11.1.1 Ocean Thermal Energy Conversion (OTEC)

The principle of OTEC is the utilisation of the temperature differential between warm surface sea water and cold deep sea water, at about 1000 m depth, for the generation of electrical energy. Recognising the rich potential from OTEC in the tropical waters around India, DOD has taken up a technology development and demonstration programme in this area. Under this programme being implemented by NIOT, one OTEC demonstration plant of 1MW gross output will be established at about 38 kms. off the shore of Kulasekarapatnam, Tamil Nadu. A preliminary design of this plant, prepared by NIOT, was reviewed and approved by a technical experts' committee in August `98.

The proposed OTEC plant will be of closed Rankine cycle type with ammonia as the working fluid. The OTEC group at NIOT has finalised the specifications of all the major subsystems and global tenders were floated. The offers have been evaluated and orders for turbine-generator module, plate heat exchangers, cold water/warm water pipes and the circulating water pumps have been placed. The plant is expected to be commissioned by June 2000.

11.1.2 Wave Energy

The National Test Facility at Vizhinjam, Kerala established by DOD for developing wave energy conversion system is being continuously used by NIOT for the design and testing of turbine-generator modules for wave energy applications.

The new impulse turbine with self-pitching linked guide blades developed during 1997-98 was tested for wide ranging programmes upto July 98. The best average power with self-pitching linked guide vanes was 13.5 kW and the peak power pumped to the grid was 70 kW. Subsequently, in order to improve the reliability of the turbine in marine environment, the self pitching linked guide blades were modified to fixed guide vanes. The angle of guide vanes at entrance to turbine rotor was varied and the performance of the turbine was monitored. The optimum performance was obtained for a guide vane angle of 30ø with a best power output of 12.1 kW and a peak output power of 60 kW.

In parallel, model tests were conducted on Backward Bent Ducted Buoys' which are to be used as floating platforms for mounting the wave energy turbine-generator system. Two moored buoys are being developed for wave energy conversion ratings of 100 W and 50 kW (peak), applicable to remote instrumentation platforms and remote islands respectively.