OTEC Power Generation Saves Mankind

Dr. Haruo Uehara, President
Saga University
Japan

OTEC Power Generation Saves Mankind
Dr. Haruo UEHARA President
Saga University
1 Honjo, Saga, Japan 840-8502
Phone: +81-952-28-8100 ; Fax: +81-952-28-8822
E-mail ueharah@cc.saga-u.ac.jp

Introduction
Foodstuffs, water, energy and comfortable living environment are indispensable elements forhuman beings to sustain modest daily life. In pursuit of better and peaceful life we have been
struggling to think of improved means on many fronts and a lot of wonderful inventions have beenmade. Science and technology have thus been progressed. So is our civilization too.
Today at the beginning of the 21st century, however, we are confronting to new problems. They areglobal warming of the earth, energy crises, population problem, foodstuffs problem and water
problem. People call them the 5 major problems in the 21st century.

The major cause for global warming is blamed at burning of fossil fuels such as oil, coal and gas in
the developed countries since 1850s. Utilization of fossil fuels has spewed huge volume of CO2
gas into the air.

And the overall CO2 density on the earth has been increasing ever since.

Rising of the sea surface level and irregular climate changes are immediate issues brought on by
global warming of the earth. Republic of Palau, Republic of Nauru and Fiji are, among other South
Pacific island nations, most severely hit by this dreadful phenomenon. It is our grave concern oftoday that some of them are already loosing the precious coastlines to the seawater due to therising of the sea level. Seawater erosion into living houses, mixing of seawater into fresh drinking
water, invasion of seawater into farm land are taking place commonly in these countries. And
unexpected heavy drought occurs occasionally.

It is well known to us that these man-made misfortunes and irregularities are happening not only inthe regions I just mentioned but also in many other parts of the world. But I say that we, the earth
fellow, must put the first priority to challenge the problems the South Pacific island nations arefacing to. In order to help preserve the beautiful countries in the region and for happiness ofwonderful people there we must get together and do utmost efforts to realize commercial OTEC
power generation plants.

Among other issues to tackle the global warming problems I have been urging to build OTEC
power generation plants in the South Pacific island nations. I am very pleased to address at thisForum the following subjects;
1) Temperature distribution of seawater and principle of OTEC technology2) ,High potentials of seawater in relation to OTEC technology,
3) History of development of OTEC technology,4) Impact of OTEC power plants,
5) The Indian 1000 kW OTEC power plant and India’s future trend,6) OTEC technology and multifunctional systems and7) Floor plan to build an OTEC power plant in the South Pacific island countries.

2. Temperature distribution and principle of OTEC technology
2 – (A)

Temperature distribution of seawater:

Fig. 1, which depicts seawater distribution near Palau, Fiji, Nauru and the nearby region,
provides us with the following information.
Temperature(℃)

Temperature(℃)
Depth(m)

5

10

15

20

25

30

Depth(m)

0

0

-200

-200

-400

-400

-600

-600

-800

-800

-1000
-1200

AugustFebruary

10

20

-1000

30

AugustJanuary

-1200
-1400

-1400

Marshall Islands （off the coast of Majuro）

Micronesia (off the coast of Pohnpei)
from Japan Oceanographic Data Center

Fig.1-1 Seawater Temperature in the countries
participating in Pre-World Water Forum in PalauTemperature(℃)

Temperature(℃)
Depth(m)

5

10

15

20

25

30

0

Depth(m)

5

10

15

20

25

30

0

-200

-200

-400

-400

-600

-600

-800

-800

-1000

-1000

February
August-1200

February
August

-1200

-1400

-1400

Fiji Islands
Temperature(℃)

Samoa

Temperature(℃)
Depth(m)

5

10

15

20

25

30

Depth(m)

0

0

-200

-200

-400

-400

-600

-600

-800

-800

-1000

15

20

25

30

March
September

-1200
-1400

-1400

JamaicaTemperature(℃)
Depth(m)

