The Project for Ocean Thermal Energy Conversion (OTEC)
and its Multi-purpose Utilization in the Republic of Palau
Gregorio Decherong
Ministry of Resources & Development
The Republic of Palau
1.

Understanding of Pacific Islanders for the Crisis and Way out
The most profound global threat facing humanity today is the prospect that our economic

activities result in global warming, with serious consequences for the earth’s entire ecosystem andfor the way of life in rich and poor societies alike.
The global warming and climate change triggered by the increase of CO2 is not just a matter ofcritical, but survival in Palau. It is proved that Palau is one of the four countries which are facing
the greatest risk in the world because the sea-level rise will lead to the loss of coastal zone of thecountry. The expected sea-level rise would inundate the lowland, damaging coastal croplands anddisplacing millions of people from small island communities. Water resources of small islands are
at risk also. Seawater intrusion will degrade the quality of underground water and reduce thequantity of fresh water supplies. The recent El Nino has caused severe draught in the pacific region
as well as in Palau.
On the contrary, the flood is causing a spill out of coastal soil to the sea, destroying thelivelihood as well as the agricultural production of the islands, also giving a severe impact to themarine life, and may cause a decrease of fish resources. Palau is proud of its beautiful islands andocean surrounded by coral reef, which makes the place one of the most beautiful scenery in theworld. Tourism with its beautiful natural resources represents industry in Palau, however thesea-level rising would totally destroy the industries and economic activities of the country. Energyin Palau is totally depending on the imported oil, of which purchase cost is equivalent to 10% of
Gross Domestic Products. Considering the above situations, people must change the energy
system, which is based on fossil fuels.
In this context, Palau chaired the South Pacific Forum in 1999 and appealed to the world
the characteristics of island country, which have limited energy resources, land and undergroundresources, unstable water resources, and tourism are the basis of islands economies, and therefore
islands countries must preserve the ecosystem. At the representative conference, it was recognized
and confirmed that energy system of island country must be self-sufficient, and stable water
resource development is quite important. Thus, the country is actively appealing to the developed
countries on the decrease of CO2 amount, as well as the establishment of domestic policy on theshift of diesel-powered generation to that of utilizing renewable energy. Contrary to the limited

resources in the islands, the surrounding ocean is an immense source of energy and water.
2.

Achievement of Palau for the Practical Use of Ocean Thermal Energy Conversion
In order to convert the energy sources to renewable energy, Palau kept her eyes on oceanenergy, and especially on the Ocean Thermal Energy. Ocean Thermal Energy Conversion (OTEC)
is a technique in converting the thermal energy to electricity from temperature difference between
the warm surface and cold deep seawater. The ocean is occupying 2/3 of the whole earth surface
area and always receiving solar radiation, thus the ocean thermal energy is huge and renewable
resource. According to the data, temperature differences between surface and 1000m depth at theequatorial region of the Pacific Ocean, includes the Palauan sea, is the biggest and most favorable
for OTEC.
There are other merits of OTEC, such as:
No emissions of green house gas such as CO2 gas.
Stable power generation through the year, no matter what climate such as Solar PV or Wind.
Under the initiative of the former President Nakamura, the Government ofPalau has started its study on the Ocean Thermal Energy Conversion since 1999 and has requested
technical cooperation from Saga University of Japan. This policy is being carried over to theAdministration of the new President Tommy E. Remengesau Jr., and in April 2001, theGovernment of Palau has signed an Agreement on the research and development with Saga
University as well as Japanese private company Xenesys Inc.
By the series of researches and studies conducted under this Agreement, it has resulted that;
There are many potential sites, which are close to the deep sea, suitable for the Ocean
Thermal Energy Conversion along eastern coastal line of the Island, which is estimated tofulfill the power demand of the country;
Permanent water resources can be expected by the spray-flash desalination plant which
utilize temperature differences of the sea water after power generation; andDeep seawater can be utilized as natural resources such as for air conditioning, fish culture
and production of mineral water.
3.

