Solar thermal systems refer to devices that use solar energy in the form of heat as themain source of energy. The main application areas of solar thermal systems are: Cooking, Water heating, Absorption adsorption refrigeration, Electric power generation. At the heart of a solar thermal system is the solar collector. It absorbs solar radiation asheat, and transfers useful heat to the solar system. There are different design conceptsfor collectors such as flat-plate collectors, evacuated flat-plate collectors, evacuated-tube collectors and concentrating collectors.