10

-1000

October
February

-1200

5

5

10

15

20

25

30

0

Depth(m)India (off the coast of Tuticorin)
Temperature(℃)
5
10
15
20
25
30

0

-200

-200

-400

-400

-600

-600

-800

-800

-1000

March
October

-1200
-1400

-1000

AugustFebruary

-1200
-1400

Tonga

Kiribati (Christmas Islands)
from Japan Oceanographic Data Center

Fig.1-2 Seawater Temperature in the countries
participating in Pre-World Water Forum in PalauTemperature(℃)
Depth(m)

5

10

15

20

25

30

Temperature(℃)
Depth(m)

5

10

15

20

25

30

0

0

-200
-200

-400
-400

-600
-800

-600

AugustFebruary

-800

-1000

AugustFebruary

-1200
-1000

-1400

Guam

Saipantemperature(℃)
Depth(m)

5

10

15

20

25

Temperature(℃)

300Depth(m)

-200

-200

-400

-400

-600

-600

-800

-800

5

January
September

-1200
-1400

25

30

March
October

-1200
-1400

Cook Islands
Temperature(℃)

Temperature(℃)
5

10

15

20

25

30

Depth(m)

0

0

-200

-200

-400

-400

-600

-600

-800

-800

-1200

20

-1000

Australia (off the coast of Cooktown)

-1000

15

0

-1000

Depth(m)10

AugustFebruary

5

10

15

-1000

20

25

30

AugustJanuary

-1200
-1400

-1400

Taiwan (off the coast of Ho Peng)

Philippines (off the coast of Manila）
from Japan Oceanographic Data Center

Fig.1-3 Seawater Temperature in the countries
participating in Pre-World Water Forum in Palau

[℃]
0

0

5

10

15

20

25

30

35

-250

[m]

-500
-750

-1000
Anguar Data
Melekeok Data

-1250
-1500

Seawater temperature

(1)

Koror

Palau

Melekeok

Anguar［ SITE2 ］［ SITE1 ］

Land survey
from 9am to 3pm
on December 10,
2001
Ocean survey
from 7am to 9am
on December 14,
2001

Ocean survey
from 3pm to
5pm
on December
13, 2001

From Report on OTEC Site in Palau

Fig.1-4 Seawater temperature in Palau（1） Surface seawater (at less than 50m from sea level) is warm at 25〜32℃. We callseawater with warm temperature “Warm Sea Water”.
（2） Seawater temperature in the depth of 1000m or more is always cold at about 4〜5℃.
Seawater in the depth of 300 m or more is called “Depth Sea Water”. Sea- water in the
Depth sea water is referred to “Cold Sea Water”.
（3） We know from the above that there is the temperature difference between warm andcold seawaters is about 21〜27℃.

2 – (B)

Principles of OTEC technology

Power generation by OTEC technology is to utilize the temperature difference between warmand cold seawaters. There are 4 different “Cycles” known for this technology, they are① Rankine Cycle② Kalina Cycle③ Uehara Cycle and④ Open Cycle.
Rankine Cycle will be the ideal model for non-professional people to get to know of
the basics of OTEC technology, although Uehara Cycle f my own invention can
attain the most effective cost performance as compared to the others.

Fig. 2 explains the basic principle of OTEC technology.
① As shown, there are 6 major component machines and equipment in an OTEC power plant.
They are Evaporator, Turbine, Condenser, Working fluid pump, Warm seawater pump andCold seawater pump. These are interconnected with each other by pipings.
② Evaporator has a lot of thin metal plates installed in it. We fill it with a substance, which
evaporates at a fairly low temperature at 20〜30℃. This substance is referred to Working
Fluid. Ammonia NH3 is regarded the most suitable one at the moment. Surface seawater of
20〜30℃ temperature taken up by Warm Seawater Pump will be directed to flow throughthose thin plates in Evaporator. Then, liquefied ammonia sitting in Evaporator gets heatedby warm surface seawater and becomes steamed ammonia.
③ Ammonia-steam goes into Turbine passing through Evaporator pipes, by which Turbine
starts rotating.
④ Generator coupled to rotating Turbine starts running to generate power.
⑤ In the meantime, ammonia-steam which has lost its temperature after doing its business in
Turbine is to be drawn into Condenser, which has a similar construction to Evaporator with

