WATER POLLUTION CONTROL RESEARCH SERIES • 16130DHS11/70
A SURVEY OF ALTERNATE METHODS
FOR COOLING CONDENSER DISCHARGE
WATER
Total Community Considerations
in the Utilization of Rejected
Heat
U.S. ENVIRONMENTAL PROTECTION AGENCY
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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 pollution
in our Nation's vaters. They provide a central source of
information on the research., development and demonstration
activities in the Environmental Protection Agency, through
inhouse research and grants and contracts vith Federal,
State, and local agencies, research institutions, and
industrial organizations.
Inquiries pertaining to Water Pollution Control Research
Reports should be directed to the Chief, Publications Branch
(Water), Research Information Division, RScM, Environmental
Protection Agency, Washington, B.C. 2046C.
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A SURVEY OF ALTERNATE METHODS FOR COOLING
CONDMSER DISCHARGE WATER
Total Community Considerations in the
Utilization of Rejected Heat
Dynatech R/D Company
A Division of Dynatech Corporation
17 Tudor Street
Cambridge, Massachusetts 02139
for the
ENVIRONMENTAL PROTECTION AGENCY
Project #16130 DHS
Contract # 12-1
June 1970
Revised: November 1970
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EPA Review Notice
This report has been reviewed by the Water
Quality Office, EPA, and approved for publication.
Approval does not signify that the contents
necessarily reflect the views and policies of
the Environmental Protection Agency, nor does
mention of trade names or commercial products
constitute endorsement or reconiiiendation for
use.
For sale by the Superintendent of Documents, U.S. Government Printing OffIce, Washington, D.C. 20402-Price 65 cents
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ABSTRACT
The quantities of electric energy consumption and associated
heat rejection quantities, their present and projected alloca-
tion throughout the different sections of the country, their
relation to other forms of energy consumption are reviewed and
tabulated. Thermodynamic constraints on a solution to the
thermal pollution problem are defined. Feasibility of possible
application of waste heat usage are reviewed in the field of
heating and air-conditioning, aquaculture, process industry,
irrigation, sewage treatment, desalination, snow or ice melting
and integration with municipal water system.
111
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TABLE OF CONTENTS
Section Page
INTRODUCTION 1
1.1 Overall Program Goals 1
1.2 Consolidation of Phase I and Phase II 1
1.3 Scope of Present Task - Format of Report 2
2 INTEGRATION OF THE POWER PLANT WiTH THE COMMUNITY 3
2. 1 Thermal Pollution - What is “A Solution” 3
2.2 The Magnitude of the Problem 8
2. 2. 1 The Residential Market 11
2.2.2 The Industrial Market 12
2.3 Potential Areas 13
2.4 Conclusions 19
REFERENCES - Section 2 21
3 HIGH DENSITY POPULATION CENTERS 23
3.1 District Heating 23
3. 1. 1 Tapiola Garden City, Finland 25
3.1.2 Role of District Heating System Power in Finland 29
3.2 Odense, Denmark 33
REFERENCES - Section 3 35
4 AQUACULTURE 37
4.1 Introduction 37
4.2 General Principles of Aquaculture 39
4.3 Some Specific Examples 41
4.3. 1 Hunterston Nuclear Station 41
4.3.2 Growing of Carp 44
4.3.3 Lobsters 44
4.3.4 The Thermo-Nutrient Pump 45
REFERENCES - Section 4 47
5 DECENTRALIZED POWER GENERATION TOTAL ENERGY
SYSTEMS 49
5.1 Introduction 49
5. 2 Total-Energy Power Generation--A Typical System
Description 50
5. 2. 1 Load Requirements vs. System Output Capabilities 54
REFERENCES - Section 5 57
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Section 1
INTRODUCTION
1. 1 Overall Program Goals
In December 196 , Dvnatech R D Company initiated an investigation for
the Federal Water Pollution Control Administration with the overall aim of surve\ ing
and providing a comprehensive, economic analysis of alternate methods for cooling
condenser discharge water from thermal power plants. The program was structured
to focus on three aspects of the overall problem in a two phase study. The three
subject areas were:
1. Large-Scale Heat Rejection Equipment
2. Power Plant Operating Characteristics
3. Total Community Considerations
The first phase of the effort was to bring together available information on
state-of-the-art technology in each of these areas. The second was to propose and
evaluate advanced concepts. This report will present the results of the total effort of
Task III - Phase I and Task IV - Phase II of this study -—— Total Community Considera-
tion in the Utilization of Heat Rejected from Thermal Power Plants.
1. 2 Consolidation of Phase I and Phase H
It became clear at the outset that a distinction between state—of-the-art
and “advanced concepts” in the area of Total Community Considerations was an artifi-
cial one. There were, in fact, no instances of what could be called state—of-the—art concepis
in that no installations existed in which beneficial, community-oriented distribution of
the waste heat was being carried out. The occasional instances of warmed waters
leading to apparently increased fish catches were purely fortuitous.
Such consideration as had been given to beneficial uses of waste heat was
usually in the category of non-technical speculation. Most of the proffered concepts
fell short in that they
1. did not really understand what constitutes a “solution” to the
problem of thermal pollution; or
2. did not appreciate the simple “problems of scale” which are
involved in the quantities of heat rejected from a modern power plant.
1
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It was recognized that none of the concepts were developed to a sufficient
degree to permit even the crudest economic analysis. The best that could be accom-
plished within the scope of this program was the identification of those areas where
1. a real need existed in the community which could be met in a
technologically reasonable way with low temperature heat; and
2. a capacity match with the heat rejection requirements of
modern power plants.
3. a consideration of the technical and economic feasibility of
moving away from centralized power generation based on the
steam cycle.
1. 3 Scope of Present Task -- Format of Report
This task, as reflected by the format of this report, was broken into three
parts. The first part, documented in Section 2, constituted a review of the magnitude
of the problem. That is, the quantities of electric energy consumption and the
associated heat rejection quantities, their present and projected allocation throughout
the different sectors of society, their relationship to other forms of energy consump-
tiion are reviewed and tabulated. A clear definition of the thermodynamic constraints
on a “solution” to the thermal pollution problem is provided. Finally, a number of
possible applications of waste heat usage are reviewed. From these,two areas are
chosen for further consideration and the reasons for these choices are documented.
Sections 3 and 4 deal with the two areas selected for further consideration
in the integration of a power plant with the larger community. These areas are “High
Density Population Centers” and “Aquaculture”.
Section 5 provides a brief introduction to some of the recent concepts of
total-energy systems based around the gas turbine. This refers not to the simple adoption
of gas turbine units to meet peak loads in conjunction with steam plants, but to the
decentralization of electric power production. This would be accomplished through the
distribution of gas turbine driven generators throughout the load using region and the
extraction of high temperature waste heat from the turbine exhausts for the fulfillment of
all energy requirements which can be satisfied by heat input.
2
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Section 2
INTEGRATION OF THE POWER PLANT WITH THE COMMUNITY
2. 1 Thermal Pollution -- What Is”A Solution ”
Ever since the ecological dangers of uncontrolled rejection of large quanti-
ties of heat to our environment became widely recognized and identified as “thermal
pollution,” a favorite subject of speculation among “pseudo-scientists and the popular
press has been on “ways to use waste heat.” Many of the proposed solutions, while
creative and ingenious, often lose sight both of the nature of the problem and of the
simple fact that energy does not simply “go away” when it is put to some use in a process.
It is well, at this stage, to review the fundamental thermodynamics of the thermal
pollution problem and to define what can be considered to be “a solution.”
The thermodynamics of the electric power generation cycle are straight-
forward. Figures 2. 1 and 2. 2 present the basic block diagram and thermodynamic
state diagram (temperature/entropy) for a simple, idealized Rankine power cycle.
Figure 2. 1
Block Diagram of Simplified Power Cycle
(4)
U)
rej
3
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T
Figure 2. 2
Idealized Thermodynamic State (T-S) Diagram
The second law of thermodynamics, which states that 1T a system cannot
operate in a cycle, and produce net work, while exchanging heat with but a single
reservoir and that such a device constitutes a ‘perpetual motion machine of the second
kind’ “ defines the amount of heat which must be rejected in the condenser. In simpler,
physical terms, this results from the fact that,if the vapor were compressed back up
to turbine inlet pressure (P4) without being condensed, more work would be re -
quired by the compression process than is produced in the expansion through the
turbine.
