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.