Solar thermal systems use sunlight to heat water — for domestic use, swimming pools and more. A typical direct solar thermal system consists of collector, pipes and an insulated tank.

A typical 100 LPD (litre per day) system is sufficient to provide approximately 100 litres of hot water at an average temperature of 65°C every day on all sunny days. This helps save approximately 4 units of electricity daily (equivalent energy consumed by an electrical geyser) offering cost benefits of approximately Rs 4,000 per year. TPS solar water heaters are available in scalable multiples of 100. Large scale installations, for special applications involving heat transfer can also be engineered.

1 When the sun’s rays fall on a solar water heater collector, made of either an Evacuated Vacuum Tube system (EVT) or Flat Plate Collector system (FPC), the solar radiation heats up the water present in glass tubes (in EVT) / metal tubes (in FPC) due to high transmittance of the covering glass medium.
 
2 The heated water, now less dense, rises in the various tubes eventually reaching the tank at the top.
 
3 The relatively colder and denser water in the tank descends into the tubes, in turn getting heated — this cycle continues. The Thermosiphon effect ensures the movement of hot water upwards into the tank because of difference in density, eliminating the need for an external pump. The insulated tank ensures that the hot water remains hot for a long time.