U.S. Environmental Protection Agency Industrial Environmental Research EPA-600/7-77-035
Off ice of Research and Development Laboratory .. ^O77
Research Triangle Park. North Carolina 27711 Apfll 1977
HEAT PUMPS:
SUBSTITUTES FOR OUTMODED
FOSSIL-FUELED SYSTEMS
Interagency
Energy-Environment
Research and Development
Program Report
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RESEARCH REPORTING SERIES
Research reports of the Office of Research and Development, U.S. Environmental
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were established to facilitate further development and appljcation of environmental
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are:
1. Environmental Health Effects Research
2. Environmental Protection Technology
3. Ecological Research
4. Environmental Monitoring
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6. Scientific and Technical Assessment Reports (STAR)
7. Interagency Energy-Environment Research and Development
This report has been assigned to the INTERAGENCY ENERGY-ENVIRONMENT
RESEARCH AND DEVELOPMENT series. Reports in this series result from the effort
funded under the 17-agency Federal Energy/Environment Research and Development
Program. These studies relate to EPA's mission to protect the public health and welfare
from adverse effects of pollutants associated with energy systems. The goal of the
Program is to assure the rapid development of domestic energy supplies in an environ-
mentally-compatible manner by providing the necessary environmental data and
control technology. Investigations include analyses of the transport of energy-related
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This document is available to the public through the National Technical Information
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EPA-600/7-77-035
April 1977
HEAT PUMPS: SUBSTITUTES FOR
OUTMODED FOSSIL-FUELED SYSTEMS
by
E.A. Picklesimer
Lockheed Missiles and Space Co., Inc.
P.O. Box 1103
Huntsville, Alabama 35807
Contract No. 68-02-1331
Task No. 11
Program Element No. EHE623
EPA Task Officer: Lewis D. Tamny
Industrial Environmental Research Laboratory
Office of Energy, Minerals, and Industry
Research Triangle Park, N.C. 27711
Prepared for
U.S. ENVIRONMENTAL PROTECTION AGENCY
Office of Research and Development
Washington, D.C. 20460
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CONTENTS
Section
FIGURES iv
TABLES v
I INTRODUCTION 1
II BASIC HEAT PUMP CONCEPTS AND COMPONENTS 2
III CURRENT SYSTEMS 8
3.1 Capacity 8
3.2 Adequacy in the Commercial and Residential 8
Sector
IV POTENTIAL OF HEAT PUMP TO REPLACE FOSSIL 12
FUELED EQUIPMENT
4.1 New Systems 12
4.2 In Place of Outmoded Fossil Heating/Electric 12
Air Conditioning Systems
V ECONOMIC COMPARISON OF HEAT PUMPS 13
WITH FOSSIL FUELED SYSTEMS
VI PROJECTIONS OF THE RATE OF MANUFACTURE, 18
SUPPLY AND INSTALLATION OF HEAT PUMPS IN
THE COMMERCIAL AND RESIDENTIAL SECTOR AS
REPLACEMENTS FOR OUTMODED FOSSIL FUEL
FIRED EQUIPMENT
VII SUGGESTION FOR FUTURE RESEARCH AND 24
DEVELOPMENT
VIII RESULTS AND CONCLUSIONS 26
IX COMPARISON OF RESULTS WITH THOSE ARRIVED 28
AT IN EPA REPORT NO. 200-045-013
REFERENCES 29
APPENDDC: Typical Heat Pump Arrangements 30
iii
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FIGURES
Number
2-1 Simplified heat pump flow diagram in cooling mode
showing use of switchover valve to reverse flow
of refrigerant 2
2-2 Efficiency 4
*
2-3 Coefficient of performance (COPn), heating mode 5
2-4 Coefficient of performance (COPC), cooling mode 6
3-1 Relative reliability of today's heat pump systems 9
3-2 Water as heat source-sink and water as the medium
to provide simultaneous heating and cooling (fixed
refrigerant circuit—water flow reversed) 11
5-1 Seasonal heating cost comparison for residential
application—heat pump vs. gas-fired furnace 14
i
5-2 Seasonal heating cost comparison for residential
application- -heat pump vs. oil-fired furnace 15
7-1 Typical heat pump COP vs. outdoor temperature,
5-ton split system 25
A-l Air as heat source-sink and air as heating and
cooling medium (fixed air circuits—refrigerant
flow reversed). Throttling valve used to regulate
refrigerant effect 30
A-2 Air as heat source-sink and air as heating and
cooling medium (fixed air circuits refrigerant
flow reversed) 32
A-3 Water as a heat source sink and air as heating and
cooling medium (fixed air and water circuits—
refrigerant flow reversed). Throttling valves used
to regulate refrigerant effect 32
iv
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TABLES
Number
5-1 Heating costs, single family residence, 1500 ft^.
southeastern United States 17
6-1 New housing starts 20
6-2 Number of heat pump units manufactured in U.S.
(commercial and residential, single and split units) 21
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SECTION I
INTRODUCTION
Clean burning premium fuels such as natural gas and distillate oil No. 2
are marketed primarily as combustion fuels in the commercial and res-
idential sector in the United States. This extensive use of premium fuels
is at the expense of the most abundant energy sources in the United States,
bituminous coal, oil shale and some lignite. Modern combustion technol-
ogy has now progressed to the point where these "dirtier" fuels can be
used efficiently as boiler fuels with the use of modern fuel processing
and stack-gas cleaning technologies (i.e., wet scrubbers, dry scrubbers
and catalytic oxidation) to reduce the pollutant emissions to such a level
as to be competitive with the "premium" fuels.
In order to reduce significantly the demand for clean premium fuels by
the major consumers, the more abundant fuels can be used for genera-
ting electrical energy to be supplied as a clean energy source in the
commerical and residential sector. Consideration of this means of re-
ducing the demand for clean premium fuels should be included in all
future discussions of an Energy Program by the U. S. Government. The
potential benefits that might result from the primary use of electrical
energy by the commercial and residential sector are that the premium
fuels can then be used in energy demand areas which are not amenable
to fuel substitution and in the manufacture of chemicals and fertil-
izer where feed stock shortages already exist. Also, the conversion of
outmoded "premium" fossil fuel heating systems to heat pumps in the
residential and commercial sector where the electricity is generated by
steam coal or nuclear power plants may significantly reduce our national
consumption of scarce natural gas and fuel oil.
