More on Chapter 7
Energy Conservation
Lecture #16
HNRT 228 Spring 2013
Energy and the Environment
1
Overview of Chapter 7
•
Energy Conservation
– Space Heating
– Thermal Insulation
– Air Infiltration
– Lighting
– Appliances
– Some considerations of agriculture and
industry
2
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
3
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
4
iClicker Question
•
Which type of washing machine conserves
the most energy and water?
– A
Top loader
– B
Front loader
5
iClicker Question
•
Which type of washing machine conserves
the most energy and water?
– A
Top loader
– B
Front loader
6
iClicker Question
Turning off your computer
will harm it.
A
True
B
False
7
iClicker Question
Turning off your computer
will harm it.
A
True
B
False
8
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
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
10
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
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
12
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
13
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
14
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
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
16
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
17
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
18
National Average Home Energy Costs
14%
Heating and Cooling
44%
Refrigrator
Lighting, Cooking and
other Appliances
Water Heating
33%
9%
19
Why do we need Heating?
30 F
70 'F
Furnace
20
Typical Heat losses- Conventional House
5% through ceilings
17% through
frame walls
1% through
basement floor
16%
through
windows
3% through door
38% through cracks
in walls, windows,
20%
through and doors
basement
walls
21
iClicker Question
•
Energy transfer by electromagnetic waves
is
– A
Radiation
– B
Convection
– C
Conduction
22
iClicker Question
•
Energy transfer by electromagnetic waves
is
– A
Radiation
– B
Convection
– C
Conduction
23
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
24
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
25
iClicker Question
•
Energy transfer by contact of molecule
with another molecule is one way to define
– A
Radiation
– B
Convection
– C
Conduction
26
iClicker Question
•
Energy transfer by contact of molecule
with another molecule is one way to define
– A
Radiation
– B
Convection
– C
Conduction
27
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
28
Convection
Energy is carried by the
bulk motion of the fluid
29
Radiation
Energy is carried by
electromagnetic waves.
No medium is required
30
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
31
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
32
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
33
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
•
34
Degree Days for the Heating Season
For Virginia data see
http://cdo.ncdc.noaa.gov/climatenormals/clim81/VAnorm.pdf
PLACE
Birmingham,
ALABAMA
Anchorage,
ALASKA
Barrow, ALASKA
Tucson, ARIZONA
Miami, FLORIDA
State
College
Sterling,
VA
DEGREE DAYS
2,780
10,780
19,994
1,776
173
???5237
35
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?
Solution
HDD in Anchorage, Alaska = 10,780
HDD in State College PA = 6,000
Difference = 10,780 - 6,000 = 4,780
Saving in heating fuel costs are
•

4,780
100  44.3%
10,780
36
Home Energy Saver Online
•
http://homeenergysaver.lbl.gov/
37
Home Heating Costs in State College, PA
Average House
$232 $106
$890
$305
Heating
Cooling
Hot water
Appliances
Misc.
Energy Efficient
Lighting
House
Energy Effcient House
$227 $133
Total $1,891
$52
$327
$232
$205
$114
$89
Total $1,019
38
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
39
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
40
R-values for Building Materials
41
Thickness of various materials for R-22
110"
18"
6"
Cellulose
Fiber
7"
Fiberglass
Pine wood
Common
brick
42
R-Value for a Composite Wall
R-Value of material
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
43
Home Heating Energy
•
Heat loss depends on
– Surface Area (size)
– Temperature
Difference
– Property of the
wall ( R value)
Q (Btus)
t (time, h)
=
1
R
Inside
65¨F
Outside
30¨F
A (area) x Temperature Diff (Ti – To)
44
Heat Loss
AreaxTinside  Toutside 
(Thermal Re sis tan ce oftheWall , R)
Thot
AreaxTinside  Toutside 
Tcold
Heat Loss =
Q
t
Q
(Thermal Re sis tan ce oftheWall , R)
t
Id Q/t is in Btu/h
Area in ft2
Tin-Tout in °F
Then the thermal resistance is
R-value. The units of R-value are
ft 2 x oF
Btu / hr
45
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:



Q 320 ft 2 x 68 F  280 F
Heatloss Rate  
 674 Btu / hr
2 0
ft x F
t
19
BTU / h
46
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
47
Calculate loss per "degree day"
•This is the loss per day with a one degree
difference between inside and
outside temperature.
