WATER POLLUTION CONTROL RESEARCH SERIES
16130FHJ09/70
BENEFICIAL USES OF WASTE HEAT
AN EVALUATION
ENVIRONMENTAL PROTECTION AGENCY • WATER QUALITY OFFICE
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WATER POLLUTION CONTROL RESEARCH; SERIES
The Water Pollution Control Research Series describes the
results and progress in the control and abatement of pollu-
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Inquiries pertaining to the Water Pollution Control Research
Reports should be directed to the Head, Project Reports
System, Office of Research and Development, Water Quality
Office, Environmental Protection Agency, Washington, D.C. 20242,
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BENEFICIAL USES OF WASTE HEAT—AN EVALUATION
by
Ronald R. Garton, Ph.D.
and
Alden G. Christiansen, P. E.
Presented At: Conference on Beneficial Uses of Thermal Discharges
Sponsored by New York State Department of Environmental Conservation
Albany, New York, September 18, 1970
Environmental Protection Agency
National Thermal Pollution Research Program
Water Quality Office
Pacific Northwest Water Laboratory
Corvallis, Oregon
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BENEFICIAL USES OF WASTE HEAT—AN EVALUATION
There are a number of proposed beneficial uses of the waste heat
contained in power plant cooling water. Included are those for which
the technical feasibility has been demonstrated in pilot programs and
those which are, at best, imaginative ideas. So, where do we stand
today, and what remains to be done to determine if waste heat can ever
be widely used for beneficial purposes?
As representatives of a regulatory agency, we are concerned pri-
marily with solving the environmental pollution problem. In the overall
environmental-ecological framework, a beneficial use of waste heat must
help reduce the thermal pollution problem directly or it must provide
a profit to help offset the cost of cooling devices. Furthermore, the
use must not result in additional pollution such as that resulting from
untreated organic wastes.
With these thoughts in mind we would like to discuss some potential
uses of waste heat in a little more detail. In our analysis the emphasis
is placed on needs since accomplishments have been reviewed in detail by
previous speakers.
Aquaculture already has been successfully carried out in small pilot
projects so the feasibility of raising at least a few species at con-
trolled, elevated temperature has been demonstrated. For example: Til ton
and Kelley (1) have described a successful small-scale commercial operation
in Texas where catfish are raised in cages in a power plant discharge canal
which maintains suitable temperatures for optimum growth. Marine fishes
have been raised in warmed sea water in Scotland (2) and University of
Miami scientists (3) have been successfully raising shrimp in warm power
plant effluent in Florida. But, although feasibility has been demonstrated
on a small scale, we are still a long way from large-scale production and
from solving the thermal pollution problem.
We still must answer questions about economic feasibility. It is one
thing to raise fish in power plant effluent on a research basis with free
support of the company but yet another to pay for distribution systems and
perhaps purchase the hot water for a commercial enterprise.
Even if feasibility of warm-water aquaculture is demonstrated, has
the pollution problem been alleviated or will it be compounded? In almost
all conceivable instances no single aquacultural enterprise will be able
to handle all the cooling water from a large power plant, so cooling de-
vices will still be required. Even the water used for aquaculture may
not be cooled sufficiently to meet water quality requirements. If not,
how will it be treated? In view of the increasing stress on environmental
quality, it is almost certain that warm-water aquaculture will have to be
practiced in closed systems; there will be few, if any, instances where
hot water will be dumped into natural water courses in hopes of increasing
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fish production. Water released from these systems will have to meet
the same temperature requirements as those set for the power plants.
The problem or organic pollution has been largely ignored in past
aquaculture studies and even in the building of government-owned hatcher-
ies. This situation is changing, however, and anyone planning an aqua-
cultural facility must be aware of the potential expense of waste treat-
ment.
In a recently completed study in the Pacific Northwest, Bodien (4)
found that 114 hatcheries were releasing approximately 23 tons of BOD
per day. This is equivalent to a city of approximately 270,000 total
population, or an average of about 2,400 people per hatchery. In addi-
tion, large amounts of nutrients were being lost to the receiving waters.
A large aquacultural set-up connected to a power plant might release
many times this amount of organic waste. We know that small towns are
being forced to treat their sewage so it is not likely that similar wastes
from fish farming will be allowed to go without treatment.
We have a good start on solving problems related to waste heat use
in aquaculture but much more needs to be done. Areas of concentration
for future work are:
1. More research is needed to determine optimum conditions for
some of the likely commercial species.