(4)
.5
4
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It is possible, through the use of auxiliary equipment
(feed water heaters, extraction steam, reheats) to reduce the thermodynamic in—
efficiencies and to approach a theoretical maximum efficiency. (References 2. 1 and
2. 2.) This theoretical maximum efficiency, known as the Carnot efficiency, is set
by the maximum and minimum cycle temperaWres and is approximately
T.
mm
ri = 1 - (Rankmne)
max T
max
- 70 + 460 (“-‘ambient) (9—i)
— 700 + 460 ( critical point)
= 1-0.46
= 54C)
Present day plants operate at lower cycle efficiencies. The actual efficiencies depend on
the type of plant and some representative values are summarized below:
Fossil 38 — 40
Nuclear, lightwater 30 - 33 2 - 2)
Nudlear, gas-cooled 37 - 39
These actual efficiencies represent an economic optimization since plant
designs which yield higher efficiencies entail greater increases in capital costs than
can be recovered in reduced operating costs. Furthermore, while increases in
efficiency over typical present-day values toward the theoretical maximum do yield
significant reductions in quantities of rejected heat, even if the maximum efficiency
were immediately attainable, the projected growth rates in electric power consump-
tion would soon wipe out these gains.
A sample calculation is given below.
From a simple heat balance:
Q - Mwe - 1’ (2-3)
rej
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Therefore, for a 500 Mwe plant, a typical heat rejection requirement for
present-day plants might be
Fossil: Q . = 500 [ - 1
rej .38
9 Btu
1a i\lwe = 2. i8 x 10
hr
Nuclear: rej = 500 - i]
- 9Btu
= 1, O 6 o M\ve = 3. 6 o X 10
hr
while if the maximum efficiency were attainable
Carnot: rej = soo [ -_ - - i]
9 Btu
= 425 Mwe= 1.45x10
hr
which is about one-half of a well-designed, present day fossil-fuel plant. However,
with expected growth rates of total power consumption of 7-8 per annum, even this
advantage would be nullified in eight to ten years.
However, the problem is not definable simply in terms of the total amount
of heat rejected in the power plant condensers. The identification of heat as a pollutant
comes primarily from the localized nature of the thermal discharges. Two items point
this out. First, even though the quantities of energy involved in thermal discharges
are huge, they are still small in terms of the overall heat balance on the surface of
the earth. Crude estimates of the incident solar radiation on the continental United
States indicate an average heating rate of the order of 5 x io8 Mwe. T h e t o t a I i n -
stalled capacity of electric power in the United States is approximately 3. 3 x io’ Mwe
(Reference 2. 3) or less than one-tenth of 19( of the solar incidence.
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Second, it is clear that lithe basic concern is that of quantities of heat
released to the environment, then not only the “rejected heat”, but the useful power
generated as well,must be included since virtually all of the generated power is
eventually, either directly as in resistance heating elements, or indirectly as in
light or motors, dissipated to the surroundings in the form of heat. Again, although
these quantities are great, they are small in comparison to a global heat balance.
The identification of heat as a pollutant, therefore, is only relevant if the
dissipation is so localized as to cause significant temperature rises in natural water-
ways so as to cause ecological imbalance. Even the distinction between once-through
cooling and the use of cooling towers is really only one of alleviating local effects in
natural waters , since the ultimate heat rejection mechanisms of evaporation and con-
duction to the atmosphere are the same in both cases. There is, in fact, no present
alternative to rejecting heat to the atmosphere,but this appears acceptable at the pre-
sent time simply because the atmosphere represents a vaster sink than any natural
waterway and is capable of dispersing local disturbances more quickly.
Therefore, in order to qualify as a “solution” to thermal pollution, a heat
rejection or usage technique must do one of four things:
1. reject the heat directly to the atmosphere in a way which,
although still localized, does not involve natural waterways
(cooling towers, air-cooled condensers, etc.)
2. reject the heat over a wide area (decentralize the rejection
process) in a manner similar to the way the electrical power
itself is eventually dissipated (district heating, defrosting of
highways, irrigation)
3. use the heat in such a way as to satisfy (1) or (2) and, at the
same time, reduce the demand for electricity (district heating,
industrial process)
4. use the heat in such a way as to generate additional profitability
to bear the cost of solutions of type (1) (aquaculture, recreational
sites, sewage treatment).
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The integration of the power plant with the community in such a way as to
insure solutions of these types was first seriously studied in regard to underdeveloped
nations (and quite unrelated to the question of thermal pollution) in a study performed
at Oak Ridge National Laboratory and reported on to the AEC in 1968 (Reference 2.4).
The concept was referred to as an “Agro—Industrial Complex and centered around a
nuclear-fueled power plant. It was intended to be a $1-billion unit, operated by a
community of approximately 100, 000 farmers, factory workers and their families,
producing food and water for about 5 million people. Here the major concern is the
production of food from formerly arid land, and most of the electric power would go
into desalination and into some industrial processes related to the recovered salts and
chemicals. The waste heat would be rejected to the irrigation system. While this sort
of technology is not relevant to our industrialized, non-arid society, the inter-related
systemic approach reflected in the concept is the key to the simultaneous implementa-
tions of the four criteria set down as necessary for “solutions.
2. 2 The Magnitude of the Problem
In Section 1 it was implied that a large part of the difficulty in dealing with
the thermal pollution problem derived from the enormous quantities of heat to be
handled, while in Section 2. 1 it was suggested that the overall quantities of heat are
small on a global basis. While this is an apparent contradiction, the essence of the
problem has been shown to be the intense localization of the power generation sites
and the thermal discharges.
The economics of power generation have tended to intensify the problem
of localization. As was shpwn in Reference 2. 5, the average plant size has steadily
increased until single units of 1000 Mwe or above are not uncommon. From the point
of view of thermal pollution, just the opposite trend would be more favorable. Indivi-
dual gas turbine/generator units in each dwelling or factory, while posing difficult
maintenance problems and perhaps contributing more heavily to air pollution, would
represent an improved situation with regard to thermal pollution.
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In addition, the major users of electric power, namely industry and large
population centers, tend to cluster together into densely populated urban regions. In
order to decrease transmission costs, the power plants also cluster in selected loca-
tions, and, in an attempt to maximize operating efficiencies, prefer to utilize once-
through cooling with minimum condenser cooling water temperature rises. Therefore,
Lhe rejected heat intrudes on the environment in a concentrated form involving a tre-
mendous amount of energy in a small geographical areas. The simple dissemination
of this heat over a sufficiently wide area as to minimize its consequences involves
considerable distribution problems while the utilization of the heat in areas close to
the power plant normally results in a bad capacity match.
It was suggested that one response might be to utilize waste heat in such a
way as to supplant the need for prime energy (electric power) and hence reduce the
total amount of required heat rejection. To evaluate the possibility of that approach,
it is necessary to know the present and projected breakdown of power demands. The
following tables indicate the distribution of required power by user category and
application.
The total capacity figures, both installed capacity and net generation are
listed through 1980 in Table 2. 1. The fraction of the total attributable to nuclear plants
is indicated.
1960 1965 1970 1975 1980
Total Inst. Cap. (Thous. Mwe) 168 236 328 440 575
Nuclear 0.1 0.9 11.7 51 120
Percent Nuclear -- -- 3. 5 11. 5 21
Net Generation (bkwh) 753 1055 1461 2009 2730
Nuclear 0. 1 4 72 337 814
Percent Nuclear 4. 9 16. 8 29. 9
Table 2. 1
Power Generation - Projected Growth
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In comparison to the total energy consumption in the United States, which
has grown at approximately 3% per year for the past thirty years (Reference 2.3),
electrical energy has grown at more than twice that rate (i—. 7% per year). While in
1965, electric power accounted for approximately 20% of all the energy consumed, by
1980 it is expected to represent nearly 30%.
The distribution of electric power consumption among different classes of
users, as of 1965, is indicated in Table 2. 2.
% of Output Generation % of Revenue
( -) ( bkwh) ( - )
Industrial 45% 475 26%
Commercial 21% 222 28%
Residential 30% 317 42%
Other 4% 41 4%
Total: ‘ $15 x i0
Table 2. 2
Distribution of Electric Power Usage -- 1965
The distribution in the future is expected to shift slightly toward in-
creased industrial use, with the residential market continuing to represent approxi-
mately 1/3 of the total usage.
1965 1980 2000
bkwh % bkwh bkwh %
Industrial 475 45 1100 55 2240 56
Commercial 222 21 308 15 554 14
Residential 317 30 594 30 1188 30
Table 2. 3
Projected Distribution of Electric Power Usage
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2. 2. 1 The Residential Market
In terms of the residential market, the biggest potential increase in con-
sumption is electric space heating followed by air-conditioning.
The total energy per household required for space heating is expected to
decrease with the result that between 1960 and 2000 the following changes are expected:
Population + 84’/
No. of Households + 89
Energy for Heating + 50 /
This apparent discrepancy is due to these items:
1. increased use of the “heat pump’ concept with effective
“efficiencies” of 200—300 /.
2. gradual population shift to warmer climates.
3. increased use of multiple-family dwellings (higher ratio
of inside space to outside walls).
Since an electrically heated home consumes approximately 20, 000 kwh
annually as compared to only 5,000 kwh for non-electric, the power industry has set
a target of 19 million electrically heated homes by 1980. The “best” estimates from
several sources of the breakdown of the residential market are given in Table 2. 4.