An independent assessment has been made of the state of the art relative
to the development, capacity, adequacy and application of the heat pump
as a potential replacement for fossil-fueled equipment designed to serve
in the space heating and cooling mode. A projection has been made of
the rate at which heat pumps could be manufactured, supplied, and in-
stalled in the commercial and residential sector as replacements for
for outmoded fossil fueled equipment whose service life has been ex-
hausted and is scheduled for replacement.
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SECTION II
BASIC HEAT PUMP CONCEPTS AND COMPONENTS
The key components of a heat pump system are shown in Figure 2-1.
The main function of the compressor is to pump a refrigerant vapor
from a relatively low suction pressure to a higher head pressure. The
suction and head pressures that a compressor experiences are a func-
tion of the design, the ambient temperatures, and possible abnormal
fault situations which develop during the life of a heat pump system.
Compressor rf^\ -^ ^ Switchover valve
(heating position)
Figure 2-1 - Simplified Heat Pump Flow Diagram in Cooling Mode Show-
ing Use of Switchover Valve to Reverse Flow of Refrigerant
Under cooling conditions, the refrigerant is pumped from the compres-
sor through the condenser or outdoor coil. Upon leaving the outdoor
coil in liquid form, the refrigerant travels through the evaporator or
indoor coil, and here, as it changes from a liquid into a gas, it removes
heat from the interior, thereby cooling the indoor coil. The gas is then
drawn back into the compressor where it is compressed again into a
very-high-pressure hot gas, which is liquefied or condensed in the out-
door coil.
The first heat pumps were more or less simplified versions of this
cooling unit, and were obtained by merely reversing the flow of refrig-
erant as shown in Figure 2-1. With the aid of a switchover valve, the
outdoor condensing unit became, in essence, the evaporator, and the
indoor evaporator became in essence, the condensing unit. The hot gas,
therefore, was pumped indoors, where it gave off heat as it was con-
densed into a liquid in the indoor section. The liquid was then pumped
-------
into the outdoor section now the evaporator where the refrigerant
changed back into a gas, absorbing heat during this process from out-
door air.
The four basic heat pump designs for space heating and cooling employ:
(1) air as the heat source-sink and air as the heating and cooling
medium; (2) air as the heat source-sink and water as the heating and
cooling medium; (3) water as heat source-sink and air as the heating
and cooling medium; or (4) water as heat source-sink and water as the
heating and cooling medium.
Each of these basic designs can supply the required heating and cooling
effect by changing the direction of the refrigerant flow, or by maintain-
ing a fixed refrigerant circuit and changing the direction of the heat
source-sink media. A third alternative is to incorporate an interme-
diate transfer fluid in the design. In this case the direction of the fluid
is changed to obtain heating or cooling and both the refrigerant and heat
source-sink circuits are fixed. The fixed refrigerant circuit designs,
generally referred to as the indirect type of application, are becoming
increasingly popular, particularly in the larger capacities.
The basic designs are quite flexible and are readily adaptable to a
number of different types of applications. Flow diagrams, together with
a brief description, are given for some of the more typical arrangements
in Appendix A (Ref. 1).
It is easy to confuse the heat pump coefficient of performance (COP) with
efficiency (Eff) since they both represent an index of performance of a
cycle. Efficiency is defined as the desired effect divided by the energy
required to produce the desired effect. For a fossil furnace as shown in
Figure 2-2, the efficiency is
x 100% < 100%
Classically, the efficiency is less than 100%. However for a heat pump
operating on the Brayton cycle, the index of performance is the COP which
can be greater than 100%. In the heating cycle the COP^ of the heat pump
is, by definition, the desired effect (heat into the home, QJJ) divided by the
energy required to produce the desired effect (electrical input — W) as
shown in Figure 2-3 or
x 100% > 100%.
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Thermal Energy Released
by Fuel Combustion, T,r
rl
Q
H
Fossil
Furnace
(Desired Effect-
Heat into Home)
W
Ambient Heat
Sink
Efficiency =
W
Q
x 100% < 100
H
Since W = QH ~ QL
Figure 2-2 - Efficiency
For the cooling cycle, the heat pump COPC is defined as the desired
effect (heat removal from the home, Q,.) divided by the energy re-
quired to produce the desired effect (electrical input — W) as shown in
Figure 2-4 or
COPC =
W
x
100%
-------
Desired Effect — Heat
into Home at T
Q
H
W
Electrical
Energy
Ambient Heat
Source at TT
COPh = -^j2- x 100% > 100%
Since Q = W +
Figure 2-3 - Coefficient of Performance (COP,), Heating Mode
-------
Ambient Heat Sink at T
H
Q
H
W
Electrical
Energy
Desired Effect — Heat Removed
From Home at TT
where
QT
COP = -^ x 100%
c W
QL=QH-W
Figure 2-4 - Coefficient of Performance (COPc), Cooling Mode
-------
Efficiency normally refers to the transfer of energy from a high tem-
perature (TTT) source (fuel) to a low temperature (Tjj) receiver whereas
COP refers to the transfer of energy from a low temperature (TL)
source to a high temperature (Tj^) receiver to produce a desired effect.
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SECTION III
CURRENT SYSTEMS
3.1 CAPACITY
There are many companies which produce quality heat pumps for both
residential and commercial applications. The Air-Conditioning and
Refrigeration Institute lists 32 participants in their Directory of Certi-
fication, January 1 through June 30, 1976 (Ref. 2). The heat pump man-
ufacturers offer a. complete range of heat pump sizes from small
residential units (i. e., less than 5 tons = 60,000 Btuh cooling) to large
commercial systems (i.e., greater than 500,000 Btuh cooling). Larger
systems may be designed by utilizing multiple units. A few of the
largest manufacturers of heat pumps are the Trane Company, General
Electric, Lennox Industries and Carrier. There arc many other small
companies which manufacture heat pumps only for the residential
market (i.e., less than 5 tons).
3.2 ADEQUACY AND APPLICATION IN THE COMMERCIAL AND
RESIDENTIAL SECTOR
When sized properly for the particular application, heat pump systems
have performed adequately in both the residential and commercial sec-
tors since the middle 1960s. Heat pumps have been available for resi-
dential application since the early 1950s. Based on its concept and
efficiency, the heat pump was an immediate success in 1950. History
can be simplified by stating that the heat pump was marketed before it
was sufficiently developed. It failed from the reliability standpoint
during the 1950s. The compressor, the key component of the heat pump,
was not designed to withstand the high head and suction pressure which
can result during conditions of switchover, high ambient temperatures
and possible abnormal fault conditions. These conditions require high
electrical input resulting in high mechanical stresses in bearings, crank-
shafts, and valves producing early compressor failure. By the early
1960s, recognition of these problems resulted in compressor redesign,
high and low pressure cutoff switches and other protective devices for
heat pump systems. With many more improvements, today's heat pump
systems are as reliable as the fossil fuel heat systems with electric air
conditioning as shown in Figure 3-1 (Ref. 3).
