical energy in plants via photosynthesis

ndash total is 401012 W half in ocean (plankton)ndash humans are 6 billion times 100 W = 061012 Wndash this is 15 of bio-energy 000034 of incident

powerbull All of this (bio-activity wind weather etc) ends up

creating heat and re-radiating to spacendash except some small amount of storage in fossil fuels

21

The Hydrologic Cycle

Lots of energy associated with evaporationboth mgh (4 for 10 km lift) and latent heat (96) of water

22

Energetics of the hydrologic cycle

bull It takes energy to evaporate water 2444 J per gramndash this is why ldquoswamp coolersrdquo work evaporation

pulls heat out of environment making it feel cooler

ndash 23 of sunrsquos incident energy goes into evaporation

bull By contrast raising one gram of water to the top of the troposphere (10000 m or 33000 ft) takes

mgh = (0001 kg)(10 ms2)(10000 m) = 100 J

bull So gt 96 of the energy associated with forming clouds is the evaporation lt 4 in lifting against gravity

23

Let it Rain

bull When water condenses in clouds it re-releases this ldquolatent heatrdquo

ndash but this is re-radiated and is of no consequence to hydro-power

bull When it rains the gravitational potential energy is released mostly as kinetic energy and ultimately heat

bull Some tiny bit of gravitational potential energy remains IF the rain falls on terrain (eg higher than sea level where it originated)

ndash hydroelectric plants use this tiny left-over energy itrsquos the energy that drives the flow of streams and rivers

ndash damming up a river concentrates the potential energy in one location for easy exploitation

24

How much of the process do we get to keep

bull According to Figure 51 401015 W of solar power goes into evaporation

ndash this corresponds to 161010 kg per second of evaporated water

ndash this is 35 mm per day off the ocean surface (replenished by rain)

bull The gravitational potential energy given to water vapor (mostly in clouds) in the atmosphere (per second) is thenmgh = (161010 kg)(10 ms2)(2000 m) = 321014 J

bull One can calculate that we gain access to only 25 of the total amount (and use only 125)

ndash based on the 18 land area of the US and the maximum potential of 1477 GW as presented in Table 52

25

iClicker Question

bull With respects to energy hydroelectric power representsndash A remnant electric power from stormsndash B remnant water energy from chemical

bondsndash C remnant energy of chemical bondingndash D remnant gravitational potential

energy of precipitationndash E a form of fictitious energy

26

iClicker Question

bull With respects to energy hydroelectric power representsndash A remnant electric power from stormsndash B remnant water energy from chemical

bondsndash C remnant energy of chemical bondingndash D remnant gravitational potential

energy of precipitationndash E a form of fictitious energy

27

Power of a hydroelectric dam

bull Most impressive is Grand Coulee in Washington on Columbia River

ndash 350 feet = 107 m of ldquoheadrdquondash gt 6000 m3s flow rate (Pacific Northwest gets

rain)ndash each cubic meter of water (1000 kg) has potential

energy mgh = (1000 kg)(10 ms2)(110 m) = 11 MJ

ndash At 6000 m3s get over 6 GW of powerbull Large nuclear plants are usually 1ndash2 GWbull 11 other dams in US in 1ndash2 GW rangebull 74 GW total hydroelectric capacity presently

28

Importance of Hydroelectricity

29

Hydroelectric potential by region in GW

Region Potential

Developed

Undeveloped

Developed

New England 63 19 44 301

Middle Atlantic 98 49 49 500

East North Central 29 12 17 413

West North Central

62 31 31 500

South Atlantic 139 67 72 482

East South Central 83 59 24 711

West South Central

73 27 46 369

Mountain 286 95 191 332

Pacific 644 382 262 593

Total 1477 741 736 502

30

iClicker Question

bull What is true about hydroelectric power generation since 1950ndash A It has always increased in MW producedndash B It has always decreased in MW producedndash C It has increased and decreased in total

MW produced but is now at a peakndash D It has both increased and decreased in

total MW producedndash E The percentage of electric power

produced by hydroelectric plants has generally increased over time

31

iClicker Question

bull What is true about hydroelectric power generation since 1950ndash A It has always increased in MW producedndash B It has always decreased in MW producedndash C It has increased and decreased in total

MW produced but is now at a peakndash D It has both increased and decreased in

total MW producedndash E The percentage of electric power

produced by hydroelectric plants has generally increased over time

32

Hydroelectricity in the future

bull Wersquore almost tapped-outndash 50 of potential is developedndash remaining potential in large number of small-scale

unitsbull Problems with dams

ndash silt limits lifetime to 50ndash200 years after which dam is useless and in fact a potential disaster and nagging maintenance site

ndash habitat loss for fish (salmon) etc wrecks otherwise stunning landscapes (Glenn Canyon in UT)

ndash Disasters waiting to happen 1680 deaths in US alone from 1918ndash1958 often upstream from major population centers

33

Sorry try againhellip

bull So hydroelectricity is a nice ldquofreebeerdquo handed to us by nature but itrsquos not enough to cover our appetite for energy

bull Though very efficient and seemingly environmentally friendly dams do have their problems

bull This isnrsquot the answer to all our energy problems though it is likely to maintain a role well into our future

34

Wind Energy

35

The Power of Wind

bull Wersquove talked about the kinetic energy in wind beforendash a wind traveling at speed v covers v meters

every second (if v is expressed in ms)ndash the kinetic energy hitting a square meter is

then the kinetic energy the mass of air defined by a rectangular tube

ndash tube is one square meter by v meters or v m3

ndash density of air is = 13 kgm3 at sea levelndash mass is v kgndash KE = frac12(v)v2 = frac12v3 (per square meter)

065v3 at sea level

36

Wind Energy proportional to cube of velocity

bull The book (p 134) says power per square meter is 061v3 which is a more-or-less identical resultndash might account for average density in

continental US (above sea level so air slightly less dense)

bull So if the wind speed doubles the power available in the wind increases by 23 = 222 = 8 times

bull A wind of 10 ms (22 mph) has a power density of 610 Wm2

bull A wind of 20 ms (44 mph) has a power density of 4880 Wm2

37

Canrsquot get it all

bull A windmill canrsquot extract all of the kinetic energy available in the wind because this would mean stopping the wind entirely

bull Stopped wind would divert oncoming wind around it and the windmill would stop spinning

bull On the other hand if you donrsquot slow the wind down much at all you wonrsquot get much energy

bull Theoretical maximum performance is 59 of energy extractedndash corresponds to reducing velocity by 36

38

Practical Efficiencies

bull Modern windmills attain maybe 50ndash70 of the theoretical maximumndash 05ndash07 times 059 is 030ndash041 or

about 30ndash40ndash this figure is the mechanical energy

extracted from the windbull Conversion from mechanical to

electrical is 90 efficientndash 09 times 030ndash041 is 27ndash37

39

iClicker Question

bull What is about the maximum efficiency of energy generation using the windndash A 20ndash B 40ndash C 60ndash D 80ndash E 100

40

iClicker Question

bull What is about the maximum efficiency of energy generation using the windndash A 20ndash B 40ndash C 60ndash D 80ndash E 100

41

Achievable efficiencies

42

Typical Windmillsbull A typical windmill might be 15 m in diameter

ndash 176 m2

bull At 10 ms wind 40 efficiency this delivers about 100 kW of power

ndash this would be 800 kW at 20 msndash typical windmills are rated at 50 to 600 kW

bull How much energy per yearndash 10 ms 610 Wm2 40 240 Wm2 8760 hours per

year 2000 kWh per year per square meterndash but wind is intermittent real range from 100ndash500 kWhm2

ndash corresponds to 11ndash57 Wm2 average available power density

bull Note the really high tip speeds bird killers

43

Average available wind powerrecall that average solar insolation is about 150ndash250 Wm2

44

Comparable to solar

bull These numbers are similar to solar if not a little biggerndash Letrsquos go to wind

bull BUT the ldquoper square meterrdquo is not land areamdashitrsquos rotor area

bull Doesnrsquot pay to space windmills too closelymdashone robs the other of energy

bull Typical arrangements have rotors 10 diameters apart in direction of prevailing wind 5 diameters apart in the cross-wind directionndash works out to 16 ldquofill factorrdquo

45

Current implementations

bull Rapidly developing resourcendash 1400 MW in 1989 up to 6400 MW in 2003ndash but still insignificant total (compare to large

dams)ndash cost (at 5ndash7cent per kWh) is competitivendash growing at 25 per yearndash expect to triple over next ten years

bull Current capacity 116 GW (April 2007)ndash Texas 2768 MW (recently took lead over

California)ndash California 2361 MWndash Iowa 936 MWndash Minnesota 895 MWndash Washington 818 MW

46

Flies in the Ointment

bull Find that only 20 of rated capacity is achievedndash design for high wind but seldom get it

bull Only 12 of electrical capacity in US is now windndash total electrical capacity in US is 948 GWndash tripling in ten years means 36ndash but achieving only 20 of capacity reduces

substantiallybull If fully developed we could generate an average

power almost equal to our current electrical capacity (764 GW)

ndash but highly variable resource and problematic if more than 20 comes from the intermittent wind

47

iClicker Question

bull Which state generates the most amount of electricity derived from wind powerndash A Virginiandash B Alaskandash C Montanandash D Californiandash E Texas

48

iClicker Question

bull Which state generates the most amount of electricity derived from wind powerndash A Virginiandash B Alaskandash C Montanandash D Californiandash E Texas

• Renewable Energy Sources II Alternatives Part I
• Chapter 5 Summary
• Slide 3
• Slide 4
• Slide 5
• Slide 6
• Slide 7
• Slide 8
• Slide 9
• Slide 10
• Slide 11
• Slide 12
• Slide 13
• Slide 14
• Renewable Resources Discussed in Book
• Renewable Energy Consumption
• Another look at available energy flow
• The Renewable Budget
• Outstanding Points from Fig 51
• Energy Flow continued
• The Hydrologic Cycle
• Energetics of the hydrologic cycle
• Let it Rain
• How much of the process do we get to keep
• iClicker Question
• Slide 26
• Power of a hydroelectric dam
• Importance of Hydroelectricity
• Hydroelectric potential by region in GW
• Slide 30
• Slide 31
• Hydroelectricity in the future
• Sorry try againhellip
• Wind Energy
• The Power of Wind
• Wind Energy proportional to cube of velocity
• Canrsquot get it all
• Practical Efficiencies
• Slide 39
• Slide 40
• Achievable efficiencies
• Typical Windmills
• Average available wind power
• Comparable to solar
• Current implementations
• Flies in the Ointment
• Slide 47
• Slide 48

19

Outstanding Points from Fig 51

bull Incident radiation is 1741015 Wndash this is 1370 Wm2 times area facing sun

(R2)bull 30 directly reflected back to space

ndash off clouds air landbull 47 goes into heating air land waterbull 23 goes into evaporating water

precipitation etc (part of weather)bull Adds to 100 so wersquore done

ndash but wait therersquos morehellip

20

Energy Flow continued

bull 021 goes into wind waves convection currentsndash note this is 100 times less than driving the water

cyclendash but this is the ldquootherrdquo aspect of weather

bull 0023 is stored as chemical energy in plants via photosynthesis

ndash total is 401012 W half in ocean (plankton)ndash humans are 6 billion times 100 W = 061012 Wndash this is 15 of bio-energy 000034 of incident

powerbull All of this (bio-activity wind weather etc) ends up

creating heat and re-radiating to spacendash except some small amount of storage in fossil fuels

21

The Hydrologic Cycle

Lots of energy associated with evaporationboth mgh (4 for 10 km lift) and latent heat (96) of water

22

Energetics of the hydrologic cycle

bull It takes energy to evaporate water 2444 J per gramndash this is why ldquoswamp coolersrdquo work evaporation

pulls heat out of environment making it feel cooler

ndash 23 of sunrsquos incident energy goes into evaporation

bull By contrast raising one gram of water to the top of the troposphere (10000 m or 33000 ft) takes

mgh = (0001 kg)(10 ms2)(10000 m) = 100 J

bull So gt 96 of the energy associated with forming clouds is the evaporation lt 4 in lifting against gravity

23

Let it Rain

bull When water condenses in clouds it re-releases this ldquolatent heatrdquo

ndash but this is re-radiated and is of no consequence to hydro-power

bull When it rains the gravitational potential energy is released mostly as kinetic energy and ultimately heat

bull Some tiny bit of gravitational potential energy remains IF the rain falls on terrain (eg higher than sea level where it originated)

ndash hydroelectric plants use this tiny left-over energy itrsquos the energy that drives the flow of streams and rivers

ndash damming up a river concentrates the potential energy in one location for easy exploitation

24

How much of the process do we get to keep

bull According to Figure 51 401015 W of solar power goes into evaporation

ndash this corresponds to 161010 kg per second of evaporated water

ndash this is 35 mm per day off the ocean surface (replenished by rain)

bull The gravitational potential energy given to water vapor (mostly in clouds) in the atmosphere (per second) is thenmgh = (161010 kg)(10 ms2)(2000 m) = 321014 J

bull One can calculate that we gain access to only 25 of the total amount (and use only 125)

ndash based on the 18 land area of the US and the maximum potential of 1477 GW as presented in Table 52

25

iClicker Question

bull With respects to energy hydroelectric power representsndash A remnant electric power from stormsndash B remnant water energy from chemical

bondsndash C remnant energy of chemical bondingndash D remnant gravitational potential

energy of precipitationndash E a form of fictitious energy

26

iClicker Question

bull With respects to energy hydroelectric power representsndash A remnant electric power from stormsndash B remnant water energy from chemical

bondsndash C remnant energy of chemical bondingndash D remnant gravitational potential

energy of precipitationndash E a form of fictitious energy

27

Power of a hydroelectric dam

bull Most impressive is Grand Coulee in Washington on Columbia River

ndash 350 feet = 107 m of ldquoheadrdquondash gt 6000 m3s flow rate (Pacific Northwest gets

rain)ndash each cubic meter of water (1000 kg) has potential

energy mgh = (1000 kg)(10 ms2)(110 m) = 11 MJ

ndash At 6000 m3s get over 6 GW of powerbull Large nuclear plants are usually 1ndash2 GWbull 11 other dams in US in 1ndash2 GW rangebull 74 GW total hydroelectric capacity presently

28

Importance of Hydroelectricity

29

Hydroelectric potential by region in GW

Region Potential

Developed

Undeveloped

Developed

New England 63 19 44 301

Middle Atlantic 98 49 49 500

East North Central 29 12 17 413

West North Central

62 31 31 500

South Atlantic 139 67 72 482

East South Central 83 59 24 711

West South Central

73 27 46 369

Mountain 286 95 191 332

Pacific 644 382 262 593

Total 1477 741 736 502

30

iClicker Question

bull What is true about hydroelectric power generation since 1950ndash A It has always increased in MW producedndash B It has always decreased in MW producedndash C It has increased and decreased in total

MW produced but is now at a peakndash D It has both increased and decreased in

total MW producedndash E The percentage of electric power

produced by hydroelectric plants has generally increased over time

31

iClicker Question

bull What is true about hydroelectric power generation since 1950ndash A It has always increased in MW producedndash B It has always decreased in MW producedndash C It has increased and decreased in total

MW produced but is now at a peakndash D It has both increased and decreased in

total MW producedndash E The percentage of electric power

produced by hydroelectric plants has generally increased over time

32

Hydroelectricity in the future

bull Wersquore almost tapped-outndash 50 of potential is developedndash remaining potential in large number of small-scale

unitsbull Problems with dams

ndash silt limits lifetime to 50ndash200 years after which dam is useless and in fact a potential disaster and nagging maintenance site

ndash habitat loss for fish (salmon) etc wrecks otherwise stunning landscapes (Glenn Canyon in UT)

ndash Disasters waiting to happen 1680 deaths in US alone from 1918ndash1958 often upstream from major population centers

33

Sorry try againhellip

bull So hydroelectricity is a nice ldquofreebeerdquo handed to us by nature but itrsquos not enough to cover our appetite for energy

bull Though very efficient and seemingly environmentally friendly dams do have their problems

bull This isnrsquot the answer to all our energy problems though it is likely to maintain a role well into our future

34

Wind Energy

35

The Power of Wind

bull Wersquove talked about the kinetic energy in wind beforendash a wind traveling at speed v covers v meters

every second (if v is expressed in ms)ndash the kinetic energy hitting a square meter is

then the kinetic energy the mass of air defined by a rectangular tube

ndash tube is one square meter by v meters or v m3

ndash density of air is = 13 kgm3 at sea levelndash mass is v kgndash KE = frac12(v)v2 = frac12v3 (per square meter)

065v3 at sea level

36

Wind Energy proportional to cube of velocity

bull The book (p 134) says power per square meter is 061v3 which is a more-or-less identical resultndash might account for average density in

continental US (above sea level so air slightly less dense)

bull So if the wind speed doubles the power available in the wind increases by 23 = 222 = 8 times

bull A wind of 10 ms (22 mph) has a power density of 610 Wm2

bull A wind of 20 ms (44 mph) has a power density of 4880 Wm2

37

Canrsquot get it all

bull A windmill canrsquot extract all of the kinetic energy available in the wind because this would mean stopping the wind entirely

bull Stopped wind would divert oncoming wind around it and the windmill would stop spinning

bull On the other hand if you donrsquot slow the wind down much at all you wonrsquot get much energy

bull Theoretical maximum performance is 59 of energy extractedndash corresponds to reducing velocity by 36

38

Practical Efficiencies

bull Modern windmills attain maybe 50ndash70 of the theoretical maximumndash 05ndash07 times 059 is 030ndash041 or

about 30ndash40ndash this figure is the mechanical energy

extracted from the windbull Conversion from mechanical to

electrical is 90 efficientndash 09 times 030ndash041 is 27ndash37

39

iClicker Question

bull What is about the maximum efficiency of energy generation using the windndash A 20ndash B 40ndash C 60ndash D 80ndash E 100

40

iClicker Question

bull What is about the maximum efficiency of energy generation using the windndash A 20ndash B 40ndash C 60ndash D 80ndash E 100

41

Achievable efficiencies

42

Typical Windmillsbull A typical windmill might be 15 m in diameter

ndash 176 m2

bull At 10 ms wind 40 efficiency this delivers about 100 kW of power

ndash this would be 800 kW at 20 msndash typical windmills are rated at 50 to 600 kW

bull How much energy per yearndash 10 ms 610 Wm2 40 240 Wm2 8760 hours per

year 2000 kWh per year per square meterndash but wind is intermittent real range from 100ndash500 kWhm2

ndash corresponds to 11ndash57 Wm2 average available power density

bull Note the really high tip speeds bird killers

43

Average available wind powerrecall that average solar insolation is about 150ndash250 Wm2

44

Comparable to solar

bull These numbers are similar to solar if not a little biggerndash Letrsquos go to wind

bull BUT the ldquoper square meterrdquo is not land areamdashitrsquos rotor area

bull Doesnrsquot pay to space windmills too closelymdashone robs the other of energy

bull Typical arrangements have rotors 10 diameters apart in direction of prevailing wind 5 diameters apart in the cross-wind directionndash works out to 16 ldquofill factorrdquo

45

Current implementations

bull Rapidly developing resourcendash 1400 MW in 1989 up to 6400 MW in 2003ndash but still insignificant total (compare to large

dams)ndash cost (at 5ndash7cent per kWh) is competitivendash growing at 25 per yearndash expect to triple over next ten years

bull Current capacity 116 GW (April 2007)ndash Texas 2768 MW (recently took lead over

California)ndash California 2361 MWndash Iowa 936 MWndash Minnesota 895 MWndash Washington 818 MW

46

Flies in the Ointment

bull Find that only 20 of rated capacity is achievedndash design for high wind but seldom get it

bull Only 12 of electrical capacity in US is now windndash total electrical capacity in US is 948 GWndash tripling in ten years means 36ndash but achieving only 20 of capacity reduces

substantiallybull If fully developed we could generate an average

power almost equal to our current electrical capacity (764 GW)

ndash but highly variable resource and problematic if more than 20 comes from the intermittent wind

47

iClicker Question

bull Which state generates the most amount of electricity derived from wind powerndash A Virginiandash B Alaskandash C Montanandash D Californiandash E Texas

48

iClicker Question

bull Which state generates the most amount of electricity derived from wind powerndash A Virginiandash B Alaskandash C Montanandash D Californiandash E Texas

• Renewable Energy Sources II Alternatives Part I
• Chapter 5 Summary
• Slide 3
• Slide 4
• Slide 5
• Slide 6
• Slide 7
• Slide 8
• Slide 9
• Slide 10
• Slide 11
• Slide 12
• Slide 13
• Slide 14
• Renewable Resources Discussed in Book
• Renewable Energy Consumption
• Another look at available energy flow
• The Renewable Budget
• Outstanding Points from Fig 51
• Energy Flow continued
• The Hydrologic Cycle
• Energetics of the hydrologic cycle
• Let it Rain
• How much of the process do we get to keep
• iClicker Question
• Slide 26
• Power of a hydroelectric dam
• Importance of Hydroelectricity
• Hydroelectric potential by region in GW
• Slide 30
• Slide 31
• Hydroelectricity in the future
• Sorry try againhellip
• Wind Energy
• The Power of Wind
• Wind Energy proportional to cube of velocity
• Canrsquot get it all
• Practical Efficiencies
• Slide 39
• Slide 40
• Achievable efficiencies
• Typical Windmills
• Average available wind power
• Comparable to solar
• Current implementations
• Flies in the Ointment
• Slide 47
• Slide 48

20

Energy Flow continued

bull 021 goes into wind waves convection currentsndash note this is 100 times less than driving the water

cyclendash but this is the ldquootherrdquo aspect of weather

bull 0023 is stored as chemical energy in plants via photosynthesis

ndash total is 401012 W half in ocean (plankton)ndash humans are 6 billion times 100 W = 061012 Wndash this is 15 of bio-energy 000034 of incident

powerbull All of this (bio-activity wind weather etc) ends up

creating heat and re-radiating to spacendash except some small amount of storage in fossil fuels

21

The Hydrologic Cycle

Lots of energy associated with evaporationboth mgh (4 for 10 km lift) and latent heat (96) of water

22

Energetics of the hydrologic cycle

bull It takes energy to evaporate water 2444 J per gramndash this is why ldquoswamp coolersrdquo work evaporation

pulls heat out of environment making it feel cooler

ndash 23 of sunrsquos incident energy goes into evaporation

bull By contrast raising one gram of water to the top of the troposphere (10000 m or 33000 ft) takes

mgh = (0001 kg)(10 ms2)(10000 m) = 100 J

bull So gt 96 of the energy associated with forming clouds is the evaporation lt 4 in lifting against gravity

23

Let it Rain

bull When water condenses in clouds it re-releases this ldquolatent heatrdquo

ndash but this is re-radiated and is of no consequence to hydro-power

bull When it rains the gravitational potential energy is released mostly as kinetic energy and ultimately heat

bull Some tiny bit of gravitational potential energy remains IF the rain falls on terrain (eg higher than sea level where it originated)

ndash hydroelectric plants use this tiny left-over energy itrsquos the energy that drives the flow of streams and rivers

ndash damming up a river concentrates the potential energy in one location for easy exploitation

