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Ocean Thermal Energy Conversion (OTEC)and &Deep Ocean Water Applications(DOWA).market opportunities for European industry.
A summary of the paper presented at an EC conference on "New and Renewable Technologies for sustainable development", in June 2000, at Madeira Island, Portugal.

Michel GAUTHIER. IOA Acting Chairman;
Lars GOLMEN. Norwegian Institute for Water Research (NIVA);
Don LENNARD. Ocean Thermal Energy Conversion System Ltd


IOA's review of the most recent results obtained (mainly in USA, Japan, India and Taiwan) indicates that the Deep Ocean Water should be now considered as a renewable resource for ?clean? production of many commercial products including not only electricity but also fresh water, food, energy saving, air-conditioning, etc. Technologies to tap into these resources are available and OTEC/DOWA facilities can contribute to the development of isolated coastal areas located in the tropical belt and some sub-tropical areas. But OTEC/DOWA according to the criteria adopted by the European Union Commission for defining the priorities of its Fifth Framework Program has not yet reached the status of ?already developed technology? as are wind, photovoltaic, biomass, and other energy resources located in the European continental region.

This paper made a case for the European Union Commission to assess the full potential of OTEC/DOWA and support its development as it already represents : a) export markets opportunities for European industry, b) opportunities for the development of European Overseas Territories, and c) potential supply of synthetic fuel to respond to Europe's own future demand for primary energy and world sustainable development.


This section of the paper, as presented at the Madeira conference, described the beginnings of OTEC- d'Arsonval in 1881, Claude in 1930 and so on; how OTEC systems work; pointed out the environmental benefits; briefly described the developments following World War 2; and concluded by referring to the huge drop in crude oil prices in 1985-86 which led to a worldwide loss of interest in all renewable energies - all of which will be well known to the readers of this IOA Newsletter.


As a result, since 1986 European countries have put on hold all practical activities in OTEC. But research efforts have continued in Hawaii at the US Natural Energy Laboratory of Hawaii Authority (NELHA) and in Japan where several research facilities have been funded by JAMSTEC and local Prefectures in Kochi (1989), Toyama (1995) and Okinawa (2000). The effort is still directed towards OTEC to produce electricity. Main results are : the one year operation of a 200 kW gross power Open-Cycle OTEC at the NELHA in 1992, the design of a 1MW elec. floating OTEC to be installed in 2000 by a joint Japanese-Indian venture (Saga - NIOT), offshore the Tamil Nadu coast and the growing interest of Korea and Taiwan for OTEC as a contributor to their energy demand. Modular OTEC plants of several hundreds of MW have been designed. They are mounted on floating platforms either anchored offshore and connected to shore by an electric cable, or ? grazing ? the heat stored in huge warm water ?pools? that exist in tropical oceans to produce transportable liquid fuels (energy carriers).

Deep Ocean Waters (DOW) are not only cold, they are also nutrient rich, and clean and free from surface layer germs and pollutants. In the short term, by sharing among several users the cost of pumping the DOW, the OTEC multi-products concept is expected to help to develop small OTEC plants of a few tens of MW, to supply electricity, fresh water, etc. to small coastal communities located in the tropical and some sub-tropical regions.

In the medium term, floating OTEC plants of a few hundreds of MW capacity could supply a significant share of the need for electricity in industrialized countries with direct access to the resource. A one GW OTEC has a production capacity of 7 TG kWh/year (equivalent to 1.54 Mtoe).

In the longer term OTEC could also produce synthetic fuels, like ammonia or hydrogen, on-board of OTEC platforms to supply liquid fuel (energy carriers) to any country in the world. A one GW liquid ammonia OTEC plant could produce 0.6 Mtoe of NH3 fuel per year.

The tropical ocean regions most suitable to extract OTEC power have an approximate area of 60 million km2. The power that can be generated per one square kilometre area of the tropical ocean without significant environmental effect is estimated to about 0.2 MWe. . And an approximate estimate of the scale for the world OTEC resource is 12,000 GWe or 18 Gtoe i.e. twice the 1990 world demand for primary energy.

In its principle OTEC is a base load solar renewable energy, available 24 hours a day. It does not produce any heat or chemicals (except for spurious use of antifouling agents) as do fossil and nuclear energy. Local natural ocean circulation and stratification may be somewhat modified by OTEC plants, and in turn have some effect on the distribution of the solar heat in our Earth biosphere, but this is likely to be of significance only if a considerable density of very large OTEC plants are considered, which then raises the question of the actual consequences and limitation of OTEC's intensive exploitation.

