Economic utilization of cold water effluent from a proposed land-based OTEC plant

[From the U.S. Government Printing Office, www.gpo.gov]

Coastal Zone
Information
Center
Prepared For:

Government of Guam
Guam Energy Office
Agana Guam

ECONOMIC UTILIZATION OF COLD

WATER EFFLUENT FROM A PROPOSED

LAND-BASED OTEC PLANT

Prepared Under Contract:

C-0-3400014

CACI, Inc.-Federal

Marine Systems Engineering Department
1815 N. Fort Myer Drive
Arlington, Virginia ZZZ09

Prepared By:

TK Jon Buck and
1073 Dr. James Roney
B83
1980 October 1980

TABLE OF CONTENTS

Secondary Utilization of Cold Water from OTEC

Summary . . . . . . . . . . . . . . . . . . . . . .

Introduction . . . . . . . . . . . . . . . . . . . . .
1.1 Objective . . . . . . . . . . . . . . . . . . . . . .
1.2 Background . . . . . . . . . . . . . . . . . . . . .
1.3 Range of Uses of OTEC Cold Water . . . . . . . . . . . 1-2
1.3.1 Cold Water for Direct Cooling . . . . . . . . . . . . . 1-3
1.32 Assisting Cooling Systems . . . . . . . . . . . . . . . 1-3
1.3.3 Nutrient or Minerals Source . . . . . . . . . . . . . . 1-6

Technical Factors . . . . . . . . . . . . . . . . . . . Z-1

Z. 1 OTEC Plant Characteristics . . . . . . . . . . . . . . Z-1
Z.Z Physical and Commerical Characteristics

of the OTEC Site . . . . . . . . . . . . . . . . . . . Z-5

Z.Z.1 Port of Guam . . . . . . . . . . . . . . . . . . . . . Z-5
Z.Z.Z Cabras Island Vicinity . . . . . . . . . . . . . . . . . z-6

Z.Z.3 Environmental Data . . . . . . . . . . . . . . . . . . Z-8
ock)
CA
3 Applications of OTEC Cold Water Utilization . . . . . . . 3-1
3.1 Direct Refrigeration or Cooling . . . . . . . . . . . . . 3-1

3.1.1 Introduction . . . . . . . . . . . . . . . . . . . . . 3-1

3.1.2 Cold Water Quantities Required . . . . . . . . . . . . . 3-Z
3.1.3 Physical Arrangements . . . . . . . . . . . . . . . . 3-2
3.1.4 Savings of Energy & Cost . . . . . . . . . . . . . . . 3-4
32 Indirect Assistance to Cooling Systems . . . . . . . . . . 3-6
3.2.1 Precooling . . . . . . . . . . . . . . . . . . . . . . 3-6
3.22 Providing Heat Dissipation for Cooling Systems . . . . . . 3-6
3.3 Mariculture . . . . . . . . . . . . . . . . . . . . . 3-11

3.3.1 Introduction . . . . . . . . . . . . . . . . . . . . . 3-11
3.32 Algae . . . . . . . . . . . . . . . . . . . . . . . . 3-13

3.3.3 Shellfish . . . . . . . . . . . . . . . . . . . . . . . 3-14

3.3.4 Finfish . . . . . . . . . . . . . . . . . . . . . . 3-14

3.3.5 Conclusion . . . . . . . . . . . . . . . . . . . . . . 3-15

4 Implementing the Utilization of
of OTEC Cold Water . . . . . . . . . . . . . . . . . 4-1

4.1 Short Term Utilization . . . . . . . . . . . . . . . . . 4-1
42 Long Term Utilization . . . . . . . . . . . . . . . . . 4-3

5 Economic Inputs of OTEC Cold

Water Utilization . . . . . . . . . . . . . . . . . . . 5-1
5.1 Construction Costs . . . . . . . . . . . . . . . . . . 5-1
5.2 Employment Resulting From OTEC Cold
Water Utilization . . . . . . . . . . . . . . . . . . . 5-3

5.3 Private Sector Income Derived . . . . . . . . . . . . . 5-5
5.4 Ef f ects on Port of Guam Development . . . . . . . . . . 5-6
APPENDIX A . . . . . . . . . . . . . . . . . . . . . . 5-9
APPENDIX B . . . . . . . . . . . . . . . . . . . . . 5-11

Bibliography . . . . . . . . . . . . . . . . . . . . . 5-12

SUMMARY

This study of the secondary uses of cold water from an OTEC

power plant was carried out for the Guam Energy Office to assist

them and other agencies of the Government of Guam on planning for

effective and economic use of this byproduct resource. If an OTEC

power plant were installed on Cabras Island, there are several

possible uses of the cold water discharged from the power plant

after being drawn from the deep ocean and used in the OTEC power

plant condensers. These uses can enhance the Port of Guam and

local commercial activities.

Many possible uses were examined; the most promising are:
(1) Direct cooling, such as for cold storage of foods, including

tuna or other fish,

(2) Assisting cooling systems, such as steam power plant condenser

cooling, chemical or refinery plant heat dissipation, etc.,

(3) Mariculture, and other uses of the chemical nutrients and

minerals in the deep seawater.

Negative Possibilities: It was found that there are no problems

that could produce negative environmental impacts that cabnot be

managed to prevent undesirable consequences. That is, there are

sufficient controllable variables to adjust to any foreseeable

situation that might be a problem.

Positive Consequences: There are potential benefits of great

magnitude for using cold water discharged from an OTEC plant for

secondary uses. These benefits are both economic and helpful to

the environment. Additional commerce could be expected from cold

storage facilities increasing use of the Port, and from mariculture

products. In addition, longer range benefits could be expected

from expanded industry on Guam partly attributable to the availability

of cold water for cooling operations.

Recommended Strategy:

1. A conceptual design for the OTEC plant is needed to provide the

detailed information for specific design and analysis of the cold

water utilization system, and the exact calculation of economic

benefits for commercial investment decisions.

2. Given a conceptual design for an OTEC plant, lay out the possible

arrangements for cold water distribution in detail: the dimensions,

quantities of water pumped, heat exchanger characteristics, etc.

3. With this plan developed, perform a complete cost-benefits
analysis to aid.in final decisions on facility installation and

expansion.

