Solar radiation sustains all forms of life on earth. According to estimates, sun radiates about 1.74 x 1017 W of power per hour to earth. The
main features of solar radiation are its wide spread distribution,
inexhaustible supply and pollution free source of energy. India receives solar
energy equivalent to about 500 trillion kWh per annum which is much
more than the total energy consumption in the country. The daily solar
energy incidence varies from 4 – 7 kWh per m2 and there are 250 to 300
sunny days in a year. The power potential of solar energy is 20 MW per sq.km.
Two ways of harnessing solar energy
Solar energy comprises two components, namely, heat and light. Solar thermal systems capture the heat energy through solar
thermal collectors using specially coated metal plates and are used
for heating of water / air and for cooking.
The light rays of solar energy are harnessed for power generation through solar
cells and are called Solar Photovoltaic (SPV) systems, where light is
directly converted into electricity using silicon (solar) cells. The
electricity thus generated can be used for lighting or other
electrical applications.
In case of Solar thermal systems, since
conversion efficiency is higher, the cost is relatively less and
saving is more.
In respect of Solar PV systems, since
efficiency of conversion is less i.e. 16%, the cost is higher and
saving is less; but in places where conventional power sources are not
available, Solar PV systems are the most suitable ones.
