SOLAR WATER HEATERS
Solar water heaters employ the principle of conversion of sunlight into heat for water heating using a solar thermal collector. Solar water heaters are systems used to heat water via light-concentrating mirrors. The system comprises of collectors and an insulated hot water tank. Solar water heaters have a direct and indirect heating system. Direct or open loop system heats water directly in the collector while indirect or closed loop systems heat water indirectly by a transfer fluid that is heated in the collector then passed through a heat exchanger to transfer heat to the water. The system can either be pressurized or non-pressurized. Pressurized systems contain a pump so as to deliver required amount of hot water to taps especially those that are not too close to the system and are mostly recommended for hotels and commercial use. Non-pressurized systems use gravity to supply hot water from a roof tank and are ideal for domestic use. Evacuated-tube (vacuum-tube) collectors are made of glass tubes with a vacuum layer in between the tubes giving it a low heat loss co-efficient. Flat-plate collectors are made of an absorber panel, commonly copper that is attached to copper pipes where water passes through. Solar water heaters use a thermosiphon process where heated water settles on top and cold water settles at the bottom. This is because hot water density is lower than cold water.
How it works
- Reduced energy bills – sunlight is a free resource.
- Solar water heaters hardly require maintenance.
- It is a one-time investment that goes a long way (has a lifespan of 15-20 years).
- Have an electric boost for cold and rainy weather.
- Are electricity independent.
- Environmentally friendly.
FLAT PLATE WATER HEATER
This is a system flat in shape and consist of different layers of surfaces. A layer of glass or plastic is placed at the top where sunlight falls. The storage tank allows the system to provide hot water at any time of the day, whether the sun is shinning or not.
EVACUATED-TUBE WATER HEATER
This is a system with many tubes, made in glass in the outer part and metal in the inner part and positioned parallel to each other so that direct sunlight fall on them. The metal absorbs heat.