The first component of a solar thermal system is the solar collector. This is usually installed on the rooftop. It represents the major component of the system. It is made up of specially coated tubing that absorbs the solar radiation and converts it into heat. There is a need to minimize thermal losses. This need is addressed by embedding the tubing in a heat-insulated container that is equipped with a transparent cover. Inside this tubing, a heat transfer fluid flows inside and circulates between the collector and the hot water tank. This water is normally a mixture of water and an anti-freeze that is ecologically safe.
The key part of the solar collector is the absorber, which comprises of several narrow metal strips. Typically, absorbers are made of aluminum or copper. These are good conductors of heat. These absorbers are often black so as to enable a high degree of light absorption. In order to reduce the loss of heat energy through heat emission, efficient absorbers have selective surface coating which enables the conversion a substantial amount of solar radiation into heat. This also reduces heat emission. The degree of absorption that can be provided by usual coatings is about 90% (Solar-is-Future.com 1). Selective coatings can also be applied using galvanizing, and such coatings include black nickel, black chrome, and aluminum oxide with nickel. As such, there are different types of solar collectors which include flat-plate collectors, parabolic collectors, and evacuated-tube collectors.