Most Promising Areas of Utilization:

1. Col d Storage, using the cold water directly for cooling of

spaces or foods,

2. Modifying the Cabras Island Power Plant condenser cooling

system (would be part of OTEC plant construction),

3. Mariculture, to a limited extent in the Apra Harbor area,

4. Cooling water to GORCO, to enhance refinery operation and

possible expansion.

Longer Term Potentialities

1. More extensive mariculture, south of Apra Harbor area, using

water sent first to GORCO,

2. For expanded industry such as aluminum refining or ammonia

production.

SECONDARY UTILIZATION OF COLD WATER FROM OTEC

1.1 OBJECTIVE: 1. INTRODUCTION

The objective of this project was to analyze the possible uses,

economic and environmntal impact of cold ocean water dischaged from

a land-based OTEC plant on Guam, and to furnish the Guam Energy

Office with a report of the results of the analysis. The report

includes strategies toward developing the economic use of coldwater

effluent and of mitigating any possible adverse environmental impacts

of effluent discharge.

1.2 BACKGROUND:

The Guam Energy OFfice and Bureau of Planning's Guam Coastal

Management Program has been assessing the environmental and economic

impact of a land-based OTEC plant at the proposed site on Cabras

Island. An "Economic and Land-Use Plan for Cabras Island and

Surrounding Area" has been developed, and this study supports and

augments this pl an.

The installation of an OTEC plant on Cabaras Island will involve

a nunber of direct environmental impacts. These need not be negative,

but under controlled circumstances, certain benefits can be accrued.

For example, the cold water drawn from the dep ocean is relatively

nutrient rich and if properly utilized, can stimulate biological

productivity. Warm water dishcarges from existing power plants can be

tempered with cold water. Furthermore, an OTEC plant can provide

economic enhancement beyond the electric power generated. The cold

water can be used to advantage inconjunction with Port of Guam

activities to aid in several commercial areas such as food handling,

processing and storage.

Thus the presence of an OTEC plant can provide benefits beyond

the electric power generated and the displacement of petroleum needed

for conventional power plants. This report describes the analysis and

conclusions reached on this topic.

1.3 RANGE OF USES OF OTEC COLD WATER

The possible secondary uses of OTEC cold water might include:

1. For chilling of food produce, including fish,

2. For space air conditioni ng,

3. As an aid to mechanical refrigeration/freezing systems, to

increase the eff iciency of operation and eliminate air heat

rejectors,

4. To aid in condenser cooling at the existing oil fueled

power plants, increasing efficiency and reducing thermal

discharges,

5. To provide nutrients for mariculture,

6. To aid certain industrial operations where cooling water is

required,

7. As a possible source of minerals from the sea.

These can be grouped conveniently into three main categories:

Direct refrigeration

Assisting cooling systems

Nutrient or mineral source.

1-2

1.3.1 Cold Water For Direct Cooling

This projected use would principally be involved in air

conditioning or cooling of materials such as foodstuffs (e.g., fish)

for cold storage. Here, the temperature of the cold water from the

OTEC plant is sufficiently low that it can directly cool either a

work space or storage space. In most applications, a heat exchanger

would be used to provide cooling of air or fresh water derived from

the cold ocean water. Figure 1-1 provides a schematic representation

of this class of applications.

1.3.2 Assisting Cooling Systems

This projected use would principally be involved as working in

conjunction with a mechanical cooling system, or some process where

it is necessary to reject heat. For example, an electric powered

-mechanical refrigeration system typically uses a set of cooling tubes

over which air is forced in order to remove the heat rejhected from

the refrigeration cycle. With warm humid air, the removal requires

sufficiently large heat exchangers and fans to blow the air over the

coils. If cold water were available, the heat could be rejected to

the cold water using a suitable heat exchanger. This could be a much

smaller unit and could be less costly than tha air cooler, and the

lower temperature of the reject side could make the system more

efficient (less regrigerant flow required, etc.).

Figure 1-2 illustrates this class of applications for OTEC cold

water utilization.

1-3

0 Cold Air
T Water
E
C Cold
Storage

Cold OTEC
Water Air Room 10i

A Air Room 2dj
Tank

Fresh AIR CONDITIONING
Water

Cold OTEC
Cold
Water Tank

Figure 1-1 Schematic for OTEC Cold Water
Direct Cooling
Cold

r
-Wate

1-4

Steam

Sea Water Power
in CONDENSER Plant "A"
80 + OF

Reject Warm Wa ter
goo - 100OF

OTEC Cold
Water
in Power
50OF Plant

OTEC
Go Cooling
Reject Water 70OF Water

Warmed Air

Cooling
Tower

Reject Heat

Air 80+OF

TYPICAL INDUSTRIAL PROCESS

OTEC
Cold
Reject Water

Heat

OTEC COOLED
Cold@
Lter

5 0OF

Figure 1-2 Schematic for OTEC Assisted Cooling

1-5

1.3.3 Nutrient or Minerals Source

In this class of applications of OTEC cold water, it is

recognized that deep ocean water contains relatively higher levels of

chemical and organic nutrients for marine life, and that seawater

contains low concentrations of certain valuable minerals that can be

extracted. The most probably use of OTEC water in this category is in

support of mariculture. In mariculture, the sea is "farmed" by

pf-oviding conditions for higher rates of growth of marine plant and

animal life, controlling the growth and setting up conditions where

the yield can be harvested conveniently and economically. Certain

seaweeds are potefitial commercial crops, as well as shellfish and

some finfish suitable for mariculture.

Seawater contai,ns important and valuable minerals such as

uranium. Commercial extraction of these minerals is usually not

feasible due to the high cost of pumping vast quantities of ocean

water through a separator. But with OTEC already pumping very large

volumes of water for power plant operations, the added use of mineral

extraction becomes an economic possibility.

Figure 1-3 illustrates this classification of possible uses of

OTEC water.

1-6

TEC
P @la n t 0 Deep Ocean

Water
Discharge Shellfish
Racks

Mariculture
Impoundment

Uranium

Discharge

Figure 1-3 Schematic for OTEC Cold Water Nutrient
and Minerial Utilization

1-7

2. TECHNICAL FACTORS

2.1 OTEC PLANT CHARACTERISTICS

A 50 megawatt OTEC power plant is planned for Cabras Island,

Guam. This plant would draw cold water from the deep ocean offshore

at a temperature of approximately 40 to 45 degrees F. for use in the

OTEC power cycle. Figure 2-1 shows the basic schematicarrangement of

an OTEC power plant. The OTEC plant operates on the temperature

difference between the warm ocean surface water and the deep cold(

water, by drawing the energy from warm water in the following power

cycle: !