The future acceptance of heat pumps for both industrial aad-Residential
applications depends on the total annual cost to* own. a3a^«wea&£e a heat
pump system r'eJative to other systems as distcvjssect iajS^fcp^p V. Cur-
rent residential heat pump systems are cornpietifcfve only wheia used as a
total space comfort conditioning system.
-------
>N
•»->
r-J +->
'^ TO
-2 <"
.53 E
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for the reheat cycle and for the perimeter areas. This latter method
of heating and cooling can add considerably to the operating cost.
Water can be used as the heat source-sink and as the medium to pro-
vide simultaneous heating and cooling to the conditioned space. In this
arrangement the refrigerant flow is always in the same direction, going
from the compressor to the condenser, then to the cooler. The major
refrigerant components together with all refrigerant piping and acces-
sories can be purchased as a compact package with a hermetically
sealed refrigerant circuit. The hot and cold water piping, the indirect
and cooling surfaces, and other needed accessories for a particular
installation can, in turn, be installed by the contractor
During a considerable portion of the year the heating and cooling re-
quirements of the structure may be in balance, so that an external heat
source or sink is not required. Thus, the heat removed from the zones
requiring cooling is automatically transferred to the condenser circuit
and made available to the zones requiring heat. In this way the coeffi-
cient of performance is materially improved to give a considerable
saving in operating cost.
Figure 3-2 (Ref. 1) illustrates how simultaneous heating and cooling
are readily available at all times. For the basic heating cycle, valves
are positioned to path 1-3 to provide two water circuits. Pump 1 cir-
culates the warm water through the condenser-liquid receiver, valves
A, the conditioner coils, and valves B in a closed loop. Pump 2 cir-
culates the cold water through the cooler, valve D, the exchanger
(where heat is taken from the well water), and valve E back to pump 2
to repeat the cycle.
For the basic cooling cycle, valves are positioned to path 1-2. Pump 1
circulates the warm water through the condenser, valve E, the ex-
changer (where heat is rejected to the well water), and valve D back to
pump 1. Pump 2 circulates the cold water through the cooler (where
heat is taken from the water by the refrigerant), valves A, the condi-
tioner coil, and valves B back to pump 2 in a closed loop.
During the intermediate cycle, simultaneous heating and cooling are
provided by modulating valves D and E to maintain the desired tempera-
tures in the two circuits. Usually, during this cycle the water is main-
tained at 100 to 120 F in the condenser circuit and 45 to 50 F in the
chiller circuit. The excess heating and cooling are rejected from the
exchanger to the well water. The well water can be supplied directly
to the condenser and chiller circuits instead of through the heat ex-
changer, as indicated. The direct use of the well water is most attrac-
tive, provided it is chemically acceptable and does not unduly
contaminate the heat transfer surfaces.
10
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•_ INTERNAL ~-:
CONDITIONER"
•/-:; COIL is
HEAT; VALVE POSITION 1-3
COOI_: ' "
VALVE 384 MODULATE TO
MAINTAIN THE DESIRED TEMP
WELL WATER AND WASTE HEAT
AS HEAT SOURCE-SINK.
WATER SUPPLIES SIMULTANEOUS
HEATING AND COOLING TO
CONDITIONED SF»C£.
FIXED REFRIGERANT CIRCUIT
BETWEEN COMPRESSOR (NOT
SHOWN), CONDENSER AND
COOLER,
VALVES "C" £OUrtLlZE
THE PRESSU'i? BETWEEN
THE CIRCUITS
Figure 3-2 - Water as Heat Source-Sink and Water as the Medium to
to Provide Simultaneous Heating and Cooling (Fixed
Refrigerant Circuit — Water Flow Reversed)
The compressor (not shown) delivers the hot compressed gas to the
condensed-liquid receiver where it is liquefied, giving up its latent
heat of condensation to the circulating water. From the condenser the
liquid refrigerant flows through an expansion valve to the cooler (where
it changes into a gas), absorbing the heat of vaporization by reducing
the temperature of the circulating water, and then returns to the com-
pressor.
•v
The heat pump system can be a versatile cooling system and is cleaner
and as quiet as comparable fossil fueled systems but the heat pump
system may require more maintenance (see Section V).
11
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SECTION IV
POTENTIAL OF HEAT PUMP TO REPLACE FOSSIL
FUELED EQUIPMENT
If air conditioning is not necessary, a heat pump heating system is not
competitive with a comparable fossil fueled heating system based on cap-
ital cost and operating cost. Therefore, only the total space comfort-
conditioning concept will be considered in the subsequent discussion.
4.1 NEW SYSTEMS
Utilization of the heat pump system is most economical when the
system is designed as the initial space comfort-conditioning system in
the new home or the new commercial facility. Once the decision to uti-
lize electric air conditioning has been made, the decision to use a heat
pump system over a fossil fueled/electric air conditioning system can
be made by considering the total annual cost of each system, the avail-
ability of fuel, the dynamics of the fossil-fueled/electric price ratio
and the climate (which affects both the amount of heating and cooling
required and the efficiency of the system) (Refs. 1, 5). (See Section V
for economic analysis.)
4.2 IN PLACE OF OUTMODED FOSSIL HEATING /ELECT RIG AIR
CONDITIONING SYSTEMS
In discussions with heating and air conditioning contractors, there are
many factors to consider in replacing an outmoded fossil fueled heating/
air conditioning system with a heat pump system.
If the air circulation system already exists, installation of the heat pump
can be very competitive with replacing the outmoded system. However,
if the air handling system does not exist, installation can be very diffi-
cult and expensive.
In many cases, either the outmoded fossil fueled heating system or the
electric air conditioning system may need replacing but not both. It
may be difficult to justify the capital expense of a heat pump system as
opposed to replacing only the fossil fueled furnace or an electric air
conditioner.
If a home or business was wired initially for a fossil fueled heating
system, a heat pump system requires an additional electrical load
which may necessitate the additional expense of rewiring.
Thus heat pump retrofit is most attractive if the air handling system
is already in place and both the fossil fueled heating and electric air
conditioning systems need replacement.