2. Systems must be designed to maintain proper temperature.
3. Marketing systems must be developed for the products.
4. Waste treatment procedures must be defined.
5. Economic analyses must be conducted to integrate all the
costs and potential profits to determine whether a power
company can make enough profit from the waste heat to
warrant the trouble and expense of distribution.
We have heard several presentations on applications of waste heat
in agriculture. As evidenced through these discussions, agricultural
uses appear to hold considerable promise; this is one area where use
of waste heat, in the true sense of the term, may have almost unlimited
potential if proper techniques can be developed.
Here, again, economic feasibility is the most important considera-
tion at the present time. Dr. Boersma and Mr. Miller have noted the
increased crop quality and yield which have been indicated in their
projects. What we need to know now is how much these benefits are
actually worth in terms of dollars. Where warm-water irrigation is
involved, we need to quantify the contribution due to warrn water use
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as opposed to the value of irrigation with water of normal temperature.
Once we have determined the benefit of warm-water use in terms of crop
value, we can determine how much we can afford to invest in distribution
and control systems.
The design of distribution, irrigation, and heating systems is
important for minimizing cost while achieving the desired operational
characteristics. In on-going projects, experimentation is necessary for
finding the best method of supplying water and heat for optimum results.
In the future a more cost-conscious optimization of entire systems will
be required. Potential suppliers of warm water will need to know the
overall economics of a proposed system; potential users of waste heat
will need to know costs as well as specific design criteria for their
local heat or water distribution systems.
As with other uses of waste heat, agricultural applications will
need close scrutiny to detect undesirable effects which may occur.
Pollutional side-effects could include: 1) changes in temperature or
chemical characteristics of ground water, 2) spreading of pesticides,
3) stream warming through short-circuiting of return water. Temperature
tolerance ranges for crops should be established so adverse effects of
high temperatures can be avoided. Heat transfer and moisture relation-
ships of different soils should be studied to enable control of optimum
conditions without excessive soil drying. Finally, the effect of warm-
water use on plant diseases and soil microorganisms needs evaluation.
Hot water or steam space heating, which has been used for years,
is now mentioned as a possible use of waste heat. The city of Tapiola,
Finland, with a population of 20,000 is supplied with hot water heating
and electrical power from the same steam plant (5). In Iceland,
geothermal discharges have been used for 25 years for heating and
industrial uses in Reykjavik. When one thinks of all the Btu's lost
by power plants each day and the number of Btu's needed for space
heating, the natural reaction is: Why not use the waste heat to
serve as a free substitute for fuel?
The first discouragement we encounter is the low temperature of
typical power plant waste water. 120° F is a high temperature for
cooling discharge water and 90-100° F is more nearly normal. But, hot
water space heating systems generally require much higher temperatures.
For example, the system at Reykjavik (6) uses water at 194°F and the
Montreal Airport uses water at 375-500° F (7). If the job could be
accomplished with 90-120° F water it would be with the penalty of
unacceptably high pumping costs.
Another problem with space heating systems is their relatively
low load factor. For example: At the Montreal Airport, the winter
heating load is 160 million Btu/hr and the summer load is only 10
million Btu/hr (7). Auxilliary power plant cooling devices would
certainly be needed for at least part of the year.
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One approach to the problem is the design of dual systems which
provide high quality steam taken from the steam cycle instead of from
the cooling water. This system is used in Tapiola with apparently good
results. But we are no longer using waste heat since this steam is
still of value for production of electricity.
If we want this high value steam we will have to pay for it. The
price is especially high if we take the steam from a power plant de-
signed strictly for generation of electricity. For example, if we postu-
late a typical nuclear plant at 100% capacity, the steam at the end of
the cycle, after passage through the turbines, will be 92° F at a pressure
of 1.5" Hg. This plant will have a heat rate of about 10390 Btu/kwh of
electricity produced. Using the same system but taking the steam at 61° F
increases the backpressure to 9.0" Hg and increases the heat rate to 12000
Btu/kwh.
What is this in terms of dollar cost? If we use a typical fuel
cost of $ .20 per 106 Btu we determine that fuel cost at a heat rate
of 10390 is 2.08 mills/kwh. If we want 161° F steam, the heat rate
is 12000 Btu/kwh and the fuel cost is 2.40 mills/kwh. This is an in-
crease in fuel cost of 0.32 mills/kwh, which will be added to bus-bar
cost. If the plant generates 1000 mw for 7000 hours/year it produces
7 x 109 kwh/yr of electricity. At an additional cost of 0.32 mills/kwh,
the increase in cost is (7 x 109 kwh) x (0.32 mills/kwh) = 2.24 x 109
mills, or $2,240,000 per year.
