Principle:
A glazed flat-plate solar collector consists of a shallow rectangular box with a flat black plate behind a tempered glass cover. The plate is attached to a series of parallel tubes or one serpentine tube through which water or another liquid (such as an antifreeze solution) passes. Sunlight passes through the glazing and strikes the absorber plate, which heats up, changing solar energy into heat energy. The heat is transferred to liquid passing through pipes attached to the absorber plate. Sunrain Absorber plates are commonly painted with selective coatings. As the liquid circulates through the system, it absorbs the heat from sunlight falling on the collectors. The heated liquid then enters a heat exchanger or is added directly to the conventional system. In commercial applications, the solar-heated water flows to a storage tank that is connected to the conventional water heating system. Although flat-plate solar collectors could mainly be used under the circumstance of the temperature above zero centigrade as they are less efficient in cold weather than in warm, sunrain system is best suited to applications that require medium to high temperatures .
