Solar power thermal energy conversion

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. 

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. 

Since the oceans comprise over 70% of the earth s surface area, the absorbed solar energy that is stored as latent heat of the oceans represents a very large potential source of energy. As a result of variation in the density of ocean water with temperature, the ocean water temperature is not uniform with depth. Warm surface ocean water with low density tends to stay on the surface and cold water with high density within a few degree of 4°C tends to settle to the depths of the ocean. In the tropics, ocean surface temperatures in excess of 25° C occur. The combination of the warmed surface water and cold deep water provides two different temperature thermal reservoirs needed to operate a heat engine called OTEC (ocean thermal energy conversion). Since the temperature difference of the OTEC between the heat source and the heat sink is small, the OTEC power plant cycle efficiency... 

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,... 

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). 

Energy Efficiency Comparisons Between Countries Energy Flows in Ecology and in the Economy Fossil Fuel Power Stations Hydroelectric Power Stations Nuclear Power Reactors Ocean Thermal Energy Conversion Petroleum Geology Renewable Energy from Biomass Solar Thermal Power Stations Tidal Power Sys-... 

C.E. Byvik, A.M. Buoncristiani, B.T. Smith, Limits to solar power conversion efficiency with applications to quantum and thermal systems, J. Energy 7 (1983) 581-588. 

The assumed conditions used in evaluating characteristics of the systems are summarized in Table 2. The total areas of the solar collectors and photovoltaic arrays are assumed to be 10 ha. In the solar thermal and hybrid systems, the type of collector is parabolic trough, the condenser outlet pressure 0.1 kg/cm a, and the capacity (maximum net power output) has been determined so as to minimize the unit cost of generated power energy. In the solar photovaltaic system, the conversion efficiency at the array is assumed to be 15 %. The tracking scheme of the solar collector and photovoltaic array is single north-south axis. 

---