12
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SECTION V
ECONOMIC COMPARISON OF HEAT PUMPS WITH FOSSIL
FUELED SYSTEMS
The heat pump should only be sold under the aegis of a total-space
comfort-conditioning concept. The heat pump system can be econom-
ical except when air conditioning is excluded. In that case, the total
annual cost of owning and operating a heat pump system will be higher
than that of a gas fired heating system without air conditioning, thus
making the heat pump unattractive economically to the homeowner.
To the average homeowner paying 3^/kWhr for electricity but only
0.82^/kWhr for gas, the fact that electricity can be competitive with
gas for space heating is difficult to accept. The disparity between the
two seems even greater when the higher installation and maintenance
costs of the heat pump are considered. However, there are several
other factors in an electric/gas cost analysis that, more often than not,
offset the basic cost differential. Among them are special rates for
space heating and water heating, the decision to use electric air con-
ditioning, and the dynamics of the relative gas/electric price ratio
where the price of gas has grown faster than that of electricity. With
a worsening of the gas shortage, escalation in gas prices is likely to
continue.
An economic analysis was made by Lockheed-Huntsville comparing the
heat pump, gas fired and oil fired furnaces with electric air conditioning
on the total-space comfort-conditioning concept. Equipment efficiencies
assumed are: gas fired furnace, 45%; oil fired furnace, 45%; electric
air-conditioning, 300%. The heating value of natural gas was assumed
to be 1000 Btu/ft^. Figure 5-1 shows the result of economic compari-
son of the heat pump and the gas fired furnace. The current retail cost
of natural gas for residential use is about 24j^/therm (equal to . 82^/kWhr)
and for electricity is about 3j^/kWhr giving a unit energy cost difference
ratio of 8. At an energy cost difference ratio of 8 (see dashed lines in
Figure 5-1), the heat pump is more expensive to operate by about 25%
for a coefficient of performance (COP) of 3. However, if electric rates
increase by 1.5 and gas rates triple by 1980 as forecast (Refs. 6 and 7),
the heat pump will be more economical than the gas fired furnace as
shown in Figure 5-1. Figure 5-2 shows the results of a comparison of
the heat pump and an oil fired furnace burning No. 2 fuel oil with a heat-
ing value of 140,000 Btu/gal. The current retail cost of No. 2 oil is
about 39f£/gal and 3^/kWhr for electricity giving a unit energy cost
ratio of 13. If the cost of electricity increased by 1.5 and the cost of
No. 2 fuel oil triples by 1980 (Refs. 7, 8), the heat pump will be more
economical on a total space-comfort conditioning concept. Figures 5-1
and 5-2 do not account for captial cost, depreciation and maintenance.
13
-------
CO
O
U
0)
a
CO
o
I
a
as
w
ii
o
•i-t
•8
a>
u
a
0)
fn
0)
CO
O
U
bO
n)
cu
ffi
100' •
80 • •
60' •
-20"
1. Heating cost difference ratio vs unit
energy cost ratio
2. Gas furnace efficiency = 45% with
electric air conditioner in summer
3. Gas heating value - 1000 Btu/ft
Seasonal Heat Pump Coefficient
of Performance (COP)
Equal
Operating
Line
Figure 5-1 - Seasonal Heating Cost Comparison for Residential
Application — Heat Pump vs Gas-Fired Furnace
14
-------
4J
(0
O
U
h
0)
a
O
0)
u
n)
fi
Jj
h
O
i
a
g
fi
-H
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ffi
•8
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O
00
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2
a>
a,
O
a
fi
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Pn
13
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ffi
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h
V
ta
O
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a
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13
4)
HH
hM
20 • •
10 ..
- 10 -
-20 -•
Notes:
1. Heating cost difference ratio vs unit
energy cost ratio
2. Oil furnace efficiency = 45% with
electric air conditioning in summer
3. No. 2 heating oil - 140,000 Btu/gal
Heat Pump COP
Equal
Operating
Line
Figure 5-2 - Seasonal Heating Cost Comparison for Residential
Application — Heat Pump vs Oil-Fired Furnace
15
-------
Table 5-1 shows a comparison of the annual cost of operating a heat
pump, a gas furnace with electric air conditioning and an oil furnace
with electric air conditioning in a residential application. Depreciation
has been figured on a 15-year equipment life and 40-year life for duct
work. Capital cost has been figured on a 7% mortgage ratio of the total
installed cost. Maintenance has been figured on a percentage of the orig-
inal equipment cost with a factor based on relative equipment complexity.
Data were obtained by surveying Heating and Air Conditioning Contractors
in the Southeastern United States. Note that the heat pump system is
more expensive to own and operate based on 1975 retail fuel prices. As -
suming a threefold price increase in natural gas and fuel oil as compared
to a 1.5 increase in electricity by 1980, the heat pump will be less expen-
sive to own and operate than both oil and gas furnaces with electric air
conditioning.
Annual costs for heating and air conditioning depend upon the location
within the U. S. In the Northern U. S. the mean temperature may be 10
to 20 degrees lower than in the Southern U. S. Therefore, heat pump
efficiencies would be somewhat less but fossil furnace efficiencies
would be somewhat greater than in the South. Therefore the operating
cost for the alternatives presented may change by as much as 20% de-
pending on location but the trends would not change. In Alaska, almost
no homes are equipped with air conditioning; based on the low efficiency
of a heat pump at low ambient temperatures and the current fuel prices,
a heat pump is not economical compared with a similar fossil fueled
system when considering the heating mode only.
On the other hand, in Southern Florida many homes and commercial bus-
inesses do not have a heating system; more than 95% of air conditioning
systems are conventional electric.
In some locations, homes and commercial businesses utilizing electric
heating receive reduced electric rates due to the utility's reduced costs
in delivering larger amounts of electricity to a customer. Although the
actual operating cost would depend on the particular rate, the reduced
rates can make heat pumps more economical (Ref. 7).
16
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Table 5-1
HEATING COSTS, SINGLE FAMILY RESIDENCE,
1500 FT3, SOUTHEASTERN UNITED STATES
Item
Operating 1975
Costs 1976
1977
Depreciation
Capital Cost
Maintenance
Total Annual Cost
1975
1980
1985
Heat Pump
$ 281
$ 422
$ 632
$1,800<£ 6.7% = $120
$1.200 (S 2.5%= $ 30
$3.000 x 0.07 = $210
$1,100 x 0.04 - $ 44
$ 685
$ 826
$1036
Gas Furnace
with Electric
Air Conditioning
$ 237
$ 535
$ 803
$1400 @ 6.7% = $ 93
$1200 @ 2.5%= $ 30
$2600 x 0.07 = $182
$ 200 x 0.02 = $ 4
$ 500 x 0.03 = $ 15
$ 561
$ 859
$1127
Oil Furnace
with Electric
Air Conditioning
$ 260
$ 603
$ 905
$1400 @ 6.7% = $ 93
$1200 (§ 2.5% = $ 30
$2600 x 0.07 = $182
$ 800 x 0.03 = $ 4
$ 500 x 0.03 = $ 15
$ 604
$ 947
$1249
Energy Costs
Electric
3 //kWH
4.5
6.75
Gas
24 //them-.