many thin metal plates. Cold Seawater at 5〜8℃ flows through Condenser’s thin plates,
then portion of steam in ammonia-steam gets condensed at opposite side of plates andthere remains only liquefied ammonia.
⑥ The liquefied ammonia will then be sent back by Working fluid pump (or ammonia pump) to
Evaporator. Continuous operation of the above mentioned cycle enables us to getelectricity from seawater only almost on permanent basis.
Warm Seawaterat Surface

TurbineGenerator

Light

Ammonia

Evaporator

Ｐ
Pump

Condenser
Pump

Ｐ
Pump

Ｐ

Ammonia
Cold Seawaterin Depth

Fig. 2 Closed Cycle

2 – (C) Now, about Uehara Cycle:
It is theoretically proven that even Rankine Cycle OTEC technology combined with Uehara system
can generate power more economically than other power systems like thermal, solar energy andwind power. But I would strongly recommend to go with Uehara Cycle for enhanced economics ofpower generation.

Rankine Cycle is designed to use pure ammonia as Working Fluid, while it is a Mixed Mediums ofammonia and water that is used in Uehara Cycle. Heat efficiency attainable by Uehara Cycle ishigher by 50〜70% than that of Rankine Cycle. This means that, for the same output capacity of
OTEC power plant, our method consumes far less, say 70〜100% less, volume of surface andcold seawater as compared to the needs by Rankine Cycle. This influences greatly on economy of
OTEC power plant.

The principle of Uehara Cycle is given in Fig. 3.

Fig.3 Uehara cycle①

Mixed Medium of ammonia and water will be sent first by two working fluid pumps into
Re-generator and then further into Evaporator.

②

Warm seawater pump takes in surface seawater into Evaporator, where liquid portion ofammonia-water gets evaporated and it turns into mixed vapor of ammonia-water. As thismixed vapor is a saturated vapor, it gets separated in Separator into ammonia water andvapor containing ammonia-water. Mixed vapor of ammonia-water goes in Turbine #1 anddrives this Turbine to rotate. Part of mixed vapor, which comes out of Turbine #1, will be
extracted into Heater and the rest of them is directed into Turbine #2 to drive Generator.

③ In the meantime, ammonia water separated in Separator passes through Re-generator andthen into Absorber via pressure reducing valve. In Absorber ammonia water absorbs mixed
vapor from Turbine #2. Some of mixed vapor which Absorber can’t possibly take will becooled down and condensed by cold seawater to turn into liquid. Working fluid pump takes it
into Heater and it is then forwarded again back to Evaporator.
④ Repetition of this operation ensures power generation by seawater alone on permanent
basis.

3. History of development of OTEC technology
The principle of OTEC technology is not of any new invention, but rather very old.

It goes back to 1881, when a French scientist Mr. J.D’Arsonval had announced for the first time in
the world history his principle theory of OTEC power generation, The year 1881 enjoyed anotherepoch making history. A proto-type model of thermal power plant was introduced for the first timein human history. As far as OTEC technology goes, another French scientist Mr. G. Claude had
most actively challenged in trying to enhance the technology for commercial use. He had
repeated a lot of experiments and tests but no positive results had been obtained. Then, theresearch study of OTEC technology had gradually come to stop until 1973,largely because offlooding supply of fossil fuel into the market.

But this situation had suddenly and drastically changed in 1973 when soaring price shock of oil
was announced. This incident had brought economic confusion to many parts of the world but
Japan was hit particularly severely. We refer that year to the year of “oil shock”. After the oil shockin 1973, researchers in Japan as well as in the USA started to look into OTEC technology seriously.
The USA government at that time had endorsed OTEC study a national project and allotted at one
time a budget of US$10 billion. They had built two pilot plants during that stage of research
programs. But today they have scaled down their study programs.

