Is their working difficult to understand for a layperson/ How do they work?
The working of solar water heaters is very simple to understand. Two common phenomena observed in everyday life are the key to functioning of solar water heaters. These are, first, a black surface heats up when left in the sun, by absorption of solar radiation; and second, the inside of a car becomes very hot, if it is left in the sun with windows closed. A car becomes hot in sun because solar radiation can pass through the glass windows but cannot come out. It is trapped inside and thus heats up the car. The heat trapping principle is the famous Green House Effect. The good absorption property of black surfaces is used to improve solar energy absorption in a solar heater. These two phenomena are utilized in flat plate collectors of commonly available solar water heaters. A typical domestic solar water heater consists of a hot water storage tank and one or more flat plate collectors. The collectors are glazed on the sun facing side to allow solar radiation to come in. A black absorbing
