How Does Solar Water Heating Work?

A solar heating system collects the sun’s energy to heat water or another heat transfer fluid. The water or other fluid then transfers solar heat directly or indirectly to your home, water, pool or industrial process. A solar water heater is a very good investment. Although solar water heaters cost more initially than conventional water heaters, the fuel they use, sunshine, is free. To take advantage of solar energy you need to have an un-shaded area, such as a roof, that faces north, northeast or northwest.

Solar water heaters are made up of solar collectors, and all systems except pool heaters have some kind of storage. In pool systems, the swimming pool itself is the storage, and the pool’s filtration pump circulates the pool water through the collectors. Active systems also have circulating pumps and controls, passive systems work without this added equipment. Two types of solar collectors are used for residential applications: flat-plate and evacuated-tube collectors.

Flat Plate collectors are traditionally the most common type because they are easy to manufacture. Glazed flat-plate collectors essentially are weatherproofed boxes that contain a dark absorber plate under a glass cover.

Evacuated tubes collectors consists of a copper manifold where the water flows through and a number of evacuated tube heat pipes connected to it.

Evacuated tube solar collectors convert direct and diffused solar radiation into heat. Infra-red rays, which can pass through clouds, are also absorbed and converted into usable heat. The tubes efficiently collect and transfer this energy through a special collector plate and a rapid heat transfer channel called a heat-pipe, situated in an evacuated glass tube, to a highly insulated manifold heat exchanger.

The collector plate has a special wavelength-selective coating using a semi- conductor layer. This special absorber plate converts the maximum amount of solar radiation into heat whilst having very low radiation losses. The heat-pipe has a very low heat capacity but an exceptionally rapid conductivity and therefore is a very efficient and speedy heat conductor.