# Home Heating and Cooling

Document Sample

```					 EGEE 102 – Energy Conservation
And Environmental Protection

Home Heating Basics
National Average Home
Energy Costs
14%                         Heating and Cooling

44%   Refrigrator

Lighting, Cooking and
33%                               other Appliances
Water Heating
9%

EGEE 102                           2
Why do we need
Heating?

30 F
70 'F

Furnace

EGEE 102             3
Typical Heat losses-
Conventional House

5% through ceilings

16%
through
17% through                                  windows
frame walls

3% through door
38% through cracks
20%        in walls, windows,
1% through                    and doors
basement floor     through
basement
walls
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Heat Transfer

• Conduction
• Convection

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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 energetic

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Convection

Energy is carried by the
bulk motion of the fluid

EGEE 102   7

Energy is carried by
electromagnetic waves.
No medium is required

EGEE 102   8
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,       2,780
ALABAMA
Anchorage,        10,780
Tucson, ARIZONA   1,776
Miami, FLORIDA    173
State College     ???

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EGEE 102   14
Class work

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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?
Solution
HDD in Anchorage, Alaska = 10,780
HDD in State College PA = 6,000
Difference = 10,780 - 6,000 ,= 4,780
4 780
       100  44 .3%
Saving in fuel costs are 10 ,780
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Home Energy Saver

• http://homeenergysaver.lbl.gov/

EGEE 102            17
Home Heating Costs in
State College
Average House
\$232 \$106                        Heating
Cooling
\$890         Hot water
\$305                                Appliances    Energy Efficient
Misc.         House
Energy Effcient House

\$227 \$133                        Lighting
\$52
\$232                                          \$327
Total \$1,891

\$205                                    \$89
\$114
EGEE 102                                  Total 18
\$1,019
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-11
• R-30 better than 102
EGEE                 19
Places to Insulate
• Attic is usually the
cost effective
insulation
• Floors above
unheated
basements should
be insulated
• Heated basements
should be
insulated around EGEE 102   20
R-values for Building
Materials

EGEE 102      21
Thickness of various
materials for R-22

110"

18"

7"
6"

Cellulose   Fiberglass    Pine wood   Common
Fiber                                 brick

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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
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Home Heating Energy
• Heat loss depends
on
• Surface Area
(size)                                                 Outside
Inside
• Temperature                   65¨F
30¨F
Difference
• Property of the
wall ( R value)

Q (Btus)          1    A (area) x Temperature Diff (Ti – To)
=
t (time, h)       R
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Heat Loss

Thot   Tcold                 Q           AreaxTinside  Toutside 
Heat Loss =
Areax Re sis  ce ofthe 
t      (ThermalTinsidetanToutsideWall , R)
(Thermal Re sis tan ce oftheWall , R)

Q         Id Q/t is in Btu/h
t         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

EGEE 102                                                25
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:

Heatloss Rate  
       
Q 320 ft 2 x 68  F  28 0 F 674 Btu / hr
2 0
t            ft x F
19
BTU / h

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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"
•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.
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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 MM Btus

The typical number of degree-days of heating
or cooling for a given geographical location
can usually be obtained from the weather service.

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Numerical Example

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Heat loss Calculation

1    
Qtotal     A    Number of Annual deg ree days 24 h / day 
R    

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Problem
• A wall is made up of four elements, as
follows
• ½” wood siding
• ½” plywood sheathing
• 3 ½ in of fibber glass
• ½” of sheet rock
• How many Btus per hour per sq.ft. will be
lost through the wall when the outside
temperature is 50F colder than inside?
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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).                     EGEE 102                               33
Pay Back Period
Calculation
• Suppose that you want to know how many years
it will take to recover the cost of installing
planning to increase the level of insulation from
R-19 (6 inch fiberglass batts with moisture
barrier on the warm side) to R-30 by adding R-11
(3.5 inch unfaced fiberglass batts). You have a
gas furnace with an AFUE of 0.88. You also pay
\$0.70/therm for natural gas.
• Given
• C(i) = \$0.18/square foot; C(e) = (\$0.70/therm)/(100,000
Btu/therm) = \$0.000007/Btu; E = 0.88; R(1) = 19; R(2) = 30;
R(2) - R(1) = 11; HDD = 7000 102
EGEE                              34
Household Heating Fuel
90%
80%
70%
56%
60%
50%
40%                                             Heating Fuel
26.00%
30%
20%                          11.00%    10.00%
10%
0%
Natural   Electricity Fuel Oil   Other
Gas

EGEE 102                       35
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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Typical Heating Furnace
Efficiencies
Fuel Type - Heating Equipment                      Efficiency (% )
Coal (bituminous)
Central heating, hand-fired                              45
Central heating, stoker-fired                            60
Water heating, pot stove (50 gal.[227.3 liter])         14.5
Oil
High efficiency central heating                          89
Typical central heating                                  78
Water heater (50 gal.[2227.3 liter])                    59.5
Gas
High efficiency central heating                          92
Typical central heating                                  82
Room heater, unvented                                    91
Room heater, vented                                      78
Water heater (50 gal.[227.3 liter])                      62
Electricity
Central heating, resistance                              97
Central heating, heat pump                              200+
Ground source heat pump                                 300+
Water heaters (50 gal.[227.3 liter])                     97
Wood & Pellets
Franklin stoves                                      30.0 - 40.0
Stoves with circulating fans                         40.0 - 70.0
Catalytic stoves                                     65.0 - 75.0
Pellet stoves               EGEE             102     85.0 - 95.0     37
Comparing the Fuel
Costs

Energy Cost 
Cost perUnit ofFuel
HeatingValue( MMBtu / unitoffuel )  Efficiency

EGEE 102                       38
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
•                •

EGEE 102   40
Heating Systems
• Some hot water
systems circulate
water through
plastic tubing in
the floor, called
heating.

EGEE 102   41
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 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"
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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
http://www.eren.doe.gov/erec/factsheets/geo_heatpumps.html#sidebar
EGEE 102 cooling                     43
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
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
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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)
• Indirect gain systems also such as
large concrete walls to transfer heat
inside
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Passive Solar Heating

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EGEE 102   49
Passive Heating
Direct   Gain   Thermal      Storage Suns pace
W all

Passive Cooling
Shading           Ve nt ilat io n    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.       EGEE 102             51
Active
Solar
Heating

EGEE 102        52
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
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Efficiencies of Home
Heating
.

9

110
space heat (106 Btu/1000 ft2)

Btu/ft2 per degree day
100
U.S. stock
7
90
Annual fuel input for

80

70                                          1975-1976 building practice
(NAHB)                 5
60
LBL standard
50                                              (medium infiltration)

40                                                   LBL standard           3
(low infiltration)
30
20
Mastin      Ivanhoe Pasqua
10                                                                          1
Phelps
Balcomb                    wan house
0
0   2000   4000       6000         8000         10,000

1 Btu/ft2 per degree day

EGEE 102                                                                            55
Degree days (base 65°F)
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
EGEE 102                   56
• 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
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.

EGEE 102                    57
• 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