Solar water heaters use the sun energy to heat water using a solar thermal collector. This hot water is stored inside an insulated solar hot water tank for use whenever required. The sun rays have enough energy to heat water to 100°C which is more than sufficient for bathing and washing purpose in bathrooms and kitchen.
With minimal maintenance requirement, solar heater provides a low cost long term solution to getting hot water. For cloudy days, solar water heater have a inbuilt electric heating element for backup.
There are two types of collectors in solar hot water services:
- Flat plate collectors
- Evacuated tubes
Flat plate solar collectors
Flat plate collectors work on copper pipes running through a glass covered collector, often connecting to a water storage tank on the roof. The sun heats the copper pipes and the resulting hot water is thermo-siphoned out of storage tank.
Evacuated tube solar collectors
Evacuated tubes consist of two glass tubes fused at the top and bottom. The space between the two tubes is evacuated to form a vacuum. A copper pipe (called a heat pipe) running through the centre of the tube meets a common manifold. The hot water can be used at night or the next day due to the insulation of the tank.
Evacuation tube systems are superior as they can extract the heat out of the air on a humid day and don’t need direct sunlight.
Due to the vacuum inside the glass tube, the total efficiency in all areas is higher. There’s also better performance when the sun is not at an optimum angle. This could include times such as when it’s early in the morning or in the late afternoon