Total Usage kwh
Totals - Billion kwh Per Household
1960 1980 2000 1960 1980 2000
All Uses 193 594 1,188* 3,669 8,137 11,952
Lighting 43 97 181 817 1,329 1,821
Ranges 21 43 59 399 589 594
Waterheaters 45 120 240 855 1,644 2,414
A/C 7.7 61 130 146 836 1,318
Space Heating 11.7 108 258 222 1,480 2,595
All Other 63.7 165 319 1,211 2,260 3,209
*By the year 2000, electricity will furnish 50 percent of the total domestic energy
requirement.
Table 2.4
Breakdown of the Residential Market
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Estimated increased use of room and central air-conditioning is given in
Table 2.5.
1960 1980 2000
Millions of Households 52.6 73.0 99.4
With Central A/C 0.5 12.7 43.7
With Room A/C 7. 4 29. 2 34. 8
Consumption of Electricity
per Central A/C Unit (kwh) 3500 3200 2500
per Household w/Room Unit
(kwh) 800 700 600
Aggregate Annual (bil. kwh) 7. 7 61. 0 130
Table 2. 5
Projected Increase in Power Required for Air-Conditioning
Clearly, any approach which will provide heating and air-conditioning from
non-electric sources will constitute a proper !!solution in that the demand for electric
power will be greatly reduced, the heat release will be dispersed over a wide geo-
graphical region, and considerable profit potential can be realized for heating and air-
conditioning of large population centers. These possibilities will be explored more fully
in Section 3.
2. 2. 2 The Industrial Market
A recent publication by ORNL for the Department of Housing and Urban
Development (Reference 2. 6) has provided estimated projections of energy consumption
by United States manufacturing industries for 1980. In this study, which sought to
identify possibilities for the use of low-temperature heat in urban areas, six industries
were identified as major users of process heat. These were (1) food products, (2) paper
products, (3) chemical products, (4) petroleum refining and related industries, (5) rubber
and plastic products, and (6) textile mill products. Estimates of steam consumption for
those industries ranges from 2, 000-3, 000 bkwh which is roughly equivalent to the pro-
jected electric power generation for 1980 (see Table 2.1). Therefore, a rough scaling
indicates that a significant amount of thermal discharge from power plants might be
utilized by an urban center’s manufacturing plant if the area served by the electric plant
had a fraction of the nation’s steam-consuming industries roughly equivalent to its
fraction of the nation’s population.
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A comparison was provided for the amount of steam consumed per kilowatt-
hour of electricity used for these same industries over the last few years and similar
comparisons projected forward into the 1980’s. Figure 2. 3 indicates these comparisons
based on figures from a study by the Texas Eastern Transmission Corporation. A
brief summary of these results indicates that the relative amount of electricity are
rising and that, while the pounds of steam per kilowatt-hour of electricity was once in
the range of 30 lb/kw, it had declined to less than 10 lb/kw by 1965, and is expected to continue tc
decrease in the future. This is, of course, counter to the desired trend of decreasing
the demand for electricity by utilizing heated discharge.
The primary difficulty in this sort of utilization, however, is the match, or
mismatch between the required temperature for industrial process heat and the avail-
able temperature of discharges. It is expected that with present power plant designs
and present manufacturing processes, that there is no useful inter-relation. What
would be required, are analyses of turbine designs to determine the penalties associated
with very high back pressure turbines, considerations of the use of extraction steam from
power plant boilers to reduce electrical demands, or the restructuring of industrial pro-
cesses to operate at lower temperatures.
2. 3 Potential Areas
As a first approach to identifying segments of society which might inter-
relate with the power producing sector in such a way as to satisfy our definition of a
“solution,” a number of these alternatives were identified. These included:
1. heating and air-conditioning of high density pppulation
centers
2. aquaculture
3. process industry
4. irrigation
5. sewage treatment
6. desalination
7. snow or ice melting
8. integration with municipal water system
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60,000
40,000
20,000
40,000
8000
6000
z
2 4000
-J
-J
a:
2000
1000
800
600
400
200
4947 4950
Source: Competition and Growth in American Energy Markets
1947—1985 , Texas Eastern Transmission Corp., Houston, Texas,
1968.
Figure 2.3
Ratios of Total Energy Consumed to Electric Power
1955 4960 1965 1970 1975 4980 4985
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Of these, only the first was considered to represent a reasonable concept
which satisfies the criteria for a solution to the thermal pollution problem at the time.
Aquaculture, while possibly representing a source of additional profitability as required
by criterion #4, has ill-defined energy requirements and ecological side effects.
Chapter 4 attempts to categorize what information exists in this area, but further con-
sideration of aquaculture as an immediate solution to thermal pollution power plants
is not recommended.
The fourth area, irrigation, has been suggested as a menas for disposing
of condenser discharge water. This would appear to be an acceptable solution, satis-
fving the criterion of decentralizing the heat rejection process and possibly serving
as source of revenue. While the water will eventually return to the waterways through
natural run-off, the processes of evaporation (particularly in the case of spray irrigation)
and interaction with the ground should ensure that the run-off is at essentially “ambient”
conditions. A possible site benefit to the use of warmed water for irrigation purposes
might be a slight lengthening of the growing season through a warming of the soil. This
has been demonstrated on a laboratory scale but how to take advantage of this effect
in a reliable manner is not yet well understood.
Some disadvantages are noteworthy. First, irrigation itself has been
recognized as a form of thermal pollution, particularly if ditch-type irrigation methods
are used. Water as it is held up in the irrigation ditches is warmed by the sun and can
return to the river at elevated temperatures. The use of initially warmer water will
probably not have much effect on the final equilibrium temperature, however.
Second, while the use of the discharge water for irrigation does eliminate the
problem of highly localized, high temperature mixing regions in the river at an outfall, it
can represent an enormous decrease in flow rate of the river for a great distance below
the plant with resultant changes in the waterway which are both thermal and physical.
Furthermore, those organisms which are entrained in the intake and which might have
survived a brief heating and quenching are almost certainly doomed if they are held at
elevated temperatures for long periods of time while being used in an irrigation system
(Reference 2. 7). Tn addition, the run-off of nutrient-rich water from the fertilized fields
can have its own effect, for good or ill on the ecology of the river (Reference 2.8).
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Finally, the potential hazards of contamination of edible crops by these
amounts of radioactive materials in the condenser water and any associated naturally
occurring concentrating mechanisms should be investigated thoroughly before giving
further consideration to such a scheme.
The use of heated discharges in conjunction with sewage treatment plants
seemed inappropriate for three reasons. First, and foremost, in order to produce
attractive benefits to any aspect of sewage treatment temperature levels far in excess
of any that might reasonably be expected from even highly futuristic plant designs were
required (of the order of 200-250° F at a minimum) (Reference 2.9). Second, the capa-
city matches were poor. It was difficult to see how any sewage treatment plant of a size
commensurate with a given population could use even a few percent of the heated dis-
charge from a power plant a size appropriate for the same population. Third, the
thermal pollution load would simply be transferred from the power plant to the sewage
plant with no net benefit to the environment. Each of these considerations applies in
equal measure to the use of waste heat for desalination purposes. In this case, a
proper capacity match, while not even close for municipal water, could perhaps be
attained if one considered desalination of sea water for irrigation. While this may
have some merit (Reference 2.4), the problems of intrusion on the environment which
are posed by the desalination and irrigation processes far exceed the simple thermal
pollution from power plants (Reference 2. 10).
The use of water heat for melting snow and ice on highways or for main-
taining ice-free navigation routes has been discussed at some length in the popular
press. The use of the heat on highways appears to provide insurmountable distribu-
tion problems and, even in the northern-most areas of the country, provides a suitable
heat sink only for a small fraction of the year, and, in particular, that fraction of the
year for which thermal pollution is not a severe problem. Furthermore, the installa-
tion of piping in the roadways would add enormous costs to highway construction. While
the same can be said for ice-free navigation routes, the distribution problem and con-
struction problems are not nearly so acute. A serious study of this application of
waste heat to maintaining the St. Lawrence Seaway in an ice-free condition was carried
out by Dingman et al f the Cold Regions Lab at Hanover, New Hampshire (Reference 2. 11).
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The abstract of this report is repeated:
An attempt is made to calculate the length of the ice—free reach that
develops during the winter below a thermal pollution site on a river. A differential
equation for the steady-state heat balance of a volume element of a river is developed,
which leads to the expression
x C dT/Q
where x is distance downstream from the pollution site to the cross section where the
water temperature equals T , 0 is water temperature at x equals zero, Q* is rate
of heat loss from the water surface, and C is a constant that includes flow velocity
and depth. The value of x at T equals 0°C is taken as the length of the ice—free reach.