24

How much of the process do we get to keep

bull According to Figure 51 401015 W of solar power goes into evaporation

ndash this corresponds to 161010 kg per second of evaporated water

ndash this is 35 mm per day off the ocean surface (replenished by rain)

bull The gravitational potential energy given to water vapor (mostly in clouds) in the atmosphere (per second) is thenmgh = (161010 kg)(10 ms2)(2000 m) = 321014 J

bull One can calculate that we gain access to only 25 of the total amount (and use only 125)

ndash based on the 18 land area of the US and the maximum potential of 1477 GW as presented in Table 52

25

iClicker Question

bull With respects to energy hydroelectric power representsndash A remnant electric power from stormsndash B remnant water energy from chemical

bondsndash C remnant energy of chemical bondingndash D remnant gravitational potential

energy of precipitationndash E a form of fictitious energy

26

iClicker Question

bull With respects to energy hydroelectric power representsndash A remnant electric power from stormsndash B remnant water energy from chemical

bondsndash C remnant energy of chemical bondingndash D remnant gravitational potential

energy of precipitationndash E a form of fictitious energy

27

Power of a hydroelectric dam

bull Most impressive is Grand Coulee in Washington on Columbia River

ndash 350 feet = 107 m of ldquoheadrdquondash gt 6000 m3s flow rate (Pacific Northwest gets

rain)ndash each cubic meter of water (1000 kg) has potential

energy mgh = (1000 kg)(10 ms2)(110 m) = 11 MJ

ndash At 6000 m3s get over 6 GW of powerbull Large nuclear plants are usually 1ndash2 GWbull 11 other dams in US in 1ndash2 GW rangebull 74 GW total hydroelectric capacity presently

28

Importance of Hydroelectricity

29

Hydroelectric potential by region in GW

Region Potential

Developed

Undeveloped

Developed

New England 63 19 44 301

Middle Atlantic 98 49 49 500

East North Central 29 12 17 413

West North Central

62 31 31 500

South Atlantic 139 67 72 482

East South Central 83 59 24 711

West South Central

73 27 46 369

Mountain 286 95 191 332

Pacific 644 382 262 593

Total 1477 741 736 502

30

iClicker Question

bull What is true about hydroelectric power generation since 1950ndash A It has always increased in MW producedndash B It has always decreased in MW producedndash C It has increased and decreased in total

MW produced but is now at a peakndash D It has both increased and decreased in

total MW producedndash E The percentage of electric power

produced by hydroelectric plants has generally increased over time

31

iClicker Question

bull What is true about hydroelectric power generation since 1950ndash A It has always increased in MW producedndash B It has always decreased in MW producedndash C It has increased and decreased in total

MW produced but is now at a peakndash D It has both increased and decreased in

total MW producedndash E The percentage of electric power

produced by hydroelectric plants has generally increased over time

32

Hydroelectricity in the future

bull Wersquore almost tapped-outndash 50 of potential is developedndash remaining potential in large number of small-scale

unitsbull Problems with dams

ndash silt limits lifetime to 50ndash200 years after which dam is useless and in fact a potential disaster and nagging maintenance site

ndash habitat loss for fish (salmon) etc wrecks otherwise stunning landscapes (Glenn Canyon in UT)

ndash Disasters waiting to happen 1680 deaths in US alone from 1918ndash1958 often upstream from major population centers

33

Sorry try againhellip

bull So hydroelectricity is a nice ldquofreebeerdquo handed to us by nature but itrsquos not enough to cover our appetite for energy

bull Though very efficient and seemingly environmentally friendly dams do have their problems

bull This isnrsquot the answer to all our energy problems though it is likely to maintain a role well into our future

34

Wind Energy

35

The Power of Wind

bull Wersquove talked about the kinetic energy in wind beforendash a wind traveling at speed v covers v meters

every second (if v is expressed in ms)ndash the kinetic energy hitting a square meter is

then the kinetic energy the mass of air defined by a rectangular tube

ndash tube is one square meter by v meters or v m3

ndash density of air is = 13 kgm3 at sea levelndash mass is v kgndash KE = frac12(v)v2 = frac12v3 (per square meter)

065v3 at sea level

36

Wind Energy proportional to cube of velocity

bull The book (p 134) says power per square meter is 061v3 which is a more-or-less identical resultndash might account for average density in

continental US (above sea level so air slightly less dense)

bull So if the wind speed doubles the power available in the wind increases by 23 = 222 = 8 times

bull A wind of 10 ms (22 mph) has a power density of 610 Wm2

bull A wind of 20 ms (44 mph) has a power density of 4880 Wm2

37

Canrsquot get it all

bull A windmill canrsquot extract all of the kinetic energy available in the wind because this would mean stopping the wind entirely

bull Stopped wind would divert oncoming wind around it and the windmill would stop spinning

bull On the other hand if you donrsquot slow the wind down much at all you wonrsquot get much energy

bull Theoretical maximum performance is 59 of energy extractedndash corresponds to reducing velocity by 36

38

Practical Efficiencies

bull Modern windmills attain maybe 50ndash70 of the theoretical maximumndash 05ndash07 times 059 is 030ndash041 or

about 30ndash40ndash this figure is the mechanical energy

extracted from the windbull Conversion from mechanical to

electrical is 90 efficientndash 09 times 030ndash041 is 27ndash37

39

iClicker Question

bull What is about the maximum efficiency of energy generation using the windndash A 20ndash B 40ndash C 60ndash D 80ndash E 100

40

iClicker Question

bull What is about the maximum efficiency of energy generation using the windndash A 20ndash B 40ndash C 60ndash D 80ndash E 100

41

Achievable efficiencies

42

Typical Windmillsbull A typical windmill might be 15 m in diameter

ndash 176 m2

bull At 10 ms wind 40 efficiency this delivers about 100 kW of power

ndash this would be 800 kW at 20 msndash typical windmills are rated at 50 to 600 kW

bull How much energy per yearndash 10 ms 610 Wm2 40 240 Wm2 8760 hours per

year 2000 kWh per year per square meterndash but wind is intermittent real range from 100ndash500 kWhm2

ndash corresponds to 11ndash57 Wm2 average available power density

bull Note the really high tip speeds bird killers

43

Average available wind powerrecall that average solar insolation is about 150ndash250 Wm2

44

Comparable to solar

bull These numbers are similar to solar if not a little biggerndash Letrsquos go to wind

bull BUT the ldquoper square meterrdquo is not land areamdashitrsquos rotor area

bull Doesnrsquot pay to space windmills too closelymdashone robs the other of energy

bull Typical arrangements have rotors 10 diameters apart in direction of prevailing wind 5 diameters apart in the cross-wind directionndash works out to 16 ldquofill factorrdquo

45

Current implementations

bull Rapidly developing resourcendash 1400 MW in 1989 up to 6400 MW in 2003ndash but still insignificant total (compare to large

dams)ndash cost (at 5ndash7cent per kWh) is competitivendash growing at 25 per yearndash expect to triple over next ten years

bull Current capacity 116 GW (April 2007)ndash Texas 2768 MW (recently took lead over

California)ndash California 2361 MWndash Iowa 936 MWndash Minnesota 895 MWndash Washington 818 MW

46

Flies in the Ointment

bull Find that only 20 of rated capacity is achievedndash design for high wind but seldom get it

bull Only 12 of electrical capacity in US is now windndash total electrical capacity in US is 948 GWndash tripling in ten years means 36ndash but achieving only 20 of capacity reduces

substantiallybull If fully developed we could generate an average

power almost equal to our current electrical capacity (764 GW)

ndash but highly variable resource and problematic if more than 20 comes from the intermittent wind

47

iClicker Question

bull Which state generates the most amount of electricity derived from wind powerndash A Virginiandash B Alaskandash C Montanandash D Californiandash E Texas

48

iClicker Question

bull Which state generates the most amount of electricity derived from wind powerndash A Virginiandash B Alaskandash C Montanandash D Californiandash E Texas

• Renewable Energy Sources II Alternatives Part I
• Chapter 5 Summary
• Slide 3
• Slide 4
• Slide 5
• Slide 6
• Slide 7
• Slide 8
• Slide 9
• Slide 10
• Slide 11
• Slide 12
• Slide 13
• Slide 14
• Renewable Resources Discussed in Book
• Renewable Energy Consumption
• Another look at available energy flow
• The Renewable Budget
• Outstanding Points from Fig 51
• Energy Flow continued
• The Hydrologic Cycle
• Energetics of the hydrologic cycle
• Let it Rain
• How much of the process do we get to keep
• iClicker Question
• Slide 26
• Power of a hydroelectric dam
• Importance of Hydroelectricity
• Hydroelectric potential by region in GW
• Slide 30
• Slide 31
• Hydroelectricity in the future
• Sorry try againhellip
• Wind Energy
• The Power of Wind
• Wind Energy proportional to cube of velocity
• Canrsquot get it all
• Practical Efficiencies
• Slide 39
• Slide 40
• Achievable efficiencies
• Typical Windmills
• Average available wind power
• Comparable to solar
• Current implementations
• Flies in the Ointment
• Slide 47
• Slide 48

21

The Hydrologic Cycle

Lots of energy associated with evaporationboth mgh (4 for 10 km lift) and latent heat (96) of water

22

Energetics of the hydrologic cycle

bull It takes energy to evaporate water 2444 J per gramndash this is why ldquoswamp coolersrdquo work evaporation

pulls heat out of environment making it feel cooler

ndash 23 of sunrsquos incident energy goes into evaporation

bull By contrast raising one gram of water to the top of the troposphere (10000 m or 33000 ft) takes

mgh = (0001 kg)(10 ms2)(10000 m) = 100 J

bull So gt 96 of the energy associated with forming clouds is the evaporation lt 4 in lifting against gravity

23

Let it Rain

bull When water condenses in clouds it re-releases this ldquolatent heatrdquo

ndash but this is re-radiated and is of no consequence to hydro-power

bull When it rains the gravitational potential energy is released mostly as kinetic energy and ultimately heat

bull Some tiny bit of gravitational potential energy remains IF the rain falls on terrain (eg higher than sea level where it originated)

ndash hydroelectric plants use this tiny left-over energy itrsquos the energy that drives the flow of streams and rivers

ndash damming up a river concentrates the potential energy in one location for easy exploitation

24

How much of the process do we get to keep

bull According to Figure 51 401015 W of solar power goes into evaporation

ndash this corresponds to 161010 kg per second of evaporated water

ndash this is 35 mm per day off the ocean surface (replenished by rain)

bull The gravitational potential energy given to water vapor (mostly in clouds) in the atmosphere (per second) is thenmgh = (161010 kg)(10 ms2)(2000 m) = 321014 J

bull One can calculate that we gain access to only 25 of the total amount (and use only 125)

ndash based on the 18 land area of the US and the maximum potential of 1477 GW as presented in Table 52

25

iClicker Question

bull With respects to energy hydroelectric power representsndash A remnant electric power from stormsndash B remnant water energy from chemical

bondsndash C remnant energy of chemical bondingndash D remnant gravitational potential

energy of precipitationndash E a form of fictitious energy

26

iClicker Question

bull With respects to energy hydroelectric power representsndash A remnant electric power from stormsndash B remnant water energy from chemical

bondsndash C remnant energy of chemical bondingndash D remnant gravitational potential

energy of precipitationndash E a form of fictitious energy

27

Power of a hydroelectric dam

bull Most impressive is Grand Coulee in Washington on Columbia River

ndash 350 feet = 107 m of ldquoheadrdquondash gt 6000 m3s flow rate (Pacific Northwest gets

rain)ndash each cubic meter of water (1000 kg) has potential

energy mgh = (1000 kg)(10 ms2)(110 m) = 11 MJ

ndash At 6000 m3s get over 6 GW of powerbull Large nuclear plants are usually 1ndash2 GWbull 11 other dams in US in 1ndash2 GW rangebull 74 GW total hydroelectric capacity presently

28

Importance of Hydroelectricity

29

Hydroelectric potential by region in GW

Region Potential

Developed

Undeveloped

Developed

New England 63 19 44 301

Middle Atlantic 98 49 49 500

East North Central 29 12 17 413

West North Central

62 31 31 500

South Atlantic 139 67 72 482

East South Central 83 59 24 711

West South Central

73 27 46 369

Mountain 286 95 191 332

Pacific 644 382 262 593

Total 1477 741 736 502

30

iClicker Question

bull What is true about hydroelectric power generation since 1950ndash A It has always increased in MW producedndash B It has always decreased in MW producedndash C It has increased and decreased in total

MW produced but is now at a peakndash D It has both increased and decreased in

total MW producedndash E The percentage of electric power

produced by hydroelectric plants has generally increased over time

31

iClicker Question

bull What is true about hydroelectric power generation since 1950ndash A It has always increased in MW producedndash B It has always decreased in MW producedndash C It has increased and decreased in total

MW produced but is now at a peakndash D It has both increased and decreased in

total MW producedndash E The percentage of electric power

produced by hydroelectric plants has generally increased over time

32

Hydroelectricity in the future

bull Wersquore almost tapped-outndash 50 of potential is developedndash remaining potential in large number of small-scale

unitsbull Problems with dams

ndash silt limits lifetime to 50ndash200 years after which dam is useless and in fact a potential disaster and nagging maintenance site

ndash habitat loss for fish (salmon) etc wrecks otherwise stunning landscapes (Glenn Canyon in UT)

ndash Disasters waiting to happen 1680 deaths in US alone from 1918ndash1958 often upstream from major population centers

33

Sorry try againhellip

bull So hydroelectricity is a nice ldquofreebeerdquo handed to us by nature but itrsquos not enough to cover our appetite for energy

bull Though very efficient and seemingly environmentally friendly dams do have their problems

bull This isnrsquot the answer to all our energy problems though it is likely to maintain a role well into our future

34

Wind Energy

35

The Power of Wind

bull Wersquove talked about the kinetic energy in wind beforendash a wind traveling at speed v covers v meters

every second (if v is expressed in ms)ndash the kinetic energy hitting a square meter is

then the kinetic energy the mass of air defined by a rectangular tube

ndash tube is one square meter by v meters or v m3

ndash density of air is = 13 kgm3 at sea levelndash mass is v kgndash KE = frac12(v)v2 = frac12v3 (per square meter)

065v3 at sea level

36

Wind Energy proportional to cube of velocity

bull The book (p 134) says power per square meter is 061v3 which is a more-or-less identical resultndash might account for average density in

continental US (above sea level so air slightly less dense)

bull So if the wind speed doubles the power available in the wind increases by 23 = 222 = 8 times

bull A wind of 10 ms (22 mph) has a power density of 610 Wm2

bull A wind of 20 ms (44 mph) has a power density of 4880 Wm2

37

Canrsquot get it all

bull A windmill canrsquot extract all of the kinetic energy available in the wind because this would mean stopping the wind entirely

bull Stopped wind would divert oncoming wind around it and the windmill would stop spinning

bull On the other hand if you donrsquot slow the wind down much at all you wonrsquot get much energy

bull Theoretical maximum performance is 59 of energy extractedndash corresponds to reducing velocity by 36

38

Practical Efficiencies

bull Modern windmills attain maybe 50ndash70 of the theoretical maximumndash 05ndash07 times 059 is 030ndash041 or

about 30ndash40ndash this figure is the mechanical energy

extracted from the windbull Conversion from mechanical to

electrical is 90 efficientndash 09 times 030ndash041 is 27ndash37

39

iClicker Question

bull What is about the maximum efficiency of energy generation using the windndash A 20ndash B 40ndash C 60ndash D 80ndash E 100

40

iClicker Question

bull What is about the maximum efficiency of energy generation using the windndash A 20ndash B 40ndash C 60ndash D 80ndash E 100

41

Achievable efficiencies

42

Typical Windmillsbull A typical windmill might be 15 m in diameter

ndash 176 m2

bull At 10 ms wind 40 efficiency this delivers about 100 kW of power

ndash this would be 800 kW at 20 msndash typical windmills are rated at 50 to 600 kW

bull How much energy per yearndash 10 ms 610 Wm2 40 240 Wm2 8760 hours per

year 2000 kWh per year per square meterndash but wind is intermittent real range from 100ndash500 kWhm2

ndash corresponds to 11ndash57 Wm2 average available power density

bull Note the really high tip speeds bird killers

43

Average available wind powerrecall that average solar insolation is about 150ndash250 Wm2

44

Comparable to solar

bull These numbers are similar to solar if not a little biggerndash Letrsquos go to wind

bull BUT the ldquoper square meterrdquo is not land areamdashitrsquos rotor area

bull Doesnrsquot pay to space windmills too closelymdashone robs the other of energy

bull Typical arrangements have rotors 10 diameters apart in direction of prevailing wind 5 diameters apart in the cross-wind directionndash works out to 16 ldquofill factorrdquo

45

Current implementations

bull Rapidly developing resourcendash 1400 MW in 1989 up to 6400 MW in 2003ndash but still insignificant total (compare to large

dams)ndash cost (at 5ndash7cent per kWh) is competitivendash growing at 25 per yearndash expect to triple over next ten years

bull Current capacity 116 GW (April 2007)ndash Texas 2768 MW (recently took lead over

California)ndash California 2361 MWndash Iowa 936 MWndash Minnesota 895 MWndash Washington 818 MW

46

Flies in the Ointment

bull Find that only 20 of rated capacity is achievedndash design for high wind but seldom get it

bull Only 12 of electrical capacity in US is now windndash total electrical capacity in US is 948 GWndash tripling in ten years means 36ndash but achieving only 20 of capacity reduces

substantiallybull If fully developed we could generate an average

power almost equal to our current electrical capacity (764 GW)

ndash but highly variable resource and problematic if more than 20 comes from the intermittent wind

47

iClicker Question

bull Which state generates the most amount of electricity derived from wind powerndash A Virginiandash B Alaskandash C Montanandash D Californiandash E Texas

48

iClicker Question

bull Which state generates the most amount of electricity derived from wind powerndash A Virginiandash B Alaskandash C Montanandash D Californiandash E Texas

• Renewable Energy Sources II Alternatives Part I
• Chapter 5 Summary
• Slide 3
• Slide 4
• Slide 5
• Slide 6
• Slide 7
• Slide 8
• Slide 9
• Slide 10
• Slide 11
• Slide 12
• Slide 13
• Slide 14
• Renewable Resources Discussed in Book
• Renewable Energy Consumption
• Another look at available energy flow
• The Renewable Budget
• Outstanding Points from Fig 51
• Energy Flow continued
• The Hydrologic Cycle
• Energetics of the hydrologic cycle
• Let it Rain
• How much of the process do we get to keep
• iClicker Question
• Slide 26
• Power of a hydroelectric dam
• Importance of Hydroelectricity
• Hydroelectric potential by region in GW
• Slide 30
• Slide 31
• Hydroelectricity in the future
• Sorry try againhellip
• Wind Energy
• The Power of Wind
• Wind Energy proportional to cube of velocity
• Canrsquot get it all
• Practical Efficiencies
• Slide 39
• Slide 40
• Achievable efficiencies
• Typical Windmills
• Average available wind power
• Comparable to solar
• Current implementations
• Flies in the Ointment
• Slide 47
• Slide 48

22

Energetics of the hydrologic cycle

bull It takes energy to evaporate water 2444 J per gramndash this is why ldquoswamp coolersrdquo work evaporation

pulls heat out of environment making it feel cooler

ndash 23 of sunrsquos incident energy goes into evaporation

bull By contrast raising one gram of water to the top of the troposphere (10000 m or 33000 ft) takes

mgh = (0001 kg)(10 ms2)(10000 m) = 100 J

bull So gt 96 of the energy associated with forming clouds is the evaporation lt 4 in lifting against gravity

23

Let it Rain

bull When water condenses in clouds it re-releases this ldquolatent heatrdquo

ndash but this is re-radiated and is of no consequence to hydro-power

bull When it rains the gravitational potential energy is released mostly as kinetic energy and ultimately heat

bull Some tiny bit of gravitational potential energy remains IF the rain falls on terrain (eg higher than sea level where it originated)

ndash hydroelectric plants use this tiny left-over energy itrsquos the energy that drives the flow of streams and rivers

ndash damming up a river concentrates the potential energy in one location for easy exploitation

24

How much of the process do we get to keep

bull According to Figure 51 401015 W of solar power goes into evaporation

ndash this corresponds to 161010 kg per second of evaporated water

ndash this is 35 mm per day off the ocean surface (replenished by rain)

bull The gravitational potential energy given to water vapor (mostly in clouds) in the atmosphere (per second) is thenmgh = (161010 kg)(10 ms2)(2000 m) = 321014 J

bull One can calculate that we gain access to only 25 of the total amount (and use only 125)

ndash based on the 18 land area of the US and the maximum potential of 1477 GW as presented in Table 52

25

iClicker Question

bull With respects to energy hydroelectric power representsndash A remnant electric power from stormsndash B remnant water energy from chemical

bondsndash C remnant energy of chemical bondingndash D remnant gravitational potential

energy of precipitationndash E a form of fictitious energy

26

iClicker Question

bull With respects to energy hydroelectric power representsndash A remnant electric power from stormsndash B remnant water energy from chemical

bondsndash C remnant energy of chemical bondingndash D remnant gravitational potential

energy of precipitationndash E a form of fictitious energy

27

Power of a hydroelectric dam

bull Most impressive is Grand Coulee in Washington on Columbia River

ndash 350 feet = 107 m of ldquoheadrdquondash gt 6000 m3s flow rate (Pacific Northwest gets

rain)ndash each cubic meter of water (1000 kg) has potential

energy mgh = (1000 kg)(10 ms2)(110 m) = 11 MJ

ndash At 6000 m3s get over 6 GW of powerbull Large nuclear plants are usually 1ndash2 GWbull 11 other dams in US in 1ndash2 GW rangebull 74 GW total hydroelectric capacity presently

28

Importance of Hydroelectricity

29

Hydroelectric potential by region in GW

Region Potential

Developed

Undeveloped

Developed

New England 63 19 44 301

Middle Atlantic 98 49 49 500

East North Central 29 12 17 413

West North Central

62 31 31 500

South Atlantic 139 67 72 482

East South Central 83 59 24 711

West South Central

73 27 46 369

Mountain 286 95 191 332

Pacific 644 382 262 593

Total 1477 741 736 502

30

iClicker Question

bull What is true about hydroelectric power generation since 1950ndash A It has always increased in MW producedndash B It has always decreased in MW producedndash C It has increased and decreased in total

MW produced but is now at a peakndash D It has both increased and decreased in

total MW producedndash E The percentage of electric power

produced by hydroelectric plants has generally increased over time

31

iClicker Question

bull What is true about hydroelectric power generation since 1950ndash A It has always increased in MW producedndash B It has always decreased in MW producedndash C It has increased and decreased in total

MW produced but is now at a peakndash D It has both increased and decreased in

total MW producedndash E The percentage of electric power

produced by hydroelectric plants has generally increased over time

32

Hydroelectricity in the future

bull Wersquore almost tapped-outndash 50 of potential is developedndash remaining potential in large number of small-scale

unitsbull Problems with dams

ndash silt limits lifetime to 50ndash200 years after which dam is useless and in fact a potential disaster and nagging maintenance site

ndash habitat loss for fish (salmon) etc wrecks otherwise stunning landscapes (Glenn Canyon in UT)

ndash Disasters waiting to happen 1680 deaths in US alone from 1918ndash1958 often upstream from major population centers

