Special Topic: Alternative Energy

Aaron Glieberman

August 10, 2010

In the news today

Portugal Gives Itself a Clean-Energy Makeover

NY Times August 10, 2010Front page story

Overview

- Energy overview, key concepts- State of energy usage- Types of alternative energy- Thought problems- Guest Speaker: Dr. Chris Bull, Ph.D.

- Guest Speaker: Gordon Barr

Energy Review

We’ve discussed numerous types of energy so far:

MechanicalChemicalElectromagneticThermal

Remember: conservation of energy

Key terminology and relationships

Force – phenomenon acting upon an object or particle that causes it to undergo acceleration, measured in newtons (N)

Work – energy transfer from one system to another, affecting the second system in a particular fashion (and often involving movement), measured in joules (J)

Power – rate of work done, measured in watts (W)

Key terminology and relationships

Force = m*a

Mechanical Work = F*d

Mechanical Power = Work/t

Electrical work = V*Q

Electrical Power = V*I = I2*R (remember: V= IR)

(also, electromagnetic)

Key terminology and relationships

In energy industry talk, energy usage is typically described in British thermal units (Btu) or kilowatt-hours (kWh),

megawatt-hours (MWh), etc.

1 British thermal unit = 1055 joules

1 kilowatt-hour = 3.6 megajoules = 3412 Btu

Energy “consumption”Petroleum used for transportation accounts for 27.9% of all supply in US

Coal used for energy accounts for 20.7% of all supply in US

By comparison, renewables for transportation and energy account for only 0.6% and 3.5%, respectively

We use more nuclear energy than renewable

Petroleum usage

Coal power plant

Coal power plant

Internal combustion engine

The dangers of modern energy sources

Pollution

- Both contribute substantially to greenhouse gasses, coal especially being the largest human-made contributor

- Ash, mercury, arsenic, selenium from burning coal can cause health problems

Limited supplies

- Spills – petroleum is extremely toxic

- Environmental toll from extraction, transportation, and processing of coal and petroleum

- Future mining efforts will eventually become more difficult

- If supply dwindles, this will drastically affect the economy, which depends on electricity and transportation

- Political considerations – self-dependency

Hubbert’s peak

Projections of world oil production

Deepwater Horizon oil spill

Largest marine oil spill in history of petroleum usage

April 20, 2010

Deepwater Horizon oil spill

Estimated total volume of 4-5 million barrels spilled

1 barrel = 42 US gallons = 159 L

How much oil is this?

April 20, 2010

168 million gallons of oil spilled

Deepwater Horizon oil spill

Estimated total volume of 4-5 million barrels spilled

April 20, 2010

BUT . . .

Significant, but not even that much compared to daily use

The alternatives

HydroelectricSolarWind

BiomassGeothermal

Hydrogen fuelElectric cars(Nuclear power)

The alternatives

Consider:

EfficiencyCostResource requirementsImpact

Hydroelectric

Generation of electrical energy using mechanical energy of moving water

Largest source of renewable energy in the world

HydroelectricTypical operation scheme

Dam is used to create a water reservoir that stores energy

Functions according to potential energy

Water flowing from high to low pressure turns a turbine, which is connected to a generator

Hydroelectric

Most simply, the power produced by hydroelectric means can be calculated as:

P = ρ*h*Q*g*e

h = height difference between upstream and downstream water

Q = flow rate of water

e = efficiency of system (turbine and generator)

ρ = density of water

g = acceleration due to gravity

Hydroelectric

Hydroelectric schemes can be large or small

Excess power generation can be used to pump water to higher ground, thus storing it for later

Tidal power utilizes a similar concept but may not require a dam, instead harnessing tidal flow to turn turbines

Additional concern over salinity of water

HydroelectricStrengths

Limitations

- Can have a significant environmental impact- Can only be in areas close to a river

- No carbon dioxide emissions- Can be used to control water flow in a river for other purposes (tourism, agriculture, flood reduction)

