Parabolic trough
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A parabolic trough is a type of solar thermal collector. It is constructed as a long parabolic mirror (usually coated silver or aluminum)with a Dewar tube running its length at the focal point. Sunlight is reflected by the mirror and concentrated on the Dewar tube. Heat transfer fluid (usually oil)runs through the tube to absorb heat from the concentrated sunlight. The HTF is then used to heat steam in a standard turbine generator. The process is economical and for heating the pipe, efficiency rates range from 60-80%. Because the plants are hybrids (fossil fuels are used during night hours) and plants include cooling stations, condensers, accumulators and other things besides the actual solar collectors, the kWh per square meter of space ranges enormously.
The largest operational solar power system at present is of this type. Named SEGS, it is located at [Kramer Junction (http://www.solel.com/products/pgeneration/ls2/kramerjunction/)] in California, USA. contributors to this article include M. Baskin Template:Physics-stub