Q* is the sum of heat losses due to evaporation, convection, long- and short-wave
radiation, and other processes, each of which is evaluated by an empirical or theoreti-
cal expression. The two principal limitations in accurately calculating downstream
temperature changes are related to difficulties in evaluating the degree of lateral
mixing in natural rivers and the convective and evaporative heat losses under unstable
atmospheric conditions. Observations of lengths of ice-free reaches on the Mississippi
River are in good agreement with the calculated values. Significant portions of the St.
Lawrence Seaway can be kept ice-free by the installation of nuclear reactors at
appropriate locations.
Table 2. 7 indicates a comparison of the results obtained from the analysis
with those observed at two locations on the Mississippi River. The agreement is
reasonably good.
A review of conditions on the St. Lawrence Seaway which is closed by ice
for 3-1/2 to 5 months each year indicated that the proper location of nuclear plants in
the 1,000 to 3,000 Mwe size range could effectively lengthen the shipping season and
perhaps keep the seaway open year round. No account was taken of the possible
ecological effects of this practice nor were any considerations made of how to reject
the heat in the remaining 7 to 10 months. For these reasons, this concept was not
pursued further.
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Riverside Highbridge
Calculated Length Calibrated Length
Observed ?Observed? Russian Observed ‘Observed’ Russian
Area Length’ Winter Eq. Kohier Eq. Area Length Winter Eq. Kohier Eq.
Date km 2 km km km km 2 km km km
Jan65 2.169 12.0 17.9 26.6 4.597 40.0 42.6 62.5
Jan65 0.777 4.3 4.3 7.0 0.882 7.8 11.8 18.6
Feb65 0.890 4.9 5.8 10.0 1.036 9.0 15.1 25.6
Jan 66 2.428 21.2 15.7 21.8
Jan 66 2.023 11.3 16.0 28.9 4.233 36.8 11. 3 73. 2
Jan66 1.311 7.3 3.2 5.8 1.546 13.4 12.1 21.2
Jan66 1.287 7.2 3.5 5.3 1.076 9.4 10.4 13.8
Feb66 2.161 12.0 17.1 60.8 5.063 44.0 39.5 124.6
Table 2.7
Ice-Free Reaches for Heated Water Discharge
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A final concept was the use of municipal water supplies as cooling ponds.
It was felt that, at least for the residential market, much of the water consumption
was either for purposes for which the temperature was not critical or required further
heating. Therefore, the possibility of having city water enter the home at somewhat
higher temperatures (70 - 90°F) (with perhaps each home provided with a small chiller
unit on the sinks for drinking water) might well be acceptable and result in a reduction
of domestic electric consumption.
It was found, however, that residential usage of municipal water normally
represents a small fraction of the total usage, most of which is consumed by industry
for cooling. On this basis the 1968 report of the Technical Advisory Committee
(Reference 2. 12) recommends strongly against “any water temperature change that de-
creases the acceptability of the water for cooling and drinking purposes. Brief computa-
tions, based on electric power consumption and water usage in the Boston area, also
indicate a somewhat unfavorable capacity match involving water temperature uses of
the order of 50°F to 100°F. This, of course, could be alleviated by using the water
supply as only a partial solution but gives further evidence of the magni ude of the
problem.
2.4 Conclusions
The essential conclusion of these considerations is that the concept of using
waste heat from steam power plants as a solution to the problem of thermal pollution is
probably not a viable one. Of all the areas considered, only the heating and air—conditioning
of buildings gives a reasonable capacity match at conceivable temperature levels without
major modifications to existing cycles and processes. Even here, the distribution problems
are formidable, and the seasonal fluctuations in hot water demand do not correspond well
to seasonal variations in electric power demand. However, as will be documented in
Section 3, such an integration has been accomplished in certain European installations and
should be kept in mind.
It seems clear, however, that the continuing use of centralized Rankine cycle
steam power plants for the nation’s power production will inevitably result in large
localized thermal discharges to the environment. Furthermore, the only feasible
approaches to this situation are the following.
19
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1. the use of heat dissipation equipment such as cooling towers
to protect natural waterways by rejecting directly to the
atmosphere.
2. a reversal of the trend toward large central power plants
and the increased use of small total-energy systems each
tied to a particular user.
20
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REFERENCES -- Section 2
2. 1 Keenan, J. H., Thermodynamics , McGraw—Hill, 1942.
2. 2 Babcock and Wilcox Company, Steam , Band W Co., Inc., New York, 1963.
2. 3 Requirements for Future Living , Pub. by Resources for the Future, New
York, 1968.
2. 4 Lyons, R. D. , “Scientists Studying Nuclear-Powered Agro-Industrial
Complexes,” New York Times, Sunday, March 10, 1968.
2. 5 Fuller, W. D., and Maulbetsch, J. S., “Task II —- Phase I Report. A Survey
of Power Plant Operating Characteristics and Design Criteria.” Dynatech
Report No. 886 for FWQA, May, 1970.
2.6 Miles, F.W. , “Urban Nuclear Energy Study: Estimates of Steam Consump-
tion b Manufacturing Industries in the United States for the Year 1980,
Oak Ridge National Lab Report No. ORNL - HUD-2; UC-38 for Department
of Housing and Urban Development, January, 1970.
2. 7 Mihursky, J. M., “The Effect of Thermal Pollution on the Ecology of a
Natural Body of Water; Studies Made of the Chesapeake Bay,” Pub. at
Institute of Environmental Sciences, Thermal Pollution Seminar, Boston,
Mass. , April 1970.
2. 8 Smith, N., and Maulbetseh, J. S., “Task U - Phase II Report. Considerations
of Advanced Concepts in Large-Scale Heat Rejection Equipment.” Dynatech
Report No. 925 for FWQA, June 1970.
2. 9 Morrison, S. W., “The Mechanisms of Waste Water Treatment at Low Tem-
perature.” Colorado State University, Fort Collins, Colorado, 1968.
2. 10 Mandelli, B. F., “A Study of the Effects of Desalination Plant Effluents on
on Marine Benthic Organisms.” Dow Chemical Co., Freeport, Texas, 1969.
2. 11 Dingman, S. L., et. al, “The Effects of Thermal Pollution on River Ice
Conditions.” Water Resources Research, Vol. 4, No. 2, April 1968.
2. 12 National Technical Advisory Committee Report on Water Quality Criteria,
Department of the Interior, Washington, D. C.
21
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Section 3
HIGH DENSITY POPULATION CENTERS
The heavily populated areas of the United States, particularly cities in
which builders are in close proximity to one another, are not only heavy users of
electricity, but may also be potential users of waste heat from power plants. District
heating is discussed below as one of the more promising potential uses of low grade heat.
3. 1 District Heating
The first successful attempt at district heating took place in Lockport,
New York in 1877. This installation involved a short underground steam line supplying
steam to a small number of residences. Since this first attempt, district heating has
become reasonably popular in the major population centers. Figure 3. 1 indicates the
locations of a number of such systems, both steam and hot water in the United States
and Canada.
Figure 3. 1
Locations of District Heating Plants in U. S. and Canada
(from Reference 3. 2)
23
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Although some early district heating systems in the United States used hot
water as a heating medium, most present systems use steam, generated solely for
heating purposes. In a few cases (Reference 3.1), electricity is generated when the
heating demand is small, and supplied to the local electrical system, but these opera-
tions normally represent economic compromise. It should also be remembered that
an enormous quantity of low grade waste heat is generated in the United States, and
this total heat would be more than sufficient to heat every home in America (see Section
2. 2). Furthermore, the usefulness of this concept is limited to the northern half of the
country during the winter months.
Some low-pressure hot-water systems (with temperatures up to 200°F) were
installed in the early days of district heating. Due to the advantages of steam over hot
water most of the systems built in the United States during the past twenty-five years
use steam except a number supplying small groups of buildings, such as institutions.
In 1949 there were in the United States seventeen hot-water systems and eighteen sys-
tems supplying both steam and hot water commercially. Of the latter, some have con-
verted portions of their hot—water systems to steam.
The use of high-pressure hot water as a heat-distributing medium has
been successfully developed in Europe. These systems are quite different from the
conventional hot—water systems in this country. The high price and shortage of fuel
in Europe require more complete utilization of the heat content in fuel at the expense
of higher investment.
24
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3. 1. 1 T piola Garden City, Finland (Reference 3. 4)
A rather unique experiment has taken place in Finland, and appears to
have been successful.
In 1952, a private non-profit organization, Asuntosaatio (Housing Authority)
purchased 670 acres in the rural district of Espoo, outside the city of Helsinki, and
planned a modern garden city for 17, 000 inhabitants.
The community, called Tapiola Garden City, was planned from the be-
ginning from virgin country. A population density of 26 persons per acre was planned,
and a district heating system supplying both heat and electricity for the entire commun-
ity was built. This district heating system even supplies heat to single family dwellings.
The climate of Finland allows this district heating system to be economical.
The heating season in Finland is 270 days per year. The mean temperature of the
heatingseason is 33.1° F. The heating system has been designed for -16. 6°F.