1. Warm water is drawn through an evaporator which boils

ammonia, .

2 . The ammonia passes through a turbine which drives an

electric generator,.

3. Cold ocean water is used to condense the ammonia in a

condenser,

4. The ammonia is pumped back to the evap orator completing the

cycle.

A very large volume of cold water would be pumped, approximately

500,000 gallons per minute. In the condenser the cold water would

experience a slight temperature rise of only a few degrees (F) until

discharged from the plant. Thus the cold water discharged from the

OTEC plant is still relatively cold. This discharged water could be

used for secondary uses, such as refrigeration or mariculture.

Alternatively, a small amount of water could be diverted directly to

2-1

ELECTRIC
POWER
WARM WATER OUTPUT
I NTAKt

HIGH-PRESSURE, LOW PRESSURE
250C (770F) N" VAPOR
Niti VAPOR 3
20PC 100c,
(680F)
n (50'DF)

CONDEN5

0
lopc 10 C
(509F) (600F)
SOC
t LOW PRESSURE
HIGH PRESSURE N" LIQUID
3
NN LIQUID
3 LIQUID COLD
rt WARM WATER PRESSURIZED INT
EXHAUSTED
AT 23 C
(730F)
LEVEL
cl

2
TECHNICAL FACTORS
.

2.1 OTEC PLANT CHARACTERISTICS

A 50 megawatt OTEC power plant is planned for Cabras Island,

Guam. This plant would draw cold water from the deep ocean offshore

at a temperature of approximately 40 to 45 degrees F. for.use in the

OTEC power cycle. Figure 2-1 shows the basic schematic.arrangement of

an OTEC power plant. The OTEC plant operates on the temperature

difference between the warm ocean surface water and the deep cold

water, by drawing the energy from warm water in the following power

cycle:

1. Warm,water is drawn through an evaporator which boils

ammonia,

2 The ammonia passes through a turbine which drives an

electric generator,.

3. Cold ocean water is used to condense the ammonia in a

condenser,

4. The ammonia is pumped back to the evaporator completing the

cycle.

A very large volume of cold water would be pumped, approximately

500,000 gallons per minute. In the condenser the cold water would

experience a slight temperature rise of only a few degrees (F) until

discharged from the plant. Thus the cold water discharged from the

OTEC plant is still relatively cold. This discharged water could be

used for secondary uses, such as refrigeration or mariculture.

Alternatively, a small amount of water could be diverted directly to

2-1

a secondary user in order to provide the coldest temperature posible,

should that be sufficiently important.

The amount of flow of cold water for most of these secondary

uses is estimated to be small in comparison with the large flows

required through the OTEC condenser (mineral extraction is the

principal exception); therefore, bypassing cold water directly may be

a more suitable and economic method of using the dep, cold water

pumped for an OTEC plant. This is illustrated in Figure 2-2.

Generally, the cold water would be used after discharge from the OTEC

condenser. This would provide a remaining sufficiently low

temperature for most of the applications. In the case of mariculture,

where the nutrient content is desired, the higher temperature is

desirable; in facti some warming of the deep ocean water discharge
may be needed in the mariculture application. Small quantities of

cold water directly pumped directly to a cooling use would tend to be

needed for some direct refrigeration uses where the lowest

temperature achievable is required.

2-3

OTEC

Conden r

Cold Secondary
Uses
Bypass

Deep Cold
Water
@@S e;

Figure 2-2 Schematic for OTEC Cold Water Bypass

2-4

2.2 PHYSICAL AND COMMERCIAL CHARACTERISTICS OF THE OTEC SITE

2.2.1 Port of Guam

The port facilities are operated by the Port Authority of Guam.

In Apra Harbor, the Port Authority's terminal facilities are located

on 33 acres of reclaimed land on Cabras Island. Along 2725 lineal

feet of dock area, the depth of the docks average 28 to 35 feet. Much

of the activity at the port is container operations, and the

container terminal covers 12 acres. Two large breakbulk warehouses

contain a total of 108,000 square feet of storage space, and another

shed area contains 24,000 square feet of cargo space.

The total Port Authority annual revenue is in excess of

$8,000,000. The annual tonnage of cargo is over 100,000 tons, having

a reached a level of over 200,000 tons in 1978. Tuna tonnage handled

is approximately 15,000 tons each year. Vessels calls per year at the

port are approximately 100 per year for each of container ships,

breakbulk ships, and tankers. Over 200 fishing vessels call per year,

having reached a total of 267 in FY 1979. Most of these are Japanese.

Of particular importance to this analysis of potential OTEC cold

water uses, is the fact that Apra Harbor and the Port of Guam is one

of the best ports the western Pacific. There is room for expanded

growth of industrial and commercial activities should conditions

favor a greater usage, particularly if an industry could develop

which would take advantage of the superb harbor facilities. Over 373

acres of land bordering Apra Harbor have been identified by the U.S.

Department of Defense as excess land which can be released.

2-5

2.2.2 Cabras Island and Vicinity

The principal features of Cabras Island is the Port of Guam and

the power plant complex owned by the Guam Power Authority. The

proposed OTEC plant site is seaward of the Cabras Power Plant,

adjacent to the warm water discharge canal from this plant. From the

shoreline, the ocean bottom slopes off at a very steep angle, over 30

degrees at most parts and greater than 45 degrees for much of the

drop-off. The distance to a water depth of 600 meters is less than

one mile. At this depth, the water temperature is approximately 45

degrees F., providing a temperature difference from the surface of 40

degrees, very suitable for OTEC. Thus it is feasible to lay a cold

water intake pipe along the slope of the ocean floor from the

shoreline to deep water, and to locate the OTEC plant on land. This

greatly reduces the projected cost of an OTEC plant and makes this

site one of the best in the world for OTEC.

Presently warm water from the Cabras Power Plant is discharged

through a surface canal into the ocean just to the eastward of the

OTEC plant site. Therefore, it is possible to redirect this hot water

through the OTEC plant adding to the thermal resouce, and by mixing

this with the cold water discharge, to eliminate the thermal plume

from the outfall.

