Question

7: What is the basic principle underlying in solar water heaters? Explain the types of solar water heaters and

thier applications.??

Answer 1

7. The basic principle underlying in solar water heaters is water is heated by absorping the solar thermal energy by the collectors . The hot water in the insulated tank which has low density due to more temperature of water moves upward but the cold water moves downward in the tank due to action of gravity head. Some collectors are placed in parallel combination to get high quantity of water and the area of collectors are 2 m². Generally , from a 100 litres insulated tank get water of temperature 60-80°c.

Types: Generally two types of solar water heater based on collector system

i) Flat plate Collector (FPC) based solar water heator :

ii) Evacuted Tube collector (ETC) based solar water heator

Applications:

i) Both types of solar water heater installed in colder region to avoid the freezing problem of water at sub zero temperature but FPC systems are most costly due to use of antifreeze solution.

ii) FPC system have more durability than ETC because of using metallic pipe in FPC system.

iii) In the region, where water is hard and have cholrine content, the FPC system must be installed to avoid the deposition of chlorine in the collector , which can block the flow of water.