The surface of the earth receives about 1014 kW from sun in the form of solar energy which is approximately five orders of magnitude greater than that currently being consumed from all resources. It is evident that sun will last for 1011 years.There are two obvious obstacles to harnessing solar energy. Firstly it is not constantly available on earth. Thus some form of storage is needed to sustain solar energy through the night and during rainy season. Secondly the solar energy is diffused. Although the total amount of energy is enormous, the collection and conservation of solar energy into useful forms must be carried out over a large area which entails large capital investments.