To the south of Cabras Island is an area of tidal flats, on

either side of Drydock Peninsula. The area on the southern side is

particularly large, and could be a possible site for mariculture.

Figure 2-3 shows these arrangements and areas of interest.

Approximately three miles to the south of Cabras Island is the

Guam Oil Refining Company (GORCO), with a petroleum pipeline

2-6

PHILIPPINE SEA
cam

CAMM" IMULAM tu ==$a

cow two us C@ a."
uwing R@
Pm p%w
P.M *an." .0 0.
us Umv no^L FL^T
OUTERAPRAHARBOR

LEGEND oww
NNW
It,
D
ft-
S=ftw

3@ 1-. LOW
BUREAU OP PLMMING 19"

Figure 2-3 Cabras, Island Guam OTEC Site

2-7

connecting the Port to the refinery complex. The refinery occupies

approximately 500 acres of land, and has a capacity of 35,000

bbl/day. Expansion is reported limited by availability of water. Cold

water from OTEC could be of use to a typical refining operation,

particularly where water supplies are limited.

The major population and coninercial center, Agana, is

approximately 5 miles from the OTEC site on Cabras island. One of the

major areas requiring air conditioning is the hotel area on Tumon

Bay, approximately 9 miles from the OTEC site. It is conceivable that

cold water could be piped to either or both these areas for space

cooling, although the economic suitability requires substantiation.

2.2.3 Environmental Data

The vicinity of the OTEC site and the neighboring commercial

facilities is characterized by:

1. A tropical reef, Luminao Reef,

2. A relatively barren ocean, nutrient poor near the surface,

3. A relatively undisturbed estuarine system,

4. A system of embayments, including tidal flats and mangrove

stands,

5. A very large and deep harbor.

The harbor operations include commercial and military ship movements,

and petroleum tanker offloading. Power plant condenser cooling water

is drawn from the ocean to the eastward of Cabras Island, and

discharged to the ocean northward through a canal through the island.

Indicative of the relatively low biological activity of the ocean

2-8

water is the near absence of biofouling in the power plant condenser

to the extent that chlorination is not required(!).

An assessment of the environmental conditions and potential

impacts of an OTEC plant on the environment is contained in a study

performed by Dames & Moore for the government of Guam [11 *. The

oceanographic conditions are described in a report on this topic by

the University of Guam Marine Laboratory (21

Figure 2-4, reproduced from Reference 2, shows the deep ocean

water temperature off Cabras Island. It is seen that 45 degree F.

water is achievable at a depth of 1500 ft. and that 41 degree F.

water is available at 2800 ft. depth. It is noteworthy that most

OTEC applications require reaching to a 3000 ft. depth to achieve 45

degree water. This points out one of the great advantages of Guam for

an OTEC site.

Figure 2-5 shows the nutrient content of the ocean water off the

OTEC site. It can be seen that the surface water is relatively

nutrient poor, typical of tropic ocean waters. By contrast, the

deeper water is relatively nutrient rich, indicating the possible use

of this water for mariculture activities.

Numbers-in brackets refer to References contai ned in Bibliography

2-9

En 80
M
P) 0-% 1
0 LjL
;j

rt
Cr.
M W
C3

W 50-
rt

----------
40-

MONTH (JAN. DEC.)

Mean monthly temperatures for surface, 1500, 2000, 2500 and 2800-3000'ft
the vicinity of Cabras Island, Luminao Reef and Glass Breakwater, Guam.

N03 -N (parts per million)

0 10 20 30 40
W j

310

620

930

1240

N -N
1550, PO,-F@,

CL
1860

2170

2480

279

3100
0 3
P04-P (parts per million)

Figure 2-5

Mean nitrate-nitrogen (NO -N) and reactive phosphorous (P04-P) profiles
from surface to 883 m (2980 ft) in the vicinity of Cabras Island, Luminao
Reef and Glass Breakwater, Guam (Feb., 1978 Feb., 1979).

2-11

3. APPLICATIONS OF OTEC COLD WATER UTILIZATION

3.1 DIRECT REFRIGERATION OR COOLING

3.1.1 Introduction

Cold water from OTEC could he used directly for cooling of

either materials such as foodstuffs, or of air spaces for air

conditioning. Rather than use electrically powered mechanical

cooling and refrigeration systems, cold water from the deep ocean can

be used under certain conditions. The temperature of the cold water

drawn from the deep ocean off Cabras Island for OTEC can be as low as

41 degrees F. and would probably not be above 45 degrees F. In

passing through the OTEC plant, the cold water temperature will rise

only a few degrees, thus will remain below 50 degrees F. For some

applications, this will be sufficiently cold. For others, the

coldest water will be required and cold water would have to be

delivered directly, bypassing the OTEC condenser. The cold water

temperature is limited to 41 degrees F. or higher so that

applications must be above freezing temperatures. However, cold

water can be used to precool so that freezing can be accomplished

with less net energy.

For utilization of cold water from OTEC for direct cooling,

proximity to the cold water is the primary requirement. This will

allow piping systems for delivery of the cold water to be reasonably

short. Some special situations may permit relatively long runs of

cold water piping.

3-1

3.1.2 Cold Water Quantities Required

Every pound of cold water absorbs 1 BTU for each degee F. rise

in temperature. Cold seawater, with a density of 64 pounds per cubic

foot, flowing through reasonably sized piping, has the capacity to

absorbe large quantities of heat and provide effective cooling.

Appendix A summarizes the calculations for relating air conditioning

and refrigeration to cold water flows through heat exchangers. The

results are summarized in Figure 3-1, which tabulates the flow rates,

flow areas, heat exchanger sizes, etc. needed to provide cooling.

3.1.3 Physical Arrangements

A temperature of 45 degrees F. is suitable for holding produce

or fish and is similar to temperatures of electro-mechanical

refrigerators. However for extended storage of fish, a lower

temperature may be required. This would require additional cooling

by electro-mechanical means beyond the capability of direct cooling

by OTEC cold water.

