Solar Flat Plate Collectors

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. Absorber plates are commonly painted with "selective coatings," these coatings absorb UV and visible radiation, but are reflective to long wavelenght (cold) infrared so that they retain heat much better than ordinary black paint. Some source claim 25-30% higher output over the course of a year using selective rather than non-selective coverings. Absorber plates are normally made of copper welded to a copper pipe.