Abstract
Ocean Thermal Energy Conversion (OTEC) plants will employ the temperature difference (ΔT) between the solar-heated surface layer of a tropical ocean (24–29.5°C) and the water at 500–1200 m depth (7-3.5°C) as the source and sink for a Rankine cycle system to generate electric power. An annual average ΔT near 24°C is available to grazing tropical OTEC plants. The resource is tremendous in terms of suitable ocean siting areas and is available 24 hr per day. It could supply a significant fraction of the world's energy needs in the year 2000. The first commercial plants could be deployed in the mid 1980s, and we believe they will be competitive then with fossil fuel and nuclear energy sources for selected applications. Ammonia (for fertilizers) is a particularly attractive product, because 95 per cent of the ammonia produced in the U.S. is now made from natural gas, our scarcest resource. Direct delivery of electric power to shore may also be competitive for, e.g. the southeastern United States. In the late 1980s or early 1990s, ammonia produced by grazing tropical OTEC plants could also be used as a hydrogen carrier for production of electricity by fuel cells anywhere in the world, and production of other chemicals and metals (aluminum, magnesium) should become attractive. Various OTEC plant-ship concepts, their economics, onboard production plants and some of the environmental considerations are discussed.