A solar water heating system consists of the components such as collectors, storage tank, pumps, water/heat transfer fluid, heat exchanges and controllers. The sun radiates energy in the form of heat and light. The collector, when exposed to sun, absorbs most of the heat and the water or heat transfer fluid gets heated up. As a result there is rise in temperature of the water/heat transfer fluid by way of conduction. The collector also loses heat to the by convection and radiation.
By controlling the exchange of heat between the collector and the water/heat transfer fluid, through conduction or convection, it would be considered as a desirable heat exchange. The solar collector tried to increase this desirable heat exchange and reduce the undesirable heat loss to air, atmosphere or other materials in contact. Solar water heating uses both the direct solar radiation that comes directly from the sun and diffused solar radiation that is scattered by the atmosphere.
There are two types of solar water heating systems: active, which have circulating pumps and controls, and passive, which don’t. Most solar water heaters require a well-insulated storage tank. Solar storage tanks have an additional outlet and inlet connected to and from the collector.
Though the initial investment for a solar water heater is high compared to available conventional geysers, the return on investment has become increasingly attractive with the increase in prices of conventional energy. Solar water heating is also an environmentally friendly technology that contributes towards reduction in emissions.