Small multi-products OTEC can be commercially attractive when the prices of oil fuel and fresh water reach respectively $US 30 a barrel and 0.85 $ m-3 but in general the main obstacle to OTEC development is its capital cost. As for most other renewables the cost of OTEC energy is claimed to be too high to generally compete with traditional supply. Obviously this situation would change if one considers the environmental and social costs of traditional energy. And it is significant that, since the Madeira paper was presented, crude oil prices have gone above $35 a barrel!

There are also other obstacles to OTEC development presently. One - and true of nearly all new technologies as they are introduced - is the lack of experience with the operation of an OTEC pilot plant of sufficient size and duration to build up confidence of investors for OTEC technology, and to better assess its environmental benefits and the limit of the resource.


In 1950 the world energy consumption was 1.6 Gtoe with a population of 2.5 billion. In 1995 consumption had risen to 9 Gtoe with a population of 5.7 billion. Hundreds of books and reports have been written to describe the present characteristics of the world energy supply, its main issues and predictions for the coming decades. In what follows the information source is the OECD 1999 report ?Energy : the Next Fifty Years? . The present main features of the global primary energy supply are:
a) The supply is based on burning fossil and nuclear fuels i.e. non-renewable resources. Ultimate Proved Recoverable Reserve (PRR) for oil and natural gas liquids is estimated to be 146 Gtoe with a present consumption of 3.3 Gtoe/year; PRR for coal is 994 Gtoe with a consumption of 4.6 Gtoe/year; PRR for uranium is 3 Mtu with a 1996 consumption of 0.036 Mtu/year.
b) The geographical distribution of the major resources : oil and gas, is different from that of the main consumers. The situation generates dependence and vulnerability of supply and is a source of severe conflicts.
c) The annual average energy consumption per capita varies by more than a factor of 100 between the richest and the poorest countries: the world average consumption is ~1.6 toe/year per capita with 4.5 toe/year for OECD countries and 0.05 toe/year for less advanced countries.
d) With carbon dioxide emission and storage of nuclear wastes the current energy supply system presents severe threats to our natural environment.
e) This supply system is incompatible with sustainability.

The OECD study considered three different cases for predicting the changes in the supply system and examined three time periods starting from now to 2020, to 2050 and to 2100.

The first study cases involved (A) ? Business-as-usual ? scenarios implying a high growth for future development without significant changes in the world energy policies and international relations. One scenario (A1) assumes high future availability of oil & gas resources until the end of the 21st century. A second (A2) scenario assumes oil & gas resources to be scarce resulting in a massive return to coal. A third scenario (A3) assumes rapid changes in nuclear and renewable energies that result in phasing-out fossil fuels, for economic reason rather than for resource scarcity.
The second case (B) scenario assumes moderate economic growth, more modest in the developing countries than in other scenarios, and modest technology progress.
The third case (C) scenario is the most challenging with a progressive change in energy policies and a strong incentive to use energy with ? sobriety ? and more efficiently. It includes ? green-taxes ?, (e.g. carbon taxes), and changes in international co-operation and international agreements that are focused on environmental protection (e.g. greenhouse gas mitigation) and international equity, with strong economic assistance and technology transfer.

For the period from now to 2020 the general trends are :
a ) The demand will continue to be met mostly by fossil fuels because of the lack of economic viability of non-fossil sources (for wind and solar photovoltaic), or lack of public acceptance (for nuclear). Oil will remain the dominant fuel and gas will catch up slowly with coal. The share for nuclear power will remain static. Renewables will grow but their scale will remain small. For most renewable energies, site specific issues and political considerations will dominate over economic considerations.
b ) The geographical pattern of energy demand has shifted from the developed to the developing countries : from ? North ? to ? South ?.
c ) ? Business-as-usual ? trends will dominate. Unless new policies are put in place to curb energy uses and greenhouse gas emissions, the total world energy demand is projected to increase from 9 Gtoe in 1990 to a maximum of 15.4 Gtoe in 2020 with a net carbon dioxide emissions increase of 80 per cent. Together with China, the developing countries will account for almost 70 per cent of that increase.

For the longer term period from 2020 to 2100 the global results are:
a) The maximum total demand for primary energy may rise from 15 Gtoe in 2020, up to 25 Gtoe in 2050 (and 45 Gtoe in 2100).
b) The energy market will continue to grow primarily in the developing world.
c) The increase in energy supply will be accompanied bywith a change in primary energy structure. At least through 2020, the world will rely upon fossil fuels, with relatively few opportunities for alternatives. After 2020, despite a wide range of uncertainties on the level of energy demands across different scenarios, the results start to diverge and depend on political choices and development strategies chosen in the first decade of the 21th century.