- Often requires significant land investment and long construction time

- Possibility for storage- Long-term

- Possibility for indirectly creating methane emissions- Potential for failure

Three Gorges DamYangtze river in China

- Largest electricity-producing plant in the world- Eventual production potential of 22,500 MW- Replacement for coal, reducing estimated coal consumption by as much as 31 million metric tons per year- Regulates water flow downstream, either providing water during the dry season or preventing flooding

Three Gorges Dam

However,

- Displaced 1.3 million people during construction

- Has directly affected habitat for much wildlife, including endangered species

- Some estimate that erosion and sedimentation will interfere with dam function

- Flooding in July 2010 has demonstrated that dam is not fool-proof

- Substantial environmental impact, such as deforestation

Solar Energy

Utilization of energy from the sun for lighting, thermal purposes or to produce electrical energy

Solar energy is an extremely abundant resource

Solar EnergyPhotovoltaic technology

Sunlight hits photovoltaic cells, generating an electric current

Solar EnergyPhotovoltaic technology

Solar EnergyConcentrating solar power (CSP)

Solar EnergyThe power produced by photovoltaic cells can be calculated as follows:

A single square inch of photovoltaic cell produces about 0.45 V and 0.224 A in full sunlight

This means that photovoltaic cells produce roughly:

P = 0.45 V * 0.224 A = 0.10 watts per square inch = 156 watts/m2

Cells can be arranged in series or in parallel to produce different voltages and currents

Solar EnergyOther applications

Water heating

Solar EnergyOther applications

Water treatment Cooking

Solar EnergyStrengths

Limitations- No energy source at night or in sunless weather conditions- Specialized technology that is difficult to manufacture

- Quiet- Electricity and heating capabilities- Abundant supply- No pollution during use- Low operating/maintenance requirements- Resource is most available during peak energy usage- Small-scale technology

- High installation costs that require solid investment- Generate DC current that must be converted to AC, reducing efficiency

Solar EnergySolar Impulse, a company in Switzerland, accomplishes first ever 24-hour flight by a solar-powered plane

Wind Energy

Generation of electrical energy from the mechanical energy in wind

Wind EnergyWind electric power generation

Wind rotates the blades, which then spin the internal rotor, shafts and generator

Gears, pulleys, or chains are necessary to convert the rotational velocities and to alter the axis of rotation

Note that wind speed and direction are not constant, so one calculates the capacity factor (the ratio between the actual productivity and the theoretical maximum productivity)

Capacity factors are normally 20-40%

Wind EnergyTwo designs for wind power utilize drag and lift

Lift-oriented wind turbine

Drag-oriented wind turbine

Wind Energy

The power produced by a wind turbine can be calculated as follows:

P = 0.5*ρ*A*v3*e

A = area swept by blades

e = efficiency of system (turbine and generator)

ρ = density of water

v = velocity of air

Wind EnergyStrengths

Limitations- Unattractive to some- Large capital cost

- World potential exceeds current world energy usage- No pollution during operation

- Possible harm to birds - Large land requirement (should be 10 times blade span away from one another)- Preferably located in windy regions, which might be far from urban centers

Combining wind and solarBluenergy Solar-Wind-Turbine

Geothermal Energy

Utilizing the energy from geothermal vents for heating or to produce electricity

Geothermal Energy

Heated steam from beneath the ground transfers its thermal energy to a fluid with low boiling point that drives a turbine at high pressure

Cooled substances from the earth return below

Energy efficiency of this technology is low, on the order of 10-20%

Surrounding rocks keep steam insulated as it is piped from the ground

Binary geothermal plant

Geothermal Energy

For generating electricity, deeper wells are typically drilled to harness higher heat

Direct applications – Low temperature (<300°C) and shallower implementations are often applied for small-scale use, especially geothermal heating

Geothermal EnergyStrengths

Limitations- Limited by location (must be near tectonic plate boundaries)- Low efficiency

- Relatively cheap- Reliable

- Some designs release fluids from the earth, which may include harmful emissions

- Constant supply of resource (high capacity factor)

Biomass Energy

Utilizing the chemical energy stored in biological substances for heating or to produce electricity

