However, they have the disadvantage of having a smaller angle of view, and therefore, require some form of tracking system or manual adjustment to keep them at the correct focal point.Īlso parabolic trough reflectors can not collect most of the diffused solar radiation. Solar concentrators such as parabolic troughs, have a small absorber area and therefore smaller heat losses and provide high efficiencies of around 12% at much higher working temperatures compared to standard flat panel collectors. Also connecting together parabolic troughs to form collector fields requires large areas of land for the installation, yet they offset the need for conventional energy and provide energy savings and environmental benefits. ![]() The oil circulating around a closed loop active system is used to heat high volumes of water or to generate steam at very high temperatures of up to 400 oC which can then be used to generate electricity. In these types of installations, the solar energy trapped by the solar troughs heats a special type of thermal oil to very high temperatures. Many single troughs connected together form a collector field were they are connected together in series and parallel rows.Īs line-focused concentrating collectors, parabolic trough reflectors are more efficient for industrial and commercial applications that require large amounts of hot water around the clock. The advantage here is that connecting them together creates a larger surface area of absorber producing large amounts of solar hot water than can be created by an individual trough. ![]() Like many other solar collectors, parabolic trough reflectors are modular, meaning that the individual troughs can be connected together. The advantages of this type of tracking mode is that very little collector adjustment is required during the day resulting in the solar trough always facing the sun at noon time, but the collector performance early in the morning or late in the afternoon is greatly reduced due to the large incidence angles of the trough.Įven though solar trough collectors use tracking systems to keep them facing the sun, they are most effective in sunnier climates where there are good solar resources. Parabolic troughs are generally aligned on a north-to-south axis, and are rotated to track the sun as it moves across the sky each day from morning to night. The collector generally has a single rotation axis along the length of the trough which can be orientated in an east-to-west direction, tracking the sun from north to south, or orientated in a north-to-south direction and tracking the sun from east to west. This can be achieved by using a Tracking Solar Concentrator that aligns the trough with the sun throughout the day, maximising the solar heat gain. To overcome this problem, most concentrating collectors require some form of mechanical equipment that constantly orients the collectors towards the sun keeping the heat pipe absorber at the correct focal point. ![]() The heat transfer fluid which is usually a mixture of water and other additive’s or thermal oil, is pumped through the tube and absorbs the solar heat reaching temperatures of over 200 oC. The parabolic trough reflector can generate much high temperatures more efficiently than a single flat plate collector, since the absorber surface area is much smaller. The heat tube contains a heat-transfer fluid which is pumped around a loop within the tube absorbing the heat as it pass through. ![]() A metal black heat tube inside a sealed glass tube which can also be evacuated is used to reduce heat losses. The parabolic trough reflector when used as a solar thermal energy collector is constructed as a long parabolic reflecting mirror which is usually painted a reflective silver, or made from polished aluminium, or uses mirrors which extends linearly into the trough shape. Since solar light waves essentially travel parallel to each other, this type of solar collector can be pointed directly into the sun and still achieve a total focal output from all parts of the trough shaped reflector as shown. Parabolic Trough Reflectors or PTR, are made by simply bending a sheet of reflective or highly polished material into a parabolic shape called a parabola.
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