1

More on Chapter 7 Energy Conservation

Lecture #16HNRS 228Energy and the Environment

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Overview of Chapter 7

• Energy Conservation– Space Heating– Thermal Insulation– Air Infiltration– Lighting– Appliances– Some considerations of agriculture

and industry

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iClicker Question

• How many fewer power plants might be needed if every household changed to compact fluorescent lighting?– A About one– B More than one– C More than 100– D Depends on power plant output

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iClicker Question

• How many fewer power plants might be needed if every household changed to compact fluorescent lighting?– A About one– B More than one– C More than 100– D Depends on power plant output

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iClicker Question

• Which type of washing machine conserves the most energy and water?– A Top loader– B Front loader

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iClicker Question

• Which type of washing machine conserves the most energy and water?– A Top loader– B Front loader

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iClicker Question

Turning off your computer

will harm it.

A True

B False

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iClicker Question

Turning off your computer

will harm it.

A True

B False

9

iClicker Question

Leaving your heat on is more efficient than turning it down because you need so much energy to heat the house back up.

A True

B False

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iClicker Question

Leaving your heat on is more efficient than turning it down because you need so much energy to heat the house back up.

A True

B False

11

iClicker Question

• Which unit is used to measure insulation of walls?– A Q-value– B R-value– C S-value– D T-value– E U-value

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iClicker Question

• Which unit is used to measure insulation of walls?– A Q-value– B R-value– C S-value– D T-value– E U-value

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iClicker Question

• Which unit is used to measure insulation of windows?– A Q-value– B R-value– C S-value– D T-value– E U-value

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iClicker Question

• Which unit is used to measure insulation of windows?– A Q-value– B R-value– C S-value– D T-value– E U-value

15

iClicker Question

• Which of the following will conserve more energy.– A A wall with R-value 12– B A wall with R-value 14– C A wall with R-value 16– D A wall with R-value 18– E A wall with R-value 20

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iClicker Question

• Which of the following will conserve more energy.– A A wall with R-value 12– B A wall with R-value 14– C A wall with R-value 16– D A wall with R-value 18– E A wall with R-value 20

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iClicker Question

• Which of the following will conserve more energy.– A A window with U-value 0.12– B A window with U-value 0.14– C A window with U-value 0.16– D A window with U-value 0.18– E A window with U-value 0.20

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iClicker Question

• Which of the following will conserve more energy.– A A window with U-value 0.12– B A window with U-value 0.14– C A window with U-value 0.16– D A window with U-value 0.18– E A window with U-value 0.20

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National Average Home Energy Costs

9%

33%

14%

44%

Heating and Cooling

Refrigrator

Lighting, Cooking andother AppliancesWater Heating

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Why do we need Heating?

70 'F

Furnace

30 F

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Typical Heat losses- Conventional House

5% through ceilings

16%throughwindows

1% throughbasement floor

17% throughframe walls

3% through door38% through cracksin walls, windows,and doors

20%throughbasementwalls

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iClicker Question

• Energy transfer by electromagnetic waves is– A Radiation– B Convection– C Conduction

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iClicker Question

• Energy transfer by electromagnetic waves is– A Radiation– B Convection– C Conduction

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iClicker Question

• Energy transfer by the bulk motion, or large scale motion of molecules in gas or liquid form from one location to another is– A Radiation– B Convection– C Conduction

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iClicker Question

• Energy transfer by the bulk motion, or large scale motion of molecules in gas or liquid form from one location to another is– A Radiation– B Convection– C Conduction

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iClicker Question

• Energy transfer by contact of molecule with another molecule is one way to define– A Radiation– B Convection– C Conduction

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iClicker Question

• Energy transfer by contact of molecule with another molecule is one way to define– A Radiation– B Convection– C Conduction

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Conduction

Energy is conducted down the rod as the vibrations of one molecule are passed to the next, but there is no movement of bulk material

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Convection

Energy is carried by the bulk motion of the fluid

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Radiation

Energy is carried by electromagnetic waves. No medium is required

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Degree Days• Index of fuel consumption indicating how

many degrees the mean temperature fell below 65 degrees for the day

• Heating degree days (HDD) are used to estimate the amount of energy required for residential space heating during the cool season.

• Cooling degree days (CDD) are used to estimate the amount of air conditioning usage during the warm season

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How do we calculate HDD?