The use of OTEC cold water for air space conditioning could be

readily be accomplished with OTEC cold water, but the amount needed

in the near vicinity of the OTEC site is quite limited. To be an

effective utilization in large amounts, the cold water would have to

be piped to Agana or beyond, if economically feasible. It is not

projected that this would be an economic system; therefore, the

realistic utilization of direct cooling by OTEC cold water is in cold

storage wharehouse applications in expanded facilities at the Port of

Guam or new sites around the harbor, or for use by industries, In

this application, piping cold water to the refinery is feasible. The

3-2

A 1 ft. Diameter Pipe Provides:

Flow rate = 1. 96 cu -ft. Isec at flow velocity of 10 fps.

Thermal energy exchange = 628 BTU/sec at temperature
rise of 5'0 F.

Regrigeration equivaInt 188 tons

Space Cooling Capability of Cold Water Flow

Nominal 81 x 81 x 501 van requires: 1 ton refrigeration for

internal temperature of 45 to 50 OF.

Nominal 1 ft. pipe can cool a 2001 x 2001 warehouse.

Figure 3-1 Flow Rates, Areas, versus Heat Exhanger Sizes

3-3

major advantage of having large amounts of cold water available would

tend to be in support of new industry which could take direct

advantage of this resource. Aluminum processing or ammonia

manufacture would be particularly suitable for utilization of OTEC

discharge cold water. Having copious supplies of cooling water would

be a strong attraction to such industry, in addition ta the other

advantages offered by a Guam site.

3.1.4 Savings of E'nergy and Cost

The calculations of savings in electric power and energy cost

from using cold ocean water for cooling are also included in Appendix

A. The results are summarized in Figure 3-2, showing that the

savings can be appreciable, savt.ngs that.could be obtained by usi.ng

OTEC cold water, particularly if cold water were-to-be used by

expanded industry, wouTd b6-considerable.

3-4

ELECTRIC ENERGY REQUIRED FOR REGRIGERATION:

Each ton of refrigeration requires 10 kW power (33% efficiency)

COST SAVINGS FROM PIPED COLD WATER:

For 188 tons refrigeration - equivalent to cold water in a I ft. pipe

electric power cost savings = $197,000 per year.

Figure 3-2 Potential Savings in Energy and Cost

3-5

3.2 INDIRECT ASSISTANCE To r@OOLING SYSTEMS

3.2.1 Precooling

In the operation of refrigeration systems, warm fluid (air or

water) is drawn over the cooling surfaces to lower the temperature.

In the case of refrigeration or freezing of food produce, the food

material may be near natural air temperatures and have to be cooled

before low temperature storage or freezing. Thus if the temperature

of the fluid or food material coming into the refrigerator or freezer

is precooled to some degree, the total energy required for the final

lowering of temperature by the electro-mechanical system is reduced.

Figure 3-3 illustrates the concept of precooling.

The savings in energy and cost of electricity are calculated to

be significant if the equipment needed for precooling is part of a

total system for circulating OTEC cold water for multiple purposes

and several users. Then the cost of precooling would be that of the

individual heat exchangers for each application. Appendix A contains

the calculations reflecting the energy savings and cost estimates.

3.2.2 Providing Heat Dissipation for Cooling Systems

Many commercial and industrial processes involve an

electro-mechanical or thermal process where heat must be rejected and

dissipated from the system. For example, a mechanical refrigerator

uses energy to draw heat from the refrigerated space and reject the

heat through some device, typically an air cooled set of coils, a

cooling tower or similar device. Cold water from OTEC could be

utilized as a replacement for the air coolers. Figure 3-4

3-6

Precooler
Materials

at
Ambient
Temperatures

(80-85'F+)

OTEC
Cold
'Water

45-58OF

Fre er

20-30*F

Figure 3-3 Schematic for OTEC Pre-Cooling

3-7

illustrates the conventional and OTEC-modified arrangements. A

refrigerant-water heat exchanger would be employed in place of the

refrigerant-air heat exchanger. This is particularly useful in the

warm, humid climate of Guam where the efficiency of air cooled heat

exchangers is relatively low, and as a result, larger units are

required. The amount of heat exchanger area required is related

directly to the temperature difference between the refrigerant and

the air, or in the case of water cooled, between the refrigerant and

the water. Using cold ocean water would provide a much larger

temperature difference, and thus a lower amount of heat exchanger

surface area. Furthermore, the heat transfer from refrigerant to

water is more "efficient" than from refrigerant to air; i.e., the

heat transfer coefficient is much higher.

Another application where water cooling can assist is in

chemical-industrial processes such as petrolelm refining. These

operations also require rejecting heat, and large air cooling towers

are typically seen at petrolelum refineries or petro-chemical plants.

Similarly, industrial plants such as for aluminum processing or

ammonia manufacture need heat dissipation systems and often use air

cooling towers. Having cold ocean water available would aid in ths

design of these plants, and be an influence in attracting such

industry to Guam.

Finally, cold ocean water can be useful in steam condenser

applications, such as power plants. In the existing power plant on

Cabras Island, ocean water is drawn in to condense the steam

exhausted from the turbine. This water is raised in temperature as

it receives the heat rejected from the steam power plant, and the

3-8

Hot Exhaust Air

Very Warm
Waterl

Cooling
Tower

Fan Cooler Water

Ve Discharge
Wa7m

Water

Cool
Water

OTEC Cold Water

Figure 3-4 Schematic for OTEC Assisted Heat
Rejection System

3-9

heated water is discharged from a surface canal to the ocean. The

efficiency of the power plant can be lowered if the incoming ocean

water is too warm. Providing cold OTEC water to the steam plant

condenser intake could provide a higher thermodynamic efficiency for

plant operation and would correspondingly lower the temperature of

the condenser discharge. In fact, OTEC cold water provides the means

of totally eliminating thermal pollution from any power plant source.

However, another arrangement would direct the discharge water from

the Cabras Island Power Plant to the warm water intake of OTEC, where

it would be added to the intake of warm surface ocean water. After

passing through the OTEC evaporator, this warm water would be mixed

with the cold water discharge for release back to the ocean. In this

arrangement, the added heat in the Cabras Island Power Plant

condenser discharge water would improve the efficiency of the OTEC

power plant, and produce the most net gain in arrangement.

