Energy conversion ocean thermal

In tropical zones, the temperature difference of seawater at the surface (27-30 °C) and at a depth of 1000 m (4 °C) is sufficient for use as the hot and cold reservoir of a thermal engine. The idea of Ocean Thermal Energy Conversion (OTEC) was worked out in 1881 by d Arsonval and taken up by Georges Claude, who in 1934 attempted, unsuccessfully, to set up such a machine off Cuba. 

During the 1970s, the idea of producing electrical energy in tropical zones by means of OTEC was reconsidered in the United States, Japan and Europe. Two approaches can be envisioned  

The second approach implies two seawater-ammonia exchangers. Two materials are in competition for the manufacture of these exchangers titanium and aluminium. Copper is excluded because of the presence of ammonia. 

Many studies were carried out between 1975 and 1980 in order to qualify the materials for the manufacture of these exchangers. Several questions had to be addressed  

The tested aluminium alloys have very good corrosion resistance in contact with surface seawater. For example, the extrapolated decrease in thickness after 30 years would be on the order of 200 xm for alloys 3004 and 5052. In contact with deep seawater, the same alloys exhibit pitting corrosion with a depth up to 200 p.m after 3 months of operation [33]. 

---

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. 

Oceanic zooplankton species, wax esters in, 26 204-205 Ocean ranching, 3 198 Ocean raw materials, 17 684-699 consolidated deposits of, 17 691-694 economic aspects of, 17 697 fluid deposits of, 17 694-695 minerals recovery from, 17 695—697 unconsolidated deposits of, 17 686-691 Ocean resources, global, 17 684—686 Oceans, selenium content of, 22 11. See also Marine entries Seawater Ocean thermal energy conversion (OTEC) power plants, 13 267, 268 26 92-93 Ocean transportation, 25 328 Ochratoxin A, 7 267-268 Ochre (mineral hematite) color, 7 333... 

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. 

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,... 

NRHL Ocean Thermal Energy Conversion http //www.nrel.gov/otec/whatJitiril... 

One of the more ambitious underseas projects involving syntactic foam is a 23-ton flotation collar that provides 32 tons of buoyancy 46). The part, 5.5 m in diameter and 3 m long, encases cold-water pipes, in an oceanic thermal-energy conversion system being developed by the US Department of Energy it has been tested off the coast of Hawaii, at depths of 915 m. 

Johnson, D. H., "Exergy of the Ocean Thermal Resource and the Second-Law Efficiency of Idealized Ocean Thermal Energy Conversion Power Cycles," Solar Energy Research Institute, Golden, CO, Report No. SERI/TR-252-1420R, Available as NTIS PCA03/MF 01, National Technical Information Service (1982). 

---