Japanese government had also launched right after the oil shock year a vigorous project titled“Sunshine Project”. A number of power generation companies and other institutes had participatedin the research studies and several pilot plants had been put up since then. But after some yearsof hectic studies all of them had retired from the scene, saying they had failed to get persuasive
data to go further.

On the contrary to the above, we at Saga University have been conducting strong efforts since theyear 1973 without intermission to bring forth OTEC technology applicable for commercial use. We
have built so far 11 pilot plants, which are quite essentials for our studies and analysis of all
possible aspects. We firmly believe that we have now reached a stage to be able to put our OTEC
technology into commercial application.

In the meantime, we have obtained a number of international patents. National Institute of Ocean
Technology, Chennai, India, who is the authoritative research center of marine related projects in
India, had built a floating type of 1000kw OTEC pilot plant under our technical assistance andcooperation. And as far as I know, planning of OTEC power plant are under way in Republic of

Palau, Cook Islands, Taiwan, the Philippines and others.

4. Impact of OTEC power plants
Currently we are all confronting to serious problems such as ;(1) environmental problems,(2) energy problem,(3) population problem,(4) foodstuff problem and(5) water problem.
These 5 problems are all inter-related each other.
Primary suspect of environmental problems is utilization of fossil fuels such as coal, oil and gas.
Burning of fossil fuels spews CO2 and NOX into the air. CO2 has triggered the global warming. The
worsening global warming causes melting down of glaciers in the Arctic and in turn brings about
rising of seawater level. Due to this, flat land area is getting smaller globally, while desert in the
USA and China keeps expanding its territory much larger.

Rainfall sprays massive NOX contained in acid rain and damages forests. Forests with damaged
tress loose its water holding capacity endorsed to forests. Rained water flows down immediately
into rivers and to sea. Water availability on land thus gets smaller and shortages of water andfoodstuffs are looming as the serious problems in the 21st century. To loose valuable trees andforests means lesser availability of phytoplankton in the sea, which definitely causes reduction ofmarine life such as fish, shells and algae and seaweed. In other words, food chain on the scale ofthe plant earth is being threatened now by the global warming.

As such, it is the most important and urgent tasks to solve this environmental problems, which
bend over us as a matter of life-or-death in the 21st century.

Any attempt to solve these criticalproblems, however, must generate public interest by bringing continued growth of economy. In thissense, I am very much convinced that OTEC power plant has the greatest possibility to attainimprovement to the environ mental conditions and also continued economic growthsimultaneously.

Now, let us review once again.

(1) OTEC technology and environmental problems
Environmental problem is of course directly connected to the other 4 issues and it sits in thecenter of these issues.
① OTEC power plant exhausts far less volume CO2 as compared to thermal power plant andsolar battery method. We have made thorough calculations of exhausted CO2 . Pleaserefer to table 2 for this information. As is given there, OTEC is categorized the power
generation method to exhaust the least minimum CO2. Actually it is only 2.4% of thermal
power plant operated by LNG. From this, if 10% of the world energy sources are switched to
OTEC technology, we can reduce CO2 emission drastically globally.
② Deep cold seawater pumped up into OTEC power plant is rich in nutrition. This nutritious
seawater can be sprayed after passing through OTEC system over to surface seawater. This
will reduce the density of inorganic carbon substance molten in surface seawater. According
to the latest reports, 30µmol CO2 per 1kg seawater can be drawn into sea from theatmosphere.
③ CO2 exhausted on land can be reduced by drawing it into depth sea water. This means there
is another possibility of economic gain by building an OTEC power plant, whereby you could
trade the CO2 emission right with advanced countries who are under the international
obligation to reduce CO2 emission,(2) OTEC technology and energy saving:① There are almost 100 countries in the world who could offer ideal place for OTEC power
plant. Within the exclusive economic zone of Japan alone there is a possibility to generate
1014 kWh OTEC power plant, which is equivalent to 8.6billion tons of oil. If even 1% of thishuge energy consumption can be switched to source of OTEC, then we are talking about
very bright future surrounding the environmental problems.
② The 21st century is sometimes referred to the age of hydrogen. OTEC technology provides
easy access to make hydrogen from desalinated fresh water using its own electricity.
Hydrogen is deemed to be a “future fuel” for internal combustion engines, since it exhausts
no toxic substances at all. Most ideal is, however, to produce fuel battery utilizing thishydrogen. Fuel battery shall become definitely a major energy source in the 21st century.
③ It is known that uranium and lithium are contained richly in deep cold seawater. The
technology to extract these substances from seawater are making big progresses. The
South Pacific island nations have a great potential to become eligible exporters of suchenergy,.

