【Construction】

There are two major parts in this particular solar water heater. First part is called a solar collector. Second part is called a water tank. This solar collector and water tank are connected with each other by using various pipelines.

The solar collector faces towards the sun. In fact the face of the solar collector should always be towards the sun. Inside we have a number of tubes which are circulated and above them we have a transparent glass. One external tube has an inlet pipeline which is coming from the bottom and an exit pipeline. This exit pipeline is going to the water tank and at the same time the inlet pipeline is coming from the water line. The solar collector will collect heat from the sun. 

 Next part is called a water tank. Basically the water tank has a four pipe connection. First pipe connection is the one which is coming from a solar collector. Second pipe connection is going towards a solar collector. Whereas the other two are coming from outside. The cold water will be coming inside the water tank with this particular pipeline. Whereas the hot water will be taken from the other one.The green colour shows an insulation which is provided on the water tank. Insulation will avoid loss of heat to the atmosphere. 

【Working】

Sun rays come from the sun and fall on the tubes. So water inside the tubes will get heated because of the heat coming from the sun. The blue colour shows the cold water whereas the orange colour shows the hot water. The upper part has heated water whereas in the lower part we have cold water which is coming from the water plant. Now once water gets heated because of the sun's heat, this water will become lighter because its density will get reduced. Thus it will try to move in an upwards direction. This is why the water tank is provided at a higher height, whereas the collector is provided on a lower height.

So if water gets heated in the solar collector, it becomes lighter and it will try to move on the upward side through the pipeline and it will be deposited in the water tank. The upper part of this particular tank will be occupied by hot water and the lower part will be occupied by the cold water, which is coming from outside generally. As hot water is entering on this side, the volume of this water tank is constant. The cold water thus enters into the solar collector. This total movement of water is because of the density difference without providing any external device like pump. This kind of solar water heater is called a thermosyphon solar water heater.