The Grand Project of OTEC and Multi-purpose Utilization in Palau
Ministry of Resources and Energy carried out survey on several possible OTEC site andmarine investigations with Saga University and Xenesys. Inc., which is a private engineering
company of Japan, and the survey team reported the feasibility of comprehensive ocean energy
utilization project in Palau. The outlines of the Grand Project are described as follows:(1) Power Generation
The present public power supply in Palau is generated completely by diesel engine. The
main power stations are located in Koror and southern Babeldeob Island, with total generating
capacity of 24.8 MW, which can hardly meet the demand of the island.
When development of Babeldaob Island, such as metropolitan relocation to Melkeok androad network maintenance, was taken into consideration, the demand rate would increase andprobably its increasing rate would be accelerated in the future. Therefore, an increase in 4% a year
until 2010 expects 23 MW (1.5 times) of peak loads, thus 35 MW is required as the power
generation capability. Department of Resource and Energy in Palau planned to provide 20 MW in
the electricity demand in 2010 with OTEC. Shortage during peak hours and detached islands withsmall population was considered to compensate with diesel power generation. Then, the amount ofgross power generation is set to 30 MW for 20 MW electric power supply.
In the east coast of Babeldaob Island, which is the largest island of Palau, the geographicalfeature, which the depth of water becomes deeper on the outside of the lagoon, is the most optimal
to pump-up deep seawater, to utilize for the OTEC plant. The coast of Pelilue and Angaur Island
are also suitable. Moreover, in order to lessen a power transmission loss, the locations should be
distributed in 7 sites to cover the nation. It is proposed that around ten sets of 2 to 4 MW plant will
be built in the future. The proposed site is shown in the table below and Figure 1 shown in next
page.
Table.1 Location and Size of Potential OTEC Site in PalauPotential OTEC Site
Size of OTEC plant
Melkeok
3MW x 2 + 4MW x 1 = 10MWAirai
3MW x 2 + 4MW x 1 = 10MW
Ngarchelongs
2MW x 1= 2MW
Ngaraard
2MW x 1= 2MW
Ngiwal2MW x 1= 2MW
Peleliu
2MW x 1= 2MW
Angaur2MW x 1= 2MW
Total
30MW
(2) Seawater Desalination for Permanent Water Resource
There are still about 15℃ temperature difference between cold water after OTEC power
generation and surface water. This thermal energy can desalinate seawater 1,200 m3 per day per
1MW OTEC plant. When a total of 30MW OTEC plants are installed, fresh water ofapproximately 30,000 m3 per day will be available automatically. The amount of fresh water fully
covers the water demand of Palauan domestic use, which is in total 9,500 m3 per day (500 liters perperson in 19,000 population), hotel consumption by the tourists, agricultural use and industrial use
are included. It must be specially mentioned that this fresh water resource is permanent.

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

Angaur St.
2MW OTEC

Melkeok St.
10MW 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

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

Figure. 1 Grand Master Plan of OTEC Power Station in Palau(3) Aquaculture and other utilization of Deep Ocean Water(A) Fishery Culture and Seawater Ice Production
Since sunlight does not reach the deep-sea water, which is deeper than about 200m under sea
surface, photosynthesis of seaweed and plankton are not performed. Therefore, nutritive
substances, such as Lynn, Kay Acid, and Nitrogen, are contained abundantly, and oxygen
concentration is relatively high. Then, the deep seawater can be supplied to culture pond andplankton can be proliferated, and the best environment can be provided to fishery culture.
Fishery nursery shall be built near this plant, and it will raise as a main export industry. In theupland, the pipeline from this plant will supply the deep seawater directly.
In order to store various marine products in its freshness, a lot of ice is necessary. Utilizing
surplus deep-seawater and electric power after the generation, ice also can be manufactured, thus
contributes to keep the marine products fresh, especially those for export.
(B) Deep Ocean Mineral Water Production
Abundant nutritive substances mentioned above are contained in the deep seawater. Moreover,in the deep-sea, disease, germs and microbes, such as bacteria, can hardly reproduce and theinfluence of air pollution can be ignored, so it is highly regarded its safety. That is the reason why
the product development using deep-seawater is performed in various places in recent years.
Then, a part of deep-seawater pumped-up as the cooling water of OTEC will be moderately
mixed at the plant with pure water manufactured in the desalination plant, and the mineral water
will be merchandised. It will not only fill domestic demands, but also it would be valuable export
merchandise.
(C) Air conditioning and Greenhouse by Cold Seawater
The temperature of cold seawater after power generation and desalination will be about 13℃,
and very suitable for air conditioning use. Fresh water is first cooled at about 15 to 18 ℃ by cold
seawater using the heat exchanger. The fresh water is circulated through the cooling coil laid in
the ceilings, as a result, room temperature can be maintained by about 23 to 25 ℃.
The cold seawater is used also to control the temperature of the greenhouse, like the airconditioning system for the buildings. The cultivation of vegetables and fruits, which cannot beproduced in the tropical region, will be grown easier in the air-conditioned environment. It canbe considered to utilize the minerals obtained from the ocean depths or by-product for thehydroponics as nutrient.
(D) Hydrogen Manufacturing
Development competition of the fuel cell has already started by the manufacturers worldwide