72
108
Fuel Oil
40 //gal
120
180
Annual Load
Keating - 0.4 x 108 Btu/yr
Q
Cooling - 0.4 x 10 Btu/yr
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SECTION VI
PROJECTIONS OF THE RATE OF MANUFACTURE, SUPPLY
AND INSTALLATION OF HEAT PUMPS IN THE COMMERCIAL
AND RESIDENTIAL SECTOR AS REPLACEMENTS
FOR OUTMODED FOSSIL FUEL FIRED EQUIPMENT
6.1 PROJECTIONS OF THE RATE OF MANUFACTURE OF HEAT
PUMPS
In communicating with representatives of companies manufacturing heat
pumps, about 154,000 heat pump units were manufactured during 1975
(Refs. 6, 9, and 10). Approximately 139,000 units of 5 tons or less were
manufactured and sold for residential use and about 15,000 units of greater
than 5 tons were sold for use in commercial applications. Thus, 90% of
all heat pumps manufactured during 1975 were for the residential market.
Due to the reduced supply of natural gas and heating oil, manufacturers
of heat pumps are projecting an industry-wide production rate of 250,000
to 275,000 (Refs. 6, 9) heat pump units for supply and installation during
1976. The manufacturers feel that the percentage of residential and
commercial heat pumps will remain the same. Less than 5% of this is
for retrofit application.
6.2 REPLACEMENT RATE
In order to estimate the rate at which outmoded fossil fueled heating
systems could be replaced with heat pumps in the residential and com-
mercial sector, let
N. = total number of heat pump units needed for both
residential and commercial sector
N = maximum nuber of residential heat pumps units
required
N = maximum number of replacement heat pump units
r in residential sector
L = gas heating system life
o
L = oil heating system life
N = number of heat pump units needed for new homes
n r r
N = number of residential gas customers
g
F = fraction of residential customers using gas for
^ space heating
N = number of residential oil customers
p
F = fraction of residential customers using oil for
0 space heating
18
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Then the maximum number of heat pumps required for replacement of
of outmoded fossil fired equipment in the residential sector is
N . F N . F-
N = + -
Lg Lo
Data from the American Gas Association (Ref. 6) indicate that there were
41,336,500 residential gas customers in the U.S. in 1974; of those, 84%
of the customers used natural gas for space heating with an average con-
sumption of 1140 therms. Data from the Department of Commerce (Ref.
8) indicate that there were 16,827,000 residential heating oil customers
in the U.S. in 1975; of those, 99% of the customers used oil for space
heating with an average annual consumption of 900 gallons.
Assuming an average life of a gas and an oil heating system to be 15 years
(Ref. 2), the maximum number of replacement heat pump units required in
the residential sector for outmoded fossil fueled systems is
(2)
41,336,500 (0.84)
r ~ 15
16.827,000 (0.99)
15
= 3.43 x 10 heat pump units
year
N represents the maximum number of heat pump units needed per year
to replace all of the outmoded fossil heating systems in the residential
sector during the next 15 years. Since data were not available for 1975,
Nr is based on the number of gas customers in 1974. Due to the gas
shortage, it is unlikely that this number has increased. Obviously, not
every fossil fueled heating system installed in 1965 will be replaced in
1980; some will be replaced sooner, others later. However, assigning
finite lifetimes to each type of fossil fueled heating system should not
affect the relative replacement rate.
Table 6-1 (Ref. 8) shows the annual number of new housing starts during
the last four years and an estimate of starts for 1976. Although the
number of new housing starts has been decreasing since 1972, the esti-
mate for 1976 is up. For simplicity, assume that the number of new
housing starts per year during the next 15 years is 1,250,000. If heat
pumps are installed in all new homes, the number of units required will
be
N = 1,250,000 units year. (3)
n
19
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Table 6-1
NEW HOUSING STARTS (REF. 8)
Year
1972
1973
1974
1976 (Est.)
Number of New
Starts
2,378,500
2,057,500
1,352,500
1.3 to 1.7
Housing
x 106
Therefore, the number of residential heat pump units needed as replace-
ments for outmoded fossil fueled heating systems and for installation in
new homes is
N = N + N
r n
(4)
_ 4 ,„ ,,.6 heat pump units
X year
If one assumes that the ratio of the number of residential units manufac-
tured to the number of commercial units remains 9/1, the total numbers
of units needed is
Nt = N (1 + 1/9)
- 5 15 10^ heat pump units
x year
(5)
In order to put this number into perspective, Table 6-2 (Refs. 10, 11)
shows the number of heat pump units manufactured in the U.S. from 1972
to 1975 and an estimated production for 1976. The numbers include both
single and split units for residential (i.e., less than 5 tons) and commeri-
cal use. It is apparent that the number of heat pumps needed for replace-
ment and new applications is 5.15 x 10°/154,000 = 33 times greater than
the total number of units manufactured in 1975.
Several comments are in order at this point. Although heat pump manu-
facturers feel that their industry could respond to any demand rate for heat
pump-units by the general public (Refs. 10, 11), several of the large manu-
facturers expressed concern about a large number of untested and un-
reliable heat pump units on the market today; with a high demand for heat
20
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Table 6-2
NUMBER OF HEAT PUMP UNITS MANUFACTURED IN U. S.
(Commercial and Residental, Single and Split Units)
Year
1972
1973
1974
1975
1976 (Est.)
Number of Units
97,000
120,000
128,000
154,000
250,000
pump systems, sale of a large number of these units could cause a simi-
lar situation that developed in the heat pump market in tin- 1950s (see
Section 3.2). The second point is that possibly as many as one-third of
the outmoded fossil fueled heating systems in both the residential and
commercial sector cannot be replaced due to the problems in the physi-
cal arrangement of the existing fossil fueled heating system using hot
water pipes, convection radiators, etc. Also, it may not be practical to
replace another third of the outmoded fossil fueled heating /electric air
conditioning from an economic standpoint because only the heating or the
cooling system may need replacing, not both. A more realistic manufac-
turing rate may be less that 25% of Nt or less than 1.3 x 10^ heat pump
units per year which is still 8.4 times the 1975 industry-wide heat pump
manufacturing rate.