33

Sorry try againhellip

bull So hydroelectricity is a nice ldquofreebeerdquo handed to us by nature but itrsquos not enough to cover our appetite for energy

bull Though very efficient and seemingly environmentally friendly dams do have their problems

bull This isnrsquot the answer to all our energy problems though it is likely to maintain a role well into our future

34

Wind Energy

35

The Power of Wind

bull Wersquove talked about the kinetic energy in wind beforendash a wind traveling at speed v covers v meters

every second (if v is expressed in ms)ndash the kinetic energy hitting a square meter is

then the kinetic energy the mass of air defined by a rectangular tube

ndash tube is one square meter by v meters or v m3

ndash density of air is = 13 kgm3 at sea levelndash mass is v kgndash KE = frac12(v)v2 = frac12v3 (per square meter)

065v3 at sea level

36

Wind Energy proportional to cube of velocity

bull The book (p 134) says power per square meter is 061v3 which is a more-or-less identical resultndash might account for average density in

continental US (above sea level so air slightly less dense)

bull So if the wind speed doubles the power available in the wind increases by 23 = 222 = 8 times

bull A wind of 10 ms (22 mph) has a power density of 610 Wm2

bull A wind of 20 ms (44 mph) has a power density of 4880 Wm2

37

Canrsquot get it all

bull A windmill canrsquot extract all of the kinetic energy available in the wind because this would mean stopping the wind entirely

bull Stopped wind would divert oncoming wind around it and the windmill would stop spinning

bull On the other hand if you donrsquot slow the wind down much at all you wonrsquot get much energy

bull Theoretical maximum performance is 59 of energy extractedndash corresponds to reducing velocity by 36

38

Practical Efficiencies

bull Modern windmills attain maybe 50ndash70 of the theoretical maximumndash 05ndash07 times 059 is 030ndash041 or

about 30ndash40ndash this figure is the mechanical energy

extracted from the windbull Conversion from mechanical to

electrical is 90 efficientndash 09 times 030ndash041 is 27ndash37

39

iClicker Question

bull What is about the maximum efficiency of energy generation using the windndash A 20ndash B 40ndash C 60ndash D 80ndash E 100

40

iClicker Question

bull What is about the maximum efficiency of energy generation using the windndash A 20ndash B 40ndash C 60ndash D 80ndash E 100

41

Achievable efficiencies

42

Typical Windmillsbull A typical windmill might be 15 m in diameter

ndash 176 m2

bull At 10 ms wind 40 efficiency this delivers about 100 kW of power

ndash this would be 800 kW at 20 msndash typical windmills are rated at 50 to 600 kW

bull How much energy per yearndash 10 ms 610 Wm2 40 240 Wm2 8760 hours per

year 2000 kWh per year per square meterndash but wind is intermittent real range from 100ndash500 kWhm2

ndash corresponds to 11ndash57 Wm2 average available power density

bull Note the really high tip speeds bird killers

43

Average available wind powerrecall that average solar insolation is about 150ndash250 Wm2

44

Comparable to solar

bull These numbers are similar to solar if not a little biggerndash Letrsquos go to wind

bull BUT the ldquoper square meterrdquo is not land areamdashitrsquos rotor area

bull Doesnrsquot pay to space windmills too closelymdashone robs the other of energy

bull Typical arrangements have rotors 10 diameters apart in direction of prevailing wind 5 diameters apart in the cross-wind directionndash works out to 16 ldquofill factorrdquo

45

Current implementations

bull Rapidly developing resourcendash 1400 MW in 1989 up to 6400 MW in 2003ndash but still insignificant total (compare to large

dams)ndash cost (at 5ndash7cent per kWh) is competitivendash growing at 25 per yearndash expect to triple over next ten years

bull Current capacity 116 GW (April 2007)ndash Texas 2768 MW (recently took lead over

California)ndash California 2361 MWndash Iowa 936 MWndash Minnesota 895 MWndash Washington 818 MW

46

Flies in the Ointment

bull Find that only 20 of rated capacity is achievedndash design for high wind but seldom get it

bull Only 12 of electrical capacity in US is now windndash total electrical capacity in US is 948 GWndash tripling in ten years means 36ndash but achieving only 20 of capacity reduces

substantiallybull If fully developed we could generate an average

power almost equal to our current electrical capacity (764 GW)

ndash but highly variable resource and problematic if more than 20 comes from the intermittent wind

47

iClicker Question

bull Which state generates the most amount of electricity derived from wind powerndash A Virginiandash B Alaskandash C Montanandash D Californiandash E Texas

48

iClicker Question

bull Which state generates the most amount of electricity derived from wind powerndash A Virginiandash B Alaskandash C Montanandash D Californiandash E Texas

• Renewable Energy Sources II Alternatives Part I
• Chapter 5 Summary
• Slide 3
• Slide 4
• Slide 5
• Slide 6
• Slide 7
• Slide 8
• Slide 9
• Slide 10
• Slide 11
• Slide 12
• Slide 13
• Slide 14
• Renewable Resources Discussed in Book
• Renewable Energy Consumption
• Another look at available energy flow
• The Renewable Budget
• Outstanding Points from Fig 51
• Energy Flow continued
• The Hydrologic Cycle
• Energetics of the hydrologic cycle
• Let it Rain
• How much of the process do we get to keep
• iClicker Question
• Slide 26
• Power of a hydroelectric dam
• Importance of Hydroelectricity
• Hydroelectric potential by region in GW
• Slide 30
• Slide 31
• Hydroelectricity in the future
• Sorry try againhellip
• Wind Energy
• The Power of Wind
• Wind Energy proportional to cube of velocity
• Canrsquot get it all
• Practical Efficiencies
• Slide 39
• Slide 40
• Achievable efficiencies
• Typical Windmills
• Average available wind power
• Comparable to solar
• Current implementations
• Flies in the Ointment
• Slide 47
• Slide 48

23

Let it Rain

bull When water condenses in clouds it re-releases this ldquolatent heatrdquo

ndash but this is re-radiated and is of no consequence to hydro-power

bull When it rains the gravitational potential energy is released mostly as kinetic energy and ultimately heat

bull Some tiny bit of gravitational potential energy remains IF the rain falls on terrain (eg higher than sea level where it originated)

ndash hydroelectric plants use this tiny left-over energy itrsquos the energy that drives the flow of streams and rivers

ndash damming up a river concentrates the potential energy in one location for easy exploitation

24

How much of the process do we get to keep

bull According to Figure 51 401015 W of solar power goes into evaporation

ndash this corresponds to 161010 kg per second of evaporated water

ndash this is 35 mm per day off the ocean surface (replenished by rain)

bull The gravitational potential energy given to water vapor (mostly in clouds) in the atmosphere (per second) is thenmgh = (161010 kg)(10 ms2)(2000 m) = 321014 J

bull One can calculate that we gain access to only 25 of the total amount (and use only 125)

ndash based on the 18 land area of the US and the maximum potential of 1477 GW as presented in Table 52

25

iClicker Question

bull With respects to energy hydroelectric power representsndash A remnant electric power from stormsndash B remnant water energy from chemical

bondsndash C remnant energy of chemical bondingndash D remnant gravitational potential

energy of precipitationndash E a form of fictitious energy

26

iClicker Question

bull With respects to energy hydroelectric power representsndash A remnant electric power from stormsndash B remnant water energy from chemical

bondsndash C remnant energy of chemical bondingndash D remnant gravitational potential

energy of precipitationndash E a form of fictitious energy

27

Power of a hydroelectric dam

bull Most impressive is Grand Coulee in Washington on Columbia River

ndash 350 feet = 107 m of ldquoheadrdquondash gt 6000 m3s flow rate (Pacific Northwest gets

rain)ndash each cubic meter of water (1000 kg) has potential

energy mgh = (1000 kg)(10 ms2)(110 m) = 11 MJ

ndash At 6000 m3s get over 6 GW of powerbull Large nuclear plants are usually 1ndash2 GWbull 11 other dams in US in 1ndash2 GW rangebull 74 GW total hydroelectric capacity presently

28

Importance of Hydroelectricity

29

Hydroelectric potential by region in GW

Region Potential

Developed

Undeveloped

Developed

New England 63 19 44 301

Middle Atlantic 98 49 49 500

East North Central 29 12 17 413

West North Central

62 31 31 500

South Atlantic 139 67 72 482

East South Central 83 59 24 711

West South Central

73 27 46 369

Mountain 286 95 191 332

Pacific 644 382 262 593

Total 1477 741 736 502

30

iClicker Question

bull What is true about hydroelectric power generation since 1950ndash A It has always increased in MW producedndash B It has always decreased in MW producedndash C It has increased and decreased in total

MW produced but is now at a peakndash D It has both increased and decreased in

total MW producedndash E The percentage of electric power

produced by hydroelectric plants has generally increased over time

31

iClicker Question

bull What is true about hydroelectric power generation since 1950ndash A It has always increased in MW producedndash B It has always decreased in MW producedndash C It has increased and decreased in total

MW produced but is now at a peakndash D It has both increased and decreased in

total MW producedndash E The percentage of electric power

produced by hydroelectric plants has generally increased over time

32

Hydroelectricity in the future

bull Wersquore almost tapped-outndash 50 of potential is developedndash remaining potential in large number of small-scale

unitsbull Problems with dams

ndash silt limits lifetime to 50ndash200 years after which dam is useless and in fact a potential disaster and nagging maintenance site

ndash habitat loss for fish (salmon) etc wrecks otherwise stunning landscapes (Glenn Canyon in UT)

ndash Disasters waiting to happen 1680 deaths in US alone from 1918ndash1958 often upstream from major population centers

33

Sorry try againhellip

bull So hydroelectricity is a nice ldquofreebeerdquo handed to us by nature but itrsquos not enough to cover our appetite for energy

bull Though very efficient and seemingly environmentally friendly dams do have their problems

bull This isnrsquot the answer to all our energy problems though it is likely to maintain a role well into our future

34

Wind Energy

35

The Power of Wind

bull Wersquove talked about the kinetic energy in wind beforendash a wind traveling at speed v covers v meters

every second (if v is expressed in ms)ndash the kinetic energy hitting a square meter is

then the kinetic energy the mass of air defined by a rectangular tube

ndash tube is one square meter by v meters or v m3

ndash density of air is = 13 kgm3 at sea levelndash mass is v kgndash KE = frac12(v)v2 = frac12v3 (per square meter)

065v3 at sea level

36

Wind Energy proportional to cube of velocity

bull The book (p 134) says power per square meter is 061v3 which is a more-or-less identical resultndash might account for average density in

continental US (above sea level so air slightly less dense)

bull So if the wind speed doubles the power available in the wind increases by 23 = 222 = 8 times

bull A wind of 10 ms (22 mph) has a power density of 610 Wm2

bull A wind of 20 ms (44 mph) has a power density of 4880 Wm2

37

Canrsquot get it all

bull A windmill canrsquot extract all of the kinetic energy available in the wind because this would mean stopping the wind entirely

bull Stopped wind would divert oncoming wind around it and the windmill would stop spinning

bull On the other hand if you donrsquot slow the wind down much at all you wonrsquot get much energy

bull Theoretical maximum performance is 59 of energy extractedndash corresponds to reducing velocity by 36

38

Practical Efficiencies

bull Modern windmills attain maybe 50ndash70 of the theoretical maximumndash 05ndash07 times 059 is 030ndash041 or

about 30ndash40ndash this figure is the mechanical energy

extracted from the windbull Conversion from mechanical to

electrical is 90 efficientndash 09 times 030ndash041 is 27ndash37

39

iClicker Question

bull What is about the maximum efficiency of energy generation using the windndash A 20ndash B 40ndash C 60ndash D 80ndash E 100

40

iClicker Question

bull What is about the maximum efficiency of energy generation using the windndash A 20ndash B 40ndash C 60ndash D 80ndash E 100

41

Achievable efficiencies

42

Typical Windmillsbull A typical windmill might be 15 m in diameter

ndash 176 m2

bull At 10 ms wind 40 efficiency this delivers about 100 kW of power

ndash this would be 800 kW at 20 msndash typical windmills are rated at 50 to 600 kW

bull How much energy per yearndash 10 ms 610 Wm2 40 240 Wm2 8760 hours per

year 2000 kWh per year per square meterndash but wind is intermittent real range from 100ndash500 kWhm2

ndash corresponds to 11ndash57 Wm2 average available power density

bull Note the really high tip speeds bird killers

43

Average available wind powerrecall that average solar insolation is about 150ndash250 Wm2

44

Comparable to solar

bull These numbers are similar to solar if not a little biggerndash Letrsquos go to wind

bull BUT the ldquoper square meterrdquo is not land areamdashitrsquos rotor area

bull Doesnrsquot pay to space windmills too closelymdashone robs the other of energy

bull Typical arrangements have rotors 10 diameters apart in direction of prevailing wind 5 diameters apart in the cross-wind directionndash works out to 16 ldquofill factorrdquo

45

Current implementations

bull Rapidly developing resourcendash 1400 MW in 1989 up to 6400 MW in 2003ndash but still insignificant total (compare to large

dams)ndash cost (at 5ndash7cent per kWh) is competitivendash growing at 25 per yearndash expect to triple over next ten years

bull Current capacity 116 GW (April 2007)ndash Texas 2768 MW (recently took lead over

California)ndash California 2361 MWndash Iowa 936 MWndash Minnesota 895 MWndash Washington 818 MW

46

Flies in the Ointment

bull Find that only 20 of rated capacity is achievedndash design for high wind but seldom get it

bull Only 12 of electrical capacity in US is now windndash total electrical capacity in US is 948 GWndash tripling in ten years means 36ndash but achieving only 20 of capacity reduces

substantiallybull If fully developed we could generate an average

power almost equal to our current electrical capacity (764 GW)

ndash but highly variable resource and problematic if more than 20 comes from the intermittent wind

47

iClicker Question

bull Which state generates the most amount of electricity derived from wind powerndash A Virginiandash B Alaskandash C Montanandash D Californiandash E Texas

48

iClicker Question

bull Which state generates the most amount of electricity derived from wind powerndash A Virginiandash B Alaskandash C Montanandash D Californiandash E Texas

• Renewable Energy Sources II Alternatives Part I
• Chapter 5 Summary
• Slide 3
• Slide 4
• Slide 5
• Slide 6
• Slide 7
• Slide 8
• Slide 9
• Slide 10
• Slide 11
• Slide 12
• Slide 13
• Slide 14
• Renewable Resources Discussed in Book
• Renewable Energy Consumption
• Another look at available energy flow
• The Renewable Budget
• Outstanding Points from Fig 51
• Energy Flow continued
• The Hydrologic Cycle
• Energetics of the hydrologic cycle
• Let it Rain
• How much of the process do we get to keep
• iClicker Question
• Slide 26
• Power of a hydroelectric dam
• Importance of Hydroelectricity
• Hydroelectric potential by region in GW
• Slide 30
• Slide 31
• Hydroelectricity in the future
• Sorry try againhellip
• Wind Energy
• The Power of Wind
• Wind Energy proportional to cube of velocity
• Canrsquot get it all
• Practical Efficiencies
• Slide 39
• Slide 40
• Achievable efficiencies
• Typical Windmills
• Average available wind power
• Comparable to solar
• Current implementations
• Flies in the Ointment
• Slide 47
• Slide 48

24

How much of the process do we get to keep

bull According to Figure 51 401015 W of solar power goes into evaporation

ndash this corresponds to 161010 kg per second of evaporated water

ndash this is 35 mm per day off the ocean surface (replenished by rain)

bull The gravitational potential energy given to water vapor (mostly in clouds) in the atmosphere (per second) is thenmgh = (161010 kg)(10 ms2)(2000 m) = 321014 J

bull One can calculate that we gain access to only 25 of the total amount (and use only 125)

ndash based on the 18 land area of the US and the maximum potential of 1477 GW as presented in Table 52

25

iClicker Question

bull With respects to energy hydroelectric power representsndash A remnant electric power from stormsndash B remnant water energy from chemical

bondsndash C remnant energy of chemical bondingndash D remnant gravitational potential

energy of precipitationndash E a form of fictitious energy

26

iClicker Question

bull With respects to energy hydroelectric power representsndash A remnant electric power from stormsndash B remnant water energy from chemical

bondsndash C remnant energy of chemical bondingndash D remnant gravitational potential

energy of precipitationndash E a form of fictitious energy

27

Power of a hydroelectric dam

bull Most impressive is Grand Coulee in Washington on Columbia River

ndash 350 feet = 107 m of ldquoheadrdquondash gt 6000 m3s flow rate (Pacific Northwest gets

rain)ndash each cubic meter of water (1000 kg) has potential

energy mgh = (1000 kg)(10 ms2)(110 m) = 11 MJ

ndash At 6000 m3s get over 6 GW of powerbull Large nuclear plants are usually 1ndash2 GWbull 11 other dams in US in 1ndash2 GW rangebull 74 GW total hydroelectric capacity presently

28

Importance of Hydroelectricity

29

Hydroelectric potential by region in GW

Region Potential

Developed

Undeveloped

Developed

New England 63 19 44 301

Middle Atlantic 98 49 49 500

East North Central 29 12 17 413

West North Central

62 31 31 500

South Atlantic 139 67 72 482

East South Central 83 59 24 711

West South Central

73 27 46 369

Mountain 286 95 191 332

Pacific 644 382 262 593

Total 1477 741 736 502

30

iClicker Question

bull What is true about hydroelectric power generation since 1950ndash A It has always increased in MW producedndash B It has always decreased in MW producedndash C It has increased and decreased in total

MW produced but is now at a peakndash D It has both increased and decreased in

total MW producedndash E The percentage of electric power

produced by hydroelectric plants has generally increased over time

31

iClicker Question

bull What is true about hydroelectric power generation since 1950ndash A It has always increased in MW producedndash B It has always decreased in MW producedndash C It has increased and decreased in total

MW produced but is now at a peakndash D It has both increased and decreased in

total MW producedndash E The percentage of electric power

produced by hydroelectric plants has generally increased over time

32

Hydroelectricity in the future

bull Wersquore almost tapped-outndash 50 of potential is developedndash remaining potential in large number of small-scale

unitsbull Problems with dams

ndash silt limits lifetime to 50ndash200 years after which dam is useless and in fact a potential disaster and nagging maintenance site

ndash habitat loss for fish (salmon) etc wrecks otherwise stunning landscapes (Glenn Canyon in UT)

ndash Disasters waiting to happen 1680 deaths in US alone from 1918ndash1958 often upstream from major population centers

33

Sorry try againhellip

bull So hydroelectricity is a nice ldquofreebeerdquo handed to us by nature but itrsquos not enough to cover our appetite for energy

bull Though very efficient and seemingly environmentally friendly dams do have their problems

bull This isnrsquot the answer to all our energy problems though it is likely to maintain a role well into our future

34

Wind Energy

35

The Power of Wind

bull Wersquove talked about the kinetic energy in wind beforendash a wind traveling at speed v covers v meters

every second (if v is expressed in ms)ndash the kinetic energy hitting a square meter is

then the kinetic energy the mass of air defined by a rectangular tube

ndash tube is one square meter by v meters or v m3

ndash density of air is = 13 kgm3 at sea levelndash mass is v kgndash KE = frac12(v)v2 = frac12v3 (per square meter)

065v3 at sea level

36

Wind Energy proportional to cube of velocity

bull The book (p 134) says power per square meter is 061v3 which is a more-or-less identical resultndash might account for average density in

continental US (above sea level so air slightly less dense)

bull So if the wind speed doubles the power available in the wind increases by 23 = 222 = 8 times

bull A wind of 10 ms (22 mph) has a power density of 610 Wm2

bull A wind of 20 ms (44 mph) has a power density of 4880 Wm2

37

Canrsquot get it all

bull A windmill canrsquot extract all of the kinetic energy available in the wind because this would mean stopping the wind entirely

bull Stopped wind would divert oncoming wind around it and the windmill would stop spinning

bull On the other hand if you donrsquot slow the wind down much at all you wonrsquot get much energy

bull Theoretical maximum performance is 59 of energy extractedndash corresponds to reducing velocity by 36

38

Practical Efficiencies

bull Modern windmills attain maybe 50ndash70 of the theoretical maximumndash 05ndash07 times 059 is 030ndash041 or

about 30ndash40ndash this figure is the mechanical energy

extracted from the windbull Conversion from mechanical to

electrical is 90 efficientndash 09 times 030ndash041 is 27ndash37

39

iClicker Question

bull What is about the maximum efficiency of energy generation using the windndash A 20ndash B 40ndash C 60ndash D 80ndash E 100

40

iClicker Question

bull What is about the maximum efficiency of energy generation using the windndash A 20ndash B 40ndash C 60ndash D 80ndash E 100

41

Achievable efficiencies

42

Typical Windmillsbull A typical windmill might be 15 m in diameter

ndash 176 m2

bull At 10 ms wind 40 efficiency this delivers about 100 kW of power

ndash this would be 800 kW at 20 msndash typical windmills are rated at 50 to 600 kW

bull How much energy per yearndash 10 ms 610 Wm2 40 240 Wm2 8760 hours per

year 2000 kWh per year per square meterndash but wind is intermittent real range from 100ndash500 kWhm2

ndash corresponds to 11ndash57 Wm2 average available power density

bull Note the really high tip speeds bird killers

43

Average available wind powerrecall that average solar insolation is about 150ndash250 Wm2

44

Comparable to solar

bull These numbers are similar to solar if not a little biggerndash Letrsquos go to wind

bull BUT the ldquoper square meterrdquo is not land areamdashitrsquos rotor area

bull Doesnrsquot pay to space windmills too closelymdashone robs the other of energy

bull Typical arrangements have rotors 10 diameters apart in direction of prevailing wind 5 diameters apart in the cross-wind directionndash works out to 16 ldquofill factorrdquo

45

Current implementations

bull Rapidly developing resourcendash 1400 MW in 1989 up to 6400 MW in 2003ndash but still insignificant total (compare to large

dams)ndash cost (at 5ndash7cent per kWh) is competitivendash growing at 25 per yearndash expect to triple over next ten years

bull Current capacity 116 GW (April 2007)ndash Texas 2768 MW (recently took lead over

California)ndash California 2361 MWndash Iowa 936 MWndash Minnesota 895 MWndash Washington 818 MW

46

Flies in the Ointment

bull Find that only 20 of rated capacity is achievedndash design for high wind but seldom get it

bull Only 12 of electrical capacity in US is now windndash total electrical capacity in US is 948 GWndash tripling in ten years means 36ndash but achieving only 20 of capacity reduces

substantiallybull If fully developed we could generate an average

power almost equal to our current electrical capacity (764 GW)

ndash but highly variable resource and problematic if more than 20 comes from the intermittent wind

47

iClicker Question

bull Which state generates the most amount of electricity derived from wind powerndash A Virginiandash B Alaskandash C Montanandash D Californiandash E Texas

48

iClicker Question

bull Which state generates the most amount of electricity derived from wind powerndash A Virginiandash B Alaskandash C Montanandash D Californiandash E Texas