3-10

3.3 .4@RICULTURE

3.3.1 Introduction

The open ocean, approximately 90% of its surface, has been

described as a biological desert in that it produces a neglibable

amount of fish catch for world food. Coastal regions, in general,

comprising approximately 10% of the ocean surface, yields about half

the fish catch. One tenth of one percent of the ocean surface area

produces the other half. These are the regions of Owelling where

deeper ocean water, richer in nutrients, come to the surface water

region. Most fish gathering is done in a relatively primitive way,

comparable to the hunting economy of previous centuries. Farming the

sea may provide a greatly expanded source of food and other useful

products. Mariculture provides one of the possible means of

increasing the yield of seafood in a controlled manner.

The deeper water in the ocean is far more rich in nutrient

materials than the surface waters, particularly in the tropics.

Figure 2-4 had shown the concentration of two important biological

nutrients, nitrates and phosphates, in the ocean off Cabras Island.

It is clearly seen that the surface waters are relatively nutrient

poor, while the deeper water is relatively rich. The process of

pumping deep cold ocean water for an OTEC plant therefore delivers a

large quantity of nutrient rich water for possible use in

mariculture, i.e., stimulating marine biological growth to yield a

useful crop for food or other uses. The nutrients aid in the growth

of algae, most typically diatoms or kelp-like plants. The principal

usefulness of culturing algae is as an intermediate food for higher

3-11

biological forms which may be food for hun-ans. Certain shell fish are

very suitable for this type of mariculturp, particularly clans or

oysters. A finfish, the milkfish, is very suitable for mariculture

and is presently extensively "fish farmed" in Asia.

Much work which is relatable to Guam has been carried out in St.

Croix in the Virgin Islands. The physical and oceanographic

conditions are similar, and the experiments conducted there can

provide an indication of what may be expected at Guam.

Much of mariculture is hampered by the lack of available

nutrients. In the St. Croix tests, deep ocean water was pumped and

discharged into coastal ponds or impoundments inside the reefline.

The cost of equipment to pump the deep ocean water, including the

long pipeline, and the power requirement for continued pumping act as

impedements to extens ive use of this method. OTEC obviously provides

a virtually free supply of this nutrient laden water. Care must be

exercised in the amount of discharge introduced into the mariculture

system, particularly with respect to temperature control; but the

flows are readily controllable.

Mariculture can-take many forms, ranging from direct feeding of

fish in aquatic pens, to pumping nutrient rich water to stimulate

algae. The use of deep ocean water discharged from an OTEC plant, for

mariculture falls more in the latter category; however in practical

application, a complete mariculture system may involve several

biological levels and include higher animal forms which feed on the

plant growth stimulated by nutrient laden deep ocean water.

Therefore, mariculture connected with OTEC can be considered as

leading to both plant (algae) and animal (fin fish and shellfish)

3-12

yi el ds.

3.3.2 Algae

Two major forms of marine plant life, or algae, are most

probable of importance to mariculture on Guam: seawee d and diatoms.

Seaweed may be important as a direct crop used for chemicals and

other applications not directly applicable to food, and as part of a

complex of species enhancing the culture of edible forms. Diatoms may

be important as a means of converting the nutrients in the water to

life-forms and eventually as food for shellfish.

Although some seaweeds are eaten by humans in limited regions

and in limited amounts (e.g., Laminaria in Japan), most uses are for

natural chemicals. Red and brown algae, such as kelp, are harvested

in many parts of the world to produce agar and other substances which

yeild products such as gels used in baking and food thickeners. The

market for these materials is increasing, and could provide a

s4gnificant cash crop for mariculture. Some seavieeds tend to enhance

the growth of fish colonies, particularly in open tropical waters

where shade from direct sunlight is important.

Diatom growth, stimulated by nutrient rich water, can be

important to shellfish grovith. Certain species of clams, oysters and

other crustaceons are suitable to controlled culture provided

quantities of nutrient rich water is available in areas suitable for

impoundment. One of the limitations on this approach to mariculture

has been the deep ocean water, and much of the cost of the product

can be attributed to the cost of equipment and power expended to pump

the deep water to the surface. With OTEC providing this virtually

3-13

free, mariculture through diatom nourishment for shellfish uptake is

far more economically feasible.

Thus algae mariculture probably would involve both the growth of

seaweeds, as part of the ecosystem and for harvest for chemical

products, and the growth of diatoms as eventual food for shellfish in

impoundments.

3.3.3 Shellfish

As indicated in the previous section, oysters and clams may be

grown in mariculture farms as a result of OTEC providing nutrient

rich deep ocean water for diatom growth. Experiments conducted in St.

Croix, Virgin Islands, indicate that if suitable impoundments can be
established, that the succession of algae to shellfish is quite

feasible. To become economic, the total process must be carried out

with low cost equipment, minimal cost for operational-supplies and

labor. The cost of providing deep ocean water can be slight to

negligible as a result of OTEC, therefore shellfish maricultlure can

be a profitable industry on Guam, both for local consuption and

export.

3.3.4 Finfish

Most species of fish desired as food are carnivors and not

readily suitable for mariculture, unless smaller feed species are

cultured. Generally, the more layers or levels through which a

mariculture process must pass, the greater the overall cost. Thus

direct mariculture of seaweed is economically favorable. Culture of

diatoms for further culture of shellfish is relatively favorable. A

3-14

three level system, culturing algae for small herbivors as food for

the final food fish, would appear to be too many steps to be

economic. However, it is possible that certain specific conditions

could be favorable. However, there are certain herbivorous fish that

are useful for food. The so-calledl milkfish (Chanos Chanos) is

fish-farmed in Indonesia and Phillipines. This could be a very

desirable species for ultimate consumption.

3.3.5 Conclusion

It is probable that a successful mariculture project would

involve several species and more than one layer of culture. Both

seaweed and diatom algae would be useful for direct product yield, in

the case of certain brown algae, and as an intermediate step for

shellfish or finfish harvest. The physical conditions of available

impoundments are of primary importance, as this will affect the cost

of installation and operation of such a commercial enterprise.

3-15

4. IMPLEMENTING THE UTILIZATION OF OTEC COLD 1,14TER

4.1 SHORT TERM UTILIZATION

There are certain immediate applications for OTEC cold water

that could be implemented readily, particularly for existing needs,

or for relatively short-term expansion of facilities. These are

principally:

(1) Tying in to Cabras Power Plant

(2) Providing cool water to Port of Guam for air conditioning

and refrigeration,

(3) Cooling water to Guam Oil Refining Company,

(4) Small scale mariculture.