(3) OTEC technology and water problem
Instead of relying on natural rainfall, which is quite often contaminated with toxic substances like
NOX, people can now resort to OTEC technology for supply of fresh drinking water. For yourguidance, a 100 MW OTEC power plant with Uehara Cycle version with 26℃ surface seawaterand 6℃ deep cold seawater deals with a flow of 160 tons per second warm seawater and 176
tons cold seawater flow. Abundant volume of fresh water and also mineral water is right there.

5. The Indian 1000 kW OTEC plant and India’s future trend
As was briefly touched in the Chapter 3 above, Indian government has completed the constructionof a floating type OTEC power plant of 1000kw gross output capacity and is now holding the barge
at a pier before the hurricane season there passes away. We Saga University had played a goodrole in this Indian project by rendering our expertise.

Fig. 4 is the picture of this Indian OTEC power plant installed on a barge, which is scheduled to bemoored at about 35km off Chennai coast toward Sri Ranka.

Fig.4 The Indian 1000 kW OTEC plant6. OTEC in Palau and its multiple-purpose use plan
In order to combat global warming problems and also to spur their economic development, theGovernment of Republic of Palau had been keeping an eye on possible introduction of OTEC
power plant in their county. Their ultimate goal is said, as far as we are informed, to switch fromfossil fuels to seawater for all needs of electricity. To obtain fresh water from seawater is an easytask for OTEC power plant by applying our patented desalination technology.

We are very pleased to announce hereby that we Saga University has, jointly with Xenesys Inc., aJapanese private sector company, signed an agreement with Palauan government on technicalcollaboration on OTEC technology. In accordance with the said agreement, we have studied
basics on temperature distribution of seawater etc. along the coast of Palauan islands andestablished 7 possible sites for OTEC power plant. Our study indicates that a total of 30MW OTEC
power plant at two different sites would be large enough for the time being to cover the total
demand of electricity.

I am sincerely wishing that the above plan would be put into practice at the earliest possible date.

Ngarchelong St.
2MW OTEC
with- Potable Water
Production- Aquaculture- DOW Ice
Production

Ngaraard St.
2MW OTEC

with- Potable Water
Production- Aquaculture- DOW Ice
Production

Ngiwal St.
2MW OTEC

with- Potable Water
Production- Aquaculture- DOW Ice
Production

Melkeok St.
10MW OTEC

Angaur St.
2MW OTEC

with- Potable Water
Generation- Aquaculture- Local Area
Chilling
Service- DOW Ice
Production

with- Potable Water
Production- New Capital Area
Chilling Service(for office, hotel)- DOW Ice Production- Hydrogen
Production

Peleliu St.
2MW OTEC

with- Potable Water
Generation- Aquaculture- Local Area
Chilling Service- DOW Ice
Production

The first priority to beoffered to initial 3MW
of Melkeok St..

Airai St.
10MW OTEC

with- Potable Water Generation- Local Area Chilling Service- Hydrogen Production

Fig.5 Grand Master Plan of OTEC Power Station in Palau

7.Conclusion
I may say that OTEC technology is gaining the worldwide attention as one of the most reliablemeans to give a solution to the 5 major problems in the 21st century I mentioned in the beginning. I
firmly believe OTEC technology is a good news particularly to countries who are suffering fromlack of fresh water and energy. We are ready and happy at any time to exchange views on what
we can possibly offer to the needed.