A parabolic trough is a type of solar thermal energy collector. It is constructed as a long parabolic mirror (usually coated silver or polished aluminum) with a Dewar tube running its length at the focal point. Sunlight is reflected by the mirror and concentrated on the Dewar tube. The trough is usually aligned on a north-
Alternatively the trough can be aligned on an east-
Heat transfer fluid (usually oil) runs through the tube to absorb the concentrated sunlight. The heat transfer fluid is then used to heat steam in a standard turbine generator. The process is economical and, for heating the pipe, thermal efficiency ranges from 60-
Current commercial plants utilizing parabolic troughs are hybrids; fossil fuels are used during night hours, but the amount of fossil fuel used is limited to a maximum 27% of electricity production, allowing the plant to qualify as a renewable energy source. Because they are hybrids and include cooling stations, condensers, accumulators and other things besides the actual solar collectors, the power generated per square meter of space ranges enormously.
ABOVE: SANDIA RESEARCHER Rich Diver takes a close-
ABOVE: A parabolic trough CSP system uses parabolically curved, trough-
As this renewable source of energy is inconstant by nature, methods for energy storage have been studied, for instance the single-
The largest operational solar power system at present is one of the SEGS plants and is located at Kramer Junction in California, USA, with five fields of 33 MW generation capacity each.
The 64 MW Nevada Solar One also uses this technology. In the new Spanish plant, Andasol 1 solar power station, the 'Eurotrough'-