•
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.
48
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
49
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).
50
Household Heating Fuel
90%
80%
70%
60%
50%
40%
30%
20%
10%
0%
56%
Heating Fuel
26.00%
11.00%
Natural
Gas
Electricity Fuel Oil
10.00%
Other
51
Average Heating Value of Common Fuels
Fuel Type
Kerosene (No. 1 Fuel Oil)
No. 2 Fuel Oil
Electricity
Natural Gas
Propane
Bituminous Coal
Anthracite Coal
Hardwood (20% moisture)*
Pine (20% moisture)*
Pellets (for pellet stoves; premium)
No. of Btu/Unit (Kilocalories/Unit)
135,000/gallon (8,988/liter)
140,000/gallon (9,320/liter)
3,412/kWh (859/kWh)
1,028,000/thousand cubic feet (7,336/cubic meter)
91,333/gallon (6,081/liter)
23,000,000/ton (6,400,000/tonne)
24,800,000/ton (5,670,000/tonne)
24,000,000/cord (1,687,500/cubic meter)
18,000,000/cord (1,265,625/cubic meter)
16,500,000/ton (4,584,200/tonne)
52
Typical Heating Furnace Efficiencies
Fuel Type - Heating Equipment
Coal (bituminous)
Central heating, hand-fired
Central heating, stoker-fired
Water heating, pot stove (50 gal.[227.3 liter])
Oil
High efficiency central heating
Typical central heating
Water heater (50 gal.[2227.3 liter])
Gas
High efficiency central heating
Typical central heating
Room heater, unvented
Room heater, vented
Water heater (50 gal.[227.3 liter])
Electricity
Central heating, resistance
Central heating, heat pump
Ground source heat pump
Water heaters (50 gal.[227.3 liter])
Wood & Pellets
Franklin stoves
Stoves with circulating fans
Catalytic stoves
Pellet stoves
Efficiency (% )
45
60
14.5
89
78
59.5
92
82
91
78
62
97
200+
300+
97
30.0 - 40.0
40.0 - 70.0
65.0 - 75.0
85.0 - 95.0
53
Comparing the Fuel Costs
Energy Cost 
Cost perUnit ofFuel
HeatingValue( MMBtu / unitoffuel)  Efficiency
54
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.
55
Heating Systems
56
Heating Systems
•
Some hot water
systems circulate
water through plastic
tubing in the floor,
called radiant floor
heating.
57
Electric Heating Systems
1.
2.
Resistance heating systems
Converts electric current directly into heat
1.
usually the most expensive
2.
Inefficient way to heat a building
Heat pumps
Use 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)
58
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/
59
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
60
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
61
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)
62
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
63
Passive Solar Heating
64
Source: Global Science, Energy Resources Environment
65
Passive Heating
Direct
Gain
Thermal
W all
Passive Cooling
Shading
Storage Suns pace
Ve nt ilat io n
Earth Contact
66
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
67
Active
Solar
Heating
68
Flat Plate Collector
•
Solar Collectors heat
fluid and the heated
fluid heats the space
either directly or
indirectly
69
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, cooldown, 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.
70
Efficiencies of Home Heating
.
110
100
U.S. stock
7
90
80
70
1975-1976 building practice
(NAHB)
5
60
LBL standard
(medium infiltration)
50
LBL standard
(low infiltration)
40
3
30
Brownell
20
Mastin
10
Phelps
0
0
2000
4000
6000
Saskatoon
Ivanhoe Pasqua
Leger
1
Saskatchewan house
Balcomb
8000
Btu/ft2 per degree day
Annual fuel input for
space heat (106 Btu/1000 ft2)
9
10,000
1 Btu/ft 2 per degree day
Degree days (base 65°F)
71
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.
72
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.
73
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.
74