OTEC utilizes the temperature different between warm (26 C) surface waters of low latitude tropical oceans and the cool deep waters (5-10 C) lying below a depth of a few hundred meters to run a turbine and a generator via a heat exchanger and a suitable medium (e.g. ammonia or low pressure steam).
OTEC is a method of using solar energy stored as a temperature difference in the oceans.The earth’s oceans absorb solar radiation the major part of which they store as thermal energy in the warm surface waters. On the other hand, cold water layers move slowly from polar regions towards the equator at depths of less than 100 m. Thus, a vertical temperature difference of up to 25 C exists throughout the year at many tropical locations According to the fundamental laws of thermodynamics, this temperature gradient can be exploited as an energy source.
The ocean thermal gradient does not vary significantly from day to night and hence can be regarded as a steady source of energy. It does have however, a seasonal variation which increases with the distance from the equator.The natural power potential of the thermal gradient energy is estimated to be as large as 10 W (10 TW). Obviously it is not technically feasible to extract all this energy.
A fair estimation would be approximately 10 W as against the world installed electrical generation capacity of the order of 10 W.In India activities in this area are coordinated by the OTEC Cell at Indian Institute of Technology, Madras. A feasibility study of setting up a 5 to 8 MW pilot R & D OTEC plant off the main Anandman Islands is ready and a proposal for a feasibility study for installation of a 100 MW OTEC plant off Madras is under consideration.
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