• Renewable Energy Sources II Alternatives Part I
• Chapter 5 Summary
• Slide 3
• Slide 4
• Slide 5
• Slide 6
• Slide 7
• Slide 8
• Slide 9
• Slide 10
• Slide 11
• Slide 12
• Slide 13
• Slide 14
• Renewable Resources Discussed in Book
• Renewable Energy Consumption
• Another look at available energy flow
• The Renewable Budget
• Outstanding Points from Fig 51
• Energy Flow continued
• The Hydrologic Cycle
• Energetics of the hydrologic cycle
• Let it Rain
• How much of the process do we get to keep
• iClicker Question
• Slide 26
• Power of a hydroelectric dam
• Importance of Hydroelectricity
• Hydroelectric potential by region in GW
• Slide 30
• Slide 31
• Hydroelectricity in the future
• Sorry try againhellip
• Wind Energy
• The Power of Wind
• Wind Energy proportional to cube of velocity
• Canrsquot get it all
• Practical Efficiencies
• Slide 39
• Slide 40
• Achievable efficiencies
• Typical Windmills
• Average available wind power
• Comparable to solar
• Current implementations
• Flies in the Ointment
• Slide 47
• Slide 48

25

iClicker Question

bull With respects to energy hydroelectric power representsndash A remnant electric power from stormsndash B remnant water energy from chemical

bondsndash C remnant energy of chemical bondingndash D remnant gravitational potential

energy of precipitationndash E a form of fictitious energy

26

iClicker Question

bull With respects to energy hydroelectric power representsndash A remnant electric power from stormsndash B remnant water energy from chemical

bondsndash C remnant energy of chemical bondingndash D remnant gravitational potential

energy of precipitationndash E a form of fictitious energy

27

Power of a hydroelectric dam

bull Most impressive is Grand Coulee in Washington on Columbia River

ndash 350 feet = 107 m of ldquoheadrdquondash gt 6000 m3s flow rate (Pacific Northwest gets

rain)ndash each cubic meter of water (1000 kg) has potential

energy mgh = (1000 kg)(10 ms2)(110 m) = 11 MJ

ndash At 6000 m3s get over 6 GW of powerbull Large nuclear plants are usually 1ndash2 GWbull 11 other dams in US in 1ndash2 GW rangebull 74 GW total hydroelectric capacity presently

28

Importance of Hydroelectricity

29

Hydroelectric potential by region in GW

Region Potential

Developed

Undeveloped

Developed

New England 63 19 44 301

Middle Atlantic 98 49 49 500

East North Central 29 12 17 413

West North Central

62 31 31 500

South Atlantic 139 67 72 482

East South Central 83 59 24 711

West South Central

73 27 46 369

Mountain 286 95 191 332

Pacific 644 382 262 593

Total 1477 741 736 502

30

iClicker Question

bull What is true about hydroelectric power generation since 1950ndash A It has always increased in MW producedndash B It has always decreased in MW producedndash C It has increased and decreased in total

MW produced but is now at a peakndash D It has both increased and decreased in

total MW producedndash E The percentage of electric power

produced by hydroelectric plants has generally increased over time

31

iClicker Question

bull What is true about hydroelectric power generation since 1950ndash A It has always increased in MW producedndash B It has always decreased in MW producedndash C It has increased and decreased in total

MW produced but is now at a peakndash D It has both increased and decreased in

total MW producedndash E The percentage of electric power

produced by hydroelectric plants has generally increased over time

32

Hydroelectricity in the future

bull Wersquore almost tapped-outndash 50 of potential is developedndash remaining potential in large number of small-scale

unitsbull Problems with dams

ndash silt limits lifetime to 50ndash200 years after which dam is useless and in fact a potential disaster and nagging maintenance site

ndash habitat loss for fish (salmon) etc wrecks otherwise stunning landscapes (Glenn Canyon in UT)

ndash Disasters waiting to happen 1680 deaths in US alone from 1918ndash1958 often upstream from major population centers

33

Sorry try againhellip

bull So hydroelectricity is a nice ldquofreebeerdquo handed to us by nature but itrsquos not enough to cover our appetite for energy

bull Though very efficient and seemingly environmentally friendly dams do have their problems

bull This isnrsquot the answer to all our energy problems though it is likely to maintain a role well into our future

34

Wind Energy

35

The Power of Wind

bull Wersquove talked about the kinetic energy in wind beforendash a wind traveling at speed v covers v meters

every second (if v is expressed in ms)ndash the kinetic energy hitting a square meter is

then the kinetic energy the mass of air defined by a rectangular tube

ndash tube is one square meter by v meters or v m3

ndash density of air is = 13 kgm3 at sea levelndash mass is v kgndash KE = frac12(v)v2 = frac12v3 (per square meter)

065v3 at sea level

36

Wind Energy proportional to cube of velocity

bull The book (p 134) says power per square meter is 061v3 which is a more-or-less identical resultndash might account for average density in

continental US (above sea level so air slightly less dense)

bull So if the wind speed doubles the power available in the wind increases by 23 = 222 = 8 times

bull A wind of 10 ms (22 mph) has a power density of 610 Wm2

bull A wind of 20 ms (44 mph) has a power density of 4880 Wm2

37

Canrsquot get it all

bull A windmill canrsquot extract all of the kinetic energy available in the wind because this would mean stopping the wind entirely

bull Stopped wind would divert oncoming wind around it and the windmill would stop spinning

bull On the other hand if you donrsquot slow the wind down much at all you wonrsquot get much energy

bull Theoretical maximum performance is 59 of energy extractedndash corresponds to reducing velocity by 36

38

Practical Efficiencies

bull Modern windmills attain maybe 50ndash70 of the theoretical maximumndash 05ndash07 times 059 is 030ndash041 or

about 30ndash40ndash this figure is the mechanical energy

extracted from the windbull Conversion from mechanical to

electrical is 90 efficientndash 09 times 030ndash041 is 27ndash37

39

iClicker Question

bull What is about the maximum efficiency of energy generation using the windndash A 20ndash B 40ndash C 60ndash D 80ndash E 100

40

iClicker Question

bull What is about the maximum efficiency of energy generation using the windndash A 20ndash B 40ndash C 60ndash D 80ndash E 100

41

Achievable efficiencies

42

Typical Windmillsbull A typical windmill might be 15 m in diameter

ndash 176 m2

bull At 10 ms wind 40 efficiency this delivers about 100 kW of power

ndash this would be 800 kW at 20 msndash typical windmills are rated at 50 to 600 kW

bull How much energy per yearndash 10 ms 610 Wm2 40 240 Wm2 8760 hours per

year 2000 kWh per year per square meterndash but wind is intermittent real range from 100ndash500 kWhm2

ndash corresponds to 11ndash57 Wm2 average available power density

bull Note the really high tip speeds bird killers

43

Average available wind powerrecall that average solar insolation is about 150ndash250 Wm2

44

Comparable to solar

bull These numbers are similar to solar if not a little biggerndash Letrsquos go to wind

bull BUT the ldquoper square meterrdquo is not land areamdashitrsquos rotor area

bull Doesnrsquot pay to space windmills too closelymdashone robs the other of energy

bull Typical arrangements have rotors 10 diameters apart in direction of prevailing wind 5 diameters apart in the cross-wind directionndash works out to 16 ldquofill factorrdquo

45

Current implementations

bull Rapidly developing resourcendash 1400 MW in 1989 up to 6400 MW in 2003ndash but still insignificant total (compare to large

dams)ndash cost (at 5ndash7cent per kWh) is competitivendash growing at 25 per yearndash expect to triple over next ten years

bull Current capacity 116 GW (April 2007)ndash Texas 2768 MW (recently took lead over

California)ndash California 2361 MWndash Iowa 936 MWndash Minnesota 895 MWndash Washington 818 MW

46

Flies in the Ointment

bull Find that only 20 of rated capacity is achievedndash design for high wind but seldom get it

bull Only 12 of electrical capacity in US is now windndash total electrical capacity in US is 948 GWndash tripling in ten years means 36ndash but achieving only 20 of capacity reduces

substantiallybull If fully developed we could generate an average

power almost equal to our current electrical capacity (764 GW)

ndash but highly variable resource and problematic if more than 20 comes from the intermittent wind

47

iClicker Question

bull Which state generates the most amount of electricity derived from wind powerndash A Virginiandash B Alaskandash C Montanandash D Californiandash E Texas

48

iClicker Question

bull Which state generates the most amount of electricity derived from wind powerndash A Virginiandash B Alaskandash C Montanandash D Californiandash E Texas

• Renewable Energy Sources II Alternatives Part I
• Chapter 5 Summary
• Slide 3
• Slide 4
• Slide 5
• Slide 6
• Slide 7
• Slide 8
• Slide 9
• Slide 10
• Slide 11
• Slide 12
• Slide 13
• Slide 14
• Renewable Resources Discussed in Book
• Renewable Energy Consumption
• Another look at available energy flow
• The Renewable Budget
• Outstanding Points from Fig 51
• Energy Flow continued
• The Hydrologic Cycle
• Energetics of the hydrologic cycle
• Let it Rain
• How much of the process do we get to keep
• iClicker Question
• Slide 26
• Power of a hydroelectric dam
• Importance of Hydroelectricity
• Hydroelectric potential by region in GW
• Slide 30
• Slide 31
• Hydroelectricity in the future
• Sorry try againhellip
• Wind Energy
• The Power of Wind
• Wind Energy proportional to cube of velocity
• Canrsquot get it all
• Practical Efficiencies
• Slide 39
• Slide 40
• Achievable efficiencies
• Typical Windmills
• Average available wind power
• Comparable to solar
• Current implementations
• Flies in the Ointment
• Slide 47
• Slide 48

26

iClicker Question

bull With respects to energy hydroelectric power representsndash A remnant electric power from stormsndash B remnant water energy from chemical

bondsndash C remnant energy of chemical bondingndash D remnant gravitational potential

energy of precipitationndash E a form of fictitious energy

27

Power of a hydroelectric dam

bull Most impressive is Grand Coulee in Washington on Columbia River

ndash 350 feet = 107 m of ldquoheadrdquondash gt 6000 m3s flow rate (Pacific Northwest gets

rain)ndash each cubic meter of water (1000 kg) has potential

energy mgh = (1000 kg)(10 ms2)(110 m) = 11 MJ

ndash At 6000 m3s get over 6 GW of powerbull Large nuclear plants are usually 1ndash2 GWbull 11 other dams in US in 1ndash2 GW rangebull 74 GW total hydroelectric capacity presently

28

Importance of Hydroelectricity

29

Hydroelectric potential by region in GW

Region Potential

Developed

Undeveloped

Developed

New England 63 19 44 301

Middle Atlantic 98 49 49 500

East North Central 29 12 17 413

West North Central

62 31 31 500

South Atlantic 139 67 72 482

East South Central 83 59 24 711

West South Central

73 27 46 369

Mountain 286 95 191 332

Pacific 644 382 262 593

Total 1477 741 736 502

30

iClicker Question

bull What is true about hydroelectric power generation since 1950ndash A It has always increased in MW producedndash B It has always decreased in MW producedndash C It has increased and decreased in total

MW produced but is now at a peakndash D It has both increased and decreased in

total MW producedndash E The percentage of electric power

produced by hydroelectric plants has generally increased over time

31

iClicker Question

bull What is true about hydroelectric power generation since 1950ndash A It has always increased in MW producedndash B It has always decreased in MW producedndash C It has increased and decreased in total

MW produced but is now at a peakndash D It has both increased and decreased in

total MW producedndash E The percentage of electric power

produced by hydroelectric plants has generally increased over time

32

Hydroelectricity in the future

bull Wersquore almost tapped-outndash 50 of potential is developedndash remaining potential in large number of small-scale

unitsbull Problems with dams

ndash silt limits lifetime to 50ndash200 years after which dam is useless and in fact a potential disaster and nagging maintenance site

ndash habitat loss for fish (salmon) etc wrecks otherwise stunning landscapes (Glenn Canyon in UT)

ndash Disasters waiting to happen 1680 deaths in US alone from 1918ndash1958 often upstream from major population centers

33

Sorry try againhellip

bull So hydroelectricity is a nice ldquofreebeerdquo handed to us by nature but itrsquos not enough to cover our appetite for energy

bull Though very efficient and seemingly environmentally friendly dams do have their problems

bull This isnrsquot the answer to all our energy problems though it is likely to maintain a role well into our future

34

Wind Energy

35

The Power of Wind

bull Wersquove talked about the kinetic energy in wind beforendash a wind traveling at speed v covers v meters

every second (if v is expressed in ms)ndash the kinetic energy hitting a square meter is

then the kinetic energy the mass of air defined by a rectangular tube

ndash tube is one square meter by v meters or v m3

ndash density of air is = 13 kgm3 at sea levelndash mass is v kgndash KE = frac12(v)v2 = frac12v3 (per square meter)

065v3 at sea level

36

Wind Energy proportional to cube of velocity

bull The book (p 134) says power per square meter is 061v3 which is a more-or-less identical resultndash might account for average density in

continental US (above sea level so air slightly less dense)

bull So if the wind speed doubles the power available in the wind increases by 23 = 222 = 8 times

bull A wind of 10 ms (22 mph) has a power density of 610 Wm2

bull A wind of 20 ms (44 mph) has a power density of 4880 Wm2

37

Canrsquot get it all

bull A windmill canrsquot extract all of the kinetic energy available in the wind because this would mean stopping the wind entirely

bull Stopped wind would divert oncoming wind around it and the windmill would stop spinning

bull On the other hand if you donrsquot slow the wind down much at all you wonrsquot get much energy

bull Theoretical maximum performance is 59 of energy extractedndash corresponds to reducing velocity by 36

38

Practical Efficiencies

bull Modern windmills attain maybe 50ndash70 of the theoretical maximumndash 05ndash07 times 059 is 030ndash041 or

about 30ndash40ndash this figure is the mechanical energy

extracted from the windbull Conversion from mechanical to

electrical is 90 efficientndash 09 times 030ndash041 is 27ndash37

39

iClicker Question

bull What is about the maximum efficiency of energy generation using the windndash A 20ndash B 40ndash C 60ndash D 80ndash E 100

40

iClicker Question

bull What is about the maximum efficiency of energy generation using the windndash A 20ndash B 40ndash C 60ndash D 80ndash E 100

41

Achievable efficiencies

42

Typical Windmillsbull A typical windmill might be 15 m in diameter

ndash 176 m2

bull At 10 ms wind 40 efficiency this delivers about 100 kW of power

ndash this would be 800 kW at 20 msndash typical windmills are rated at 50 to 600 kW

bull How much energy per yearndash 10 ms 610 Wm2 40 240 Wm2 8760 hours per

year 2000 kWh per year per square meterndash but wind is intermittent real range from 100ndash500 kWhm2

ndash corresponds to 11ndash57 Wm2 average available power density

bull Note the really high tip speeds bird killers

43

Average available wind powerrecall that average solar insolation is about 150ndash250 Wm2

44

Comparable to solar

bull These numbers are similar to solar if not a little biggerndash Letrsquos go to wind

bull BUT the ldquoper square meterrdquo is not land areamdashitrsquos rotor area

bull Doesnrsquot pay to space windmills too closelymdashone robs the other of energy

bull Typical arrangements have rotors 10 diameters apart in direction of prevailing wind 5 diameters apart in the cross-wind directionndash works out to 16 ldquofill factorrdquo

45

Current implementations

bull Rapidly developing resourcendash 1400 MW in 1989 up to 6400 MW in 2003ndash but still insignificant total (compare to large

dams)ndash cost (at 5ndash7cent per kWh) is competitivendash growing at 25 per yearndash expect to triple over next ten years

bull Current capacity 116 GW (April 2007)ndash Texas 2768 MW (recently took lead over

California)ndash California 2361 MWndash Iowa 936 MWndash Minnesota 895 MWndash Washington 818 MW

46

Flies in the Ointment

bull Find that only 20 of rated capacity is achievedndash design for high wind but seldom get it

bull Only 12 of electrical capacity in US is now windndash total electrical capacity in US is 948 GWndash tripling in ten years means 36ndash but achieving only 20 of capacity reduces

substantiallybull If fully developed we could generate an average

power almost equal to our current electrical capacity (764 GW)

ndash but highly variable resource and problematic if more than 20 comes from the intermittent wind

47

iClicker Question

bull Which state generates the most amount of electricity derived from wind powerndash A Virginiandash B Alaskandash C Montanandash D Californiandash E Texas

48

iClicker Question

bull Which state generates the most amount of electricity derived from wind powerndash A Virginiandash B Alaskandash C Montanandash D Californiandash E Texas

• Renewable Energy Sources II Alternatives Part I
• Chapter 5 Summary
• Slide 3
• Slide 4
• Slide 5
• Slide 6
• Slide 7
• Slide 8
• Slide 9
• Slide 10
• Slide 11
• Slide 12
• Slide 13
• Slide 14
• Renewable Resources Discussed in Book
• Renewable Energy Consumption
• Another look at available energy flow
• The Renewable Budget
• Outstanding Points from Fig 51
• Energy Flow continued
• The Hydrologic Cycle
• Energetics of the hydrologic cycle
• Let it Rain
• How much of the process do we get to keep
• iClicker Question
• Slide 26
• Power of a hydroelectric dam
• Importance of Hydroelectricity
• Hydroelectric potential by region in GW
• Slide 30
• Slide 31
• Hydroelectricity in the future
• Sorry try againhellip
• Wind Energy
• The Power of Wind
• Wind Energy proportional to cube of velocity
• Canrsquot get it all
• Practical Efficiencies
• Slide 39
• Slide 40
• Achievable efficiencies
• Typical Windmills
• Average available wind power
• Comparable to solar
• Current implementations
• Flies in the Ointment
• Slide 47
• Slide 48

27

Power of a hydroelectric dam

bull Most impressive is Grand Coulee in Washington on Columbia River

ndash 350 feet = 107 m of ldquoheadrdquondash gt 6000 m3s flow rate (Pacific Northwest gets

rain)ndash each cubic meter of water (1000 kg) has potential

energy mgh = (1000 kg)(10 ms2)(110 m) = 11 MJ

ndash At 6000 m3s get over 6 GW of powerbull Large nuclear plants are usually 1ndash2 GWbull 11 other dams in US in 1ndash2 GW rangebull 74 GW total hydroelectric capacity presently

28

Importance of Hydroelectricity

29

Hydroelectric potential by region in GW

Region Potential

Developed

Undeveloped

Developed

New England 63 19 44 301

Middle Atlantic 98 49 49 500

East North Central 29 12 17 413

West North Central

62 31 31 500

South Atlantic 139 67 72 482

East South Central 83 59 24 711

West South Central

73 27 46 369

Mountain 286 95 191 332

Pacific 644 382 262 593

Total 1477 741 736 502

30

iClicker Question

bull What is true about hydroelectric power generation since 1950ndash A It has always increased in MW producedndash B It has always decreased in MW producedndash C It has increased and decreased in total

MW produced but is now at a peakndash D It has both increased and decreased in

total MW producedndash E The percentage of electric power

produced by hydroelectric plants has generally increased over time

31

iClicker Question

bull What is true about hydroelectric power generation since 1950ndash A It has always increased in MW producedndash B It has always decreased in MW producedndash C It has increased and decreased in total

MW produced but is now at a peakndash D It has both increased and decreased in

total MW producedndash E The percentage of electric power

produced by hydroelectric plants has generally increased over time

32

Hydroelectricity in the future

bull Wersquore almost tapped-outndash 50 of potential is developedndash remaining potential in large number of small-scale

unitsbull Problems with dams

ndash silt limits lifetime to 50ndash200 years after which dam is useless and in fact a potential disaster and nagging maintenance site

ndash habitat loss for fish (salmon) etc wrecks otherwise stunning landscapes (Glenn Canyon in UT)

ndash Disasters waiting to happen 1680 deaths in US alone from 1918ndash1958 often upstream from major population centers

33

Sorry try againhellip

bull So hydroelectricity is a nice ldquofreebeerdquo handed to us by nature but itrsquos not enough to cover our appetite for energy

bull Though very efficient and seemingly environmentally friendly dams do have their problems

bull This isnrsquot the answer to all our energy problems though it is likely to maintain a role well into our future

34

Wind Energy

35

The Power of Wind

bull Wersquove talked about the kinetic energy in wind beforendash a wind traveling at speed v covers v meters

every second (if v is expressed in ms)ndash the kinetic energy hitting a square meter is

then the kinetic energy the mass of air defined by a rectangular tube

ndash tube is one square meter by v meters or v m3

ndash density of air is = 13 kgm3 at sea levelndash mass is v kgndash KE = frac12(v)v2 = frac12v3 (per square meter)

065v3 at sea level

36

Wind Energy proportional to cube of velocity

bull The book (p 134) says power per square meter is 061v3 which is a more-or-less identical resultndash might account for average density in

continental US (above sea level so air slightly less dense)

bull So if the wind speed doubles the power available in the wind increases by 23 = 222 = 8 times

bull A wind of 10 ms (22 mph) has a power density of 610 Wm2

bull A wind of 20 ms (44 mph) has a power density of 4880 Wm2

37

Canrsquot get it all

bull A windmill canrsquot extract all of the kinetic energy available in the wind because this would mean stopping the wind entirely

bull Stopped wind would divert oncoming wind around it and the windmill would stop spinning

bull On the other hand if you donrsquot slow the wind down much at all you wonrsquot get much energy

bull Theoretical maximum performance is 59 of energy extractedndash corresponds to reducing velocity by 36

38

Practical Efficiencies

bull Modern windmills attain maybe 50ndash70 of the theoretical maximumndash 05ndash07 times 059 is 030ndash041 or

about 30ndash40ndash this figure is the mechanical energy

extracted from the windbull Conversion from mechanical to

electrical is 90 efficientndash 09 times 030ndash041 is 27ndash37

39

iClicker Question

bull What is about the maximum efficiency of energy generation using the windndash A 20ndash B 40ndash C 60ndash D 80ndash E 100

40

iClicker Question

bull What is about the maximum efficiency of energy generation using the windndash A 20ndash B 40ndash C 60ndash D 80ndash E 100

41

Achievable efficiencies

42

Typical Windmillsbull A typical windmill might be 15 m in diameter

ndash 176 m2

bull At 10 ms wind 40 efficiency this delivers about 100 kW of power

ndash this would be 800 kW at 20 msndash typical windmills are rated at 50 to 600 kW

bull How much energy per yearndash 10 ms 610 Wm2 40 240 Wm2 8760 hours per

year 2000 kWh per year per square meterndash but wind is intermittent real range from 100ndash500 kWhm2

ndash corresponds to 11ndash57 Wm2 average available power density

bull Note the really high tip speeds bird killers

43

Average available wind powerrecall that average solar insolation is about 150ndash250 Wm2

44

Comparable to solar

bull These numbers are similar to solar if not a little biggerndash Letrsquos go to wind

bull BUT the ldquoper square meterrdquo is not land areamdashitrsquos rotor area

bull Doesnrsquot pay to space windmills too closelymdashone robs the other of energy

bull Typical arrangements have rotors 10 diameters apart in direction of prevailing wind 5 diameters apart in the cross-wind directionndash works out to 16 ldquofill factorrdquo

45

Current implementations

bull Rapidly developing resourcendash 1400 MW in 1989 up to 6400 MW in 2003ndash but still insignificant total (compare to large

dams)ndash cost (at 5ndash7cent per kWh) is competitivendash growing at 25 per yearndash expect to triple over next ten years

bull Current capacity 116 GW (April 2007)ndash Texas 2768 MW (recently took lead over

California)ndash California 2361 MWndash Iowa 936 MWndash Minnesota 895 MWndash Washington 818 MW

