Solar energy represents a viable alternative source of energy to the fossil fuels that are currently threatening our very existence by polluting air and water. Now is the time to take advantage of this abundant resource. Solar energy is received through radiation which covers very wide spectrum of frequencies from infrared through the visible to ultraviolet frequencies. Radiations in Infrared and Ultraviolet range cannot be seen, only visible range of radiations is seen.
Solar energy for heating
The infrared radiation causes heating effect. For ages men have been utilizing solar energy for heating. Even in the medieval ages techniques had been developed to design houses in a manner to use the solar energy to keep houses warm in winter and provide cooling draughts of air to cool and ventilate houses in summer. For a long time various methods have been used to utilize solar radiation to provide hot water for domestic use and for comfort heating of homes; solar cookers also have been used for cooking food. There was a time when vehicles driven by steam engines running on solar energy were being tried out.
In the recent years many developments have taken place by which not only large scale domestic hot water supply or space heating of large buildings is done by use of solar energy but it is being used to supplement power generation in large thermal power stations.
Solar energy for electricity
Generating electricity by photovoltaic conversion is a relatively modern development. Photo in Greek means light and Volt relates to scientist Alessandro Volta, who invented electric battery and contributed greatly to the study of electricity. The term Photo-Voltaic, this, refers to light-electricity or electricity from light. A PV (photovoltaic) cell is a device made of Silicon a metal- processed in such a manner that it will exhibit strong photovoltaic properties converting visible solar radiation into electricity. Individual PV cells or solar cells are small and give hardly 1 or 2 watts of power. PV cells are assembled in various configurations so that sufficient electricity can be generated by using them for practical purposes.
Recent developments have made it possible to use photovoltaic cells for power supplies on satellites and space stations, to supplement power generation in large power stations, to run cars on solar power and to provide clean power to remote and inaccessible communities.
We shall be reviewing the developments that have taken place in utilization of solar energy as an important inexhaustible alternative source of energy.