It is an inexhaustible and population free source of energy. This energy maintains temperature of the earth. It causes current in the atmosphere and in ocean. The total solar energy reaching on the earth's surface is 10 ¹⁶ watts, whereas worldwide power demand for all needs is 10¹³ watts. So the sun gives us 1000 times more energy than we require. Solar energy can be utilized by two different routes.

i.     Solar thermal route:

In this route, various devices are used to convert solar heat energy into mechanical, chemical or electrical energy Eg Solar cooker, solar dryer, solar heater etc.

2.  Photovoltaic conversion routes:

     In the route, solar energy is directly converted into electricity by using silicon solar cells. These cells are of many types such as mono crystalline cells, amorphic solar cell etc. this electricity can be used for lighting homes, building, running motor pumps.