46

Flies in the Ointment

bull Find that only 20 of rated capacity is achievedndash design for high wind but seldom get it

bull Only 12 of electrical capacity in US is now windndash total electrical capacity in US is 948 GWndash tripling in ten years means 36ndash but achieving only 20 of capacity reduces

substantiallybull If fully developed we could generate an average

power almost equal to our current electrical capacity (764 GW)

ndash but highly variable resource and problematic if more than 20 comes from the intermittent wind

47

iClicker Question

bull Which state generates the most amount of electricity derived from wind powerndash A Virginiandash B Alaskandash C Montanandash D Californiandash E Texas

48

iClicker Question

bull Which state generates the most amount of electricity derived from wind powerndash A Virginiandash B Alaskandash C Montanandash D Californiandash E Texas

• Renewable Energy Sources II Alternatives Part I
• Chapter 5 Summary
• Slide 3
• Slide 4
• Slide 5
• Slide 6
• Slide 7
• Slide 8
• Slide 9
• Slide 10
• Slide 11
• Slide 12
• Slide 13
• Slide 14
• Renewable Resources Discussed in Book
• Renewable Energy Consumption
• Another look at available energy flow
• The Renewable Budget
• Outstanding Points from Fig 51
• Energy Flow continued
• The Hydrologic Cycle
• Energetics of the hydrologic cycle
• Let it Rain
• How much of the process do we get to keep
• iClicker Question
• Slide 26
• Power of a hydroelectric dam
• Importance of Hydroelectricity
• Hydroelectric potential by region in GW
• Slide 30
• Slide 31
• Hydroelectricity in the future
• Sorry try againhellip
• Wind Energy
• The Power of Wind
• Wind Energy proportional to cube of velocity
• Canrsquot get it all
• Practical Efficiencies
• Slide 39
• Slide 40
• Achievable efficiencies
• Typical Windmills
• Average available wind power
• Comparable to solar
• Current implementations
• Flies in the Ointment
• Slide 47
• Slide 48

28

Importance of Hydroelectricity

29

Hydroelectric potential by region in GW

Region Potential

Developed

Undeveloped

Developed

New England 63 19 44 301

Middle Atlantic 98 49 49 500

East North Central 29 12 17 413

West North Central

62 31 31 500

South Atlantic 139 67 72 482

East South Central 83 59 24 711

West South Central

73 27 46 369

Mountain 286 95 191 332

Pacific 644 382 262 593

Total 1477 741 736 502

30

iClicker Question

bull What is true about hydroelectric power generation since 1950ndash A It has always increased in MW producedndash B It has always decreased in MW producedndash C It has increased and decreased in total

MW produced but is now at a peakndash D It has both increased and decreased in

total MW producedndash E The percentage of electric power

produced by hydroelectric plants has generally increased over time

31

iClicker Question

bull What is true about hydroelectric power generation since 1950ndash A It has always increased in MW producedndash B It has always decreased in MW producedndash C It has increased and decreased in total

MW produced but is now at a peakndash D It has both increased and decreased in

total MW producedndash E The percentage of electric power

produced by hydroelectric plants has generally increased over time

32

Hydroelectricity in the future

bull Wersquore almost tapped-outndash 50 of potential is developedndash remaining potential in large number of small-scale

unitsbull Problems with dams

ndash silt limits lifetime to 50ndash200 years after which dam is useless and in fact a potential disaster and nagging maintenance site

ndash habitat loss for fish (salmon) etc wrecks otherwise stunning landscapes (Glenn Canyon in UT)

ndash Disasters waiting to happen 1680 deaths in US alone from 1918ndash1958 often upstream from major population centers

33

Sorry try againhellip

bull So hydroelectricity is a nice ldquofreebeerdquo handed to us by nature but itrsquos not enough to cover our appetite for energy

bull Though very efficient and seemingly environmentally friendly dams do have their problems

bull This isnrsquot the answer to all our energy problems though it is likely to maintain a role well into our future

34

Wind Energy

35

The Power of Wind

bull Wersquove talked about the kinetic energy in wind beforendash a wind traveling at speed v covers v meters

every second (if v is expressed in ms)ndash the kinetic energy hitting a square meter is

then the kinetic energy the mass of air defined by a rectangular tube

ndash tube is one square meter by v meters or v m3

ndash density of air is = 13 kgm3 at sea levelndash mass is v kgndash KE = frac12(v)v2 = frac12v3 (per square meter)

065v3 at sea level

36

Wind Energy proportional to cube of velocity

bull The book (p 134) says power per square meter is 061v3 which is a more-or-less identical resultndash might account for average density in

continental US (above sea level so air slightly less dense)

bull So if the wind speed doubles the power available in the wind increases by 23 = 222 = 8 times

bull A wind of 10 ms (22 mph) has a power density of 610 Wm2

bull A wind of 20 ms (44 mph) has a power density of 4880 Wm2

37

Canrsquot get it all

bull A windmill canrsquot extract all of the kinetic energy available in the wind because this would mean stopping the wind entirely

bull Stopped wind would divert oncoming wind around it and the windmill would stop spinning

bull On the other hand if you donrsquot slow the wind down much at all you wonrsquot get much energy

bull Theoretical maximum performance is 59 of energy extractedndash corresponds to reducing velocity by 36

38

Practical Efficiencies

bull Modern windmills attain maybe 50ndash70 of the theoretical maximumndash 05ndash07 times 059 is 030ndash041 or

about 30ndash40ndash this figure is the mechanical energy

extracted from the windbull Conversion from mechanical to

electrical is 90 efficientndash 09 times 030ndash041 is 27ndash37

39

iClicker Question

bull What is about the maximum efficiency of energy generation using the windndash A 20ndash B 40ndash C 60ndash D 80ndash E 100

40

iClicker Question

bull What is about the maximum efficiency of energy generation using the windndash A 20ndash B 40ndash C 60ndash D 80ndash E 100

41

Achievable efficiencies

42

Typical Windmillsbull A typical windmill might be 15 m in diameter

ndash 176 m2

bull At 10 ms wind 40 efficiency this delivers about 100 kW of power

ndash this would be 800 kW at 20 msndash typical windmills are rated at 50 to 600 kW

bull How much energy per yearndash 10 ms 610 Wm2 40 240 Wm2 8760 hours per

year 2000 kWh per year per square meterndash but wind is intermittent real range from 100ndash500 kWhm2

ndash corresponds to 11ndash57 Wm2 average available power density

bull Note the really high tip speeds bird killers

43

Average available wind powerrecall that average solar insolation is about 150ndash250 Wm2

44

Comparable to solar

bull These numbers are similar to solar if not a little biggerndash Letrsquos go to wind

bull BUT the ldquoper square meterrdquo is not land areamdashitrsquos rotor area

bull Doesnrsquot pay to space windmills too closelymdashone robs the other of energy

bull Typical arrangements have rotors 10 diameters apart in direction of prevailing wind 5 diameters apart in the cross-wind directionndash works out to 16 ldquofill factorrdquo

45

Current implementations

bull Rapidly developing resourcendash 1400 MW in 1989 up to 6400 MW in 2003ndash but still insignificant total (compare to large

dams)ndash cost (at 5ndash7cent per kWh) is competitivendash growing at 25 per yearndash expect to triple over next ten years

bull Current capacity 116 GW (April 2007)ndash Texas 2768 MW (recently took lead over

California)ndash California 2361 MWndash Iowa 936 MWndash Minnesota 895 MWndash Washington 818 MW

46

Flies in the Ointment

bull Find that only 20 of rated capacity is achievedndash design for high wind but seldom get it

bull Only 12 of electrical capacity in US is now windndash total electrical capacity in US is 948 GWndash tripling in ten years means 36ndash but achieving only 20 of capacity reduces

substantiallybull If fully developed we could generate an average

power almost equal to our current electrical capacity (764 GW)

ndash but highly variable resource and problematic if more than 20 comes from the intermittent wind

47

iClicker Question

bull Which state generates the most amount of electricity derived from wind powerndash A Virginiandash B Alaskandash C Montanandash D Californiandash E Texas

48

iClicker Question

bull Which state generates the most amount of electricity derived from wind powerndash A Virginiandash B Alaskandash C Montanandash D Californiandash E Texas

• Renewable Energy Sources II Alternatives Part I
• Chapter 5 Summary
• Slide 3
• Slide 4
• Slide 5
• Slide 6
• Slide 7
• Slide 8
• Slide 9
• Slide 10
• Slide 11
• Slide 12
• Slide 13
• Slide 14
• Renewable Resources Discussed in Book
• Renewable Energy Consumption
• Another look at available energy flow
• The Renewable Budget
• Outstanding Points from Fig 51
• Energy Flow continued
• The Hydrologic Cycle
• Energetics of the hydrologic cycle
• Let it Rain
• How much of the process do we get to keep
• iClicker Question
• Slide 26
• Power of a hydroelectric dam
• Importance of Hydroelectricity
• Hydroelectric potential by region in GW
• Slide 30
• Slide 31
• Hydroelectricity in the future
• Sorry try againhellip
• Wind Energy
• The Power of Wind
• Wind Energy proportional to cube of velocity
• Canrsquot get it all
• Practical Efficiencies
• Slide 39
• Slide 40
• Achievable efficiencies
• Typical Windmills
• Average available wind power
• Comparable to solar
• Current implementations
• Flies in the Ointment
• Slide 47
• Slide 48

29

Hydroelectric potential by region in GW

Region Potential

Developed

Undeveloped

Developed

New England 63 19 44 301

Middle Atlantic 98 49 49 500

East North Central 29 12 17 413

West North Central

62 31 31 500

South Atlantic 139 67 72 482

East South Central 83 59 24 711

West South Central

73 27 46 369

Mountain 286 95 191 332

Pacific 644 382 262 593

Total 1477 741 736 502

30

iClicker Question

bull What is true about hydroelectric power generation since 1950ndash A It has always increased in MW producedndash B It has always decreased in MW producedndash C It has increased and decreased in total

MW produced but is now at a peakndash D It has both increased and decreased in

total MW producedndash E The percentage of electric power

produced by hydroelectric plants has generally increased over time

31

iClicker Question

bull What is true about hydroelectric power generation since 1950ndash A It has always increased in MW producedndash B It has always decreased in MW producedndash C It has increased and decreased in total

MW produced but is now at a peakndash D It has both increased and decreased in

total MW producedndash E The percentage of electric power

produced by hydroelectric plants has generally increased over time

32

Hydroelectricity in the future

bull Wersquore almost tapped-outndash 50 of potential is developedndash remaining potential in large number of small-scale

unitsbull Problems with dams

ndash silt limits lifetime to 50ndash200 years after which dam is useless and in fact a potential disaster and nagging maintenance site

ndash habitat loss for fish (salmon) etc wrecks otherwise stunning landscapes (Glenn Canyon in UT)

ndash Disasters waiting to happen 1680 deaths in US alone from 1918ndash1958 often upstream from major population centers

33

Sorry try againhellip

bull So hydroelectricity is a nice ldquofreebeerdquo handed to us by nature but itrsquos not enough to cover our appetite for energy

bull Though very efficient and seemingly environmentally friendly dams do have their problems

bull This isnrsquot the answer to all our energy problems though it is likely to maintain a role well into our future

34

Wind Energy

35

The Power of Wind

bull Wersquove talked about the kinetic energy in wind beforendash a wind traveling at speed v covers v meters

every second (if v is expressed in ms)ndash the kinetic energy hitting a square meter is

then the kinetic energy the mass of air defined by a rectangular tube

ndash tube is one square meter by v meters or v m3

ndash density of air is = 13 kgm3 at sea levelndash mass is v kgndash KE = frac12(v)v2 = frac12v3 (per square meter)

065v3 at sea level

36

Wind Energy proportional to cube of velocity

bull The book (p 134) says power per square meter is 061v3 which is a more-or-less identical resultndash might account for average density in

continental US (above sea level so air slightly less dense)

bull So if the wind speed doubles the power available in the wind increases by 23 = 222 = 8 times

bull A wind of 10 ms (22 mph) has a power density of 610 Wm2

bull A wind of 20 ms (44 mph) has a power density of 4880 Wm2

37

Canrsquot get it all

bull A windmill canrsquot extract all of the kinetic energy available in the wind because this would mean stopping the wind entirely

bull Stopped wind would divert oncoming wind around it and the windmill would stop spinning

bull On the other hand if you donrsquot slow the wind down much at all you wonrsquot get much energy

bull Theoretical maximum performance is 59 of energy extractedndash corresponds to reducing velocity by 36

38

Practical Efficiencies

bull Modern windmills attain maybe 50ndash70 of the theoretical maximumndash 05ndash07 times 059 is 030ndash041 or

about 30ndash40ndash this figure is the mechanical energy

extracted from the windbull Conversion from mechanical to

electrical is 90 efficientndash 09 times 030ndash041 is 27ndash37

39

iClicker Question

bull What is about the maximum efficiency of energy generation using the windndash A 20ndash B 40ndash C 60ndash D 80ndash E 100

40

iClicker Question

bull What is about the maximum efficiency of energy generation using the windndash A 20ndash B 40ndash C 60ndash D 80ndash E 100

41

Achievable efficiencies

42

Typical Windmillsbull A typical windmill might be 15 m in diameter

ndash 176 m2

bull At 10 ms wind 40 efficiency this delivers about 100 kW of power

ndash this would be 800 kW at 20 msndash typical windmills are rated at 50 to 600 kW

bull How much energy per yearndash 10 ms 610 Wm2 40 240 Wm2 8760 hours per

year 2000 kWh per year per square meterndash but wind is intermittent real range from 100ndash500 kWhm2

ndash corresponds to 11ndash57 Wm2 average available power density

bull Note the really high tip speeds bird killers

43

Average available wind powerrecall that average solar insolation is about 150ndash250 Wm2

44

Comparable to solar

bull These numbers are similar to solar if not a little biggerndash Letrsquos go to wind

bull BUT the ldquoper square meterrdquo is not land areamdashitrsquos rotor area

bull Doesnrsquot pay to space windmills too closelymdashone robs the other of energy

bull Typical arrangements have rotors 10 diameters apart in direction of prevailing wind 5 diameters apart in the cross-wind directionndash works out to 16 ldquofill factorrdquo

45

Current implementations

bull Rapidly developing resourcendash 1400 MW in 1989 up to 6400 MW in 2003ndash but still insignificant total (compare to large

dams)ndash cost (at 5ndash7cent per kWh) is competitivendash growing at 25 per yearndash expect to triple over next ten years

bull Current capacity 116 GW (April 2007)ndash Texas 2768 MW (recently took lead over

California)ndash California 2361 MWndash Iowa 936 MWndash Minnesota 895 MWndash Washington 818 MW

46

Flies in the Ointment

bull Find that only 20 of rated capacity is achievedndash design for high wind but seldom get it

bull Only 12 of electrical capacity in US is now windndash total electrical capacity in US is 948 GWndash tripling in ten years means 36ndash but achieving only 20 of capacity reduces

substantiallybull If fully developed we could generate an average

power almost equal to our current electrical capacity (764 GW)

ndash but highly variable resource and problematic if more than 20 comes from the intermittent wind

47

iClicker Question

bull Which state generates the most amount of electricity derived from wind powerndash A Virginiandash B Alaskandash C Montanandash D Californiandash E Texas

48

iClicker Question

bull Which state generates the most amount of electricity derived from wind powerndash A Virginiandash B Alaskandash C Montanandash D Californiandash E Texas

• Renewable Energy Sources II Alternatives Part I
• Chapter 5 Summary
• Slide 3
• Slide 4
• Slide 5
• Slide 6
• Slide 7
• Slide 8
• Slide 9
• Slide 10
• Slide 11
• Slide 12
• Slide 13
• Slide 14
• Renewable Resources Discussed in Book
• Renewable Energy Consumption
• Another look at available energy flow
• The Renewable Budget
• Outstanding Points from Fig 51
• Energy Flow continued
• The Hydrologic Cycle
• Energetics of the hydrologic cycle
• Let it Rain
• How much of the process do we get to keep
• iClicker Question
• Slide 26
• Power of a hydroelectric dam
• Importance of Hydroelectricity
• Hydroelectric potential by region in GW
• Slide 30
• Slide 31
• Hydroelectricity in the future
• Sorry try againhellip
• Wind Energy
• The Power of Wind
• Wind Energy proportional to cube of velocity
• Canrsquot get it all
• Practical Efficiencies
• Slide 39
• Slide 40
• Achievable efficiencies
• Typical Windmills
• Average available wind power
• Comparable to solar
• Current implementations
• Flies in the Ointment
• Slide 47
• Slide 48

30

iClicker Question

bull What is true about hydroelectric power generation since 1950ndash A It has always increased in MW producedndash B It has always decreased in MW producedndash C It has increased and decreased in total

MW produced but is now at a peakndash D It has both increased and decreased in

total MW producedndash E The percentage of electric power

produced by hydroelectric plants has generally increased over time

31

iClicker Question

bull What is true about hydroelectric power generation since 1950ndash A It has always increased in MW producedndash B It has always decreased in MW producedndash C It has increased and decreased in total

MW produced but is now at a peakndash D It has both increased and decreased in

total MW producedndash E The percentage of electric power

produced by hydroelectric plants has generally increased over time

32

Hydroelectricity in the future

bull Wersquore almost tapped-outndash 50 of potential is developedndash remaining potential in large number of small-scale

unitsbull Problems with dams

ndash silt limits lifetime to 50ndash200 years after which dam is useless and in fact a potential disaster and nagging maintenance site

ndash habitat loss for fish (salmon) etc wrecks otherwise stunning landscapes (Glenn Canyon in UT)

ndash Disasters waiting to happen 1680 deaths in US alone from 1918ndash1958 often upstream from major population centers

33

Sorry try againhellip

bull So hydroelectricity is a nice ldquofreebeerdquo handed to us by nature but itrsquos not enough to cover our appetite for energy

bull Though very efficient and seemingly environmentally friendly dams do have their problems

bull This isnrsquot the answer to all our energy problems though it is likely to maintain a role well into our future

34

Wind Energy

35

The Power of Wind

bull Wersquove talked about the kinetic energy in wind beforendash a wind traveling at speed v covers v meters

every second (if v is expressed in ms)ndash the kinetic energy hitting a square meter is

then the kinetic energy the mass of air defined by a rectangular tube

ndash tube is one square meter by v meters or v m3

ndash density of air is = 13 kgm3 at sea levelndash mass is v kgndash KE = frac12(v)v2 = frac12v3 (per square meter)

065v3 at sea level

36

Wind Energy proportional to cube of velocity

bull The book (p 134) says power per square meter is 061v3 which is a more-or-less identical resultndash might account for average density in

continental US (above sea level so air slightly less dense)

bull So if the wind speed doubles the power available in the wind increases by 23 = 222 = 8 times

bull A wind of 10 ms (22 mph) has a power density of 610 Wm2

bull A wind of 20 ms (44 mph) has a power density of 4880 Wm2

37

Canrsquot get it all

bull A windmill canrsquot extract all of the kinetic energy available in the wind because this would mean stopping the wind entirely

bull Stopped wind would divert oncoming wind around it and the windmill would stop spinning

bull On the other hand if you donrsquot slow the wind down much at all you wonrsquot get much energy

bull Theoretical maximum performance is 59 of energy extractedndash corresponds to reducing velocity by 36

38

Practical Efficiencies

bull Modern windmills attain maybe 50ndash70 of the theoretical maximumndash 05ndash07 times 059 is 030ndash041 or

about 30ndash40ndash this figure is the mechanical energy

extracted from the windbull Conversion from mechanical to

electrical is 90 efficientndash 09 times 030ndash041 is 27ndash37

39

iClicker Question

bull What is about the maximum efficiency of energy generation using the windndash A 20ndash B 40ndash C 60ndash D 80ndash E 100

40

iClicker Question

bull What is about the maximum efficiency of energy generation using the windndash A 20ndash B 40ndash C 60ndash D 80ndash E 100

41

Achievable efficiencies

42

Typical Windmillsbull A typical windmill might be 15 m in diameter

ndash 176 m2

bull At 10 ms wind 40 efficiency this delivers about 100 kW of power

ndash this would be 800 kW at 20 msndash typical windmills are rated at 50 to 600 kW

bull How much energy per yearndash 10 ms 610 Wm2 40 240 Wm2 8760 hours per

year 2000 kWh per year per square meterndash but wind is intermittent real range from 100ndash500 kWhm2

ndash corresponds to 11ndash57 Wm2 average available power density

bull Note the really high tip speeds bird killers

43

Average available wind powerrecall that average solar insolation is about 150ndash250 Wm2

44

Comparable to solar

bull These numbers are similar to solar if not a little biggerndash Letrsquos go to wind

bull BUT the ldquoper square meterrdquo is not land areamdashitrsquos rotor area

bull Doesnrsquot pay to space windmills too closelymdashone robs the other of energy

bull Typical arrangements have rotors 10 diameters apart in direction of prevailing wind 5 diameters apart in the cross-wind directionndash works out to 16 ldquofill factorrdquo

45

Current implementations

bull Rapidly developing resourcendash 1400 MW in 1989 up to 6400 MW in 2003ndash but still insignificant total (compare to large

dams)ndash cost (at 5ndash7cent per kWh) is competitivendash growing at 25 per yearndash expect to triple over next ten years

bull Current capacity 116 GW (April 2007)ndash Texas 2768 MW (recently took lead over

California)ndash California 2361 MWndash Iowa 936 MWndash Minnesota 895 MWndash Washington 818 MW

46

Flies in the Ointment

bull Find that only 20 of rated capacity is achievedndash design for high wind but seldom get it

bull Only 12 of electrical capacity in US is now windndash total electrical capacity in US is 948 GWndash tripling in ten years means 36ndash but achieving only 20 of capacity reduces

substantiallybull If fully developed we could generate an average

power almost equal to our current electrical capacity (764 GW)

ndash but highly variable resource and problematic if more than 20 comes from the intermittent wind

47

iClicker Question

bull Which state generates the most amount of electricity derived from wind powerndash A Virginiandash B Alaskandash C Montanandash D Californiandash E Texas

48

iClicker Question

bull Which state generates the most amount of electricity derived from wind powerndash A Virginiandash B Alaskandash C Montanandash D Californiandash E Texas

• Renewable Energy Sources II Alternatives Part I
• Chapter 5 Summary
• Slide 3
• Slide 4
• Slide 5
• Slide 6
• Slide 7
• Slide 8
• Slide 9
• Slide 10
• Slide 11
• Slide 12
• Slide 13
• Slide 14
• Renewable Resources Discussed in Book
• Renewable Energy Consumption
• Another look at available energy flow
• The Renewable Budget
• Outstanding Points from Fig 51
• Energy Flow continued
• The Hydrologic Cycle
• Energetics of the hydrologic cycle
• Let it Rain
• How much of the process do we get to keep
• iClicker Question
• Slide 26
• Power of a hydroelectric dam
• Importance of Hydroelectricity
• Hydroelectric potential by region in GW
• Slide 30
• Slide 31
• Hydroelectricity in the future
• Sorry try againhellip
• Wind Energy
• The Power of Wind
• Wind Energy proportional to cube of velocity
• Canrsquot get it all
• Practical Efficiencies
• Slide 39
• Slide 40
• Achievable efficiencies
• Typical Windmills
• Average available wind power
• Comparable to solar
• Current implementations
• Flies in the Ointment
• Slide 47
• Slide 48

31

iClicker Question

bull What is true about hydroelectric power generation since 1950ndash A It has always increased in MW producedndash B It has always decreased in MW producedndash C It has increased and decreased in total

