Abstract
Ocean Thermal Energy Conversion (OTEC) uses the temperature difference between warm surface water in the tropical ocean and the cooler water at depth to generate power. Energy extraction efficiencies are low, 2 to 4 percent (Dugger et al. 1981), relative to conventional steam generation plants, necessitating large flows of ocean water (the fuel in an OTEC system): about 10 m3/sec/MW (DOE 1979a). Two OTEC operating cycles, closed-cycle and open-cycle, are currently under development in the United States. In an earlier paper we addressed the environmental concerns associated with open-cycle OTEC operating in conjunction with several secondary uses (Quinby-Hunt et al. 1986). This paper addresses the environmental concerns associated with closed-cycle OTEC, examining, in particular, OTEC impacts in the coastal zone. Closed-cycle operations use warm surface water to evaporate a working fluid which passes through a turbine to generate power. The working fluid is then condensed by cold, deep water and recycled. In open-cycle operations, the working fluid is surface water which is separated into steam and brine under partial vacuum. The steam, after passing through a turbine, is condensed using cold ocean water. Although several configurations for OTEC plants have been considered, nearshore, bottom-resting, and shore-based plants currently are being more actively pursued in the US program due to increased technical and safety risks associated with floating and far offshore configurations (Lewis 1983). The federal environmental documents that addressed the environmental effects of closed-cycle OTEC (DOE 1979a; 1979b; 1980; 1981) focused on free-floating plants. Concerns associated with closed-cycle generation on shore-based or bottom-resting plants have been addressed only in two site/design specific documents (OTC/MSG 1985; MSG 1985).