These consist of either a Thermosyphon or forced circulation systems. The forced circulation systems employ electrical pumps to circulate the water through collectors and storage tanks. A solar collector is the key component of the solar water heating system. It basically serves as a heat exchanger that absorbs solar radiations and converts it into thermal energy, which is used to heat the water.
Systems are simple and relatively inexpensive. These are mostly suitable for domestic and small institutional systems, provided the water is treated and potable in quality. Contrarily, in several cases, Thermosyphon systems with up to 10,000 LPD capacities have been successfully installed along with heat exchangers and have displayed a satisfactory performance.
The choice of system depends on heat requirement, weather conditions, heat transfer, fluid quality, space availability, annual solar radiation, etc.
Forced Circulation If the capacity of hot water requirement is more than 4000 upto 100000 LPD, the water requires additional force to push the hot water collected in the solar collector. The DTC senses the inlet and outlet temperature of the water. If the thermal difference is more than 10 degree centigrade, the DTC switches on the pump and the hot water in the collector is forced to flow into the storage tank. This system requires continuous supply of electricity for the motor to operate.