• HDD = Tbase - Ta

– if Ta is less than Tbase • HDD = 0

– if Ta is greater or equal to Tbase

– Where: Tbase = temperature base, usually 65 F Ta = average temperature, Ta = (Tmax + Tmin) / 2

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Heating Degree Days

• Calculate the number of degree days accumulated in one day in which the average outside temperature is 17ºF.

Degree days = 1 day ( 65 – Tout)

= 1 (65-17)= 48 degree days

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Heating Degree Days in a Heating Season

• Calculate the degree days accumulated during a 150-day heating season if the average outside temperature is 17ºF

Solution:Heating Season Degree days

= 150 days ( 65 – Tout) = 150 (65-17)

= 7,200 degree days

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Degree Days for the Heating Season

PLACE DEGREE DAYS Birmingham, ALABAMA

2,780

Anchorage, ALASKA

10,780

Barrow, ALASKA 19,994 Tucson, ARIZONA 1,776 Miami, FLORIDA 173 State College ???

For Virginia data see http://cdo.ncdc.noaa.gov/climatenormals/clim81/VAnorm.pdf

Sterling, VA 5237

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Significance of HDD

• Mrs. Young is moving from Anchorage, Alaska (HDD =10,780) to State college, PA (HDD = 6,000). Assuming the cost of energy per million Btu is the same at both places, by what percentage her heating costs will change?

SolutionHDD in Anchorage, Alaska = 10,780HDD in State College PA = 6,000Difference = 10,780 - 6,000 = 4,780Saving in heating fuel costs are

%3.44100780,10

780,4

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Home Energy Saver Online

• http://homeenergysaver.lbl.gov/

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Home Heating Costs in State College, PA

$890

$133$227

$305

$232 $106 Heating

Cooling

Hot water

Appliances

Misc.

Lighting

Energy Effcient House

$327

$89$114$205

$232$52

Total $1,891

Average House

Energy EfficientHouse

Total $1,019

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Home Heating Costs

• Related to amount of insulation, material that resists the flow of heat– Insulation is rated in terms of

thermal resistance, called R-value, which indicates the resistance to heat flow. The higher the R-value, the greater the insulating effectiveness. The R-value of thermal insulation depends on the type of material, its thickness, and density.

– R-30 better than R-11

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Places to Insulate

• Attic is usually the easiest ad most cost effective place to add insulation

• Floors above unheated basements should be insulated

• Heated basements should be insulated around the foundaton

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R-values for Building Materials

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Thickness of various materials for R-22

110"

18"

7"6"

CelluloseFiber

Fiberglass Pine wood Commonbrick

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R-Value for a Composite Wall

1/2" Plasterboard 0.45

3 1/2" Fiberglass 10.90

3/4" Plywood 0.94

1/2" Wood siding 0.81 RTOTAL = 13.10

ft2 – °F – hr BTU

R-Value of material

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Home Heating Energy

• Heat loss depends on– Surface Area

(size)– Temperature

Difference– Property of the

wall ( R value)

Inside65¨F

Outside30¨F

Q (Btus) t (time, h)

= A (area) x Temperature Diff (Ti – To)1

R

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Heat Loss

),tanRe( RWallofthecesisThermal

outsideT

insideTxArea

),tanRe( RWallofthecesisThermal

outsideT

insideTxArea

ThotTcold

Q

t

Heat Loss = Q

t

Id Q/t is in Btu/hArea in ft2

Tin-Tout in °F

Then the thermal resistance is R-value. The units of R-value are

hrBtu

Fxft o

/

2

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Wall loss rate in BTUs per hour

• For a 10 ft by 10 ft room with an 8 ft ceiling, with all surfaces insulated to R19 as recommended by the U.S. Department of Energy, with inside temperature 68°F and outside temperature 28°F:

hrBtu

hBTUFxft

FFxft

t

QRateHeatloss /674

/19

286832002

02

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Calculation per Day

• Heat loss per day = (674 BTU/hr)(24 hr) = 16,168 BTU

• Note that this is just through the wall• The loss through the floor and ceiling is

a separate calculation, and usually involves different R-values

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Calculate loss per "degree day"

• If the conditions of case II prevailed all day, you would require 40 degree-days of heating, and therefore require 40 degree-days x 404 BTU/degree day = 16168 BTU to keep the inside temperature constant.

•This is the loss per day with a one degree difference between inside and outside temperature.