The turbines used for generating power are back pressure turbines, and
the return water from the district heating system is used as cooling water for their
condensers.
Electricity generation is independent of the heating load of the city through
the installation of a 2-1/2 acre spray pond at the town center. The cooling spouts in
the pond can be adjusted in height up to 69 feet and serve both as cooling controls and
park decorations.
25
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While the overall thermal efficiency of this plant is quite high (80. 8%
including line losses) the efficiency of the electrical power generating operation is
only 25%.
Approximately 62% of the electricity generated has been used in Tapiola.
The complete Tapiola system is summarized in Figure 3. 2.
Figure 3. 2
Tapiola Garden System
26
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The district heating system was built for a nominal pressure of 142 psia.
Its working pressure is 65 psia. The pressure difference at the power plant ia 28.4
psia. The distance between the plant and the farthest consumer is 1. 74 miles. The
total length of the hot water distribution system is 13. 7 miles. The temperature of
the outgoing water is between 176 - 239’F and the return water is then 122 - 158F.
A typical operating curve is shown in Figure 3. 3.
Elecfrici
937•
Outdoor Temp ,
r
-1 -
F Water Flow
0 emp.
17o 80
158 70 Return Temp.
140 tO
172 c
6 8 10 I? 14 Ic 4
Noon Time of Day Midnight
Figure 3. 3
Typical Daily Operation
27
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The capacity of this system is summarized below:
Combined Heating
Capacity of Power 15. 9 million Btu/hr
and Heating Plant
Heating Plant C
Capacity 29. 8 million Btu/hr
(peak load plant)
Heating Plant A
31. 8 million Btu/hr
(reserve plant)
Electric Capacity 12. 5 MVA
Table 3. 1
The cost of the district heating system can be summarized as follows:
District and Reserve
Heating Plants } $3,156,250
District Heating
Network $2,843,750
Total $6,000,000
Table 3. 2
Cost of District Heating System
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3. 1. 2 Role of District Heating System Power in Finland
While most of the power produced in Finland at present is of hydro
electric origin, the construction of power plants is rapidly becoming necessary due
to the almost complete utilization of the available water power. The general struc-
ture of the power supply in Finland is illustrated below: (Figure 3. 4)
10
I —
1950 55 60 65 70 75 19
General Structure of Power Supply in Finland
I. Primary water-power; 2. Secondary water-power; 3. Tertiary, water power
or surplus; 4. Industrial back-pressure power; 5. District heating power;
6. Independent thermal power. Before 1965—Statistics. After 1965—Forecast.
Figure 3.4
29
15
7,
.7 >7 ’
/
0
-------
Examination of this figure shows that district heating system produced
electricity is, at present, and is forecast to be, only a small part of the overall
power generating scheme. Figure 3. 5 presents the power demand variations for a
number of conditions.
100
‘I.
80
60
Ł0
20
0
Power Demand Variations
Diagram rerrL nt\ a typical smalkr town with the surrounding countr side
I. Day-periods during week-days, 07.22 hours; I Day-periods during sunda ,
07-22 hours; 3. Nighi-periods during all days, 22-07 hours. I0O =hourly
peak load.
Figure 3.5
30
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Figure 3. 6 presents the variation of heating load in a similar manner.
100
00
60
0
20
0
0
50
100
Basic Data for Heating Load Variations in Finland
1. Conduction and ventilating heat variations, night-periods; 2. Same for day-
periods, approximately corrected for sun radiation; 3. heat demand variations
for domestic hot water, night-periods; .4. Same for d: y-periods; 5. Monthly
ni iximum heat demand for 1; 6. Average monthly heat demand for I a)
night-periods, b) day-periods; 7. Monthly minimum for 1. The curves I are
based on daily average out-door temperatures in South-Finland 1931—1960.
+20°C=-0%, —27°C=lOO%.
Figure 3. 6
uomparison of these two figures will show that the supply of district heating power
reaches its maximum in winter at the same time as the maximum demand of electric
energy. This fact allows the district heating power to equalize yearly variation of
the electrical energy demand, thus improving the load conditions of other power
plants. When the district heating power is subtracted from the electric energy de-
mand of the community (Figure 3. 5) the remainder represents the amount of power
to be purchased. The result is shown in Figure 3.7. Load variations of short duration
remain, but the annual variation has been normalized.
31
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1: )
“S
I0
so
40
20
0
Resulting remaining Power ‘ariations
0. Power demand during day-periods, same as curve I in Fig. 4; 1. Day-periods
during week-days; 2. Day-periods during sundays; 3. Night-periods during
all days. Poisibilities for day-night regulations has not been taken into ac-
coo nt.
Figure 3. 7
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3. 2 Odense, Denmark (Reference 3. 3)
The city of Odense, Denmark has about 130, 000 inhabitants. This city is
served by Fynsvaerket power station which supplies both electricity and hot water.
The circulating water is normally heated in heat exchangers by means of steam ex-
tracted from the power plant turbines, but additional heaters are provided for stand-
by and peaking purposes. These standby heaters take live steam from the mains.
The mean temperature of the year in Odense, Denmark is 45°F. Its
average variation is from a mean of 32°F in February to a mean of 60°F in July.
The ratio of district heating load to electrical load varies over a large range. The
1964 average was about 3. 2 x io6 Btu/hr per MW, but extremes may range from
1. 2 x io6 Btu/hr/MW on a summer day to 12 x i06 Btu/hr/MW during a winter night.
Hot water used in the district heating system is heated in two stages, as
indicated below in Figure 3. 8.
Figure 3. 8
Schematic of Odense Hot Water Circuit
33
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Steam is extracted from one low pressure turbine at about 4. 2 psia and
from the other at about 9. 5 psia. Normal hot water inlet is 113°F and outlet is 185°F.
Both extractions are controlled by means of pass-out slide valves which
govern the steam flow to the low-pressure stages after the extraction points. This
divides the flow to the two heaters in the most economical way at all loads within the
governing range.
Figure 3. 9 illustrates the principle of the control system.
Measurements of speed, pressure and temperature are combined in the
governing action.
Figure 3. 9
Control System Schematic
34
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REFERENCES -- Section 3
3. 1 Chapin, J. A., Trends in Costs of Industrial Power , Chem. Eng. Progr., 64
(3), 1968, PP. 53—56.
3. 2 District Heating Handbook , National District Heating Association, Pittsburgh,
3rd. Edition.
3. 3 Frilund, Bjarne and Lehmberg, H., Combined District Heating and Power
Unit Increases System Efficiency . Power Engineering, August 1966, pp. 55-56.
3. 4 Kiruela, K., Power Generation in Connection with District Heating in Finland ,
World Power Conference, 1966, Paper 71.
3. 5 Santala, Veikko, How District Heating Serves Finnish City of 20, 000 . Heating,
Piping & Air Conditioning, September 1966, pp. 129-135.
35
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Section 4
AQUACULTURE
4.1 Introduction
The second area of usage which is most often referred to in considerations
of the disposition of waste heat from power plants is that of aquaculture, In nearly
all surveys of potential uses of rejected heat, this possibility is raised. The specific
applications range from the frivolous (raising of ornamental fish) (Reference 4. 1),
to the “luxury market” (shrimp and lobsters) (References 4.2 and 4.3), to serious
considerations of using heat input to the biological cycle to simultaneously cope with
the overall systemic problems of world-wide hunger and recycling of human waste
into reusable resources (Reference 4.4). Considering the magnitude of the heat
rejection problem, it would appear that only a full-scale, serious attempt at aqua-
culture as part of the basic food chain would be able to utilize a sufficient amount of
energy to make the project worthwhile.
It should be emphasized that, in terms of the criteria set fQrth in
Section 2. 1, aquaculture does not represent a promising “solution.” That is,
1. natural waterways are still involved
2. the heat rejection is not widely decentralized. In fact,
the whole aquaculture concept depends on a localized
alteration in the natural ecology, albeit hopefully one
which is “beneficial.”
3. the application does not reduce normal electric
power requirements.
4. while some additional profitability may accrue to the
power company from food production, the whole process
is so far removed from their normal operations, depends
on so many factors which they feel are beyond their control,
and is so ill-defined both economically and technically, that
it is virtually impossible to make a case for aquaculture on
economic grounds.
37
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Furthermore, as was indicated in Reference 4. 5 in the discussion of
cooling canals, the possibility of minute radioactive contaminants from nuclear
plants being concentrated in a food chain must always be a paramount consideration.
In fact, until sufficient research has been performed to insure beyond question that
this possibility does not exist, the potential consequences are so severe that this
type of usage should not be attempted.
