Solar Water Heating (SWH) is the conversion of sunlight into renewable energy for water heating using a solar thermal collector. Solar water heating systems comprise various technologies that are used worldwide increasingly.
In a "close-coupled" SWH system the storage tank is horizontally mounted immediately above the solar collectors on the roof. No pumping is required as the hot water naturally rises into the tank through thermosiphon flow. In a "pump-circulated" system the storage tank is ground- or floor-mounted and is below the level of the collectors; a circulating pump moves water or heat transfer fluid between the tank and the collectors.
SWH systems are designed to deliver hot water for most of the year. However, in winter there sometimes may not be sufficient solar heat gain to deliver sufficient hot water. In this case a gas or electric booster is used to heat the water.
South facing collectors at certain angle, depend on latitude and longitude of the site location, to get max sun irradiation and heat.Cold water is filled in copper tubes/EVA tubes. Due to solar radiation falling on the absorber surface and converted into heat energy and transfer to water flowing through the tubes. At this stage cold water losses its density and becomes lighter. Due to this difference of hot and cold water, the hot water is lifted automatically to the insulated hot water storage tank. Initially the hot water storage tank is filled with cold water supplied from cold water storage tank which is above hot water tank. The bottom of the cold water tank is minimum one feet above the top of the water tank to avail the pressure head of cold water which forces the heated water to rise up the cold water to take place of raised water. This process is called THEROMOSYPHON PROCESS. It is continuous automatic process and can hearts the water upto 60degreeC according to the design of system output.