OCEAN THERMAL ENERGY

THE PROSPECTS OF GENERATING RENEWABLE ENERGY TILL ETERNITY: NOT NUCLEAR,
BUT FROM THE THERMAL-ENERGY DIFFERENTIAL OF THE WATER DEPTH OFF SABAH TROUGHby

Dato’ Ir Dr A. Bakar Jaafar[1]

Malaysia is not yet on any global map showing the areas with the potential of generating ocean-thermal energy. However, with the completion of a recent marine survey in the South China Sea during the period 2006-08 (MyMRS)[2], it has been confirmed that indeed the temperature at the bottom of the North-Borneo Trough (and also known as “Sabah Tough”) at a water depth of 2900 metres (m) is about 3 degree Celsius (º C), compared to that of the surface at about 29º C. According to the popular scientific literature, any area with such a temperature-differential of over 22º C has the potential generating not only renewable energy but also freshwater[3].

Nonetheless, the latest technology using a highly efficient cycle called "Uehara Cycle” which has been developed by Dr Haruo Uehara, a former President of Saga University, can generate electricity with temperature difference of only 15º C and also desalinate seawater with 5º C temperature difference. As long as there is temperature difference, power generation and desalination are possible regardless whether or not the site is within tropical or subtropical region. That also implies that “waste heat” from industries can be recovered as energy source. This technology is called Discharged Thermal Energy Conversion (DTEC). DTEC system has been under operation at oil refineries in Chiba Prefecture[4].

Most of the planet, over 70 per cent of its surface, is covered by the oceans and their adjoining seas, and they absorb a staggering amount of energy from the Sun each day. Ocean thermal energy conversion, or OTEC, taps into this energy to produce electricity.

Ocean thermal energy conversion relies on the fact that water near the surface is heated by sunlight while seawater deep in the dark is much colder. OTEC plants use warm surface water to heat ammonia or some other fluid that boils at a low temperature. The resulting gas is used to drive turbines that produce electricity. The gas is then cooled by cold water pumped up from the ocean depths and the resulting fluid is recycled to help generate power[5].

In other words “OTEC is a power plant to use warm surface seawater to evaporate working fluid of ammonia-water, and then the ammonia vapor drives turbines to generate electricity. The ammonia vapor is cooled by cold deep seawater to be condensed and the re-liquefied ammonia-water is recycled as the working fluid.”[6]

In fact, the history of this technology is not that new; the basic of which was introduced by a French scientist Mr. A. D'Arsonval in 1881, over a century ago. Since then, there had been hardly any development or interest until the oil crisis in 1970s. Particularly, researchers in Japan, and in the USA as well, were strongly motivated for in-depth study of OTEC. The said professor at Saga University of Japan started in 1973 his OTEC study and since then, his study team has been tackling all sorts of theme needed for the realization of a commercial OTEC plant. They have built so far 11 experimental plants, acquired the necessary technical data and know-how, and have registered a number of patents both in Japan and in other countries.Xenesys Inc., Ltd., Japan, a company undertaking the commercialization of the Saga University's OTEC study, also took part in the research and development works at the university and was granted in January 2000 by the Japanese Ministry of Education to acquire all patents held by Saga University.

Among many events in the short history of the technology development is the experimental 1MW project by National Institute of Ocean Technology (NIOT), Chennnai, India, that is worthy of special mention from the point of view of its output capacity. The plant, which has been put into operation since mid 2001, has been a stepping stone for a commercial use of OTEC: Prior to this, Saga University succeeded with 1 kW experimental plant in 1977; The Mini-OTEC project by USA was a success with 50kW gross power in 1979; Tokyo Electric Co., and its subsidiary undertook successful experiment of a 120 kW OTEC in the Republic of Nauru 1981; Kyushu Electric Co., of Japan succeeded with their 50kW OTEC in Tokunoshima island in 1982; A 75 kW experimental OTEC plant was installed at Saga University in 1985; USA completed their 210kW open cycle OTEC plant off coast of Kona,Hawaii, in 1993; and Saga University built another experimental 4.5 kW OTEC plant with a newly invented cycle in 1994.[7]

Further development in Japan since 2001 has been the completion in 2002 of Enzan Facility at Enzan City, Yamanashi Prefecture which is equipped with fully automated pressing and welding lines for the production of heat plate exchangers, the key device for the OTEC, thermal energy, and seawater desalination systems; the establishment in 2003 of the Institute of Ocean Energy, Saga University (IOES) with the following activities: basic experiment facility for 30kW OTEC power plant utilizing “Uehara Cycle”; basic experiment facility for seawater desalination system utilizing spray-flash evaporation method (10tonne/day); basic experiment facility for production and storage of hydrogen; basic experiment facility for extraction of lithium from deep seawater; and simulation experiment facility for environmental impact study of deep seawater; and in 2004, the completion of the basic design of power generation system for DTEC to 4,000kW in winter, (and 3,300kW in summer), which is a joint research project undertaken by Chiyoda Corporation, Fuji Oil Co., Ltd. and Sumitomo Chemical Co., Ltd., with the support of New Energy and Industrial Technology Development Organization (NEDO), and Sodegaura Oil Refinery of Fuji Oil Co. Ltd, Japan.

What’s the potential in Malaysia, off the Sabah Trough? Based more on the advanced “Uehara Cycle”, than on the classic Rankine Cycle, 1 MW of power could be generated by “pumping” 1.5 cubic metre of “cold water” from a certain depth per second. The size of the Trough is estimated to be about 60 km in width and 100 km in length with the depth of 2500 metres on average. Thus, the amount of energy that could be generated until eternity is well above 50,000 MW, that is about 25 times the size of the 2100 MW of the coal-fired power plant of TNB Janamanjung, in Lumut, Perak, or a challenging alternative nuclear power plant of similar size.

OTEC will be worth over US $50 billion, in terms of the size of the capital required, for its total energy development alone.

What will it take for Malaysia to move forward toward such a sustainable energy future? It would not be any difference from a standard approach that ought to be in place: legal and policy framework with strong political commitment, the necessary institutional arrangement and alignment, and of course, finance. The said technology will follow through … InsyaAllah, God willing!


Penaga, Seberang Prai
1 January 2009

[1] Former Director-General, Department of Environment Malaysia (1990-1995), Advisor to Malaysia National Committee on Continental Shelf, and Elected-Member of the UN CLOS Commission on the Limits of the Continental Shelf (since 1997) (www.un.org/clcs)
[2] The survey has been conducted under the auspices of the Malaysian National Committee on Continental Shelf, Secretariat to the National Security Council, Prime Minister’s Department with the Technical Support of PETRONAS, Department of Survey and National Mapping Malaysia, the Hydrography Directorate of Royal Malaysian Navy, and the Department of GeoSciences Malaysia.
[3]http://www.nrel.gov/otec/markets.html; http://www.nrel.gov/otec/what.html
[4] www. http://www.xenesys.com/english/otec/area.html
[5] http://coolsciencenews.blogspot.com/2008/12/energy-debates-ocean-thermal-energy.html
[6] Nihon Keizai Shimbun, “Xenesys gets rolling for commercialization of its OTEC plant in Tahiti”, October 18, 2008.
[7] http://www.xenesys.com/english/otec/history.html