The sun is the ultimate source of almost all kinds of energy on earth, either directly or indirectly. Fossil fuels are the transformed forms of plants and animals which once lived on the earth and grew capturing the energy of the sun. Biomass is a product of photosynthesis where the sun has the major role. Hydro-electricity depends upon the water cycle which again is dependent on solar radiation. Similarly, wind energy, tidal power, wave power all, in some way or other, and depend on the sun.