Ocean thermal energy conversion: technology development

Abstract

The United States is developing four ocean-energy technologies which offer significant promise. These are: ocean thermal energy conversion (OTEC), wave power, ocean currents, and salinity gradients. The major funding emphasis has been in OTEC because of its potential, state of development, and availability of the resource to U.S. shores. The closed-cycle OTEC concept, with ammonia as the working fluid, has been emphasized in the U.S. Department of Energy Program, based on analyses which concluded that the closed cycle has the highest probability of achieving early economic viability. Closed-cycle systems have been used in two OTEC conceptual design configurations for 10 to 40 megawatt (MW) pilot plants; viz., a moored plant to produce electrical power for transmission ashore via cable; and a grazing plant to produce energy intensive products on-board such as ammonia. The OTEC technology development program has experimentally verified much of the analytical work and many of the component preliminary designs for the OTEC 10 40 MW pilot plant. This paper summarizes the technological accomplishments, major findings, remaining problems and action planned. The areas of major concern pertain to the cost-effective designs for the heat exchangers, including biofouling countermeasures, cold water pipe, and electrical umbilical cable and the successful system integration of these components into a working plant that can be readily deployed and operated at sea over a design life of 30 years. The 1 MW system, OTEC-1, will be constructed and ready for deployment for at-sea test in mid 1980. The preliminary designs for the 10 40 MW pilot plant is expected to be initiated in fiscal year 1981, with subsequent construction and deployment planned for the end of fiscal year 1985. Many technological advances have been made toward achieving the program objectives for proving the technical and economic feasibility and minimizing engineering risks for eventual commercial applications.