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       The device in which solar energy is directly used to heat the water is called solar water heater.

Construction of solar water heater

       In solar water heaters, a pipe of copper with its outer surface painted black is fitted in the form of a coil in a box which is painted black from inside. Outer surface of copper tube and inner walls of box are pointed black to increase absorption of heat to produce high temperature. Like solar cooker, the box of solar water heater is also covered with a glass sheet to entrap the heat inside the box. One end of the copper pipe is joined to the bottom of water storage tank, while other end is joined near its middle. The schematic arrangement of a solar water heater is shown in figure.

Solar water heater

Working of solar water heater

       The cold water present in the water storage tank enters the copper pipe joined to it at the bottom and pass slowly through the coil of copper placed in box. When the cold water passes through the coil of copper it absorbs solar heat and gets heated. The hot water comes out from the other end of the copper pipe and enters the upper part of the water storage tank. This hot water is replaced by the cold water present in the tank. In this way, all the water present in the storage tank gradually heated up. In the tank, the hot water being lighter remains in the upper part. From the upper part of storage tank, the hot water is supplied to a tap for use.

Schematic Arrangement Of Solar water heater

Test Your Understanding and Answer These Questions:

  1. What is solar water heater?

  2. How solar water heater works?