6.3 ESTIMATES OF POSSIBLE REDUCTION IN DEMAND OF PREMIUM
FUEL
Assume that all of the residential customers using natural gas and heat-
ing oil for space heating replace their outmoded fossil fuel equipment at
the time of failure with heat humps. As indicated in Section 6.2, there
were 41,336,500 natural gas customers in 1974 where 84% of the customers
used natural gas for space heating with the average annual usage of 1140
therms. Assuming a heating value of 1000 Btu/ft^, the maximum savings
of natural gas would be
Saving
41,336,500 (0.84) (1140
res. gas =
therm
year
(10
Btu
therm'
103 Btu/ft3
(6)
8.8 x 1012 ft3/yr
21
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Similarily, there were 16,827,000 residential heating oil customers in
1974 where 99% of those customers used oil for heating with an average
annual consumption of 900 gal year (Ref. 12). The maximum savings of
heating oil would be
Saving
res. oil = 16,827,000 (.99) (900 gal/year) (7)
= 1.5 x 10 gal/year
Data on the number of residential gas customers for 1975 have not been
finalized, but due to the shortage of supplies, the totals have not increased.
There were 3,392,000 commercial users of natural gas in 1974 with an
average annual consumption of 6,761 therms. The American Gas Associa-
tion (Ref. 13) estimates that two-thirds of this consumption was used for
space heating. The maximum savings of natural gas in the commercial
sector is
comm. gas = = s
10 Btu/ft
Saving 3,392,000 (0.667) (6,761
_
(8)
= 1.529 x 1012 ft3/year
Since there is no information on commercial fuel oil consumption for
space heating, assume the ratio of the number of commercial to residen-
tial fuel oil customers is the same as the ratio of the number of commer-
cial to residential gas customers.
Then, the number of commercial fuel oil customers =
3,392,000
1 A 827 000
16,827,000
= 1,380,000
Also, assume that the ratio of the average annual consumption of com-
mercial to residential natural gas is the same as the ratio of the average
annual consumption of commercial to residential fuel oil for space heating.
22
-------
Then, the average consumption of fuel oil for commercial space heating =
If all of the commercial fuel oil heating systems were replaced with heat
pumps, the maximum savings of heating oil would be
Saving
comm. oil = 1,380,000 (4238) =
0.585 x 1010 gal/year
Therefore, the maximum savings in the commercial and residential sector
that may be realized by replacing the outmoded gas heating systems with
heat pumps is from (8) and (6)
Savings ag = 10.3 x 1012 ft3/year
O
Similarity, the maximum savings of heating oil from (7) and (11) would be
5 oil
= 1.357 x 106
oil/day
Savings^ = 2.08 x 10 gal/year
= 1.357 x 10 barrels of premium fuel
The above savings would be realized at the end of a 15-year period when
all of the outmoded fossil fueled systems had been replaced. As indicated
in Section 6.2, the actual savings of natural gas and heating oil due to the
replacement of outmoded fossil fueled systems with heat pumps would
probably be less than the maximum due to the inability to install heat
pumps in some residences and the failure of only one component of the
total space heating system. A conservative savings of 25% of the maxi-
mum might be more realistic.
23
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SECTION VII
SUGGESTION FOR FUTURE RESEARCH AND DEVELOPMENT
Significant improvements have been made in the design of heat pumps
since 1950. The compressor has been redesigned to withstand high
stresses. Safety devices such as high and low pressure cutoff switches
have been added to heat pump systems to prevent operation at abnormal
conditions. However, more research and development is still needed to
make the heat pump more economical relative to other systems.
Improvements are needed in the area of low temperature operation. As
indicated in Figure 7-1, the coefficient of performance decreases rather
dramatically as the ambient temperature decreases. Evaporator icing
,is a problem at temperatures below 32 F.
Research is also needed in the area of improved working fluids and im-
proved materials to extend compressor component life.
Additional studies should be made to assess the impact of space heating
electrification on local and regional air quality due to increased load at
electric generation plants. Since a significant number of fossil fueled
heating customers do not use electric air conditioning presently, electri-
fication of space heating could significantly increase the demand for
electricity. Thus, an analysis should be made to determine if the
nation1 s electrical generating capacity could be expanded Rapidly enough
to meet increased demand since some utilities have drastically reduced
their construction schedules. Current lead times for bringing base elec-
tric generating plants on line are more than seven years for fossil fueled
plants and 12 years for nuclear plants.
In order to encourage the use of heat pumps to conserve premium fossil
fuel, to reduce air pollution from stationary sources and to help meet the
national goal of reducing our dependence on imports of natural gas and
oil, a study should be made on the use of direct incentives to encourage
customers to convert outmoded fossil systems to heat pump systems.
Such incentives could be provided by the various federal agencies in the
form of: (1) reduced electric rates for heat pump customers; (2) tax de-
ductions or an increased depreciation rates for conversion; and/or (3)
lower VA and FHA interest rates for conversion to heat pump systems;
or (4) tax credits for heat pump installation and insulation improvement
to applicable standards where appropriate.
24
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50
40' •
S. 30' '
I
h
01
o, 20-
s
O
o
o- •
-10-
Coefficient of Performance (COP)
Figure 7-1 - Typical Heat Pump COP vs Outdoor Temperature,
5 ton Split System
25
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SECTION VIII
RESULTS AND CONCLUSIONS
The widespread use of the heat pump in both the residential and com-
mercial sectors as a total comfort conditioning system will, to a large
extent, be controlled by the consumer. Modern heat pump systems are
as reliable and competitive in capital cost as fossil heating/electric
air conditioning systems. Although residential heat pump systems cur-
rently cost about 25% more to operate than comparable fossil heating/
electric air conditioning systems based on current retail energy costs,
the future availability of natural gas and oil for space heating is ques-
tionable. Even today, many utilities have decided not to add any more
residential natural gas customers to their system until further notice;
in those cases many contractors are installing heat pumps exclusively
in new homes. Certain commercial heat pump systems are already
more economical today than fossil fueled heating/electric air condition-
ing systems especially when both heating and cooling are required in
different areas of a building at the same time.
The retail price of natural gas and oil has increased much faster than
the price of electricity. Also, the natural gas and petroleum industry
may be deregulated in the future which may cause a significant increase
in the retail price of natural gas and oil relative to electricity. There-
fore, heat pump systems may be as economical to operate as fossil
fueled heating/electric air conditioning systems in the near .future.