MW produced but is now at a peakndash D It has both increased and decreased in

total MW producedndash E The percentage of electric power

produced by hydroelectric plants has generally increased over time

32

Hydroelectricity in the future

bull Wersquore almost tapped-outndash 50 of potential is developedndash remaining potential in large number of small-scale

unitsbull Problems with dams

ndash silt limits lifetime to 50ndash200 years after which dam is useless and in fact a potential disaster and nagging maintenance site

ndash habitat loss for fish (salmon) etc wrecks otherwise stunning landscapes (Glenn Canyon in UT)

ndash Disasters waiting to happen 1680 deaths in US alone from 1918ndash1958 often upstream from major population centers

33

Sorry try againhellip

bull So hydroelectricity is a nice ldquofreebeerdquo handed to us by nature but itrsquos not enough to cover our appetite for energy

bull Though very efficient and seemingly environmentally friendly dams do have their problems

bull This isnrsquot the answer to all our energy problems though it is likely to maintain a role well into our future

34

Wind Energy

35

The Power of Wind

bull Wersquove talked about the kinetic energy in wind beforendash a wind traveling at speed v covers v meters

every second (if v is expressed in ms)ndash the kinetic energy hitting a square meter is

then the kinetic energy the mass of air defined by a rectangular tube

ndash tube is one square meter by v meters or v m3

ndash density of air is = 13 kgm3 at sea levelndash mass is v kgndash KE = frac12(v)v2 = frac12v3 (per square meter)

065v3 at sea level

36

Wind Energy proportional to cube of velocity

bull The book (p 134) says power per square meter is 061v3 which is a more-or-less identical resultndash might account for average density in

continental US (above sea level so air slightly less dense)

bull So if the wind speed doubles the power available in the wind increases by 23 = 222 = 8 times

bull A wind of 10 ms (22 mph) has a power density of 610 Wm2

bull A wind of 20 ms (44 mph) has a power density of 4880 Wm2

37

Canrsquot get it all

bull A windmill canrsquot extract all of the kinetic energy available in the wind because this would mean stopping the wind entirely

bull Stopped wind would divert oncoming wind around it and the windmill would stop spinning

bull On the other hand if you donrsquot slow the wind down much at all you wonrsquot get much energy

bull Theoretical maximum performance is 59 of energy extractedndash corresponds to reducing velocity by 36

38

Practical Efficiencies

bull Modern windmills attain maybe 50ndash70 of the theoretical maximumndash 05ndash07 times 059 is 030ndash041 or

about 30ndash40ndash this figure is the mechanical energy

extracted from the windbull Conversion from mechanical to

electrical is 90 efficientndash 09 times 030ndash041 is 27ndash37

39

iClicker Question

bull What is about the maximum efficiency of energy generation using the windndash A 20ndash B 40ndash C 60ndash D 80ndash E 100

40

iClicker Question

bull What is about the maximum efficiency of energy generation using the windndash A 20ndash B 40ndash C 60ndash D 80ndash E 100

41

Achievable efficiencies

42

Typical Windmillsbull A typical windmill might be 15 m in diameter

ndash 176 m2

bull At 10 ms wind 40 efficiency this delivers about 100 kW of power

ndash this would be 800 kW at 20 msndash typical windmills are rated at 50 to 600 kW

bull How much energy per yearndash 10 ms 610 Wm2 40 240 Wm2 8760 hours per

year 2000 kWh per year per square meterndash but wind is intermittent real range from 100ndash500 kWhm2

ndash corresponds to 11ndash57 Wm2 average available power density

bull Note the really high tip speeds bird killers

43

Average available wind powerrecall that average solar insolation is about 150ndash250 Wm2

44

Comparable to solar

bull These numbers are similar to solar if not a little biggerndash Letrsquos go to wind

bull BUT the ldquoper square meterrdquo is not land areamdashitrsquos rotor area

bull Doesnrsquot pay to space windmills too closelymdashone robs the other of energy

bull Typical arrangements have rotors 10 diameters apart in direction of prevailing wind 5 diameters apart in the cross-wind directionndash works out to 16 ldquofill factorrdquo

45

Current implementations

bull Rapidly developing resourcendash 1400 MW in 1989 up to 6400 MW in 2003ndash but still insignificant total (compare to large

dams)ndash cost (at 5ndash7cent per kWh) is competitivendash growing at 25 per yearndash expect to triple over next ten years

bull Current capacity 116 GW (April 2007)ndash Texas 2768 MW (recently took lead over

California)ndash California 2361 MWndash Iowa 936 MWndash Minnesota 895 MWndash Washington 818 MW

46

Flies in the Ointment

bull Find that only 20 of rated capacity is achievedndash design for high wind but seldom get it

bull Only 12 of electrical capacity in US is now windndash total electrical capacity in US is 948 GWndash tripling in ten years means 36ndash but achieving only 20 of capacity reduces

substantiallybull If fully developed we could generate an average

power almost equal to our current electrical capacity (764 GW)

ndash but highly variable resource and problematic if more than 20 comes from the intermittent wind

47

iClicker Question

bull Which state generates the most amount of electricity derived from wind powerndash A Virginiandash B Alaskandash C Montanandash D Californiandash E Texas

48

iClicker Question

bull Which state generates the most amount of electricity derived from wind powerndash A Virginiandash B Alaskandash C Montanandash D Californiandash E Texas

• Renewable Energy Sources II Alternatives Part I
• Chapter 5 Summary
• Slide 3
• Slide 4
• Slide 5
• Slide 6
• Slide 7
• Slide 8
• Slide 9
• Slide 10
• Slide 11
• Slide 12
• Slide 13
• Slide 14
• Renewable Resources Discussed in Book
• Renewable Energy Consumption
• Another look at available energy flow
• The Renewable Budget
• Outstanding Points from Fig 51
• Energy Flow continued
• The Hydrologic Cycle
• Energetics of the hydrologic cycle
• Let it Rain
• How much of the process do we get to keep
• iClicker Question
• Slide 26
• Power of a hydroelectric dam
• Importance of Hydroelectricity
• Hydroelectric potential by region in GW
• Slide 30
• Slide 31
• Hydroelectricity in the future
• Sorry try againhellip
• Wind Energy
• The Power of Wind
• Wind Energy proportional to cube of velocity
• Canrsquot get it all
• Practical Efficiencies
• Slide 39
• Slide 40
• Achievable efficiencies
• Typical Windmills
• Average available wind power
• Comparable to solar
• Current implementations
• Flies in the Ointment
• Slide 47
• Slide 48

32

Hydroelectricity in the future

bull Wersquore almost tapped-outndash 50 of potential is developedndash remaining potential in large number of small-scale

unitsbull Problems with dams

ndash silt limits lifetime to 50ndash200 years after which dam is useless and in fact a potential disaster and nagging maintenance site

ndash habitat loss for fish (salmon) etc wrecks otherwise stunning landscapes (Glenn Canyon in UT)

ndash Disasters waiting to happen 1680 deaths in US alone from 1918ndash1958 often upstream from major population centers

33

Sorry try againhellip

bull So hydroelectricity is a nice ldquofreebeerdquo handed to us by nature but itrsquos not enough to cover our appetite for energy

bull Though very efficient and seemingly environmentally friendly dams do have their problems

bull This isnrsquot the answer to all our energy problems though it is likely to maintain a role well into our future

34

Wind Energy

35

The Power of Wind

bull Wersquove talked about the kinetic energy in wind beforendash a wind traveling at speed v covers v meters

every second (if v is expressed in ms)ndash the kinetic energy hitting a square meter is

then the kinetic energy the mass of air defined by a rectangular tube

ndash tube is one square meter by v meters or v m3

ndash density of air is = 13 kgm3 at sea levelndash mass is v kgndash KE = frac12(v)v2 = frac12v3 (per square meter)

065v3 at sea level

36

Wind Energy proportional to cube of velocity

bull The book (p 134) says power per square meter is 061v3 which is a more-or-less identical resultndash might account for average density in

continental US (above sea level so air slightly less dense)

bull So if the wind speed doubles the power available in the wind increases by 23 = 222 = 8 times

bull A wind of 10 ms (22 mph) has a power density of 610 Wm2

bull A wind of 20 ms (44 mph) has a power density of 4880 Wm2

37

Canrsquot get it all

bull A windmill canrsquot extract all of the kinetic energy available in the wind because this would mean stopping the wind entirely

bull Stopped wind would divert oncoming wind around it and the windmill would stop spinning

bull On the other hand if you donrsquot slow the wind down much at all you wonrsquot get much energy

bull Theoretical maximum performance is 59 of energy extractedndash corresponds to reducing velocity by 36

38

Practical Efficiencies

bull Modern windmills attain maybe 50ndash70 of the theoretical maximumndash 05ndash07 times 059 is 030ndash041 or

about 30ndash40ndash this figure is the mechanical energy

extracted from the windbull Conversion from mechanical to

electrical is 90 efficientndash 09 times 030ndash041 is 27ndash37

39

iClicker Question

bull What is about the maximum efficiency of energy generation using the windndash A 20ndash B 40ndash C 60ndash D 80ndash E 100

40

iClicker Question

bull What is about the maximum efficiency of energy generation using the windndash A 20ndash B 40ndash C 60ndash D 80ndash E 100

41

Achievable efficiencies

42

Typical Windmillsbull A typical windmill might be 15 m in diameter

ndash 176 m2

bull At 10 ms wind 40 efficiency this delivers about 100 kW of power

ndash this would be 800 kW at 20 msndash typical windmills are rated at 50 to 600 kW

bull How much energy per yearndash 10 ms 610 Wm2 40 240 Wm2 8760 hours per

year 2000 kWh per year per square meterndash but wind is intermittent real range from 100ndash500 kWhm2

ndash corresponds to 11ndash57 Wm2 average available power density

bull Note the really high tip speeds bird killers

43

Average available wind powerrecall that average solar insolation is about 150ndash250 Wm2

44

Comparable to solar

bull These numbers are similar to solar if not a little biggerndash Letrsquos go to wind

bull BUT the ldquoper square meterrdquo is not land areamdashitrsquos rotor area

bull Doesnrsquot pay to space windmills too closelymdashone robs the other of energy

bull Typical arrangements have rotors 10 diameters apart in direction of prevailing wind 5 diameters apart in the cross-wind directionndash works out to 16 ldquofill factorrdquo

45

Current implementations

bull Rapidly developing resourcendash 1400 MW in 1989 up to 6400 MW in 2003ndash but still insignificant total (compare to large

dams)ndash cost (at 5ndash7cent per kWh) is competitivendash growing at 25 per yearndash expect to triple over next ten years

bull Current capacity 116 GW (April 2007)ndash Texas 2768 MW (recently took lead over

California)ndash California 2361 MWndash Iowa 936 MWndash Minnesota 895 MWndash Washington 818 MW

46

Flies in the Ointment

bull Find that only 20 of rated capacity is achievedndash design for high wind but seldom get it

bull Only 12 of electrical capacity in US is now windndash total electrical capacity in US is 948 GWndash tripling in ten years means 36ndash but achieving only 20 of capacity reduces

substantiallybull If fully developed we could generate an average

power almost equal to our current electrical capacity (764 GW)

ndash but highly variable resource and problematic if more than 20 comes from the intermittent wind

47

iClicker Question

bull Which state generates the most amount of electricity derived from wind powerndash A Virginiandash B Alaskandash C Montanandash D Californiandash E Texas

48

iClicker Question

bull Which state generates the most amount of electricity derived from wind powerndash A Virginiandash B Alaskandash C Montanandash D Californiandash E Texas

• Renewable Energy Sources II Alternatives Part I
• Chapter 5 Summary
• Slide 3
• Slide 4
• Slide 5
• Slide 6
• Slide 7
• Slide 8
• Slide 9
• Slide 10
• Slide 11
• Slide 12
• Slide 13
• Slide 14
• Renewable Resources Discussed in Book
• Renewable Energy Consumption
• Another look at available energy flow
• The Renewable Budget
• Outstanding Points from Fig 51
• Energy Flow continued
• The Hydrologic Cycle
• Energetics of the hydrologic cycle
• Let it Rain
• How much of the process do we get to keep
• iClicker Question
• Slide 26
• Power of a hydroelectric dam
• Importance of Hydroelectricity
• Hydroelectric potential by region in GW
• Slide 30
• Slide 31
• Hydroelectricity in the future
• Sorry try againhellip
• Wind Energy
• The Power of Wind
• Wind Energy proportional to cube of velocity
• Canrsquot get it all
• Practical Efficiencies
• Slide 39
• Slide 40
• Achievable efficiencies
• Typical Windmills
• Average available wind power
• Comparable to solar
• Current implementations
• Flies in the Ointment
• Slide 47
• Slide 48

33

Sorry try againhellip

bull So hydroelectricity is a nice ldquofreebeerdquo handed to us by nature but itrsquos not enough to cover our appetite for energy

bull Though very efficient and seemingly environmentally friendly dams do have their problems

bull This isnrsquot the answer to all our energy problems though it is likely to maintain a role well into our future

34

Wind Energy

35

The Power of Wind

bull Wersquove talked about the kinetic energy in wind beforendash a wind traveling at speed v covers v meters

every second (if v is expressed in ms)ndash the kinetic energy hitting a square meter is

then the kinetic energy the mass of air defined by a rectangular tube

ndash tube is one square meter by v meters or v m3

ndash density of air is = 13 kgm3 at sea levelndash mass is v kgndash KE = frac12(v)v2 = frac12v3 (per square meter)

065v3 at sea level

36

Wind Energy proportional to cube of velocity

bull The book (p 134) says power per square meter is 061v3 which is a more-or-less identical resultndash might account for average density in

continental US (above sea level so air slightly less dense)

bull So if the wind speed doubles the power available in the wind increases by 23 = 222 = 8 times

bull A wind of 10 ms (22 mph) has a power density of 610 Wm2

bull A wind of 20 ms (44 mph) has a power density of 4880 Wm2

37

Canrsquot get it all

bull A windmill canrsquot extract all of the kinetic energy available in the wind because this would mean stopping the wind entirely

bull Stopped wind would divert oncoming wind around it and the windmill would stop spinning

bull On the other hand if you donrsquot slow the wind down much at all you wonrsquot get much energy

bull Theoretical maximum performance is 59 of energy extractedndash corresponds to reducing velocity by 36

38

Practical Efficiencies

bull Modern windmills attain maybe 50ndash70 of the theoretical maximumndash 05ndash07 times 059 is 030ndash041 or

about 30ndash40ndash this figure is the mechanical energy

extracted from the windbull Conversion from mechanical to

electrical is 90 efficientndash 09 times 030ndash041 is 27ndash37

39

iClicker Question

bull What is about the maximum efficiency of energy generation using the windndash A 20ndash B 40ndash C 60ndash D 80ndash E 100

40

iClicker Question

bull What is about the maximum efficiency of energy generation using the windndash A 20ndash B 40ndash C 60ndash D 80ndash E 100

41

Achievable efficiencies

42

Typical Windmillsbull A typical windmill might be 15 m in diameter

ndash 176 m2

bull At 10 ms wind 40 efficiency this delivers about 100 kW of power

ndash this would be 800 kW at 20 msndash typical windmills are rated at 50 to 600 kW

bull How much energy per yearndash 10 ms 610 Wm2 40 240 Wm2 8760 hours per

year 2000 kWh per year per square meterndash but wind is intermittent real range from 100ndash500 kWhm2

ndash corresponds to 11ndash57 Wm2 average available power density

bull Note the really high tip speeds bird killers

43

Average available wind powerrecall that average solar insolation is about 150ndash250 Wm2

44

Comparable to solar

bull These numbers are similar to solar if not a little biggerndash Letrsquos go to wind

bull BUT the ldquoper square meterrdquo is not land areamdashitrsquos rotor area

bull Doesnrsquot pay to space windmills too closelymdashone robs the other of energy

bull Typical arrangements have rotors 10 diameters apart in direction of prevailing wind 5 diameters apart in the cross-wind directionndash works out to 16 ldquofill factorrdquo

45

Current implementations

bull Rapidly developing resourcendash 1400 MW in 1989 up to 6400 MW in 2003ndash but still insignificant total (compare to large

dams)ndash cost (at 5ndash7cent per kWh) is competitivendash growing at 25 per yearndash expect to triple over next ten years

bull Current capacity 116 GW (April 2007)ndash Texas 2768 MW (recently took lead over

California)ndash California 2361 MWndash Iowa 936 MWndash Minnesota 895 MWndash Washington 818 MW

46

Flies in the Ointment

bull Find that only 20 of rated capacity is achievedndash design for high wind but seldom get it

bull Only 12 of electrical capacity in US is now windndash total electrical capacity in US is 948 GWndash tripling in ten years means 36ndash but achieving only 20 of capacity reduces

substantiallybull If fully developed we could generate an average

power almost equal to our current electrical capacity (764 GW)

ndash but highly variable resource and problematic if more than 20 comes from the intermittent wind

47

iClicker Question

bull Which state generates the most amount of electricity derived from wind powerndash A Virginiandash B Alaskandash C Montanandash D Californiandash E Texas

48

iClicker Question

bull Which state generates the most amount of electricity derived from wind powerndash A Virginiandash B Alaskandash C Montanandash D Californiandash E Texas

• Renewable Energy Sources II Alternatives Part I
• Chapter 5 Summary
• Slide 3
• Slide 4
• Slide 5
• Slide 6
• Slide 7
• Slide 8
• Slide 9
• Slide 10
• Slide 11
• Slide 12
• Slide 13
• Slide 14
• Renewable Resources Discussed in Book
• Renewable Energy Consumption
• Another look at available energy flow
• The Renewable Budget
• Outstanding Points from Fig 51
• Energy Flow continued
• The Hydrologic Cycle
• Energetics of the hydrologic cycle
• Let it Rain
• How much of the process do we get to keep
• iClicker Question
• Slide 26
• Power of a hydroelectric dam
• Importance of Hydroelectricity
• Hydroelectric potential by region in GW
• Slide 30
• Slide 31
• Hydroelectricity in the future
• Sorry try againhellip
• Wind Energy
• The Power of Wind
• Wind Energy proportional to cube of velocity
• Canrsquot get it all
• Practical Efficiencies
• Slide 39
• Slide 40
• Achievable efficiencies
• Typical Windmills
• Average available wind power
• Comparable to solar
• Current implementations
• Flies in the Ointment
• Slide 47
• Slide 48

34

Wind Energy

35

The Power of Wind

bull Wersquove talked about the kinetic energy in wind beforendash a wind traveling at speed v covers v meters

every second (if v is expressed in ms)ndash the kinetic energy hitting a square meter is

then the kinetic energy the mass of air defined by a rectangular tube

ndash tube is one square meter by v meters or v m3

ndash density of air is = 13 kgm3 at sea levelndash mass is v kgndash KE = frac12(v)v2 = frac12v3 (per square meter)

065v3 at sea level

36

Wind Energy proportional to cube of velocity

bull The book (p 134) says power per square meter is 061v3 which is a more-or-less identical resultndash might account for average density in

continental US (above sea level so air slightly less dense)

bull So if the wind speed doubles the power available in the wind increases by 23 = 222 = 8 times

bull A wind of 10 ms (22 mph) has a power density of 610 Wm2

bull A wind of 20 ms (44 mph) has a power density of 4880 Wm2

37

Canrsquot get it all

bull A windmill canrsquot extract all of the kinetic energy available in the wind because this would mean stopping the wind entirely

bull Stopped wind would divert oncoming wind around it and the windmill would stop spinning

bull On the other hand if you donrsquot slow the wind down much at all you wonrsquot get much energy

bull Theoretical maximum performance is 59 of energy extractedndash corresponds to reducing velocity by 36

38

Practical Efficiencies

bull Modern windmills attain maybe 50ndash70 of the theoretical maximumndash 05ndash07 times 059 is 030ndash041 or

about 30ndash40ndash this figure is the mechanical energy

extracted from the windbull Conversion from mechanical to

electrical is 90 efficientndash 09 times 030ndash041 is 27ndash37

39

iClicker Question

bull What is about the maximum efficiency of energy generation using the windndash A 20ndash B 40ndash C 60ndash D 80ndash E 100

40

iClicker Question

bull What is about the maximum efficiency of energy generation using the windndash A 20ndash B 40ndash C 60ndash D 80ndash E 100

41

Achievable efficiencies

42

Typical Windmillsbull A typical windmill might be 15 m in diameter

ndash 176 m2

bull At 10 ms wind 40 efficiency this delivers about 100 kW of power

ndash this would be 800 kW at 20 msndash typical windmills are rated at 50 to 600 kW

bull How much energy per yearndash 10 ms 610 Wm2 40 240 Wm2 8760 hours per

year 2000 kWh per year per square meterndash but wind is intermittent real range from 100ndash500 kWhm2

ndash corresponds to 11ndash57 Wm2 average available power density

bull Note the really high tip speeds bird killers

43

Average available wind powerrecall that average solar insolation is about 150ndash250 Wm2

44

Comparable to solar

bull These numbers are similar to solar if not a little biggerndash Letrsquos go to wind

bull BUT the ldquoper square meterrdquo is not land areamdashitrsquos rotor area

bull Doesnrsquot pay to space windmills too closelymdashone robs the other of energy

bull Typical arrangements have rotors 10 diameters apart in direction of prevailing wind 5 diameters apart in the cross-wind directionndash works out to 16 ldquofill factorrdquo

45

Current implementations

bull Rapidly developing resourcendash 1400 MW in 1989 up to 6400 MW in 2003ndash but still insignificant total (compare to large

dams)ndash cost (at 5ndash7cent per kWh) is competitivendash growing at 25 per yearndash expect to triple over next ten years

bull Current capacity 116 GW (April 2007)ndash Texas 2768 MW (recently took lead over

California)ndash California 2361 MWndash Iowa 936 MWndash Minnesota 895 MWndash Washington 818 MW

46

Flies in the Ointment

bull Find that only 20 of rated capacity is achievedndash design for high wind but seldom get it

bull Only 12 of electrical capacity in US is now windndash total electrical capacity in US is 948 GWndash tripling in ten years means 36ndash but achieving only 20 of capacity reduces

substantiallybull If fully developed we could generate an average

power almost equal to our current electrical capacity (764 GW)

ndash but highly variable resource and problematic if more than 20 comes from the intermittent wind

47

iClicker Question

bull Which state generates the most amount of electricity derived from wind powerndash A Virginiandash B Alaskandash C Montanandash D Californiandash E Texas

48

iClicker Question

bull Which state generates the most amount of electricity derived from wind powerndash A Virginiandash B Alaskandash C Montanandash D Californiandash E Texas

• Renewable Energy Sources II Alternatives Part I
• Chapter 5 Summary
• Slide 3
• Slide 4
• Slide 5
• Slide 6
• Slide 7
• Slide 8
• Slide 9
• Slide 10
• Slide 11
• Slide 12
• Slide 13
• Slide 14
• Renewable Resources Discussed in Book
• Renewable Energy Consumption
• Another look at available energy flow
• The Renewable Budget
• Outstanding Points from Fig 51
• Energy Flow continued
• The Hydrologic Cycle
• Energetics of the hydrologic cycle
• Let it Rain
• How much of the process do we get to keep
• iClicker Question
• Slide 26
• Power of a hydroelectric dam
• Importance of Hydroelectricity
• Hydroelectric potential by region in GW
• Slide 30
• Slide 31
• Hydroelectricity in the future
• Sorry try againhellip
• Wind Energy
• The Power of Wind
• Wind Energy proportional to cube of velocity
• Canrsquot get it all
• Practical Efficiencies
• Slide 39
• Slide 40
• Achievable efficiencies
• Typical Windmills
• Average available wind power
• Comparable to solar
• Current implementations
• Flies in the Ointment
• Slide 47
• Slide 48

