Energy from the ocean

Abstract

Renewable ocean energy sources can eventually supply a large fraction of man’s energy needs, starting in the 1990s. Their use will require technologies for converting to useful form such naturally occurring ocean phenomena as tides, currents, waves, salinity gradients and thermal gradients. In view of the technology’s substantial resource potential, its comparatively advanced stage of development among the ocean energy options, and other relatively attractive features, this paper focuses on ocean thermal energy conversion (OTEC). However, much of the paper’s content has relevance to the use of the other ocean energy sources. Techniques of ocean thermal energy conversion are summarized, along with the development status of the required power system and ocean system components. The worldwide ocean thermal resource is assessed as a function of geography and time. Environmental impacts and siting considerations are treated. Diverse commercial market applications of OTEC are summarized, based upon the two key options for OTEC of providing electricity by submarine cable and of manufacturing energy-intensive products for shipment to dispersed markets. By-products of OTEC such as fresh water and nutrients for mariculture are discussed. The constructability and deployment of OTEC systems are considered in the context of their overlap with the related technology for building and deploying offshore petroleum facilities. Much offshore petroleum industry technology and many of its construction facilities are shown to be relevant to OTEC requirements. OTEC cost projections are related to the competitive costs of other sources of continuous electrical energy. The prospects for the emergence of a commercial OTEC industry in the 1990s are analysed, including a description of OTEC development activity in various nations. Scenarios for the industrial development of commercial OTEC plants and plantships are presented for electricity applications and for energy-intensive products such as ammonia, hydrogen and aluminium. Economic, financial and international impacts of OTEC are explored. Market penetration forecasts for the 1990s are obtained, with a consideration of the problems and potential of the large early market in developing nations for OTEC-derived electricity. It is shown how OTEC-derived electricity and products, by increasing energy supply in an energy-interdependent world, could help reduce foreseeable polarizations between nations over limited global energy resources.