First of all we need to understand the sources of conventional and non-conventional sources of energy.

The sources of energy which are familiar to most of the people are called conventional sources of energy. For example, coal, coke, diesel, kerosene, petrol, fuel oil, etc.

The sources of energy that are not based on burning of fossil fuels or splitting of atoms of nuclear fuels are called alternative sources of energy or the non-conventional sources of energy. For example, solar energy, wind energy, etc.

Reasons for the need of harvesting non-conventional sources of energy are:

(a) The fossil fuel (conventional sources) are limited and non-renewable. So, if we keep on using them at the present rate, then they will not last longer. By using non-conventional we can help conserve fossil fuels.

(b) By using alternative sources of energy, the pollution caused by the burning of fossil fuels can be controlled.