In solar water heater system, non-concentrating solar collector type is usually used. This type uses flat plate solar collector which consist of two main parts such as flat plate collector and storage water tank (Figure 1). In the flat plate solar collector, there are pipes which fluid flow inside it and absorber of solar radiation heat. The collector surface is colored black to increase absorptivity.
|Figure 1: Solar Water Heater System|
Solar water heater system has working principle as follow:
- When solar thermal energy touch on the collector surface, the surface will become hot and will heat water within pipes.
- When the water temperature increases, its density will drop so that hot water will move up to the top of collector towards the top of storage water tank.
- While cold water which still at the bottom of tank will move down to bottom of collector because the weight density of cold water is higher than hot water.
- Water circulation occurs in solar water heater system constantly when the collector is exposed to hot sun.
- However, when solar radiation is reduced, water in collector will cools and when the temperature is lower than the temperature of water in storage tank, then the circulation will stop. This working principle of solar water heater system can be called as thermo syphon (Figure 2).
|Figure 2: Natural Circulation of Solar Water Heater System|