The principal basis for the short term applications is low cost

distribution of the cold water to users that have existing needs for

the cold water.

The tying in of the Cabras Island Power Plant would be

accomplished as part of the construction of the OTEC power plant.

Most probably, the warm water discharge from the existing power plant

would be directed to the OTEC warm water intake, and thus would be

part of the intake installation for the OTEC plant.

Supplying cold water to the Port of Guam could be accomplished

by relatively low cost piping in shallow trenches running directly

from the OTEC site for the short distance to the Port of Guam. From

this point, the cold water would be distributed to a few heat

exchangers for air conditioning and refrigeration. From here, the

cold water, now warmed a few degrees in the chill water refrigeration

4-1

and air conditioning systems, would be further piped to an area south

of Drydock Island for mariculture. The piping would be of minimum

cost, probably PVC, and would be exposed as much as possible to the

surface to warm the water before release into the mariculture area.

The providing of OTEC cold water to the GORCO area would be the

most ambitious effort, but could have longer range benefits. This

would require the installation of several miles of pipeline to the

refinery area. After use in the refinery, the cold water effluent

would be pipelined to the coastline further south for release. At

this location, a potential future large scale mariculture project

could be installed. The scale of this installation and the magnitude

of costs and operations are such that this could be more a long term

utilization than a short term one. However, the initial usage.is for

an existing industria 1 facility, GORCO, and thus falls within the

category of a near term utilization.

4-2

4.2 LONC TERM UTILIZATION

There are applications for OTEC cold viatpr that could be

implemented sometime in the future, along with the development of

expanded facilities or the addition of new industries into Guam. In

fact, the availability of OTEC electric power and OTEC cold water

byproduct could attract some enerly intensive industries, such as

aluninum refining or ammonia production. Exapanded facilities might

include food freezing, processing and transhipment facilities at the

port. A large scale, commercial mariculture development could be

included in expanded commerce. Indeed, Guam could be one of the world

centers for mariculture with the availability of copious amounts of

nutrient laden deep ocean water. To enjoy the benefits of such

expansion of conrnerce, provisions for cold water utilization would

have to be made at the earliest stages of design of the first OTEC

plant nn Guam.

The following steps are considered key to implementing long term

utilization of OTEC cold water:

(1) Develop a master plan, or as a sub-section of a Guam

economic development or port development plan, include a layout

of cold water piping systems that could be included in future

expansions.

(2) Inform all potential users of expanded facilities of the

availability of cold water from OTEC.

(3) Insure that no specific environnental permits are required

for any individual user of cold water; i.e., prequalify the use

4-3

of 'UTEII cold water by a generic environmental permit.

(4) Rijn controlled experiments, including discharging deep cold

ocean water into significant areas to measure the effect, if

any, on the environment. This might he part of the program to

obtain the generic environmental permit in (3) above.

4-4

5. ECONOMIC IMprTS OF OTEr rOLD 14ATER 'TILIZATION
U

5.1 CONSTRUCTIOM COSTS

There are two main sectors in construction costs: piping and

heat exchangers. The piping cost varies considerably with the type of

material used, the degree of insulation, if any, and the burial or

physical protection measured used in installation. The heat

exchangers will tend to have a standardized cost per unit of heat

transfer area. The cost of heat exchangers are thus relatable

directly to the amount of cooling being provided.

The pipeline cost is similar to,electric power transmission

facilities in that they represent an initial capital cost and are

expected to require relatively low maintenance costs. This analog,"

also provides a means of understanding why cold water distribution

must be limited to large volume users with relatively short

transnission distances. An electric power line can be installed

overhead with much smaller cost per unit energy transferred than a

cold water pipeline, for either small users or over long distances.

Therefore, the estimated pipeline installation has been limited to

the vicinity of Apra Harbor.

The construction cost estimates are included in Appendix C.

These are detailed out for the following cases:

1. Cold water to Port of Guam for reefers and air

conditioning,

2. Cold water tie-in to Cabras Island Power Plant,
3. Cold wat@r for mariculture in Apra Harbor vicinity,

4. Cold water to GORCO and distant imariculture complex.

All cost e stinates are based on unit values, thus if the estimated

5-1

costs of any given unit is varied, the total construction cost

estinate can easily be adjusted. For example, a unit cost of pipeline

for a given diameter per foot length is used. If one can obtain pipe

at a different cost, the estimate can be adjusted by a simple

multiplication factor.

Cost formulas are either of two forms for pipeline or heat

exchangers respectively:

For pipeline:

DIAMETER X COST/LENGTH X TOTAL LENGTH X FLOW FACTOR X

TEMPERATURE FACTOR

For heat exchangers:

COST/UNIT AREA X TOTAL AREA X TEMPERATURE FACTOR

5-2

5.2 EMPLOYMENT RESULTING FROM OTEC COLD WATER UTILI14TION

There will be two principal areas where employment will be

generated as a result of the utilization of OTEC cold water:

employment associated with construction, and emmployment associated

with operations.

Employment during construction will be a result either of the

installation of cold water piping and heat exchangers, or as a result

of expanded construction to take advantage of the availability of

ocean cold water. The latter category will generate the largest block

of employment since this could include new plant facilities which are

a direct result of the cold water opportunity.

The employment resulting from piping and heat exchanger

installation has been calculated, as shown in Appendix D, to involve

construction-type la bor, and will produce 2345 man-days of labor for

the near -term installations in support of food produce regrigeration

and air space conditioning, and mariculture. Power plant condenser

cooling water modifications (to divert the warm water discharge into

the OTEC intake) are considered to be included in OTEC plant

construction costs. Most of this labor could come from native sources

with only limited importation of labor needed.

The employment resulting from new plant facilities can be

extensive. It is considered that at least, new wharehouse facilities

will be constructed for food handling or processing, and that

mariculture facilities will be fabricated and installed. For these

activities, at least 20 man years of labor will be developed.

These estimates are based on the near-term, utilization of OTEC

cold viater without major industrial expansion. However, if OTEC power

5-3

and OTEC cold water were to attract major new industrial additions,

particularly for aluminum processing or ammonia manufacture, the

employment effects would be enormous. It is difficult to estimate the

full extent of this employment impact, it can be so extensive.

