A solar water heating system consists of a flat plate solar collector, a storage tank kept at a height behind the collector, and connecting pipes. The collector usually comprises copper tubes welded to copper sheets (both coated with a highly absorbing black coating) with a toughened glass sheet on top and insulating material at the back. The entire assembly is placed in a flat box. In certain models, evacuated glass tubes are used instead of copper; a separate cover sheet and insulating box are not required in this case.
Working of a solar water heater
The system is generally installed on the roof or open ground, with the collector facing the sun and connected to a continuous water supply. Water flows through the tubes, absorbs solar heat and becomes hot. The heated water is stored in a tank for further use. The water stored in the tank remains hot overnight as the storage tank is insulated and heat losses are small.
Uses of solar water heater
SWHs can be used at homes for producing hot water that can be used for bathing, cleaning, and washing. Solar water heaters (SWHs) of 100-300 litres capacity are suited for domestic application. Larger systems can also be used for a variety of industrial applications. Hot water at 60-80oC could be obtained through use of solar water heaters. Fuel Savings: A 100 litres capacity SWH can replace an electric geyser for residential use and saves 1500 units of electricity annually. Saves cost on power generation – The use of 1000 SWHs of 100 litres capacity each can contribute to a peak load saving of 1 MW. Environmental benefits – A SWH of 100 litres capacity can prevent emission of 1.5 tonnes of carbon-dioxide per year. Pay back period – SWHs have a life span of 15-20 years. The pay back period is about 3-4 years when electricity is replaced, 4-5 years when furnace oil is replaced and 6-7 years when coal is replaced.