On the basis of these considerations, it is not felt that the active inves-
tigation of aquaculture techniques as an immediate response to the problem of
thermal pollution from power plants is justified at this time. However, the need
for a substantial increase in the world supply of protein is well recognized. A
critical shortage already exists in many parts of the world, and all indications point
to increasing deficiencies as the human population continues to outgrow its food
resources. Clearly, every possible new source of protein must not only be con-
sidered on the theoretical basis of its relative merits, but also it must be brought
into actual production as quickly as possible, for only in this way can its potential
be properly evaluated and, at the same time, realized and utilized. Among the
several possibilities for increasing the world supply of protein is the development
and expansion of aquaculture--the rearing of aquatic organisms under controlled
conditions using the techniques of agriculture and animal husbandry.
On this basis, the study of aquaculture as a solution to the global food
problem should clearly be pursued. In addition, the role that power plants might
serve as adjuncts to additional food production should be made known to researches
directly concerned with the development of agriculture. Therefore, the following
chapter will review what little information has been accumulated in this study, not
as a proposed solution to the thermal pollution problem but as a potential resource
for another field.
38
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Much of this information has been assembled by Bardach et al in
Reference 4.6. The conclusion is that the practice of aquaculture may not only
be greatly expanded, particularly in those parts of the world most in need of its
products, but also that its yields may be very appreciably increased through the
use of modern science and technology. Existing techniques are already available
for immediate application and quick return. But the application of scientific
methods to the practice of aquaculture is a new and challenging field which holds
still greater promise for the future if the research and development capabilities
of this and other advanced countries are brought to bear on the problem.
4.2 General Principles of Aquaculture
More or less intensive culture of aquatic organisms, in contrast to
their capture from untended stocks, is practiced in many parts of the world.
While as yet more prevalent and successful in fresh and brackish waters than in
the sea proper, some true marine husbanding operations are being attempted,
most notably in Japan, the Soviet Socialist Republic and in Great Britain. No
statistical breakdown is available on world tonnage of fish, invertebrates and
aquatic plants produced by such active interference of man in the natural life
cycles of the organisms or in the management of their environment. If one comprises,
for the purpose of this report, under aquaculture any operation that subjects the
organisms in question to at least one (but usually more than one) manipulation
before their eventual harvest or capture, the total tonnage so produced may lie
between 5% and 10% of the total world fish catch.
39
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It has been estimated, only for the fresh and brackish water realm, that consistent
application of the best known techniques could raise the fish tonnage produced by
aquaculture three to five fold to somewhere around 30 million metric tons. Intensive
fish culture (aquaculture) in waters of full marine salinity is in its very infancy; it is
technically feasible with some species but it is difficult to project, from present
pilot experiments, when, where, and under what conditions larger scale operations
might become economically sound.
Fishes are the largest class of vertebrates with some 25, 000 species, but
one may almost count on the fingers of both hands those that have yielded to attempts
at intensive husbandry and even fewer species have been domesticated like some
mammals and birds. A still smaller number of aquatic invertebrates have been
successfully cultured. However, it is possible today to produce with intensive care
significantly larger amounts of high grade animal protein per unit of inshore or fresh-
water surface than on fertile dry land. The reasons for this may be found in some
basic biological and ecological principles.
Aquatic organisms live in a medium of about the same density as their
own. Hence they require less skeletal structure for their support than needed by
birds and terrestrial mammals, with a correspondingly greater percentage of their
assimilation devoted to the production of edible musculature. The metabolic advantage
of aquatic animals lies in their not having to expend a portion of their caloric intake in
maintaining a constant body temperature. This advantage would be further enhanced if
they were raised in brackish water of an osmotic (salt) level like that of their own body
fluids not having to expend metabolic energy in osmoregulatory homeostasis.
It is well-known with regard to the question of metabolic advantage that,
while the organisms assume the temperature of their environments, that relatively
narrow temperature ranges are acceptable for survival and exceeding narrow limits
correspond to conditions for optimum growth. While this is the essence of the ther-
mal pollution threat, it also suggests that a thermodynamic regulatory function could
be performed to maintain hatcheries and fish farms at the optimum conditions.
40
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4• 3 Some Specific Examples
Much of the advanced research work in developing these techniques has
been performed in England. That is due in part to the fact that the average water
temperatures there are colder than in the United States and often below levels for
optimum growth of even many native species. The efforts of farming sole and plaice are
described in Reference 4. 7.
4. 3. 1 Hunterston Nuclear Station
Before embarking on a project the White Fish Authority had to establish
that the young hatchery-bred flatfish firstly could be contained, fed and kept alive and
equally important, observed. A modest trial was mounted in an enclosed inlet on the
west coast of Scotland, and preparations were also made for a trial at a power station.
Difficulties were expected from both types of environment, but those at a power station
were thought to warrant preliminary trials on a laboratory scale, in tanks both at Port
Erin and at power stations.
The laboratory experiments began with a study of the effects of elevated
temperatures on the viability of plaice and sole, in order to get some indication of
the growth and tolerance within the expected thermal range of the effluent, and also
to establish a feeding level with an acceptable food. The results suggested that tem-
peratures of 15°C to 16°C were best for plaice, and 18°C to 20C for sole. In this
initial trial the fish were fed on a diet of chopped fresh mussel flesh (Mytilus edulis)
at a daily rate of 10 per cent to 14 per cent and eight per cent to 12 per cent of tank
biomass respectively, depending on tank conditions.
Two site trials followed early in 1966, the purpose being to explore the
likely effects of chemical additives on the survival and health of the fish. The first
trial was held at Carmarthen Bay, a conventional coal-fired station in South Wales,
and the second at Hunterston, a nuclear generating station in Scotland. These sta-
tions were chosen because they both employ a system of injecting a continuous low
level of chlorine into the intake flumes to keep marine organisms from settling. The
chemists at Carmarthen Bay had developed the continuous system in an attempt to
find an economic and efficient level of chlorine addition. Their technique had later
been adopted at Hunterston. In the preliminary experiments no attempt was made to
maintain a fixed temperature level as future development would have to accept the
41
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diurnal and seasonal variation of the discharge system. The results showed that
both plaice and sole survived the low levels of free halogens to which they were
exposed (0. 02 ppm - 0. 1 ppm) and they obviously benefited from daily feeding and
attention, and the higher temperature range. Both the trials were begun in winter, and
involved nine-month-old fish measuring between five and nine centimeters. A year
later most of the fish of both species were of marketable size, that is 23—24 cm. The
sole tolerated the conditions better than the plaice in that they withstood the higher
summer tank temperatures. This is to be expected, as their natural distribution is
in warmer latitudes. Plaice however, were distraught at temperatures above 19°C
and there was some mortality at both sites. The extension of the growth period
through the year enabled the fish to reach marketable size at least 12 months before
the most advanced individuals in natural conditions.
Hunterston is a base load station, and with the agreement of the South of
Scotland Electricity Board, it was decided to continue the feasibility study there.
Four tanks were constructed, 14.4 mx 7.2 mx 1.0 m deep. These were ready to
receive hatchery-reared sole in October, 1966, and a number of young fish, three to
four centimeteres in length, were safety transported from the Isle of Man hatchery.
But the hatchery stock that year was suffering from the effects of unsuitable larval
food, and there were high losses. At Hunterston, more than 30 percent of the fish that
died succumbed in the first week. Many more deaths must have gone unrecorded. By
March only six per cent were still alive, but of these - not yet two years old - 62 per
cent were of marketable size.
Both the preliminary trials and the first field work prove the feasibility of
using power station condenser discharges as an environment in which to grow certain
species of marine fish, and indicate a feasible system on which a commercial enter-
prise may be founded. The next stage is to acquire more comprehensive knowledge
and expertise in various areas:
1. Improvement of the survival figures at all stages.
2. The understanding of the effects of stock density and of
absolute tank dimensions.
3. The production of cheap foods containing all the nutritional
requirements.
4. General husbandry.
42
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Conditions in the tanks at Hunterston vary daily and seasonally. Free
halogens are always present in small quantity but are more easily dissipated in
summer by sunlight. The fish may, however, prefer shady conditions, and a first
trial is now underway. Oxygen levels are above saturation in the discharge which is
a considerable advantage but, because of the continual presence of free halogens at
a fluctuating level, it is not always possible to maintain flow. An auxiliary aeration
system is therefore necessary to maintain the level.
Levels of salinity provide no problem, and rainwater is continuously
voided by the surface overflow systems. One of the main concerns is the colonization
of the environment by other marine fauna and flora. Some animals are predators and
others compete for food. In general a modest number of scavenging froms would be
desirable to assist with tank hygiene, together with a number of algal browsers.
(Algal growth is the principal physical problem.) To date, tank populations have been
free from any outbreak of disease, and this may be due in some part to the chemical
content of the water suppressing bacterial growth.