35

The Power of Wind

bull Wersquove talked about the kinetic energy in wind beforendash a wind traveling at speed v covers v meters

every second (if v is expressed in ms)ndash the kinetic energy hitting a square meter is

then the kinetic energy the mass of air defined by a rectangular tube

ndash tube is one square meter by v meters or v m3

ndash density of air is = 13 kgm3 at sea levelndash mass is v kgndash KE = frac12(v)v2 = frac12v3 (per square meter)

065v3 at sea level

36

Wind Energy proportional to cube of velocity

bull The book (p 134) says power per square meter is 061v3 which is a more-or-less identical resultndash might account for average density in

continental US (above sea level so air slightly less dense)

bull So if the wind speed doubles the power available in the wind increases by 23 = 222 = 8 times

bull A wind of 10 ms (22 mph) has a power density of 610 Wm2

bull A wind of 20 ms (44 mph) has a power density of 4880 Wm2

37

Canrsquot get it all

bull A windmill canrsquot extract all of the kinetic energy available in the wind because this would mean stopping the wind entirely

bull Stopped wind would divert oncoming wind around it and the windmill would stop spinning

bull On the other hand if you donrsquot slow the wind down much at all you wonrsquot get much energy

bull Theoretical maximum performance is 59 of energy extractedndash corresponds to reducing velocity by 36

38

Practical Efficiencies

bull Modern windmills attain maybe 50ndash70 of the theoretical maximumndash 05ndash07 times 059 is 030ndash041 or

about 30ndash40ndash this figure is the mechanical energy

extracted from the windbull Conversion from mechanical to

electrical is 90 efficientndash 09 times 030ndash041 is 27ndash37

39

iClicker Question

bull What is about the maximum efficiency of energy generation using the windndash A 20ndash B 40ndash C 60ndash D 80ndash E 100

40

iClicker Question

bull What is about the maximum efficiency of energy generation using the windndash A 20ndash B 40ndash C 60ndash D 80ndash E 100

41

Achievable efficiencies

42

Typical Windmillsbull A typical windmill might be 15 m in diameter

ndash 176 m2

bull At 10 ms wind 40 efficiency this delivers about 100 kW of power

ndash this would be 800 kW at 20 msndash typical windmills are rated at 50 to 600 kW

bull How much energy per yearndash 10 ms 610 Wm2 40 240 Wm2 8760 hours per

year 2000 kWh per year per square meterndash but wind is intermittent real range from 100ndash500 kWhm2

ndash corresponds to 11ndash57 Wm2 average available power density

bull Note the really high tip speeds bird killers

43

Average available wind powerrecall that average solar insolation is about 150ndash250 Wm2

44

Comparable to solar

bull These numbers are similar to solar if not a little biggerndash Letrsquos go to wind

bull BUT the ldquoper square meterrdquo is not land areamdashitrsquos rotor area

bull Doesnrsquot pay to space windmills too closelymdashone robs the other of energy

bull Typical arrangements have rotors 10 diameters apart in direction of prevailing wind 5 diameters apart in the cross-wind directionndash works out to 16 ldquofill factorrdquo

45

Current implementations

bull Rapidly developing resourcendash 1400 MW in 1989 up to 6400 MW in 2003ndash but still insignificant total (compare to large

dams)ndash cost (at 5ndash7cent per kWh) is competitivendash growing at 25 per yearndash expect to triple over next ten years

bull Current capacity 116 GW (April 2007)ndash Texas 2768 MW (recently took lead over

California)ndash California 2361 MWndash Iowa 936 MWndash Minnesota 895 MWndash Washington 818 MW

46

Flies in the Ointment

bull Find that only 20 of rated capacity is achievedndash design for high wind but seldom get it

bull Only 12 of electrical capacity in US is now windndash total electrical capacity in US is 948 GWndash tripling in ten years means 36ndash but achieving only 20 of capacity reduces

substantiallybull If fully developed we could generate an average

power almost equal to our current electrical capacity (764 GW)

ndash but highly variable resource and problematic if more than 20 comes from the intermittent wind

47

iClicker Question

bull Which state generates the most amount of electricity derived from wind powerndash A Virginiandash B Alaskandash C Montanandash D Californiandash E Texas

48

iClicker Question

bull Which state generates the most amount of electricity derived from wind powerndash A Virginiandash B Alaskandash C Montanandash D Californiandash E Texas

• Renewable Energy Sources II Alternatives Part I
• Chapter 5 Summary
• Slide 3
• Slide 4
• Slide 5
• Slide 6
• Slide 7
• Slide 8
• Slide 9
• Slide 10
• Slide 11
• Slide 12
• Slide 13
• Slide 14
• Renewable Resources Discussed in Book
• Renewable Energy Consumption
• Another look at available energy flow
• The Renewable Budget
• Outstanding Points from Fig 51
• Energy Flow continued
• The Hydrologic Cycle
• Energetics of the hydrologic cycle
• Let it Rain
• How much of the process do we get to keep
• iClicker Question
• Slide 26
• Power of a hydroelectric dam
• Importance of Hydroelectricity
• Hydroelectric potential by region in GW
• Slide 30
• Slide 31
• Hydroelectricity in the future
• Sorry try againhellip
• Wind Energy
• The Power of Wind
• Wind Energy proportional to cube of velocity
• Canrsquot get it all
• Practical Efficiencies
• Slide 39
• Slide 40
• Achievable efficiencies
• Typical Windmills
• Average available wind power
• Comparable to solar
• Current implementations
• Flies in the Ointment
• Slide 47
• Slide 48

36

Wind Energy proportional to cube of velocity

bull The book (p 134) says power per square meter is 061v3 which is a more-or-less identical resultndash might account for average density in

continental US (above sea level so air slightly less dense)

bull So if the wind speed doubles the power available in the wind increases by 23 = 222 = 8 times

bull A wind of 10 ms (22 mph) has a power density of 610 Wm2

bull A wind of 20 ms (44 mph) has a power density of 4880 Wm2

37

Canrsquot get it all

bull A windmill canrsquot extract all of the kinetic energy available in the wind because this would mean stopping the wind entirely

bull Stopped wind would divert oncoming wind around it and the windmill would stop spinning

bull On the other hand if you donrsquot slow the wind down much at all you wonrsquot get much energy

bull Theoretical maximum performance is 59 of energy extractedndash corresponds to reducing velocity by 36

38

Practical Efficiencies

bull Modern windmills attain maybe 50ndash70 of the theoretical maximumndash 05ndash07 times 059 is 030ndash041 or

about 30ndash40ndash this figure is the mechanical energy

extracted from the windbull Conversion from mechanical to

electrical is 90 efficientndash 09 times 030ndash041 is 27ndash37

39

iClicker Question

bull What is about the maximum efficiency of energy generation using the windndash A 20ndash B 40ndash C 60ndash D 80ndash E 100

40

iClicker Question

bull What is about the maximum efficiency of energy generation using the windndash A 20ndash B 40ndash C 60ndash D 80ndash E 100

41

Achievable efficiencies

42

Typical Windmillsbull A typical windmill might be 15 m in diameter

ndash 176 m2

bull At 10 ms wind 40 efficiency this delivers about 100 kW of power

ndash this would be 800 kW at 20 msndash typical windmills are rated at 50 to 600 kW

bull How much energy per yearndash 10 ms 610 Wm2 40 240 Wm2 8760 hours per

year 2000 kWh per year per square meterndash but wind is intermittent real range from 100ndash500 kWhm2

ndash corresponds to 11ndash57 Wm2 average available power density

bull Note the really high tip speeds bird killers

43

Average available wind powerrecall that average solar insolation is about 150ndash250 Wm2

44

Comparable to solar

bull These numbers are similar to solar if not a little biggerndash Letrsquos go to wind

bull BUT the ldquoper square meterrdquo is not land areamdashitrsquos rotor area

bull Doesnrsquot pay to space windmills too closelymdashone robs the other of energy

bull Typical arrangements have rotors 10 diameters apart in direction of prevailing wind 5 diameters apart in the cross-wind directionndash works out to 16 ldquofill factorrdquo

45

Current implementations

bull Rapidly developing resourcendash 1400 MW in 1989 up to 6400 MW in 2003ndash but still insignificant total (compare to large

dams)ndash cost (at 5ndash7cent per kWh) is competitivendash growing at 25 per yearndash expect to triple over next ten years

bull Current capacity 116 GW (April 2007)ndash Texas 2768 MW (recently took lead over

California)ndash California 2361 MWndash Iowa 936 MWndash Minnesota 895 MWndash Washington 818 MW

46

Flies in the Ointment

bull Find that only 20 of rated capacity is achievedndash design for high wind but seldom get it

bull Only 12 of electrical capacity in US is now windndash total electrical capacity in US is 948 GWndash tripling in ten years means 36ndash but achieving only 20 of capacity reduces

substantiallybull If fully developed we could generate an average

power almost equal to our current electrical capacity (764 GW)

ndash but highly variable resource and problematic if more than 20 comes from the intermittent wind

47

iClicker Question

bull Which state generates the most amount of electricity derived from wind powerndash A Virginiandash B Alaskandash C Montanandash D Californiandash E Texas

48

iClicker Question

bull Which state generates the most amount of electricity derived from wind powerndash A Virginiandash B Alaskandash C Montanandash D Californiandash E Texas

• Renewable Energy Sources II Alternatives Part I
• Chapter 5 Summary
• Slide 3
• Slide 4
• Slide 5
• Slide 6
• Slide 7
• Slide 8
• Slide 9
• Slide 10
• Slide 11
• Slide 12
• Slide 13
• Slide 14
• Renewable Resources Discussed in Book
• Renewable Energy Consumption
• Another look at available energy flow
• The Renewable Budget
• Outstanding Points from Fig 51
• Energy Flow continued
• The Hydrologic Cycle
• Energetics of the hydrologic cycle
• Let it Rain
• How much of the process do we get to keep
• iClicker Question
• Slide 26
• Power of a hydroelectric dam
• Importance of Hydroelectricity
• Hydroelectric potential by region in GW
• Slide 30
• Slide 31
• Hydroelectricity in the future
• Sorry try againhellip
• Wind Energy
• The Power of Wind
• Wind Energy proportional to cube of velocity
• Canrsquot get it all
• Practical Efficiencies
• Slide 39
• Slide 40
• Achievable efficiencies
• Typical Windmills
• Average available wind power
• Comparable to solar
• Current implementations
• Flies in the Ointment
• Slide 47
• Slide 48

37

Canrsquot get it all

bull A windmill canrsquot extract all of the kinetic energy available in the wind because this would mean stopping the wind entirely

bull Stopped wind would divert oncoming wind around it and the windmill would stop spinning

bull On the other hand if you donrsquot slow the wind down much at all you wonrsquot get much energy

bull Theoretical maximum performance is 59 of energy extractedndash corresponds to reducing velocity by 36

38

Practical Efficiencies

bull Modern windmills attain maybe 50ndash70 of the theoretical maximumndash 05ndash07 times 059 is 030ndash041 or

about 30ndash40ndash this figure is the mechanical energy

extracted from the windbull Conversion from mechanical to

electrical is 90 efficientndash 09 times 030ndash041 is 27ndash37

39

iClicker Question

bull What is about the maximum efficiency of energy generation using the windndash A 20ndash B 40ndash C 60ndash D 80ndash E 100

40

iClicker Question

bull What is about the maximum efficiency of energy generation using the windndash A 20ndash B 40ndash C 60ndash D 80ndash E 100

41

Achievable efficiencies

42

Typical Windmillsbull A typical windmill might be 15 m in diameter

ndash 176 m2

bull At 10 ms wind 40 efficiency this delivers about 100 kW of power

ndash this would be 800 kW at 20 msndash typical windmills are rated at 50 to 600 kW

bull How much energy per yearndash 10 ms 610 Wm2 40 240 Wm2 8760 hours per

year 2000 kWh per year per square meterndash but wind is intermittent real range from 100ndash500 kWhm2

ndash corresponds to 11ndash57 Wm2 average available power density

bull Note the really high tip speeds bird killers

43

Average available wind powerrecall that average solar insolation is about 150ndash250 Wm2

44

Comparable to solar

bull These numbers are similar to solar if not a little biggerndash Letrsquos go to wind

bull BUT the ldquoper square meterrdquo is not land areamdashitrsquos rotor area

bull Doesnrsquot pay to space windmills too closelymdashone robs the other of energy

bull Typical arrangements have rotors 10 diameters apart in direction of prevailing wind 5 diameters apart in the cross-wind directionndash works out to 16 ldquofill factorrdquo

45

Current implementations

bull Rapidly developing resourcendash 1400 MW in 1989 up to 6400 MW in 2003ndash but still insignificant total (compare to large

dams)ndash cost (at 5ndash7cent per kWh) is competitivendash growing at 25 per yearndash expect to triple over next ten years

bull Current capacity 116 GW (April 2007)ndash Texas 2768 MW (recently took lead over

California)ndash California 2361 MWndash Iowa 936 MWndash Minnesota 895 MWndash Washington 818 MW

46

Flies in the Ointment

bull Find that only 20 of rated capacity is achievedndash design for high wind but seldom get it

bull Only 12 of electrical capacity in US is now windndash total electrical capacity in US is 948 GWndash tripling in ten years means 36ndash but achieving only 20 of capacity reduces

substantiallybull If fully developed we could generate an average

power almost equal to our current electrical capacity (764 GW)

ndash but highly variable resource and problematic if more than 20 comes from the intermittent wind

47

iClicker Question

bull Which state generates the most amount of electricity derived from wind powerndash A Virginiandash B Alaskandash C Montanandash D Californiandash E Texas

48

iClicker Question

bull Which state generates the most amount of electricity derived from wind powerndash A Virginiandash B Alaskandash C Montanandash D Californiandash E Texas

• Renewable Energy Sources II Alternatives Part I
• Chapter 5 Summary
• Slide 3
• Slide 4
• Slide 5
• Slide 6
• Slide 7
• Slide 8
• Slide 9
• Slide 10
• Slide 11
• Slide 12
• Slide 13
• Slide 14
• Renewable Resources Discussed in Book
• Renewable Energy Consumption
• Another look at available energy flow
• The Renewable Budget
• Outstanding Points from Fig 51
• Energy Flow continued
• The Hydrologic Cycle
• Energetics of the hydrologic cycle
• Let it Rain
• How much of the process do we get to keep
• iClicker Question
• Slide 26
• Power of a hydroelectric dam
• Importance of Hydroelectricity
• Hydroelectric potential by region in GW
• Slide 30
• Slide 31
• Hydroelectricity in the future
• Sorry try againhellip
• Wind Energy
• The Power of Wind
• Wind Energy proportional to cube of velocity
• Canrsquot get it all
• Practical Efficiencies
• Slide 39
• Slide 40
• Achievable efficiencies
• Typical Windmills
• Average available wind power
• Comparable to solar
• Current implementations
• Flies in the Ointment
• Slide 47
• Slide 48

38

Practical Efficiencies

bull Modern windmills attain maybe 50ndash70 of the theoretical maximumndash 05ndash07 times 059 is 030ndash041 or

about 30ndash40ndash this figure is the mechanical energy

extracted from the windbull Conversion from mechanical to

electrical is 90 efficientndash 09 times 030ndash041 is 27ndash37

39

iClicker Question

bull What is about the maximum efficiency of energy generation using the windndash A 20ndash B 40ndash C 60ndash D 80ndash E 100

40

iClicker Question

bull What is about the maximum efficiency of energy generation using the windndash A 20ndash B 40ndash C 60ndash D 80ndash E 100

41

Achievable efficiencies

42

Typical Windmillsbull A typical windmill might be 15 m in diameter

ndash 176 m2

bull At 10 ms wind 40 efficiency this delivers about 100 kW of power

ndash this would be 800 kW at 20 msndash typical windmills are rated at 50 to 600 kW

bull How much energy per yearndash 10 ms 610 Wm2 40 240 Wm2 8760 hours per

year 2000 kWh per year per square meterndash but wind is intermittent real range from 100ndash500 kWhm2

ndash corresponds to 11ndash57 Wm2 average available power density

bull Note the really high tip speeds bird killers

43

Average available wind powerrecall that average solar insolation is about 150ndash250 Wm2

44

Comparable to solar

bull These numbers are similar to solar if not a little biggerndash Letrsquos go to wind

bull BUT the ldquoper square meterrdquo is not land areamdashitrsquos rotor area

bull Doesnrsquot pay to space windmills too closelymdashone robs the other of energy

bull Typical arrangements have rotors 10 diameters apart in direction of prevailing wind 5 diameters apart in the cross-wind directionndash works out to 16 ldquofill factorrdquo

45

Current implementations

bull Rapidly developing resourcendash 1400 MW in 1989 up to 6400 MW in 2003ndash but still insignificant total (compare to large

dams)ndash cost (at 5ndash7cent per kWh) is competitivendash growing at 25 per yearndash expect to triple over next ten years

bull Current capacity 116 GW (April 2007)ndash Texas 2768 MW (recently took lead over

California)ndash California 2361 MWndash Iowa 936 MWndash Minnesota 895 MWndash Washington 818 MW

46

Flies in the Ointment

bull Find that only 20 of rated capacity is achievedndash design for high wind but seldom get it

bull Only 12 of electrical capacity in US is now windndash total electrical capacity in US is 948 GWndash tripling in ten years means 36ndash but achieving only 20 of capacity reduces

substantiallybull If fully developed we could generate an average

power almost equal to our current electrical capacity (764 GW)

ndash but highly variable resource and problematic if more than 20 comes from the intermittent wind

47

iClicker Question

bull Which state generates the most amount of electricity derived from wind powerndash A Virginiandash B Alaskandash C Montanandash D Californiandash E Texas

48

iClicker Question

bull Which state generates the most amount of electricity derived from wind powerndash A Virginiandash B Alaskandash C Montanandash D Californiandash E Texas

• Renewable Energy Sources II Alternatives Part I
• Chapter 5 Summary
• Slide 3
• Slide 4
• Slide 5
• Slide 6
• Slide 7
• Slide 8
• Slide 9
• Slide 10
• Slide 11
• Slide 12
• Slide 13
• Slide 14
• Renewable Resources Discussed in Book
• Renewable Energy Consumption
• Another look at available energy flow
• The Renewable Budget
• Outstanding Points from Fig 51
• Energy Flow continued
• The Hydrologic Cycle
• Energetics of the hydrologic cycle
• Let it Rain
• How much of the process do we get to keep
• iClicker Question
• Slide 26
• Power of a hydroelectric dam
• Importance of Hydroelectricity
• Hydroelectric potential by region in GW
• Slide 30
• Slide 31
• Hydroelectricity in the future
• Sorry try againhellip
• Wind Energy
• The Power of Wind
• Wind Energy proportional to cube of velocity
• Canrsquot get it all
• Practical Efficiencies
• Slide 39
• Slide 40
• Achievable efficiencies
• Typical Windmills
• Average available wind power
• Comparable to solar
• Current implementations
• Flies in the Ointment
• Slide 47
• Slide 48

39

iClicker Question

bull What is about the maximum efficiency of energy generation using the windndash A 20ndash B 40ndash C 60ndash D 80ndash E 100

40

iClicker Question

bull What is about the maximum efficiency of energy generation using the windndash A 20ndash B 40ndash C 60ndash D 80ndash E 100

41

Achievable efficiencies

42

Typical Windmillsbull A typical windmill might be 15 m in diameter

ndash 176 m2

bull At 10 ms wind 40 efficiency this delivers about 100 kW of power

ndash this would be 800 kW at 20 msndash typical windmills are rated at 50 to 600 kW

bull How much energy per yearndash 10 ms 610 Wm2 40 240 Wm2 8760 hours per

year 2000 kWh per year per square meterndash but wind is intermittent real range from 100ndash500 kWhm2

ndash corresponds to 11ndash57 Wm2 average available power density

bull Note the really high tip speeds bird killers

43

Average available wind powerrecall that average solar insolation is about 150ndash250 Wm2

44

Comparable to solar

bull These numbers are similar to solar if not a little biggerndash Letrsquos go to wind

bull BUT the ldquoper square meterrdquo is not land areamdashitrsquos rotor area

bull Doesnrsquot pay to space windmills too closelymdashone robs the other of energy

bull Typical arrangements have rotors 10 diameters apart in direction of prevailing wind 5 diameters apart in the cross-wind directionndash works out to 16 ldquofill factorrdquo

45

Current implementations

bull Rapidly developing resourcendash 1400 MW in 1989 up to 6400 MW in 2003ndash but still insignificant total (compare to large

dams)ndash cost (at 5ndash7cent per kWh) is competitivendash growing at 25 per yearndash expect to triple over next ten years

bull Current capacity 116 GW (April 2007)ndash Texas 2768 MW (recently took lead over

California)ndash California 2361 MWndash Iowa 936 MWndash Minnesota 895 MWndash Washington 818 MW

46

Flies in the Ointment

bull Find that only 20 of rated capacity is achievedndash design for high wind but seldom get it

bull Only 12 of electrical capacity in US is now windndash total electrical capacity in US is 948 GWndash tripling in ten years means 36ndash but achieving only 20 of capacity reduces

substantiallybull If fully developed we could generate an average

power almost equal to our current electrical capacity (764 GW)

ndash but highly variable resource and problematic if more than 20 comes from the intermittent wind

47

iClicker Question

bull Which state generates the most amount of electricity derived from wind powerndash A Virginiandash B Alaskandash C Montanandash D Californiandash E Texas

48

iClicker Question

bull Which state generates the most amount of electricity derived from wind powerndash A Virginiandash B Alaskandash C Montanandash D Californiandash E Texas

• Renewable Energy Sources II Alternatives Part I
• Chapter 5 Summary
• Slide 3
• Slide 4
• Slide 5
• Slide 6
• Slide 7
• Slide 8
• Slide 9
• Slide 10
• Slide 11
• Slide 12
• Slide 13
• Slide 14
• Renewable Resources Discussed in Book
• Renewable Energy Consumption
• Another look at available energy flow
• The Renewable Budget
• Outstanding Points from Fig 51
• Energy Flow continued
• The Hydrologic Cycle
• Energetics of the hydrologic cycle
• Let it Rain
• How much of the process do we get to keep
• iClicker Question
• Slide 26
• Power of a hydroelectric dam
• Importance of Hydroelectricity
• Hydroelectric potential by region in GW
• Slide 30
• Slide 31
• Hydroelectricity in the future
• Sorry try againhellip
• Wind Energy
• The Power of Wind
• Wind Energy proportional to cube of velocity
• Canrsquot get it all
• Practical Efficiencies
• Slide 39
• Slide 40
• Achievable efficiencies
• Typical Windmills
• Average available wind power
• Comparable to solar
• Current implementations
• Flies in the Ointment
• Slide 47
• Slide 48

40

iClicker Question

bull What is about the maximum efficiency of energy generation using the windndash A 20ndash B 40ndash C 60ndash D 80ndash E 100

