What is a parabolic trough collector?
Solar thermal technology is based on a simple principle to generate electricity in a clean manner: it concentrates solar energy to generate steam that powers a turbine. In order to complete this process, different types of solar collectors are used, among them parabolic trough.
” Collectors are a key component in solar thermal plants with parabolic trough technology.
Parabolic trough collectors are formed by a cylindrical surface of mirrors with a parabolic shape that concentrates solar radiation on a receiver tube located at the focal point of the parabola. A fluid, normally synthetic oil, circulates inside the receiver tubes and is heaten up by the sun (around 400 ºC). The fluid is then pumped through heat exchangers to generate steam which is thus used to produce electricity in a conventional turbine.
Main components of solar parabolic trough collectors are:
– Foundation and metallic structure: support the collectors and fix them to the ground so that the whole structure can support the collector.
– Parabolic trough reflector: this is the concentrating part of the collector. It reflects the solar radiation and transfers it to the receiver tube. Main reflective materials that are used include silver and alluminium, which are normally placed on a glass plate.
– Absorber tube or receiver: it converts concentrated light energy into thermal energy in the heat transfer fluid. It presents selective features to maximize energy conversion process.
– Transmission and tracking system: collectors moves so that their opening plane is pointed towards the plane of sun rays. A tracking system is used to change and focus the collector as the sun is moving.
– Heat transfer fluid: thermal oil is the most used working fluid in solar thermal plants. However, different fluids as water steam can also be used. This fluid is the medium to transport the concentrated thermal energy that permits to generate the steam to operate the turbine, thus producing electricity.
New developments of parabolic trough collectors.
The design obtained as part of the project Eurotrough II is the type of collector most widely used, with an aperture width of 5.6 metres and a length of 150 metres.
There are also new developments with different dimensions in the solar thermal industry. Abengoa commercializes its new large-aperture parabolic trough collector, the SpaceTube®, with an aperture of 8 metres, and collaborates with the Department of Energy of the United States (DOE) in the “Sunshot Initiative” to improve different elements in the production and assembly phases of the development of this collector. The SpaceTube® will be installed in projects around the world, as Xina Solar One, the 100 MW power plant that Abengoa is currently constructing in Pofadder, South Africa.
The efforts in R&D areas for the development of new components and materials for this kind of collectors, along with a commercial development of more than 20 years, make parabolic trough technology a mature and clean solution for electricity generation.