The qualitative conclusions of the authors were summarized as follows:
“It is possible to see that even now the power station environment has
economic significance. Future development must depend ultimately on the policies of
the Electricity Boards producing the primary resource, the warmed water. Maybe
we shall see private enterprise catering for a luxury market or, on a national basis,
endeavoring to make more protein available for this country and for others, perhaps
creating coastal complexes of power station and bay barrages to produce both marine
and freshwater species. All these developments are distinctly possible but the speed
at which they will be brought to fruition will depend a great deal on the amount of
effort put into the science and technology of marine fish farming. Although it is
growing, the effort is still not big enough or wide enough to meet the needs of those
engaged in development and design. They need more and better knowledge about all
aspects of the nutrition, health, environmental requirements and genetic possibilities
of sea fish.”
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4. 3. 2 Growing of Carp -- Russian Tests (Reference 4. 8)
Some work was reported on from the Soviet Union, of which only the abstract
was available in translation. The report describes attempts to grow carp in tanks placed
in the cooling pond of a hydroelectric plant. The results are summarized below.
“The carp were reared in tanks placed in the cooling pond of a hydro-
electric power plant. The effect of various stocking rates, of diets
(blood and fish meal, a new protein-vitamin preparation, duckweed
paste), of daily rations and of the number of feedings was investigated.
With a stocking rate of 250 specimens/rn 2 , fish production was 100
kg/rn 2 and the weight of carp was 400 g. Animal food in the diet
should comprise 10-15%. Although an increase in animal food in-
crease the growth rate, it leads to unproductive protein losses.
The biological value of protein-vitamin preparations is similar
to that of nutritional hydrolyzed yeast. The daily ration in
thermal waters should be 12-40% of the fish’s body weight. With
12-fold feeding its effectiveness increases 2-fold in comparison
with single feeding.”
4. 3. 3 Lobsters (Reference 4. 3)
Figures from the Maine Department of Sea and Shore Fisheries indicate
that the annual lobster (Homarus Americanus) catch has declined from 24. 5 million
pounds in 1957 to 15 million pounds in 1967. At the same time, the average water
temperature off the Maine Coast has dropped from 49. 5 to 47. 5°F (a range considered
ideal for lobsters) to an average of less than 45’F. Surveys indicate that the cooling
trend has also affected the populations of other shell fish including clartis, oysters,
shrimp and scallops. A proposed solution is to discharge warmed water from power
plants into a protected cone to bring the average temperatures back into the preferred
range. Several problems including the tendency for the discharge water to stratify at
the surface rather than to mix with the bottom waters where the lobsters live and the
strong tidal effects in Casco Bay which was selected as a test site have delayed the
implementation of the scheme. No account has yet been taken of possible concentrating
mechanisms of radioactive elements in the lobsters themselves in the case of a
nuclear plant.
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4. 3. 4 The Thermo—Nutrient Pump (Reference 4.4)
One of the important cyclic processes in nature is that of thermally induced
vertical mixing of ocean waters in which bottom waters, which are rich in nutrients are
brought to the surface where sunlight can reach them (the so-called photo—synthetic zone)
and where they are digested by living organisms. The cycle is completed when the micro-
organisms are reduced to the bottom where they live and enrich the nutrient supply.
A recent report investigates the possibility of using heated water discharge
from a power plant to convectively pump deep water to the surface for “fish farming.”
A relatively simple computation of the amount of bottom water which could be pumped
to the surface for a given amount of discharge water at different temperature levels
above the ambient water. The results of these computations are shown in Figure 4. 1.
0
Vi i IftOl I’tp —-
ii IO AT:
Inclined Pipe P°
I M Pipe DiomeI r
30CM Depth
10 I. L LJJIHI IJJHHi
102
HEAT EXC}IAI GER EIFLUENT,W, ,Kq/Sec
Figure 4. 1
Thermo-nutrient pumping rate
45
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The curves pass through a maximum since for a given size pipe the fric-
tional losses due to the heat exchanger discharge itself become dominant above a
certain flow.
Some estimates of the net increase in fish production due to such an in-
stallation are possible and are not encouraging. Based on the assumption that the
bottom nutrient concentration remains at its original, undisturbed high level even after
a long period of operation (which seems a dubious assumption), a one meter diameter
vertical pipe supplied with 60 kg/sec of heat exchanger water at a temperature 5°C
above the average sea water temperature can deliver 300 kg/sec of bottom water to
the surface. Assuming maximum utilization, this is reported to produce an additional
3000 kg per year of edible fish which is hardly a reasonable return for the investment.
However, the arrangement is structurally and thermodynamically feasible and if means
to increase the yield are found, it may bear further consideration.
46
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REFERENCES -- Section 4
4. 1 iles, R. B., “Cultivating Fuel for Food and Sport in Power Station Water,”
The New Scientists, No. 324, Jan. 31, 1963.
4.2 Anon., “Lobsters, Warmed and Simulated, “Science News, Vol. 93,
February 17, 1968.
4.3 Martino, P.A., and Marchello, J. M., “Using Waste Heat for Fish Farming,”
Ocean Industry, April 1968.
4.4 Mihursky, J.A., “On Possible Constructive Uses of Thermal Additions to
Estuaries,” Bio-Science, 17 (1967).
4. 5 Smith, N., and Maulbetsch, J. S., “Task II - Phase II Report. Consideration
of Advanced Concepts in Large-Scale Heat Rejection Equipment.” Dynatech
Report No. 925 for FWQA, June 1970.
4.6 Bardock, J. E., et al, “The Status and Potential of Aquaculture, Volume II,
Particularly Fish Culture,” Am. Inst. of Biol. Sci., PB-177- -768,
Washington, D.C. (1968).
4. 7 Nash, C. E., “Power Stations as Sea Farms,” New Scientist, November 14,
1968.
4. 8 Gribanov, L. V., et al, “Some Aspects of Carp Breeding and Nutrition in
Tanks on Thermal Waters,” Translated abstract from Ref. ZH BIOL.,, 1968.
47
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Section 5
DECENTRALIZED POWER GENERATION
TOTAL ENERGY SYSTEMS
5.1 Introduction
As indicated at the conclusion of Section 2, it is felt that the only feasible
alternative to the addition of cooling towers (or other types of equipment for rejecting
heat directly to the atmosphere) is a reversal of the trend toward large central
power plants. It seems reasonable to conclude that the total quantity of heat rejected
from power generating stations is sufficiently small in comparison to the total energy
balance on the land. The essential aspect of heat rejection which leads to its classifi-
cation as a pollutant in the concentrated nature of its discharge. Therefore, the
elimination of large central power stations in favor of small individual gas turbine/
generator “total energy” units distributed throughout the community at the individual
load sites would appear to be a direct attack on the essence of the thermal pollution
problem as it relates to energy production.
Such a system, which will be described in more detail in Section 5.2,
would have the following advantages:
• while heat must still be rejected from this system in
accordance with the laws of thermodynamics, the heat
rejected from a gas turbine is at much higher temperatures
and hence useful for heating, air-conditioning, cooling, and
other “heat input” energy requirements
• the problem of distribution of work heat is alleviated
if the system is on-site
• if such systems were adapted on a wide scale, operating
problems unique to large, inter-connected grid systems
such as the Northeast blackout of a few years ago would
be avoided
There are, of course, some obvious potential disadvantages to such
an approach. These would include those listed on the following page.
49
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• the possibility of excessive air pollution from a large
number of small gas turbine burners. While such burners
can be made quite clean, it is clearly more difficult
to monitor and maintain a large number of units than a
single large plant
• overall system efficiency, while theoretically quite
high if good use is made of the waste heat in the turbine
exhaust stream, could be lower than central plants since
the advantages of running at essentially constant load
at the design point would, in general, be lost
• maintenance of a large number of relatively complex
systems might statistically be more difficult
than maintenance of a single power plant with a full-time
maintenance team on location
5.2 Total-Energy Power Generation--A Typical System Description
A total energy system, in its simplest terms, is illustrated in Figure 5. 1.
The name derives from the concept of meeting all of the energy input requirements
of a dwelling or plant from a single system. In general, energy input requirements
can be divided into three categories depending upon which of three forms of energy
is most appropriate. These energy forms are:
1. electricity
2. heat (usually steam or hot water)
3. shaft rotation
Figure 5.2, excerpted from Reference 5.1, suggests a variety of combinations of
loads in a process plant which might be met by a total energy system. Figure 5.3,
from Reference 5.2, shows a similar schematic diagram for the possible usage of
a total energy system for a shopping center. Figures 5.3 (a), (b), and (c) illustrate
the alternative arrangements of individual metering of each unit, central purchasing
of power and resale to the units, and on-site total energy generation.
50
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Fuel
Schematic of Simple Total Energy System
Figure 5.1
Electric
Power
to
building
Air Inlet
Shaft Power
Compressor
Exhaust
Stream
Exhaust Heat
Recovery Exchanger
51
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Lighting
. Eotors
Hi•frequency
generator
(180 cycles and up)
Singly or in tandem
Centrifugal pumps
(water,
hydraulic fluids,
process liquids)
Comfort heating _ ,J . Centrifugal
!! ‘ i relrigeration.