Among the three cases, only the case C scenario is in full compliance with the short term carbon dioxide Kyoto limits. According to the C scenario, in 2020 with a world population of 8 billions the minimum demand for primary energy is predicted as 11.4 Gtoe including a share of 2.4 Gtoe for renewables. In 2050 with a population of 10 billions the minimum primary energy demand will be 14.2 Gtoe with the share of renewables over 5 G toe.

Among all scenarios the maximum future shares for renewables are for the A scenario : as high as 3.3 Gtoe in 2020 and 7.3 Gtoe in 2050. See Table 1.

Table 1 Scenarios, main features and results for 2050 and 2100 compared with 1990.

OECD report

The 3 Main Scenarios

Case- A

High Growth

1990 - 2020 - 2050

Case B

Middle Course

1990 - 2020 - 2050

Case C

Ecologically driven

1990 - 2020 - 2050

Population, in billions
1990 - 2020 - 2050

5.3 - 7.9 - 10

5.3 - 7.9 - 10

5.3 - 7.9 - 10

Resources availability
-Non fossil







Technology Costs for:
-Non fossil







Technology Dynamics for :
-Non fossil







Environmental Taxes




CO2 emission constraints




Primary Energy Demand in Gtoe

9 - 15.3 - 24.8

9 - 13.5 - 19.8

9 - 11.4 - 14.2

Energy Demand for Renewables in Gtoe

1.6 - 2.5/3.3 - 5.5/7.3

1.6 - 2.3 - 4.4

1.6 - 2.3 - 5/5.6

from   ?Energy : the Next Fifty Years?.

Albeit the global potential of renewables is large, their development has environmental and social impacts too, that we don't really know. Also the priority for development of renewables is not the same for all countries. It varies with the state of development of the countries, their geographical locations, their specific natural resources, and the sensibility of their populations to environmental problems.

To illustrate possible OTEC markets, the PAS ("Pacific Asian") region ( called : "other" Pacific Asian, in the OECD's report) was selected as one region of main interest since most of these countries have direct access to the OTEC resource.

The PAS region contains countries with different level of interest with respect to OTEC. There is a group of small isolated archipelagos including Fiji, Kiribati, New Caledonia, Tonga, Western Samoa, French Polynesia, Solomon Island and Vanuatu, and a group of 7 big countries including Korea, Taiwan, Indonesia, Philippines, Malaysia, Myanmar and Thailand.

The population of the PAS region will grow from 430 millions in 1990 to 620 millions in 2020 and 750 in 2050 The OECD predictions of the minimum and maximum annual shares for renewables and nuclear for the region are shown Table 2. The OECD predictions also indicate that the PAS demand for electricity will grow from an equivalent of 25 Mtoe in 1990, to a Min/Max of 80/100 Mtoe in 2020 and to 174/260 Mtoe in 2050. A part of this PAS demand can be provided by OTEC.

In the first group of small archipelagos which has a population (and then an energy demand) less than 0.5% that of the other group, the priority demand is most probably for small OTEC electricity plants to supply coastal communities of a few thousands to a few tens of thousand inhabitants with electricity, energy carriers and other DOWA's products. Their future demand could probably be met with a few hundreds plants of 1 to 10 MW for a total capacity in the range of 500 MW to 1 GW, constructed with rugged prefabricated modular equipment. (It is important to highlight that the marine area of the Exclusive Economic Zones (EEZ) of this group of small countries is probably above 15 million km2 and represents approximately ? of the world OTEC resource area).

The 7 large countries of the "other" group also have small isolated coastal communities and a demand for small OTEC/DOWA but in the long term they should be more interested in the development of OTEC plants with several hundreds of MW capacity which could contribute significantly to their need for renewables. Assuming a global share for renewable energy of 30 Mtoe for OTEC in 2020 (less than 10 % of the 376 Mtoe PAS maximum demand predicted for renewables) and a share of 160 Mtoe for 2050 (about 20% of the 2050 maximum demand), the total PAS demand for OTEC would be around 20 GW in 2020 and 100 GW in 2050, representing fleets of one hundred and five hundred 200 MWe OTEC floating plants respectively.

Table 2
Minimum and maximum annual shares for renewables and nuclear
in primary energy supply. Results for PAS region.

