Ocean thermal energy

W. H. Avery, R. W. Blevins, G. L. Dugyer, and E. J. Francis, Executive Summary—Maritime and Construction Aspects of Ocean Thermal Energy Conversion (OTEC) Plant Ships, Apphed Physics Laboratory, The Johns Hopkins University, Baltimore, Md., Apr. 1976. 

Fig. 18. Flow schematic of an open-cycle ocean—thermal energy conversion (OTEC) and desalination plant (77), where (—) represents liquids (-),...

One form of solar heat does offer interesting possibilities and is refeiTcd to as OTEC (Ocean-Thermal Energy Conversion). The OTEC power plant principle uses the solar heat of ocean surface water to vaporize ammonia as a working fluid in a Rankine cycle. After the fluid is expanded in the turbine, it is condensed by the 22°C colder... 

Ocean thermal energy conversion (OTEC) power plants generate electricity by exploiting the difference in temperature between warm water at the ocean surface and colder waters found at ocean depths. To effectively capture this solar energy, a temperature difference of 35°F or more between surface waters and water at depths of up to 3,000 feet is required. This situation can be found in most of the tropical and subtropical oceans around the world that are in latitudes between 20 degrees north and 20 degrees south. 

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Because of its high heat capacity, ammonia is used as the working fluid in Ocean Thermal Energy Conversion (OTEC) units. See http //www.nrel.gov/otec/for more information. 

Wave power, tidal power, municipal solid waste, gas from animal wastes (biogas), landfill, peat energy and ocean thermal energy conversion (OTEC) are the other renewable energy sources (RES). Water energy sources are hydropower, tidal and wave technologies. 

The ocean thermal energy conversion (OTEC) is an energy technology that converts solar radiation to electric power. OTEC systems use the ocean s natural thermal gradient to drive a power-prodncing cycle. As long as the temperature between the warm strrface water and the cold deep water differs by about 20 K, an OTEC system can produce a significant amormt of power. The oceans are thus a vast renewable resomce, with the potential to help tts produce billions of watts of electric power. 

Much of this chapter has been concerned with various modifications to the simple Rankine cycle at high temperature. In the following five sections, the Rankine cycle that makes possible use of energy sources at low temperature, such as solar, geothermal, ocean thermal, solar pond, and waste heat, will be discussed. Because of the small temperature range available, only a simple Rankine cycle can be used and the cycle efficiency will be low. This is not critical economically, because the fuel is free. 

Incident solar energy is absorbed by the surface water of the oceans. Ocean surface temperatures in excess of 26°C occur near the equator. Pure water has a maximum density at a temperature of 4°C. The chilled water tends to settle to the depths of the ocean. The combination of the warmed ocean surface water and cold deep ocean water provides the thermodynamic condition needed to operate a heat engine called ocean thermal energy conversion (OTEC). A typical closed-cycle OTEC Rankine cycle using a working fluid such as ammonia or a freon is suggested. 

A finite-time ideal Rankine OTEC (ocean thermal energy conversion) cycle as shown in Fig. 7.22a operates between a finite heat capacity heat source and a finite heat capacity heat sink. The following information is given ... 

OCEAN THERMAL ENERGY CONVERSION (OTEC). Utilization of ocean temperature differentials between solar-heated surface water and cold deep water as a source of electric power. In tropical areas such differences amount to 35-40°F. A pilot installation now operating near Hawaii utilizes a closed ammonia cycle as a working fluid, highly efficient titanium heat exchangers, and a polyethylene pipe 2000 feet long and 22 inches inside diameter to handle the huge volume of cold water required. Alternate uses for such a system, such as electrolysis of water,... 

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