Man needs energy in every step of life. Energy can exist in many forms such as kinetic, potential, chemical, electrical etc. One may change into another; whatever be the form, the source of energy may be primarily classified into two groups e.g. conventional source and non-conventional source. Most of our requirements of energy are met through the conventional sources of fossil fuels like coal, petroleum & gas as well as nuclear fuel i.e. radioactive element. A small amount of energy called hydroelectricity is also there. All these methods of producing energy except the hydroelectricity are great threats to the environment and as a whole ecology of the earth. Moreover, the stocks of the fossil fuels are not endless. Such stocks will also be exhausted some day. Undoubtedly one of the greatest challenges facing mankind in the new millennium is the conservation of the environment while searching for new source of energy.

Among the alternative energy sources the renewable energy sources are of prime importance and considered to be most vital inputs for our future energy requirements. These are solar energy, hydro energy, wind energy, bio-mass energy, wave energy, ocean thermal energy and tidal energy. Energy generated from these sources is free of pollution and completely ensures the conservation of the environment and maintains the ecological balance of the earth and thus our civilization in the long run. The above sources of energy are practically inexhaustible. Obviously research in the utilization of solar energy has gathered considerable momentum especially in the industrialized countries.

Considering the above factors and more other reasons, man will have to increasingly depend upon renewable resources of energy to cope up with the growing demand of energy of the developed and developing countries as well assimultaneous conservation of the environment.

Sun is the primary source of energy and all forms of energy on the earth are derived from it.

All countries in the world receive solar energy though the quantum varies from one part to another. The solar energy can be utilized either by deriving energy directly from sunlight through thermal, photovoltaic, and hydrogen gas technologies or indirectly in the form of wind, biomass, biogas and tides through other developed technologies. Research and development for more advanced technologies of both direct and indirect methods are going on full swing throughout the world to minimize the initial cost of installation especially in industrialized countries on the grounds of its free availability, pollution-free character and capability to use in a decentralized manner reducing the cost of transmission and distribution of power. In almost all sectors of such technologies, the running cost of the systems is almost negligible compared to the running cost of the conventional energy generating systems.