So, if an industry or housing complex takes all the available
steam at 161° F from this plant, it will have to pay all distribution
costs plus $2,240,000 to the power company to make the operation eco-
nomical. Of course, the cost of steam will decrease proportionally
with a decrease in amount used.
The purpose of this exercise is to show that the heat in water or
steam which is above the normal condenser temperature of 90-120° F is
not waste and will not come without cost. When we speak of special
designs for production of electricity and high quality hot water or
steam we are speaking of production of a specific product, and not of
waste heat utilization.
The many different industries in the United States use so much heat
that we naturally think of supplying some of this demand with power
plant waste heat. But, here again, we encounter the problem that higher
temperatures are required than are available in waste water.
A 1960 study showed that most of the low temperature (up to 212° F)
boiler units added to the food processing industry between 1945 and 1956
were below 30 thermal megawatts in capacity (8). A 1000 MWe plant
discharges about 2300 megawatts of thermal energy so it would take 70-80
ordinary-size food processing plants to use the waste heat from one
power plant (7). And, most food processing is seasonal so the demand
would not be steady.
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Most chemical processes fall in the same category; they need water
or steam at higher temperatures than 90-120° F. Benedict, et al., (7)
state that: "Direct application of reactor waste heat is indeed limited.
Drying and low temperature polymerization, of which paper and rubber
production are examples, respectively, might be practical when hot water
ranging from 180-200° F is made available. At temperatures lower than
180° F it is doubtful that even drying processes can be made economical."
As we pointed out before, hot water or steam at these high temperatures
is not waste, but a saleable product and it must be worth more as steam
than as the corresponding amount of electricity it could produce.
If we wish to supply high quality heat for either space heating or
industrial use, the overriding concern should be for the economics of
providing this energy at such a price that it will compensate for the
reduction in electrical production. This is where we need research em-
phasis right now.
Up to this point, we have emphasized the impracticality of many
of the popularly suggested methods of waste heat use. We do this, not
out of a desire to be pessimistic, but to illustrate that many of the
proposed methods are not practical considered in the light of providing
a profit or reducing pollution.
This country is experiencing ever increasing demands for electric
power and, unless we go back and use candles for light and toast our
bread on a green stick, those demands will have to be met. This will
result in greatly increased amounts of waste heat, but in the tempera-
ture range of 90-120° F. If we wish to reduce this waste of money and
resources, we have two alternatives.
First, we can find uses for hot water at present waste temperatures.
So far, aquaculture and agriculture seem to be the outstanding candidates
because they can use the water in fairly large amounts and at these
temperatures. Right now we need information on design and economics
of use systems to determine whether the benefits which seem apparent on
a physiologic basis are economically feasible. These economic studies
must include costs of waste treatment; we cannot substitute one kind of
pollution for another.
Second, we can begin to design for the future when integrated systems
may be built to produce electricity and steam for agro-industrial complexes
This does not imply tacking industrial and domestic uses of steam onto
power plants like those of the present but calls for total design of
systems which can use a progressively lower quality of heat in more than
one process to get the best overall efficiency attainable.
Assessment of this integrated system of energy use also depends upon
thorough economic analyses. Without these, we cannot even speculate in-
telligently on the feasibility of such systems.
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In closing, let us repeat: our primary concern is for environmental
protection. If a use of waste heat does not either reduce the pollution
directly or provide a profit to be used for auxilliary cooling it really
is not solving the problem.
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REFERENCES
1. Tilton, J. E., and Kelley, J. F., "Experimental Cage Culture of
Channel Catfish Ictalurus punctatus in the Heated Discharge Water
of the Morgan Creek Steam Electric Generating Station, Lake
Colorado City, Texas," Presented at Second Annual Workshop, World
Mariculture Society, Baton Rouge, Louisiana, February 9, 1970.
(1970).
2. Iversen, E. S., "Farming the Edge of the Sea," Fishing News (Books)
Ltd., 110 Fleet Street, London. 301 p. (1968).
3. Robinson, Peg, "Florida Aquiculture Gets Boost," National Fisherman,
May, 1968 (1968).
4. Bodien, D. G. "An Evaluation of Salmonid Hatchery Wastes," U.S.
Department of the Interior, Federal Water Quality Administration,
Northwest Region, Portland, Oregon. In Press (1970).
5. Santala, Veikko, "How District Heat Serves Finnish City of 20,000."
Heating, Piping and Air Conditioning, September 1966 (1966).