now. If fuels for vehicles and boats in Palau are converted to hydrogen, people can keep
minimum consumption of fossil fuels. It will also put up the value of tourism-based country.
However, supply of the hydrogen is also one of the subjects. Then, the fresh water with very highpurity refined by the OTEC plant is electrolyzed with self-generated electric power, which
manufactures hydrogen, is planned. Since impurities are hardly contained in the purified waterby the OTEC, efficiency of procedure is very high and maintenance/ management also becomeseasy. Moreover, cheaper hydrogen can be manufactured using the surplus electric power at night.
(E) Lithium Recovery
In the seawater, minerals, such as lithium, are in abundant. First of all, the lithium ion containedin the deep seawater, which finished its use as cooling water, can stick to a manganese dioxide
adsorbent column. Then, it is made to melt from the column with dilute-hydrochloric-acid water,
and finally 99% or more of high purity chlorinating lithium can be taken out. Since impurities,
such as organic matter and plankton, are hardly contained in deep seawater, it is mentioned thatthe absorption and melt are very efficient.
(F) Fertilization of Seawater by Density Current Diffusion Equipment
Nutrition ion, such as nitrogen and phosphorus, is contained abundantly in the seawater. If it ispumped up near the surface, where sunlight can reach, phytoplankton and algae will increase.
Increased phytoplankton and algae mean increased number of fish. As a result, rich fishingground like that of South America such as Peru will be formed. However, only by scattering on asurface as it is, cold deep-sea water sinks again and plankton is not reproduced. Then, mixing
warm surface water to deep seawater in this plan and discharging after the density adjustment,
the density current, which flows at a level into the layered seawater, would be generatedartificially. As a result, nutrition ion is made to spread and pile up at a large area and the ocean
would be fertilized. In the future, the development of the marine ranch is aimed at using thistechnology. If this is in practical use, the developing countries that are troubled not only withwater shortage but also with food difficulty will be supportable.
4.

The Pilot Project(1) Aim of the Pilot Project
It is considered that the comprehensive utilization of ocean thermal energy is available for
all Pacific Islands Nations, which are Federal States of Micronesia, Marshall Islands, Philippines,Kiribati, Nauru, Tuvalu, Samoa, Vanuatu, Solomon Islands, Cook Islands, Tonga, Fiji, NewCaledonia, Papua New Guinea, etc.
Once the project proves its feasibility, there are great chances to obtain finance source forthe construction cost, from lending institution such as the World Bank, Asian Development Bank,and many private bank which provide soft loans.
In order to prove the practicality and economic feasibility of OTEC and multi-purpose
utilization, The President of Palau, Tommy E Remengesau Jr. and the Government of Palau areproposing to the Pacific Nations to let Palau be the show case of natural energy and water supply
system from the ocean for the pacific nations, by its first pilot OTEC power plant and spray-flash
desalination plant, as multi-purpose facilities.
This pilot project provides chances to researchers and manufacturers for proof,
improvement and integration of their technology for commercial scale OTEC Plant for 3 to 10MW.
Moreover, the project aims to demonstrate OTEC system including desalination and application
technology and enlighten the leaders and citizens in the world to promote natural energy andmulti-purpose utilization of DOW, and also to train engineers to maintain and control OTEC andmulti-purpose utilization plants.
(2) Outline of the Pilot Project(A) Project Site
The pilot project site is planned to be located on Melekeok State of Babeldaob Island among theseven sites of the Grand Plan. The Government of Palau is promoting the development of thisBabeldaob Island vigorously now, for example the metropolitan relocation to Melkeok andbeltway (Compact Road) construction. In the new capital, the Diet Building, the Executive
Office of the President, the Supreme Court, etc. are under construction, and will be completed in2003 including the surrounding infrastructure.
Furthermore, the recent marine investigation executed by Saga Univ. shows that the coastline
along the proposed new Capital is very suitable for the construction of the pilot plant. The
proposed project site is shown on the map as Figure 2.
(B) Major Specifications of the Pilot Project
OTEC power generation plant: 3MW by Uehara cycle method
Desalination plant :1000 m3/day by spray flash method

Mineral water manufacturing plant:

20m3/dayHydrogen production :1 Nm3/hOff-shore Laboratory :Researchers+Technician=Total 40

Off-shore mounting barge :1 barge for plant and 1 barge for lab
Total : 2 Barges. Barges are fixed in the lagoon

Seawater Intake and discharge system :For deep seawater :φ1,600mm x L 3,000m x 2 lines

Inlet to be set at 800 m depth, out of coral reef
φ1,600mm x 2 lines

For warm seawater :Inlet to be set in the coral reef
For discharge water:

φ1,800mm x 2 lines
Outlet to be set out of the coral reef

Heat exchange system for air-condition: For new capitol area 300kW
Transform and power supply facility :2,300kVA

Supply pipeline for deep seawater :100m3/day

Supply pipeline for fresh water :100m3/dayConnecting road between off-shore
plant and lab :W 8m x L 600m

Breakwater facilities:
Supplementary facilities:

Greenhouse with cooling, workshop

Others :Equipment for R & D and education

The image of the pilot plant is shown on Figure 3.
(C) Implementing Schedule of the Pilot Project
1st YearInvestigation, survey and basic design

2nd Year

Detail designing and manufacturing of equipmentrd3 Year

Plant and seawater intake system construction

4th Year

Deployment, installation and operation(D) Approximate Cost for the Pilot Project
It is estimated as US$ 125 million (or Yen 15.6 billion)

Figure 2. Proposed Project Site

Figure. 3 Imaginary of Pilot Project