Ocean thermal energy conversion - Historical highlights, status, and forecast

Design concepts, materials, and performance data from the first OTEC demonstration plants are reviewed. The first plant, using a closed cycle fluid loop (NH3), generated 10-15 kWe in 1979 at Keahole Point, HI. Subsequently, a follow-up project provided data on 1 MWe heat exchangers and biofouling in 1981. The federal government passed legislation in 1980 mandating the generation of 500 MW from OTEC plants in 1989 and 10 GW in 1999. A resource assessment has indicated favorable temperature gradients in retrievable depths of near 24 deg C in the Atlantic and the Pacific. Sensitivity analyses have shown that the cost of electricity from OTEC plants varies with the length of cable needed to deliver the power, the resource, standardization of OTEC components, and the choice of moored or cruising ships (which could follow seasonal temperature changes). Overall efficiencies for the OTEC plants of about 2.5 pct are projected. Baseline designs have been developed for 40 MWe plants, although choices are not yet finalized for the cold water intake or final product, whether electricity, NH3, or methanol for fuel cells.