Solar water heaters are one of the common applications of conversion of solar energy to heat water. Some of the typical applications include domestic hot water, swimming pool heating and commercial and industrial hot water supplies.
Generally a solar water heater consists of 3 parts –
1. A heat collection system
A heat collector system commonly known as a collector converts the solar radiation to heat. This heat is transferred to the fluid contained within the collector unit. In a typical solar water heater, cold water is supplied at the lower side of the collector and as it is heated the warm water rises and exists from the upper side.
2. A heat storage system
The hot water from the collector is stored in the hot water tank. The tank is well insulated to prevent heat loss. Different kinds of insulation is available in the market some of the common types are Rockwool, poly urethane foam etc.
3. An auxiliary heating system
During cloudy days an auxiliary heating system can heat water through electricity or other energy source. Normally such system is used only when required.
Type of Solar Heater System:
Typically there are 2 types of solar water heaters-
- Passive systems, and
- Active system
In passive system, there are no pumps or fans used in the operation. The collector is close to the area where heat is stored or required. Natural process such as conduction, convection and radiation are used to transfer heat to the load. Passive systems are simpler and in general cheaper than active systems because they do not require the use of pumps or fans. A typical example is a thermosyphoning closed coupled of a passive solar water heater system.
In active systems, the energy is used or stored in a location away from the surface being heated by the sun. Therefore, the pump or fans are used to transport the fluid heated by the collector to the storage unit and sometimes from the storage unit to the load. A common example is solar pool heating system.