Converting solar energy into heat requires the utilization of solar thermal collectors. Solar thermal collectors can be classified based on the heat requirement into:
Non-concentrating collectors fully utilize the global radiation. The simplest design of a non-concentrating collector is the flat plate collector.
The absorbers are black painted metal-either copper, aluminum, steel or plastic plates. In order to reduce the useful heat losses-which increase with rising temperatures-transparent covers are placed on the collectors and the heat losses at the back of the absorber are reduced by appropriate insulation. With these collector temperatures up to 80°C with conversion efficiency of about 50-60% can be achieved. The properties of this collector are well known and they are manufactured in many parts of the world.