Heat pumps may be used to replace outmoded fossil heating/electric air-
conditioning systems especially in those locations where the air handling
system already exists. By converting outmoded fossil heating electric
air conditioning systems to heat pump systems, the premium fossil fuel
saved may be used in applications where conversion is not possible and
where a "critical" shortage already exists such as the manufacture
of fertilizer.
Assuming that the energy needed for space heating electrification comes
from new coal fired or nuclear units, spacing heating electrification
using heat pumps could reduce the nation's consumption of natural gas
by 10.3 x 1012 ft^/year and premium fuel oil (i.e., No. 2 or better) by
1.357 x 10^ barrels/day. Since current base load power plant lead
times are so great and utilities have drastically cut their construction
schedules, it is questionable at this time if the utilities can meet the
increased demand due to space heat electrification. Electric generation
capacity currently exists for those customers using electric air condi-
tioning. However, there are many customers in areas such as the
densely populated Northeastern U. S. where fossil fueled heating is uti-
lized without electric air conditioning; in these cases, electrification of
the heating systems would result in the need for additional generating
capacity.
26
-------
Although the projected demand for heat pump units may be significantly
greater than the current industry growth rates due to electrification of
space heating with heat pumps, this demand (see Section 5) can be met
by current heat pump manufacturers.
27
-------
SECTION DC
COMPARISON OF RESULTS WITH THOSE ARRIVED AT IN EPA
REPORT NO. 200-045-013
This study agrees with the results arrived at by EPA Report No. 200-
045-013 that electrification of fossil fueled heating systems in the resi-
dential and commercial sector can result in a significant reduction in
the demand for premium fuels for use in those areas •where conversions
cannot be made and shortages already exist. If the electrical energy re-
quired for these conversions were provided by coal-fired or nuclear
power plants, these reductions in end use consumption of premium fossil
fuels would represent a real reduction in our national consumption of
natural gas and fuel oil.
Although the projected rates of manufacture, supply and installation of
heat pump units needed for replacement of outmoded fossil fueled
systems and new applications may be more than eight times the industry
wide heat pump manufacturing rate during 1975, it is felt that the heat
pump industry could meet this projected demand.
i
This study disagrees with the EPA Report No. 200-045-013 conclusion
that the promotion of electrification of space heating should be instituted
at the present time. A brief study should be made to determine how
much additional generating capacity is needed and if it will be available
in view of reduced utility construction programs and increased power
plant lead times. Information necessary for this study will be available
in the near future from the Department of Commerce and the Federal
Power Commission (See Section VIII).
28
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REFERENCES
1. Ambrose, E. R., Heat Pumps and Electric Heating, Wiley, New York,
1966.
2. Directory of Certification, Air Conditioning and Refrigeration Insti-
tute, Arlington, VA., January 1-June 30 1976.
3. Juttermann, "Heat Pumps in Large Buildings," Heiz-Luft. -Haustechn.,
Vol. 25, No. 4, April 1974, OA - Trans - 939, pp. 124-130.
4. "Moore Turns to Heat Pumps," Power, p. 24, November 1973.
5. O'Neil, J.F., "The Economics of the Heat Pump," Engineering Journal,
Novermber, 1965, pp. 42-46.
6. American Gas Association, Department of Stastics, Personal Com-
munication, May 21, 1976.
7. Spaite P., Energy Consultant, Cincinnati, Ohio, Personal Communi-
cations, June 10, 1976.
8. U.S. Department of Commerce, Office of Consumer Affairs, Statistics
Division, Washington, D. C., Personal Communication, May 25, 1976.
9. Carrier Corporation, Syracuse, New York, Private Communication,
May 20, 1976.
10. Carrier Corporation, Syracuse, N. Y., Personal Communications, May
25, 1976.
11. General Electric, Central Air Conditioning Product Department, Pri-
vate Communications, May 21, 1976.
12. U.S. Department of Commerce, Bureau of the Census, Washington,
D. C., June 3, 1976.
13. Gas Facts, 1975, American Gas Association, Washington, D. C.
29
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APPENDIX
TYPICAL HEAT PUMP ARRANGEMENTS
An air heat source-sink design using air as the heating and cooling
medium illustrated in Figure A-l, is by far the most universally used,
particularly for the residential and smaller commercial installations
having a cooling load of about 25 tons, or lower...
ACCESSORIES
A OIL SEPARATOR
B SUCTION LINE ACCUMULATOR
Figure A-l
Air as Heat Source-Sink and Air as Heating and Cooling
Medium (Fixed Air Circuits — Refrigerant Flow Reversed).
Throttling Valve Used to Regulate Refrigerant Effect
Conventional refrigerant practice can be followed in the selection and
arrangement of the equipment, except that it is desirable to have gravity
drainage of the liquid refrigeration from the outdoor coils and the con-
ditioner coils to the liquid receiver. The diagram also indicates the
probable location of an oil separator in the discharge line, and of a
liquid refrigerant-oil accumulator in the suction line. These accesso-
ries are generally used on all except the small integral designs in order
to assure proper oil return and prevent liquid flood-back to the com-
pressor.
In this design, heating and cooling are obtained by changing the direction
of the refrigerant flow. Two fixed independent air circuits are employed,
consisting of the outdoor coil circuit and the conditioner coil circuit.
During the cooling cycle the four-way valve is positioned to paths 1-2
and 3-4. The compressor delivers the hot compressed refrigerant gas
through the four-way valve, path 1-2, to the outdoor coil where it is con-
densed, giving up the latent heat of condensation to the outside air. From
30
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the outdoor air coil the liquid refrigerant flows through the check valve
to the liquid receiver and then through the throttling valve to the con-
ditioner coil. In the conditioner coil the liquid refrigerant is changed
into a gas that absorbs the heat of vaporization from the air going to the
conditioned space. From the conditioner coil the refrigerant gas returns
through the four-way valve, path 3-4, to the compressor to repeat the
cycle.
During the heating cycle the four-way valve is positioned to path 1-3 and
2-4. The compressor delivers the hot compressed refrigerant gas
through the four-way valve, path 1-3, to the conditioner coil where it is
condensed, giving up the latent heat of condensation to the air going to
the conditioned space. From the conditioner coil the liquid refrigerant
flows through the check valve to the liquid receiver and then through the
throttling valve to the outdoor coil. In the outdoor coil the liquid refrig-
erant changes into a gas that absorbs the heat of vaporization from the
outside air. From the outdoor coil the refrigerant gas returns through
the four-way valve, path 2-4, to the compressor to repeat the cycle.