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Heat Loss for Entire Heating Season.

• The typical heating requirement for a Pittsburgh heating season, September to May, is 5960 degree-days (a long-term average).

Heat loss = Q/t = 404 Btu/degree day x 5960 degree days= 2.4 Million Btus

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Economics of Adding Insulation

• Years to Payback  =

       C(i) x R(1) x R(2) x E-------------------------------------  C(e) x [R(2) - R(1)] x HDD x 24

• C(i)  =  Cost of insulation in $/square feet• C(e)  =  Cost of energy, expressed in $/Btu• E  =  Efficiency of the heating system• R(1)  =  Initial R-value of section• R(2)  =  Final R-value of section• R(2) - R(1) =  R-value of additional insulation being considered• HDD  =  Heating degree days/year• 24  =  Multiplier used to convert heating degree days to heating hours (24

hours/day).

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Household Heating Fuel

56%

26.00%

11.00% 10.00%

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

NaturalGas

Electricity Fuel Oil Other

Heating Fuel

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Average Heating Value of Common Fuels

Fuel Type No. of Btu/Unit (Kilocalories/Unit)Kerosene (No. 1 Fuel Oil) 135,000/gallon (8,988/liter)No. 2 Fuel Oil 140,000/gallon (9,320/liter)Electricity 3,412/kWh (859/kWh)Natural Gas 1,028,000/thousand cubic feet (7,336/cubic meter)Propane 91,333/gallon (6,081/liter)Bituminous Coal 23,000,000/ton (6,400,000/tonne)Anthracite Coal 24,800,000/ton (5,670,000/tonne)Hardwood (20% moisture)* 24,000,000/cord (1,687,500/cubic meter)Pine (20% moisture)* 18,000,000/cord (1,265,625/cubic meter)Pellets (for pellet stoves; premium) 16,500,000/ton (4,584,200/tonne)

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Fuel Type - Heating Equipment Efficiency (%)Coal (bituminous)Central heating, hand-fired 45Central heating, stoker-fired 60Water heating, pot stove (50 gal.[227.3 liter]) 14.5OilHigh efficiency central heating 89Typical central heating 78Water heater (50 gal.[2227.3 liter]) 59.5GasHigh efficiency central heating 92Typical central heating 82Room heater, unvented 91Room heater, vented 78Water heater (50 gal.[227.3 liter]) 62ElectricityCentral heating, resistance 97Central heating, heat pump 200+Ground source heat pump 300+Water heaters (50 gal.[227.3 liter]) 97Wood & PelletsFranklin stoves 30.0 - 40.0Stoves with circulating fans 40.0 - 70.0Catalytic stoves 65.0 - 75.0Pellet stoves 85.0 - 95.0

Typical Heating Furnace Efficiencies

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Comparing the Fuel Costs

EfficiencyunitoffuelMMBtuueHeatingVal

ofFuelperUnitCost

CostEnergy

)/(

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Fuel Costs

• Electric resistance heat cost =$0.082 (price per kWh) / [ 0.003413 x 0.97 (efficiency)] = $24.77 per million Btu.

• Natural gas (in central heating system) cost =$6.60 (per thousand cubic feet) / [ 1.0 x 0.80 (efficiency)] = $8.25 per million Btu.

• Oil (in central heating system) cost =$0.88 (price per gallon) / [ 0.14 x 0.80 (efficiency)] = $7.86 per million Btu.

• Propane (in central heating system) cost =$0.778 (price per gallon) / [ 0.0913 x 0.80 (efficiency)] = $10.65 per million Btu.

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Heating Systems

57

Heating Systems

• Some hot water systems circulate water through plastic tubing in the floor, called radiant floor heating.

58

Electric Heating Systems

1. Resistance heating systems Converts electric current directly into heat

1. usually the most expensive 2. Inefficient way to heat a building

2. Heat pumpsUse electricity to move heat rather than to generate

it, they can deliver more energy to a home than they consume

1. Most heat pumps have a COP of 1.5 to 3.5.2. All air-source heat pumps (those that

exchange heat with outdoor air, as opposed to bodies of water or the ground) are rated with a "heating season performance factor" (HSPF)

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Geothermal Heat Pumps

• They use the Earth as a heat sink in the summer and a heat source in the winter, and therefore rely on the relative warmth of the earth for their heating and cooling production.

