Solar collectors transform solar radiation into heat and transfer that heat to a medium (water, solar fluid, or air). Then solar heat can be used for heating water, to back up heating systems or for heating swimming pools. The use of solar heat The heart of a solar collector is the absorber, which is usually composed of several narrow metal strips. 

The carrier fluid for heat transfer flows through a heat-carrying pipe, which is connected to the absorber strip. In plate-type absorbers, two sheets are sandwiched together allowing the medium to flow between the two sheets. Absorbers are typically made of copper or aluminum. Swimming pool absorbers, on the other hand, are usually made of plastic (mostly EPDM, but also of polypropylene and polyethylene), as the lower temperatures involved do not require greater heat capacity. Heating and storage are united in a reservoir collector. Arrays of reservoir collectors do not need circulating pumps or regulating mechanisms, as the drinking water is warmed and stored right in the collector.