A solar thermal collector collects heat by absorbing sunlight. The term “solar collector” commonly refers to a device for solar hot water heating, but may refer to large power generating installations such as solar parabolic troughs and solar towers or non water heating devices such as solar air heaters.
Solar thermal collectors are either non-concentrating or concentrating. In non-concentrating collectors, the aperture area (i.e., the area that receives the solar radiation) is roughly the same as the absorber area (i.e., the area absorbing the radiation). This type has no extra parts except the collector itself. Concentrating collectors have a much bigger aperture than absorber area (additional mirrors focus sunlight on the absorber) and only harvest the direct component of sunlight.
Non-concentrating collectors are typically used in residential and commercial buildings for space heating, while concentrating collectors in concentrated solar power plants generate electricity by heating a heat-transfer fluid to drive a turbine connected to an electrical generator. Visiongain research indicates that the global solar thermal collector market will be valued at $21 billion by the year 2029.