A parabolic trough is a type of solar thermal collector that is straight in one dimension and curved as a parabola in the other two, lined with a polished metal mirror. The energy of sunlight which enters the mirror parallel to its plane of symmetry is focused along the focal line, where objects are positioned that is intended to be heated. For example, food may be placed at the focal line of a trough, which causes the food to be cooked when the trough is aimed so the Sun is in its plane of symmetry. For other purposes, there is often a tube, frequently a Dewar tube, which runs the length of the trough at its focal line.
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The mirror is oriented so that sunlight which it reflects is concentrated on the tube, which contains a fluid which is heated to a high temperature by the energy of the sunlight. The hot fluid can be used for many purposes. Often, it is piped to a heat engine, which uses the heat energy to drive machinery or to generate electricity. This solar energy collector is the most common and best known type of parabolic trough. |
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Salient Features | Higher operating temperatures | A parabolic trough collector permits operating temperatures of up to 500 °C.Â
| | Simpler construction | Construction achieves greater stiffness and wind resistance.Â
| | Reduction of the collector weight and cost | Reducing the proportion of steel means the weight of the collector is reduced resulting into reduction in overall project cost.Â
| | Cost reductions in production and transport | The individual modules can be shipped without problems in standard containers, which means on-site manufacturing is no longer absolutely necessary. The modular design makes unrestricted project sizes possible.Â
| | Increase in optical efficiency | | The parabolic trough collector achieves an optical efficiency of up to 75 %. |
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