Detailed Product Description

solar hot water heater

Solar Collectors

At the heart of a solar thermal hot water system is the solar collector. It absorbs solar radiation, converts it into heat, and transfers useful heat to the solar system. There are a number of different design concepts for collectors: besides simple absorbers used for swimming pool heating, more sophisticated systems have also been developed for higher temperatures, such as integral storage collector systems, flat-plate collectors, evacuated flat-plate collectors and evacuated-tube collectors. Although commercial integral storage collectors do exist, no significant numbers have been sold, and so these are not described in detail here.

Flat-plate collectors:

The majority of solar collectors that are sold in many countries are of the flat-plate variety. The main components of these are a transparent front cover, collector housing and an absorber. The absorber, inside the flatplate collector housing, converts sunlight to heat and transfers it to water in the absorber tubes. As the collector can reach stagnation temperatures up to 200 (i.e. when no water flows through), all the materials used must be able to resist such heat. Therefore, the absorber is usually made of metal materials such as copper, steel or aluminium. The collector housing can be made of plastic, metal or wood, and the glass front cover must be sealed so that heat does not escape, and dirt, insects or humidity do not get into the collector itself. Many collectors also have controlled ventilation, so as to avoid condensation inside the glass front cover. The collector housing is highly insulated at the back and sides, keeping heat losses low. However, there are still some collector heat losses, mainly due to the temperature difference between the absorber and ambient air, and these are subdivided into convection and radiation losses. The former are caused by air movements, while the latter are caused by exchange of heat by radiation between the absorber and the environment.