41

Achievable efficiencies

42

Typical Windmillsbull A typical windmill might be 15 m in diameter

ndash 176 m2

bull At 10 ms wind 40 efficiency this delivers about 100 kW of power

ndash this would be 800 kW at 20 msndash typical windmills are rated at 50 to 600 kW

bull How much energy per yearndash 10 ms 610 Wm2 40 240 Wm2 8760 hours per

year 2000 kWh per year per square meterndash but wind is intermittent real range from 100ndash500 kWhm2

ndash corresponds to 11ndash57 Wm2 average available power density

bull Note the really high tip speeds bird killers

43

Average available wind powerrecall that average solar insolation is about 150ndash250 Wm2

44

Comparable to solar

bull These numbers are similar to solar if not a little biggerndash Letrsquos go to wind

bull BUT the ldquoper square meterrdquo is not land areamdashitrsquos rotor area

bull Doesnrsquot pay to space windmills too closelymdashone robs the other of energy

bull Typical arrangements have rotors 10 diameters apart in direction of prevailing wind 5 diameters apart in the cross-wind directionndash works out to 16 ldquofill factorrdquo

45

Current implementations

bull Rapidly developing resourcendash 1400 MW in 1989 up to 6400 MW in 2003ndash but still insignificant total (compare to large

dams)ndash cost (at 5ndash7cent per kWh) is competitivendash growing at 25 per yearndash expect to triple over next ten years

bull Current capacity 116 GW (April 2007)ndash Texas 2768 MW (recently took lead over

California)ndash California 2361 MWndash Iowa 936 MWndash Minnesota 895 MWndash Washington 818 MW

46

Flies in the Ointment

bull Find that only 20 of rated capacity is achievedndash design for high wind but seldom get it

bull Only 12 of electrical capacity in US is now windndash total electrical capacity in US is 948 GWndash tripling in ten years means 36ndash but achieving only 20 of capacity reduces

substantiallybull If fully developed we could generate an average

power almost equal to our current electrical capacity (764 GW)

ndash but highly variable resource and problematic if more than 20 comes from the intermittent wind

47

iClicker Question

bull Which state generates the most amount of electricity derived from wind powerndash A Virginiandash B Alaskandash C Montanandash D Californiandash E Texas

48

iClicker Question

bull Which state generates the most amount of electricity derived from wind powerndash A Virginiandash B Alaskandash C Montanandash D Californiandash E Texas

• Renewable Energy Sources II Alternatives Part I
• Chapter 5 Summary
• Slide 3
• Slide 4
• Slide 5
• Slide 6
• Slide 7
• Slide 8
• Slide 9
• Slide 10
• Slide 11
• Slide 12
• Slide 13
• Slide 14
• Renewable Resources Discussed in Book
• Renewable Energy Consumption
• Another look at available energy flow
• The Renewable Budget
• Outstanding Points from Fig 51
• Energy Flow continued
• The Hydrologic Cycle
• Energetics of the hydrologic cycle
• Let it Rain
• How much of the process do we get to keep
• iClicker Question
• Slide 26
• Power of a hydroelectric dam
• Importance of Hydroelectricity
• Hydroelectric potential by region in GW
• Slide 30
• Slide 31
• Hydroelectricity in the future
• Sorry try againhellip
• Wind Energy
• The Power of Wind
• Wind Energy proportional to cube of velocity
• Canrsquot get it all
• Practical Efficiencies
• Slide 39
• Slide 40
• Achievable efficiencies
• Typical Windmills
• Average available wind power
• Comparable to solar
• Current implementations
• Flies in the Ointment
• Slide 47
• Slide 48

41

Achievable efficiencies

42

Typical Windmillsbull A typical windmill might be 15 m in diameter

ndash 176 m2

bull At 10 ms wind 40 efficiency this delivers about 100 kW of power

ndash this would be 800 kW at 20 msndash typical windmills are rated at 50 to 600 kW

bull How much energy per yearndash 10 ms 610 Wm2 40 240 Wm2 8760 hours per

year 2000 kWh per year per square meterndash but wind is intermittent real range from 100ndash500 kWhm2

ndash corresponds to 11ndash57 Wm2 average available power density

bull Note the really high tip speeds bird killers

43

Average available wind powerrecall that average solar insolation is about 150ndash250 Wm2

44

Comparable to solar

bull These numbers are similar to solar if not a little biggerndash Letrsquos go to wind

bull BUT the ldquoper square meterrdquo is not land areamdashitrsquos rotor area

bull Doesnrsquot pay to space windmills too closelymdashone robs the other of energy

bull Typical arrangements have rotors 10 diameters apart in direction of prevailing wind 5 diameters apart in the cross-wind directionndash works out to 16 ldquofill factorrdquo

45

Current implementations

bull Rapidly developing resourcendash 1400 MW in 1989 up to 6400 MW in 2003ndash but still insignificant total (compare to large

dams)ndash cost (at 5ndash7cent per kWh) is competitivendash growing at 25 per yearndash expect to triple over next ten years

bull Current capacity 116 GW (April 2007)ndash Texas 2768 MW (recently took lead over

California)ndash California 2361 MWndash Iowa 936 MWndash Minnesota 895 MWndash Washington 818 MW

46

Flies in the Ointment

bull Find that only 20 of rated capacity is achievedndash design for high wind but seldom get it

bull Only 12 of electrical capacity in US is now windndash total electrical capacity in US is 948 GWndash tripling in ten years means 36ndash but achieving only 20 of capacity reduces

substantiallybull If fully developed we could generate an average

power almost equal to our current electrical capacity (764 GW)

ndash but highly variable resource and problematic if more than 20 comes from the intermittent wind

47

iClicker Question

bull Which state generates the most amount of electricity derived from wind powerndash A Virginiandash B Alaskandash C Montanandash D Californiandash E Texas

48

iClicker Question

bull Which state generates the most amount of electricity derived from wind powerndash A Virginiandash B Alaskandash C Montanandash D Californiandash E Texas

• Renewable Energy Sources II Alternatives Part I
• Chapter 5 Summary
• Slide 3
• Slide 4
• Slide 5
• Slide 6
• Slide 7
• Slide 8
• Slide 9
• Slide 10
• Slide 11
• Slide 12
• Slide 13
• Slide 14
• Renewable Resources Discussed in Book
• Renewable Energy Consumption
• Another look at available energy flow
• The Renewable Budget
• Outstanding Points from Fig 51
• Energy Flow continued
• The Hydrologic Cycle
• Energetics of the hydrologic cycle
• Let it Rain
• How much of the process do we get to keep
• iClicker Question
• Slide 26
• Power of a hydroelectric dam
• Importance of Hydroelectricity
• Hydroelectric potential by region in GW
• Slide 30
• Slide 31
• Hydroelectricity in the future
• Sorry try againhellip
• Wind Energy
• The Power of Wind
• Wind Energy proportional to cube of velocity
• Canrsquot get it all
• Practical Efficiencies
• Slide 39
• Slide 40
• Achievable efficiencies
• Typical Windmills
• Average available wind power
• Comparable to solar
• Current implementations
• Flies in the Ointment
• Slide 47
• Slide 48

42

Typical Windmillsbull A typical windmill might be 15 m in diameter

ndash 176 m2

bull At 10 ms wind 40 efficiency this delivers about 100 kW of power

ndash this would be 800 kW at 20 msndash typical windmills are rated at 50 to 600 kW

bull How much energy per yearndash 10 ms 610 Wm2 40 240 Wm2 8760 hours per

year 2000 kWh per year per square meterndash but wind is intermittent real range from 100ndash500 kWhm2

ndash corresponds to 11ndash57 Wm2 average available power density

bull Note the really high tip speeds bird killers

43

Average available wind powerrecall that average solar insolation is about 150ndash250 Wm2

44

Comparable to solar

bull These numbers are similar to solar if not a little biggerndash Letrsquos go to wind

bull BUT the ldquoper square meterrdquo is not land areamdashitrsquos rotor area

bull Doesnrsquot pay to space windmills too closelymdashone robs the other of energy

bull Typical arrangements have rotors 10 diameters apart in direction of prevailing wind 5 diameters apart in the cross-wind directionndash works out to 16 ldquofill factorrdquo

45

Current implementations

bull Rapidly developing resourcendash 1400 MW in 1989 up to 6400 MW in 2003ndash but still insignificant total (compare to large

dams)ndash cost (at 5ndash7cent per kWh) is competitivendash growing at 25 per yearndash expect to triple over next ten years

bull Current capacity 116 GW (April 2007)ndash Texas 2768 MW (recently took lead over

California)ndash California 2361 MWndash Iowa 936 MWndash Minnesota 895 MWndash Washington 818 MW

46

Flies in the Ointment

bull Find that only 20 of rated capacity is achievedndash design for high wind but seldom get it

bull Only 12 of electrical capacity in US is now windndash total electrical capacity in US is 948 GWndash tripling in ten years means 36ndash but achieving only 20 of capacity reduces

substantiallybull If fully developed we could generate an average

power almost equal to our current electrical capacity (764 GW)

ndash but highly variable resource and problematic if more than 20 comes from the intermittent wind

47

iClicker Question

bull Which state generates the most amount of electricity derived from wind powerndash A Virginiandash B Alaskandash C Montanandash D Californiandash E Texas

48

iClicker Question

bull Which state generates the most amount of electricity derived from wind powerndash A Virginiandash B Alaskandash C Montanandash D Californiandash E Texas

• Renewable Energy Sources II Alternatives Part I
• Chapter 5 Summary
• Slide 3
• Slide 4
• Slide 5
• Slide 6
• Slide 7
• Slide 8
• Slide 9
• Slide 10
• Slide 11
• Slide 12
• Slide 13
• Slide 14
• Renewable Resources Discussed in Book
• Renewable Energy Consumption
• Another look at available energy flow
• The Renewable Budget
• Outstanding Points from Fig 51
• Energy Flow continued
• The Hydrologic Cycle
• Energetics of the hydrologic cycle
• Let it Rain
• How much of the process do we get to keep
• iClicker Question
• Slide 26
• Power of a hydroelectric dam
• Importance of Hydroelectricity
• Hydroelectric potential by region in GW
• Slide 30
• Slide 31
• Hydroelectricity in the future
• Sorry try againhellip
• Wind Energy
• The Power of Wind
• Wind Energy proportional to cube of velocity
• Canrsquot get it all
• Practical Efficiencies
• Slide 39
• Slide 40
• Achievable efficiencies
• Typical Windmills
• Average available wind power
• Comparable to solar
• Current implementations
• Flies in the Ointment
• Slide 47
• Slide 48

43

Average available wind powerrecall that average solar insolation is about 150ndash250 Wm2

44

Comparable to solar

bull These numbers are similar to solar if not a little biggerndash Letrsquos go to wind

bull BUT the ldquoper square meterrdquo is not land areamdashitrsquos rotor area

bull Doesnrsquot pay to space windmills too closelymdashone robs the other of energy

bull Typical arrangements have rotors 10 diameters apart in direction of prevailing wind 5 diameters apart in the cross-wind directionndash works out to 16 ldquofill factorrdquo

45

Current implementations

bull Rapidly developing resourcendash 1400 MW in 1989 up to 6400 MW in 2003ndash but still insignificant total (compare to large

dams)ndash cost (at 5ndash7cent per kWh) is competitivendash growing at 25 per yearndash expect to triple over next ten years

bull Current capacity 116 GW (April 2007)ndash Texas 2768 MW (recently took lead over

California)ndash California 2361 MWndash Iowa 936 MWndash Minnesota 895 MWndash Washington 818 MW

46

Flies in the Ointment

bull Find that only 20 of rated capacity is achievedndash design for high wind but seldom get it

bull Only 12 of electrical capacity in US is now windndash total electrical capacity in US is 948 GWndash tripling in ten years means 36ndash but achieving only 20 of capacity reduces

substantiallybull If fully developed we could generate an average

power almost equal to our current electrical capacity (764 GW)

ndash but highly variable resource and problematic if more than 20 comes from the intermittent wind

47

iClicker Question

bull Which state generates the most amount of electricity derived from wind powerndash A Virginiandash B Alaskandash C Montanandash D Californiandash E Texas

48

iClicker Question

bull Which state generates the most amount of electricity derived from wind powerndash A Virginiandash B Alaskandash C Montanandash D Californiandash E Texas

• Renewable Energy Sources II Alternatives Part I
• Chapter 5 Summary
• Slide 3
• Slide 4
• Slide 5
• Slide 6
• Slide 7
• Slide 8
• Slide 9
• Slide 10
• Slide 11
• Slide 12
• Slide 13
• Slide 14
• Renewable Resources Discussed in Book
• Renewable Energy Consumption
• Another look at available energy flow
• The Renewable Budget
• Outstanding Points from Fig 51
• Energy Flow continued
• The Hydrologic Cycle
• Energetics of the hydrologic cycle
• Let it Rain
• How much of the process do we get to keep
• iClicker Question
• Slide 26
• Power of a hydroelectric dam
• Importance of Hydroelectricity
• Hydroelectric potential by region in GW
• Slide 30
• Slide 31
• Hydroelectricity in the future
• Sorry try againhellip
• Wind Energy
• The Power of Wind
• Wind Energy proportional to cube of velocity
• Canrsquot get it all
• Practical Efficiencies
• Slide 39
• Slide 40
• Achievable efficiencies
• Typical Windmills
• Average available wind power
• Comparable to solar
• Current implementations
• Flies in the Ointment
• Slide 47
• Slide 48

44

Comparable to solar

bull These numbers are similar to solar if not a little biggerndash Letrsquos go to wind

bull BUT the ldquoper square meterrdquo is not land areamdashitrsquos rotor area

bull Doesnrsquot pay to space windmills too closelymdashone robs the other of energy

bull Typical arrangements have rotors 10 diameters apart in direction of prevailing wind 5 diameters apart in the cross-wind directionndash works out to 16 ldquofill factorrdquo

45

Current implementations

bull Rapidly developing resourcendash 1400 MW in 1989 up to 6400 MW in 2003ndash but still insignificant total (compare to large

dams)ndash cost (at 5ndash7cent per kWh) is competitivendash growing at 25 per yearndash expect to triple over next ten years

bull Current capacity 116 GW (April 2007)ndash Texas 2768 MW (recently took lead over

California)ndash California 2361 MWndash Iowa 936 MWndash Minnesota 895 MWndash Washington 818 MW

46

Flies in the Ointment

bull Find that only 20 of rated capacity is achievedndash design for high wind but seldom get it

bull Only 12 of electrical capacity in US is now windndash total electrical capacity in US is 948 GWndash tripling in ten years means 36ndash but achieving only 20 of capacity reduces

substantiallybull If fully developed we could generate an average

power almost equal to our current electrical capacity (764 GW)

ndash but highly variable resource and problematic if more than 20 comes from the intermittent wind

47

iClicker Question

bull Which state generates the most amount of electricity derived from wind powerndash A Virginiandash B Alaskandash C Montanandash D Californiandash E Texas

48

iClicker Question

bull Which state generates the most amount of electricity derived from wind powerndash A Virginiandash B Alaskandash C Montanandash D Californiandash E Texas

• Renewable Energy Sources II Alternatives Part I
• Chapter 5 Summary
• Slide 3
• Slide 4
• Slide 5
• Slide 6
• Slide 7
• Slide 8
• Slide 9
• Slide 10
• Slide 11
• Slide 12
• Slide 13
• Slide 14
• Renewable Resources Discussed in Book
• Renewable Energy Consumption
• Another look at available energy flow
• The Renewable Budget
• Outstanding Points from Fig 51
• Energy Flow continued
• The Hydrologic Cycle
• Energetics of the hydrologic cycle
• Let it Rain
• How much of the process do we get to keep
• iClicker Question
• Slide 26
• Power of a hydroelectric dam
• Importance of Hydroelectricity
• Hydroelectric potential by region in GW
• Slide 30
• Slide 31
• Hydroelectricity in the future
• Sorry try againhellip
• Wind Energy
• The Power of Wind
• Wind Energy proportional to cube of velocity
• Canrsquot get it all
• Practical Efficiencies
• Slide 39
• Slide 40
• Achievable efficiencies
• Typical Windmills
• Average available wind power
• Comparable to solar
• Current implementations
• Flies in the Ointment
• Slide 47
• Slide 48

45

Current implementations

bull Rapidly developing resourcendash 1400 MW in 1989 up to 6400 MW in 2003ndash but still insignificant total (compare to large

dams)ndash cost (at 5ndash7cent per kWh) is competitivendash growing at 25 per yearndash expect to triple over next ten years

bull Current capacity 116 GW (April 2007)ndash Texas 2768 MW (recently took lead over

California)ndash California 2361 MWndash Iowa 936 MWndash Minnesota 895 MWndash Washington 818 MW

46

Flies in the Ointment

bull Find that only 20 of rated capacity is achievedndash design for high wind but seldom get it

bull Only 12 of electrical capacity in US is now windndash total electrical capacity in US is 948 GWndash tripling in ten years means 36ndash but achieving only 20 of capacity reduces

substantiallybull If fully developed we could generate an average

power almost equal to our current electrical capacity (764 GW)

ndash but highly variable resource and problematic if more than 20 comes from the intermittent wind

47

iClicker Question

bull Which state generates the most amount of electricity derived from wind powerndash A Virginiandash B Alaskandash C Montanandash D Californiandash E Texas

48

iClicker Question

bull Which state generates the most amount of electricity derived from wind powerndash A Virginiandash B Alaskandash C Montanandash D Californiandash E Texas

• Renewable Energy Sources II Alternatives Part I
• Chapter 5 Summary
• Slide 3
• Slide 4
• Slide 5
• Slide 6
• Slide 7
• Slide 8
• Slide 9
• Slide 10
• Slide 11
• Slide 12
• Slide 13
• Slide 14
• Renewable Resources Discussed in Book
• Renewable Energy Consumption
• Another look at available energy flow
• The Renewable Budget
• Outstanding Points from Fig 51
• Energy Flow continued
• The Hydrologic Cycle
• Energetics of the hydrologic cycle
• Let it Rain
• How much of the process do we get to keep
• iClicker Question
• Slide 26
• Power of a hydroelectric dam
• Importance of Hydroelectricity
• Hydroelectric potential by region in GW
• Slide 30
• Slide 31
• Hydroelectricity in the future
• Sorry try againhellip
• Wind Energy
• The Power of Wind
• Wind Energy proportional to cube of velocity
• Canrsquot get it all
• Practical Efficiencies
• Slide 39
• Slide 40
• Achievable efficiencies
• Typical Windmills
• Average available wind power
• Comparable to solar
• Current implementations
• Flies in the Ointment
• Slide 47
• Slide 48

46

Flies in the Ointment

bull Find that only 20 of rated capacity is achievedndash design for high wind but seldom get it

bull Only 12 of electrical capacity in US is now windndash total electrical capacity in US is 948 GWndash tripling in ten years means 36ndash but achieving only 20 of capacity reduces

substantiallybull If fully developed we could generate an average

power almost equal to our current electrical capacity (764 GW)

ndash but highly variable resource and problematic if more than 20 comes from the intermittent wind

47

iClicker Question

bull Which state generates the most amount of electricity derived from wind powerndash A Virginiandash B Alaskandash C Montanandash D Californiandash E Texas

48

iClicker Question

bull Which state generates the most amount of electricity derived from wind powerndash A Virginiandash B Alaskandash C Montanandash D Californiandash E Texas

• Renewable Energy Sources II Alternatives Part I
• Chapter 5 Summary
• Slide 3
• Slide 4
• Slide 5
• Slide 6
• Slide 7
• Slide 8
• Slide 9
• Slide 10
• Slide 11
• Slide 12
• Slide 13
• Slide 14
• Renewable Resources Discussed in Book
• Renewable Energy Consumption
• Another look at available energy flow
• The Renewable Budget
• Outstanding Points from Fig 51
• Energy Flow continued
• The Hydrologic Cycle
• Energetics of the hydrologic cycle
• Let it Rain
• How much of the process do we get to keep
• iClicker Question
• Slide 26
• Power of a hydroelectric dam
• Importance of Hydroelectricity
• Hydroelectric potential by region in GW
• Slide 30
• Slide 31
• Hydroelectricity in the future
• Sorry try againhellip
• Wind Energy
• The Power of Wind
• Wind Energy proportional to cube of velocity
• Canrsquot get it all
• Practical Efficiencies
• Slide 39
• Slide 40
• Achievable efficiencies
• Typical Windmills
• Average available wind power
• Comparable to solar
• Current implementations
• Flies in the Ointment
• Slide 47
• Slide 48

47

iClicker Question

bull Which state generates the most amount of electricity derived from wind powerndash A Virginiandash B Alaskandash C Montanandash D Californiandash E Texas

48

iClicker Question

bull Which state generates the most amount of electricity derived from wind powerndash A Virginiandash B Alaskandash C Montanandash D Californiandash E Texas

• Renewable Energy Sources II Alternatives Part I
• Chapter 5 Summary
• Slide 3
• Slide 4
• Slide 5
• Slide 6
• Slide 7
• Slide 8
• Slide 9
• Slide 10
• Slide 11
• Slide 12
• Slide 13
• Slide 14
• Renewable Resources Discussed in Book
• Renewable Energy Consumption
• Another look at available energy flow
• The Renewable Budget
• Outstanding Points from Fig 51
• Energy Flow continued
• The Hydrologic Cycle
• Energetics of the hydrologic cycle
• Let it Rain
• How much of the process do we get to keep
• iClicker Question
• Slide 26
• Power of a hydroelectric dam
• Importance of Hydroelectricity
• Hydroelectric potential by region in GW
• Slide 30
• Slide 31
• Hydroelectricity in the future
• Sorry try againhellip
• Wind Energy
• The Power of Wind
• Wind Energy proportional to cube of velocity
• Canrsquot get it all
• Practical Efficiencies
• Slide 39
• Slide 40
• Achievable efficiencies
• Typical Windmills
• Average available wind power
• Comparable to solar
• Current implementations
• Flies in the Ointment
• Slide 47
• Slide 48

48

iClicker Question

bull Which state generates the most amount of electricity derived from wind powerndash A Virginiandash B Alaskandash C Montanandash D Californiandash E Texas

• Renewable Energy Sources II Alternatives Part I
• Chapter 5 Summary
• Slide 3
• Slide 4
• Slide 5
• Slide 6
• Slide 7
• Slide 8
• Slide 9
• Slide 10
• Slide 11
• Slide 12
• Slide 13
• Slide 14
• Renewable Resources Discussed in Book
• Renewable Energy Consumption
• Another look at available energy flow
• The Renewable Budget
• Outstanding Points from Fig 51
• Energy Flow continued
• The Hydrologic Cycle
• Energetics of the hydrologic cycle
• Let it Rain
• How much of the process do we get to keep
• iClicker Question
• Slide 26
• Power of a hydroelectric dam
• Importance of Hydroelectricity
• Hydroelectric potential by region in GW
• Slide 30
• Slide 31
• Hydroelectricity in the future
• Sorry try againhellip
• Wind Energy
• The Power of Wind
• Wind Energy proportional to cube of velocity
• Canrsquot get it all
• Practical Efficiencies
• Slide 39
• Slide 40
• Achievable efficiencies
• Typical Windmills
• Average available wind power
• Comparable to solar
• Current implementations
• Flies in the Ointment
• Slide 47
• Slide 48