Biomass Energy

Covers a wide range of possible energy sources and corresponding technologies to harness the energy

Traditional cases have relied upon combustion to extract the energy

Newer focus in chemical and biochemical means of fuel conversion and energy extraction

Biomass Energy

Direct firing – biomass is burned at the bottom of a boiler, producing steam to turn a turbine

Co-firing – biomass is mixed with in traditional fossil fuel (usually coal) and directly burned to generate steam

Pyrolysis – biomass undergoes high temperature in an oxygen-depleted environment, yielding pyrolysis oil that is effective for burning

Gassification – application of thermal energy to biomass produces combustible gasses

Biomass Energy

Another nod towards synthetic biology

Engineer microbes to catalyze certain biochemical reactions, producing alcohols or other biofuels

Biomass EnergyStrengths

Limitations- Mostly results in combustion process, which releases greenhouse gasses

- Low efficiency

- Almost universally abundant- Reliable- Possibility for repurposing traditional “waste”- Can be utilized with modified fossil fuel equipment/infrastructure

- Fewer toxic byproducts compared to fossil fuels

Comparative costs

Comparative costsRETI Stakeholder Steering CommitteeRenewable Energy Transmission Initiative Phase 1A

16 May 2008

Fuel cell technology

Electrochemical process of producing electricity from a chosen fuel source

Fuel cell technology

http://auto.howstuffworks.com/fuel-efficiency/alternative-fuels/fuel-cell.htm

Also,

Hydrogen flows along one side of a maintained electric field, oxygen on the other

One example: Hydrogen fuel cell

Some hydrogen atoms selectively travel across the field to react with oxygen, producing a current as they move

Water is released as a byproduct

Electric cars

Electric cars

Generally speaking, cars that depend on batteries to store energy through chemical means and convert that energy to electrical while in use

Depends upon battery technology and energy efficicency

Energy conservation

Power requirements for common appliances

http://www.ge.com/visualization/appliances_energyuse/index.html

Power requirements for common appliances

Appliances plugged into a socket still use electricity even while turned off . . .

Power requirements for common appliances

Appliances plugged into a socket still use electricity even while turned off . . .

Power requirements for common appliances

Appliances plugged into a socket still use electricity even while turned off . . .

Light bulb comparisonEnergy Savings Calculator for Replacing Light Bulbs    

  Incandescent Light BulbsCFL(Compact Fluorescent Light Bulbs)

LED(Light-Emitting Diode Light Bulbs)

Life Span (in hours) 1,500 10,000 60,000 Watts 60 14 6 Cost $1.345 $2.98 $54.95 KWh of electricty used over 60k hours 3,600 840 360 Electricity Cost (@ $0.23 per KWh) $821.72 $191.73 $82.17 Bulbs needed for 60k hours of usage 40 6 1 Equivalent 60k hour bulb expense $53.80 $17.88 $54.95 Total 60,000 Hour Lighting Spend $875.52 $209.61 $137.12

Calculate Your Energy Savings      

# of household light bulbs 30 30 30 Your estimated daily usage (hours) 5 5 5 Days in month 30 30 30

Household savings over 60,000 hours (energy + replacement)    Household cost $26,265.54 $6,288.43 $4,113.65 Savings by switching from Incandescent $0.00 $19,977.11 $22,151.89

Monthly household energy savings      KWh used per month 270 63 27 Electricity Cost (@ $0.23 per KWh) $61.63 $14.38 $6.16 Savings by switching from Incandescent $0.00 $47.25 $55.47

Yearly household energy savings      KWh used per year 3,285 767 329 Electricity Cost (@ $0.23 per KWh) $749.82 $174.96 $74.98 Savings by switching from Incandescent $0.00 $574.86 $674.84        productdose.com comments:blue font = input your personal data here KWh = Kilowatt-hours Choose KWh rate type: * 2 black font = pre-calculated cells * change the data on the next tab. 1 = Average rateunderlined text = where to buy / product info 2 = Highest rateAll data from manufacturer as of 5/2/06 3 = Your own rate