Additional reading

http://www1.eere.energy.gov/geothermal/

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Benefits of a GHP System

• Low Energy Use• Free or Reduced-Cost Hot Water• Year-Round Comfort • Low Environmental Impact • Durability• Reduced Vandalism • Zone Heating and Cooling• Low Maintenance

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Solar Heating and Cooling

• Most American houses receive enough solar energy on their roof to provide all their heating needs all year!– Active Solar– Passive Solar

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Passive Solar

• A passive solar system uses no external energy, its key element is good design:

• House faces south• South facing side has maximum

window area (double or triple glazed)• Roof overhangs to reduce cooling costs• Thermal mass inside the house (brick,

stones or dark tile)

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Passive Solar

• Deciduous trees on the south side to cool the house in summer, let light in in the winter.

• Insulating drapes (closed at night and in the summer)

• Greenhouse addition• Indirect gain systems also such as

large concrete walls to transfer heat inside

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Passive Solar Heating

65Source: Global Science, Energy Resources Environment

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Direct Gain Thermal StorageWall

SunspacePassive Heating

Passive CoolingShading Ventilation Earth Contact

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Active Solar Heating

• Flat plate collectors are usually placed on the roof or ground in the sunlight.

• The sunny side has a glass or plastic cover.

• The inside space is a black absorbing material.

• Air or water is pumped (hence active) through the space to collect the heat.

• Fans or pumps deliver the heat to the house

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Active Solar Heating

solar water heater

watertank

standbyelectricheater

heatexchanger

fanpump2

pump 1

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Flat Plate Collector

• Solar Collectors heat fluid and the heated fluid heats the space either directly or indirectly

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Efficiency of Furnace

• The "combustion efficiency" gives you a snapshot in time of how efficient the heating system is while it is operating continuously

• The "annual fuel utilization efficiency" (AFUE) tells you how efficient the system is throughout the year, taking into account start-up, cool-down, and other operating losses that occur in real operating conditions.– AFUE is a more accurate measure of

efficiency and should be used if possible to compare heating systems.

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Efficiencies of Home Heating

.

U.S. stock

1975-1976 building practice(NAHB)

LBL standard(medium infiltration)

LBL standard(low infiltration)

Brownell Saskatoon

Pasqua

Saskatche-wan house

IvanhoeMastin

Leger

BalcombPhelps

1 Btu/ft2 per degree day

An

nu

al

fuel

inp

ut

for

sp

ace h

eat

(106 B

tu/1

00

0 f

t2 )

Btu

/ft2

per

deg

ree d

ay

Degree days (base 65°F)

110

100

90

80

70

60

50

40

30

20

10

00 2000 4000 6000 8000 10,000

9

7

5

3

1

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Tips (Individual) to Save Energy and Environment

• Set your thermostat as low as is comfortable in the winter and as high as is comfortable in the summer.

• Clean or replace filters on furnaces once a month or as needed.

• Clean warm-air registers, baseboard heaters, and radiators as needed; make sure they're not blocked by furniture, carpeting, or drapes.

• Bleed trapped air from hot-water radiators once or twice a season; if in doubt about how to perform this task, call a professional.

• Place heat-resistant radiator reflectors between exterior walls and the radiators.

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Tips (Individual) to Save Energy and Environment

• Use kitchen, bath, and other ventilating fans wisely; in just 1 hour, these fans can pull out a houseful of warmed or cooled air. Turn fans off as soon as they have done the job.

• During the heating season, keep the draperies and shades on your south-facing windows open during the day to allow sunlight to enter your home and closed at night to reduce the chill you may feel from cold windows. During the cooling season, keep the window coverings closed during the day to prevent solar gain.

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Tips (Individual) to Save Energy and Environment

• Close an unoccupied room that is isolated from the rest of the house, such as in a corner, and turn down the thermostat or turn off the heating for that room or zone. However, do not turn the heating off if it adversely affects the rest of your system. For example, if you heat your house with a heat pump, do not close the vents—closing the vents could harm the heat pump.

• Select energy-efficient equipment when you buy new heating and cooling equipment. Your contractor should be able to give you energy fact sheets for different types, models, and designs to help you compare energy usage. Look for high Annual Fuel Utilization Efficiency (AFUE) ratings and the Seasonal Energy Efficiency Ratio (SEER). The national minimums are 78% AFUE and 10 SEER.