Preheat boiler . • . cqr pre sors
feedwater •,L -
l tna1
Absorption chiller or *ocess
forA’C orpro ess J- gas co np eessOrs
Process steam heating ] t ri g pOmps
fWdt8( .
Process liquid heating ,, hydraulic fluids,
.. . process liquids)
Hot air process
drying or curi , ,, , 4 •.
Possible Total Energy System Configurations for Process Plant Application
(from Reference 5.1)
Use for these to make power
these prime with these
fueIs . • movers.., generators...
for these
plant
needs.
Recover heat using
from these these
sources.., methods
sting
for these
plant
processes...
and drive
these plant
loads, too.
Preheating
boiler feedwater
Comfort heating 1
Process liquid
Process steam h n j
Reciprocating
refrigeration
compressors
Reciprocating
air or process
gas compressors
Diesel fuel
ng
Anodizing
Battery charging
Electrochemical
processes
Gas turbine
fuel
Absorption chillers
for A ‘C or process
Process drying
or curing
Figure 5.2
-------
_ SETLR ... AS RAL
ELECTRIC
_____ METER ______
LIGHTING
CIRCULATION FANS
ELEVATORS. ETC. -.
AIR-CONDITIONING
H ELECTRIC
SYSTEM
. -e:’
-. 5..
• Indiv duaIly metered
shopping center n which ..
each tenarlt pu c 1’ase
h,sown eIectr ic’pc. er
.. natural gas. Costs br ç ’kir
)Ots,8;gnS, € c, rcrated . .
- I 1 . NATUHAL
i r [ R Ji .
- DOMESTIC HOT
- WATCh SYSTEM
• •. _ CCT FIRED
BOILER
5 ..
- BULDINGI
TO EACH’ ‘ LPt - COOLINGI
• 1EUN T .. - CYSTEM
-
: ELECTRIC
• CENTRIFUGAL •
CHILLER
t_ -
Centrally purchased power. .
for all jtti ’ resel4ir
cI ctdá pow t each tena
.5 . - -) . S;.-. -
: T t . MLIEf_ . __ .
DIJLi)I!1 L V i1 I C LOAD
CUE3ICLE 3. .
. [ ] TUFIF3INE CONTRQL
1 .JI1LI’CWEF L 5 IS:
CENERATO t.
p. .3D!JLES’; . -
. .HAUSI HEAT
CxCHA?:c .EAS- P.
‘S -
‘ S i
AUXILIA ,
FIRED
- .L S:L . ; ..
tBUILDING • . DOMLST1C AOSO 1
• HEAT!NG 101 W .TLR TION
SYSTEM SYSTEM CHILLER
—55 - -
I
5I’turbopo .er:d :
- ystem 1ng netpri’I gas ue1 Woc’o *
-, .h’ ’JtC.ip ’liCG )r cEwI litior ng a d .
. heati q. The auxIli rybŕ Ier 1$ -.
., . .needed slice tota(joads-e ceed.:
gl’i waste heat available •
- —
Possible System Arrangements for Shopping Center Application
(from Reference 5. 2)
Figure 5.3
DOMESTIC HOT
WA ER SYSTLM
SPACE
HEATING
SYSTEM
53
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5.2.1 Load Requirements versus System Output Capabilities
The essential question to be answered in evaluating the merit of a
total energy system is whether or not the user requirements for electric power,
shaft power, and heat are divided in such a ratio (or can be divided through changes
in plant operation) as to be compatible with the output of the energy system. In
order tobke good advantages of the potentially high system efficiencies, full use
must be made of the waste heat. Fortunately an additional degree of freedom is
available in terms of adjusting the systems thermal output over relatively wide
limits.
A system at Braunschweig, West Germany which supplies electrical
power and distinct heating, separates according to the following specifications.
(Reference 5. 3) The maximum electrical sendout is 32 Mwe while the thermal
output can be varied continuously from 0 to 64 Mwe and, with additional burners
can be increased to 92 Mw. The electrical power alone is generated at an efficiency
of 32%. If the full thermal output is utilized, the overall system efficiency can
reach 80%. Rating data for this plant is given in Table 1 and a schematic of the
system is shown in Figure 5.4.
The variation in thermal output is achieved in the following way. The
air delivered by the compressor can take two paths to the combustion chamber.
According to the damper setting (11 and 12 in Figure 5.4) the air flows either through
the bypass or through the regenerator. Intermediate settings provide any desired ratio
of thermal output to electrical output of 2.3:1 to 1. 3:1. If further reductions in the
thermal output are required, this is accomplished by means of dampers 13 and 16 in
the exhaust gas ducts between the air heaters and the waste heat boilers. This permits
dumping of a portion of the exhaust gas directly to the atmosphere. When the heating
demand is heavy, the exhaust gases pass through the regenerator without cooling
directly to the waste heat boiler at a high temperature ( 800° F). When the heating
demand is low, the gases enter the boiler after being cooled in the regenerator to
approximately 500° F. In addition extra burners in the waste heat boiler can supply
up to 50% more heat on cold days or be used to meet the heating demand in the event
of turbine failure.
54
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1 —turboset (1.1 —turbme; I .2—-compressor, I .3—generator); 2—
combushon chamber. 3—regenerator; 4—waste heat bode, with uddi-
t onoI burners (6) and fans (7), 5—circulating water system; Ii and I 2—
a r dampers; 13 to 1 8——e houst gas dampers.
Cycle Schematic of Braunschweig System
(from Reference 5. 3)
Figure 5.4
17
6
-s ---
6
•1
7
12
55
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Full Heating Output Half Heating output
(no regeneration) (partial regeneration)
1. Compressor Inlet Temp., F 40. 60. 40. 60.
2. Air Inlet Flow (ibm/see) 426. 405. 426; 405.
3. Pressure Ratio 6.3 6.0 6.4 6.1
4. Electrical Output, Mwe 28.6 25.8 28.1 25.3
5. Maximum Output, Mwe 3.2
6. Efficiency of Electric Power
Production, % 23.9 23.1 32.0 30.8
7. Turbine Inlet Temp., ° F 1300
8. Number of Stages
compressor 17
turbine 6
9. Speed, rpm 3000
10. Exhaust Gas Flow, ibm/sec 430. 409. 428. 407.
11. ThermalOutput, Mw 66. 64. 37. 37.5
12. FueiUtilization, % 79. 80.4 74.1 76.5
Rating Data on Braunschweig System
(from Reference 53)
Table 5.1
56
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REFERENCES---SECTION 5
5. 1 “In-Plant Power Generation is Back in ‘the Ballpark of Big Savings”
Factory, April 1966, pp. 98—101
5.2 Hoffman, R. V., “Gas Turbine for Total Energy,” Mechanical Engineering,
April 1968, pp. 92—98.
5.3 Schmoch, Otto, “Gas Turbine With Utilization of Exhaust Heat for District
Heating,” ASME Paper No. 66-GT/ CMC-61. Presented at Gas Turbine
Conference and Products Show, Zunich, Switzerland, March 1966.
57
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SELECTED WATER RESOURCES ABSTRACTS
INPUT TRANSACTION FORM
SENC TO. WATER RESOURCES SCIENTIFIC INFORMATION CENTER
U S CEPARTMENT OF THE INTERIOR
WASHINGTON, D. C. 2C04C
1
________ Ř5E
5 Or ar iiz at t on
Dynatech RID Company
Title
6 “Total Community Considerations in the Utilization of Rejected Heat
10 Auth r(s)
Smith, N.
Maulbetsch, John S.
Protect Desihriattoti
Contract 12-14-477
22 Citation
Water Pollution Control Research Series 16130 DHS 11/70
23 Descriptors (Starred First)
*Environmental engineering, *Thermal power, *Heat, *Water reuse, *Thermal
pollution, Irrigation, Desalinization, Sewage Treatment, Industrial use,
Municipal use
25 Identifiers (Starred First)
Aquacul ture
27 Abstract
The quantities of electric energy consumption and associated heat rejection
quantities, their present and projected allocation throughout the different
sections of the country, their relation to other forms of energy consumption
are reviewed and tabulated. Thermodynamic constraints on a solution to the
thermal pollution problem are defined. Feasibility of possible application
of waste heat usage are reviewed in the field of heating and air-conditioning,
aquaculture, process industry, irrigation, sewage treatment, desalination,
snd or ice melting and integration with municipal water system.
This report was submitted in fulfillment of Contract No. 12-14-477 under the
sponsorship of the Federal Water Quality Administration. (Rainwater-EPAIFWQA)
AbstractorF. H. RAINWATER ln>titutionEpAIFWQA/Natjonal_Thermal Pollution Research ProgrAm
wR.t:2 FE. JLJL’ I9S9
A F SIC
U. S. CO\ Eit5’ IENT USINT NG OUJICE . 2—
* 555: 155 5_359 33O
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