Figure A-2 is a modification of the basic air-to-air heat pump cycle.
Two additional check valves and a liquid throttling valve have been added
to the basic cycle and the expansion valves, solenoid valves, liquid re-
ceiver, and oil separator have been eliminated. In this design the liquid
refrigerant is used both to boil the condensed refrigerant from the suction
line accumulator and to superheat the suction gas entering the compres-
sor. The throttling valve, C, regulates the refrigerant flow by maintain-
ing a predetermined liquid temperature leaving the condenser. The heat
source coil, either the indoor or outdoor coil depending upon the cycle,
will operate in a flooded condition because of the absence of an expan-
sion valve. It is important, therefore, that the suction line accumulator
be adequately designed to prevent liquid floodback to the compressor.
The main advantage cited for this design is the elimination of the thermo-
static expansion valves and the need for a pressure-suction differential
to obtain the desired refrigeration effect. Consequently, the system can
operate on the cooling cycle at extremely low outdoor temperatures, and
by maintaining the predetermined liquid temperature can operate at rea-
sonably constant head pressures during both the heating and cooling cycle.
Figure A-3 shows a typical flow diagram of a system employing water as
the heat source-sink and using air as the heating and cooling medium.
In this cycle, heating and cooling are obtained by changing the direction
of the refrigerant flow. Two separate fixed circuits are employed, con-
sisting of a water circuit through the condenser-cooler and an air circuit
over the conditioner coil. During the cooling cycle the four-way valve is
positioned to paths 1-2 and 3-4. The refrigerant path is from the com-
pressor through the four-way valve, path 1-2, the condenser-cooler, the
check valve, the liquid receiver, the expansion valve, the conditioner coil,
the four-way valve, path 3-4, back to the compressor to repeat the cycle.
The refrigerant gas is liquefied in the condenser-cooler by giving up its
31
-------
V&LVE MSrT
1-2 *NO 3-4
PAT* I-J AND 1-4
»•COMPRESSOR
• SUCTION LINt ACCUMULATOR
C- THKOTTUNO VALVE USED TO HEOULATE
CFVECT.
Figure A-2 - Air as Heat Source-Sink and Air as Heating and Cooling
Medium (Fixed Air Circuits Refrigerant Flow Reversed)
TO HEAT SOURC€-SINK
4 way_yaty£
CO0UNG PATH t-Z AH?) 3-
«E*fi»6 ^-ITM I-S A'<3 Z-
*ccrssomes
A-OIL SEPARATOR
»• SUCTION LI HE ACCUMULATOR
Figure A-3 - Water as a Heat Source Sink and Air as Heating
and Cooling Medium (Fixed Air and Water Cir-
cuits — Refrigerant Flow Reversed). Throttling
Valves Used to Regulate Refrigerant Effect
latent heat of condensation to the water and is changed back into a gas
in the conditioner coil by absorbing its heat of vaporization from the
air going to the conditioned space.
During the heating cycle the four-way valve is positioned to paths 1-3
and 2-4, The refrigerant path is from the compressor through the
32
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four-way valve, path 1-3, the conditioner coil, the check valve, the
liquid receiver, the expansion valve, the condenser-cooler, the f our -
way valve, path 2-4, then back to the compressor to repeat the cycle.
Conversely to the process of the cooling cycle, the hot compressed re-
frigerant gas from the compressor is liquefied in the conditioner coil
by giving up its heat of condensation to the air going to the conditioned
space, and is changed back into a gas in the condenser-cooler by absorb-
ing the heat of vaporization from the well water.
During both the cooling and heating cycles well water is circulated by
a pump through the preconditioning coil (if used to precool or to preheat
the ventilation air), then through the condenser-cooler to the drain.
33
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TECHNICAL REPORT DATA
(Please read Instructions on the reverse before completing)
. REPORT NO.
EPA-600/7-77-035
2.
3. RECIPIENT'S ACCESSION-NO.
TITLE AND SUBTITLE
Heat Pumps: Substitutes for Outmoded Fossil-Fueled
Systems
5. REPORT DATE
April 1977
6. PERFORMING ORGANIZATION CODE
. AUTHOR(S)
E.A. Picklesimer
8. PERFORMING ORGANIZATION REPORT NO.
LMSC-HREC PR D496880
9. PERFORMING ORGANIZATION NAME AND AOORESS
Lockheed Missiles and Space Co. , Inc.
P.O. Box 1103
Huntsville, Alabama 35807
10. PROGRAM ELEMENT NO.
EHE623
11. CONTRACT/GRANT NO.
68-02-1331, Task 11
12. SPONSORING AGENCY NAME AND ADDRESS
EPA, Office of Research and Development
Industrial Environmental Research Laboratory
Research Triangle Park, NC 27711
13. TYPE OF REPORT AND PERIOD COVfchf D
Task Final; 4-6/76
14. SPONSORING AGENCY CODE
EPA/600/13
15. SUPPLEMENTARY NOTES E PA
61, 919/549-8411 Ext 2851.
officer for this report is Lewis D. Tamny, Mail Drop
16. ABSTRACT Tne repOrt reviews the state-of-the-art relative to development, capacity,
and adequacy of the heat pump as a potential replacement for outmoded fossil-fueled
heating and cooling systems in the residential and commercial sector. Projections
are made of the rate at which heat pumps need to be manufactured and installed in
the commercial and residential sectors as the projected service life of fossil-fuel
equipment expires. The conclusion is reached that the heat pump is economical only
as a total space comfort system. Based on January 1, 1976, fuel prices, the heat pump
is about 25% more expensive to operate than comparable fossil-fueled heating systems.
If the trend of increasing fuel prices continues, the heat pump will be more economical
to operate than comparable fossil-fueled heating systems by 1980.
17.
KEY WORDS AND DOCUMENT ANALYSIS
a.
DESCRIPTORS
b.lDENTIFIERS/OPEN ENDED TERMS
c. COSATI Field/Group
Air Pollution
Heat Pumps
Heating
Cooling
Energy Conversion
Energy Conversion Heat Sources
Refrigerating Map.hlnfiry
18. DISTRTBUTION ST/i
Air Pollution Control
Stationary Sources
13B
13A
10A
10B
18. DISTRTBUTION STATEMENT
Unlimited
19. SECURITY CLASS (This Report)
Unclassified
21. NO. OF PAGES
39
20. SECURITY CLASS (Thispage)
Unclassified
22. PRICE
EPA Form 2220-1 (9-73)
34
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