The tubes attach to a black absorber plate . As heat builds up in the collector, it heats the fluid passing through the tubes. The hot water or liquid goes to a storage tank. If the fluid is not hot water, water is heated by passing it through a tube inside the storage tank full of hot fluid. These collectors consist of rows of parallel transparent glass tubes, each containing an absorber and covered with a selective coating.
Sunlight enters the tube, strikes the absorber, and heats the liquid flowing through the absorber.
Concentrating Collectors Parabolic trough-shaped reflectors concentrate sunlight onto an absorber or receiver to provide hot water and steam, usually for industrial and commercial applications. Solar Collectors A transpired collector is a south facing outside wall covered by a dark sheet metal collector. The collector heats outside air, which is then sucked into the building's ventilation system through perforations in the collector. They have been used for pre-heating ventilation air and crop drying. They are inexpensive to make, and commercially, have achieved efficiencies of more than 70 percent.