6. Stewart, Ronald, and Bjornsson, Sveinbjb'rn, "Beneficial Uses of
Thermal Discharge," Summary of Adirondack Conference sponsored
by Industrial Sciences and Technology, New York State Department
of Commerce and the Atmospheric Sciences Research Center, State
University of New York at Albany. October 14-17, 1969. (1969).
7. Benedict, B. J., Andrade, T. L., and Fulcher, H.D., "Potential
Uses of Nuclear Waste Heat to Avoid Thermal Pollution," AUA-ANL
Summer Engineering Practice School, Argonne National Laboratory,
Argonne Universities Association. 43 p. (1969).
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BIBLIOGRAPHIC; Carton, R. R. and Alden G. Christiansen,
Environmental Protection Agency, Federal Water Quality
Administration, National Thermal Pollution Research Pro-
gram, "Beneficial Uses of Waste Heat - An Evaluation,"
16130FHJ09/70.
ABSTRACT: There are a number of proposed beneficial uses of the
waste heat contained in power plant cooling water. Included are
those for which the technical feasibility has been demonstrated
in pilot programs and those which are, at best, imaginative ideas.
So, where do we stand today, and what remains to be done to deter-
mine whether waste heat can ever be widely used to produce a bene-
ficial effect?
As representatives of a regulatory agency, we are primarily
concerned with solving the environmental pollution problem. Seen
from this standpoint, a beneficial use must help reduce the thermal
pollution problem directly or it must provide a profit to help off-
set the cost of cooling devices. Furthermore, the use must not re-
sult in additional pollution such as that resulting from untreated
organic wastes.
Some uses, such as the culture of certain fishes, are now at
the pilot program, or even commercial, stage. Other uses, such as
for industrial processes, require additional research. Integrated
systems planned to produce steam as well as electrical power have
been successful in special situations. In nearly all cases we need
additional information on the overall economics of the proposed
methods. This is especially true where high quality heat is taken
directly from the power plant steam cycle for another use. Only
with a complete economic analysis, including cost of distribution,
waste treatment, etc., can we come to the final decision as to
whether a "beneficial use" is truly beneficial in the long run.
ACCESSION NO.
KEY WORDS:
Thermal Pollution
Beneficial Use
Thermal Power Plants
Abatement
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Accession Number
,y I Subject Field & Group
05D
SELECTED WATER RESOURCES ABSTRACTS
INPUT TRANSACTION FORM
Organization
National Thermal Pollution Research Program, Environmental Protection Agency,
Pacific Northwest Water Laboratory, Corvallis, Oregon.
Title
Beneficial Uses of Waste Heat--An Evaluation
10
Author(s)
Carton, Ronald R.
Christiansen, Alden G.
16
21
Project Designation
16130FHJ09/70
Note
22
Citation
23
Descriptors (Starred First)
Thermal pollution, beneficial use, thermal power plants, abatement
25
Identifiers (Starred First)
27
Abstract
There are a number of proposed beneficial uses of waste heat contained in power
plant cooling water. Included are those for which the technical feasibility has been demon-
strated in pilot programs and those which are, at best, imaginative ideas. So, where do we
stand today, and what remains to be done to determine whether waste heat can ever be widely
used to produce a beneficial effect?
As representatives of a regulatory agency, we are primarily concerned with solv-
ing the environmental pollution problem. Seen from this standpoint, a beneficial use must
help reduce the thermal pollution problem directly or it must provide a profit to help off-
set the cost of cooling devices. Furthermore, the use must not result in additional pollu-
tion such as that resulting from untreated organic wastes.
Some uses, such as the culture of certain fishes, are now at the pilot program,
or even commercial,stage. Other uses, such as for industrial processes, require additional
research. Integrated systems planned to produce steam as well as electrical power have
been successful in special situations. In nearly all cases we need additional information
on the overall economics of the proposed methods. This is especially true where high quality
heat is taken directly from the power plant steam cycle for another use. Only with a complete
economic analysis, including cost of distribution, waste treatment, etc., can we come to the
final decision as to whether a "beneficial use" is truly beneficial in the long run.
National Thermal Pollution Research Program,
Abstractor
Ronald R. Carton
Environmental Protection A
Par. .North west W3ter Laboratory
W&1- I I III!—HKriML./ , rrfi. . nil i i n«/r:-» i m-^ I ^ j- Li^U'-TH 1C
SEND TO WATER RESOURCES SCIENTIFIC INFORMATION CENTER
U S DEPARTMENT OF THE INTERIOR
WASHINGTON. D C 20240
WR 102 (REV JULY 1969)
WRSI C
* GPO: 1969-359-339
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