However a conservatively low estimate is that if either one of these

new industries were to be established in Guam, at least 200 direct

new jobs would be generated, and another 400 supporting new jobs. The

employment impact would be even greater when the multiplying effects

on the local economy are taken into account. Using estimates for the

multiplier effects of new job creation in an area such as Guam, over.

1000 additional job-equivalent employment activities would result

from a single unit of industrial expansion. These additional jobs

would be in the service areas, more port-associated labor, and in

commerce which suppl ies good and services for the new industry.

5-4

encroachment on possible future expansion of the port, if the area

were well to the South of Drydock Peninsula inside Sasa Say. There is

the possibility that the nutrient rich @dater, after passing through

the mariculture growth area could further stimulate algae in other

parts of Apra Harbor and thus have a negative potential for

commercial activities. However, this is a controllable situation, and

should not be allowed to become a major problem.

It is more probable that large scale mariculture would take

place at locations outside the immediate Apra Harbor area,

particularly if the concept of routing the cold water to the refinery

area and then southward to the coastline where large mariculture

impoundments could be effective. Large scale mariculture could have a

considerable impact on the Port of Guam, particularly as it could

create a need for foo d processing, storage and shipment facilities.

Indeed, mariculture could be one of the major revenue generators for

Guam and make it one of the leading world centers for this commercial

activity.

5-8

0 APPENDIX A

COLD WATER DIMENSIONAL REQUIREMENTS

A. INTRODUCTION

This appendix provides data on the required length, diameter,

and water flow through piping and on the requirements for heat

exchangers for cooling by OTEC cold water.

B. COLD WATER CONDITIONS

The lowest temperature that could be provided by the OTEC system

is 41' F. if the cold water were delivered directly from the cold

water pipe. If water were used after passing through the OTEC plant,
the cold water temperature would range from 45 to 50' F.

C. PIPE SIZE AND FLOW RATES

A n ominal pipe size is chosen, and a reasonable flow rate; then.

any other pipe size, flow rate or temperature gain allowed in the

cold water can be used to calculate the BTU's extracted by the cold

water, by a simple multiplying factor.

The nominal pipe is: I ft.

The nominal flow is: 10 ft./sec

The nominal temperature drop is: 5 F.

Thus the thermal energy absorbed by the nominal set of conditions is:
1 j UF rX 10 Fr15-FL - 5' 0,F A-6 PI-S

X /0

tons refrigeration.

5-9

D. NOMINAL COOLING REQUIREMENTS

For the volume of a standard seavan, approximately 1 ton of

refrigeration is required to maintain its interior at approximately

45 to 50 F. in Guam.

The flow through the nominal pipeline will maintain a warehouse

of approximate 200 x 200 ft. dimensions at a comparable temperature.

5-10

0 APPENDIX 8

COLD WATER UTILIZATION ENERGY AND COST SAVINGS

A. INTRODUCTION

This appendix provides data on the savings in electric energy

and costs resulting from the utilization of cold OTEC water for space

cooling and refrigeration.

B. ENERGY REQUIREMENTS FOR REFRIGERATION

Each ton of refrigeration requires 12,000 BTU/hr energy

transfer, or 3.52kilowatts of power transfer each hour of operation.

Assuming a conversion efficiency of 33%, approximately 10 kW of

electric power is required per ton._

C. COST SAVINGS FROM PIPED COLD WATER

For 188 tons of refrigeration, the consumption of 1880 kWh per

hour at a price of $0.12/kWh requires an hourly expenditure of $22.56

per hour, or $541 per day, or $197,000 per year.

5-11

BIBLIOGRAPHY

I. Westinghouse Electric Corporation, July 1980. A Study to Determine
the Commercialization Potential of Open Cycle OTEC Water Plants.
Prepared for U.S. Department of Commerce, Maritime Administration,
Office of Commercial Development.

2. Francis, E. J.,December 1977. Investment in Commercial Development
of Ocean Thermal Energy Conversion (OTEC) Plant-Ships. Prepared for
U. S. Department of Commerce, Maritime Administration, Office of
Commercial Development.

3. Evans, D. J. and McDonald, K. R., September 1979. OTEC Environmental
Package - A Semi-Annual Updated Report. Prepared for U. S. Department
of Energy.

4. CHAO-HSIN WEI, BIN-JUINE HUANG and MING-SHENG KONG, January 1980.
Engineering Analysis of Pumping Cold Deep Nutrient-rich Seawater for
Mariculture and Nuclear Power Plant Cooling. Reprinted from
Proceedings of the National Science Council, VOL 4, No. 2, pp. 133-
142, April 1980.

5. Lather, Jay, L., Apri'l 1980. Energy Considerations in Guam's Future
Political Relations with the United States.

6. Pinkert, Walter, F. & Associates (undated). Guam Ocean Thermal Energy
Conversfdn (OTEC). Prepared for the Guam Society of Professional
Engineers.

7. Lassery, Dennis, R., July 1979. Oceanographic Conditions in the
Vicinity of Cabras Island and Glass Breakwater for the Potential
Development of Ocean Thermal Energy Conversion on Guam, University
of Guam Marine Laboratory.

8. Port Authority of Guam, July 1979. Economic and Land-Use Plan for
Cabras Island and Surrounding Area.

9. Tokyo Electric Power Services Co., LTD. (TEPSCO) 1977. Proposal for
Ocean Thermal Energy Conversion Plant in Guam Island.

10. Princeton Energy & Environmental Research Co., June 1980. OTEC
Domestic Social and Economic Impacts. Prepared for U. S. Department
of Energy.

11. Burwell, Delbert, N., and Naef, Frederick E. (undated). Mini-OTEC
Results. Prepared for the 7th Energy Technology Conference.

5-12

12. Government of Guam, Guam Energy Office & Bureau of Planning, June 1980.
Planning for the Prevention of Environmental and Recreational Losses
Due to Ocean Thermal Energy Conversion Development on Cabras Island,
Guam. Prepared for the Coastal Energy Impact Program, National
Oceanic and Atmospheric Administration.

13. Dames & Moore, October 1979. Environmental Impact Report Projected
OTEC Development for the Territory of Guam. Prepared for Coastal
Energy Impact Program, Guam Coastal Management Program, Bureau of
Planning.

14. U. S. Department of Energy, May 1980. Ocean Energy Systems
Multiyear Program Plan,

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