Supply in Mtoe




Total Primary Energy


843 to 1136

1239 to 2008



82 to 187

7 to 330



318 to 592

357 to 998



97 to 144

137 to 384



4 to 43

24 to 209



234 to 376

576 to 800

                              from ?  Energy : the Next Fifty Years?.

4 ) CONCLUSION : Assessing OTEC possible markets for the European Industry.

To respond to the future demographic and economic growth while maintaining our environment to a certain level of quality and minimizing the risk of severe accidents and conflicts between nations - in other words to allow a worldwide sustainable development of our human societies - it is necessary to increase the world primary energy supply, to develop cleaner and safer energy sources and also a more effective utilization of energy.

The pressure of public opinion will be decisive in the choices. Strong public policies and important investments are needed to develop cost effective enabling technologies and to control the environmental consequences of their intensive usage. This can only be achieved if an international agenda is set to include joint mechanisms for implementation of coherent national policies and co-operative R&D programmes.

OTEC can become a significant resource of renewable energy. In the short term the DOW resource can serve the interest of small, more generally poor, isolated coastal communities whose EEZs represent a major share of the world OTEC resource. In the longer term, OTEC development could serve the interest of all nations including industrialized ones located in the ? North ?, far from the tropical and sub-tropical zones. For the IOA, an international association created in 1990, to promote the international co-operation for OTEC R&D, these facts are favourable clues for establishing new deals in international co-operation based on common interests and solidarity.

In March 1992 a panel of IOA experts was invited to participate at a workshop to inform the European Commission on OTEC and DOWA technologies, and to determine the appropriateness of European involvement and support in that field. Although the Commission did not follow up the set of recommendations that resulted from the workshop, the benign, base load characteristics of OTEC and DOWA, together with the products in addition to energy, appear to make a strong case further to assess the techno-economic viability of this renewable resource

This presentation of recent results obtained worldwide from OTEC R&D invites the European Union Commission carefully to assess the techno-economic viability and the full potential of OTEC, together with other DOWA products , and consider supporting their development as they represent : a) new market opportunities for European maritime and energy industries willing to invest in a low/no-emission energy production system. b) political and economical interest for the development of European Overseas Territories and developing countries associated with the European Union, and c) potential sources of supply for synthetic fuel (energy carriers) to respond to global future demand for primary energy and for world sustainable development.

REFERENCES - as used for the Madeira paper

Pouvoir d'achat du franc de 1901 ? 1996, Le Particulier N˘X 899 (Mai 1997).

The Pioner OTEC Operation ? La Tunisie ? . IOA Newsletter Vol 2, Spring/Summer 1991.

Don Lennard. Ocean Thermal Energy Conversion. Survey of Energy Resources, 1998. p.331. World Energy Council.

Luis A.Vega, Donald E. Evans. Operation of a small Open-Cycle Ocean Thermal Energy Conversion Experimental Facility . IOA Newsletter Vol 5/ Autumn 94.

M.Ravidran, NIOT. ? Indian 1 MW Floating Plant: an Overview ?,IOA??9 Conference IMARI, Japan.

Thomas H. Daniel, The Natural Energy Laboratory of Hawaii Authority: A State-sponsored Aquaculture and Research Park. IOA Newsletter Vol 10, Summer 1999.

Carrie Matsuzaaki, University of Hawaii. IOA??9 Conference a Success. IOA Newsletter Vol 11, Spring 2000.

Avery and Chih Wu. Renewable Energy from the Ocean; A guide to OTEC. Oxford University Press 1994.

S. Dunn and Patrick Takahashi. Artificial Upwelling for Environmental Enhancement. IOA Newsletter Vol 8, Dec. 1997.

L.A.Vega, PICHTR,USA. Economics of of Ocean Thermal Energy Conversion. IOA Conference, Brighton UK 1994.

Energy : the Next Fifty Years. A 1999 publication by the Organization for Economic Co-operation and Development, (OECD).( includes results drawn from different scenarios studied by the International Energy Agency Institutes (IEA), the International Institute for Applied Systems Analysis (IIASA) and the World Energy Council (WEC).

World Energy Council. Survey of Energy Resources 1998.

M.Gauthier. OTEC/DOWA in the European Union Renewable Resources development strategy. IOA Newsletter Vol 9/ Autumn 1998.

The Fifth Framework Programme. The research programme of the European Union 1998-2002. Report 18764 EUR. ISBN 92-828-5811-1