Solar energy is derived ultimately from the sun. It can be divided 1 direct and indirect categories. Most energy sources on Earth are forms of indirect solar energy, 2 we usually don’t think of them in that way. Coal, oil and natural gas derived from ancient biological material 3 took its energy from the sun millions of years ago. 4 the energy in wood and foodstuffs also comes 5 the sun. Movement of the wind, and the evaporation of water to form rainfall which accumulates in rivers and lakes, are also powered by the sun. 6, hydroelectric power and wind and wave power are forms of indirect solar energy. Direct solar energy is 7 we usually mean when we speak of solar power – 8 is the use of sunlight for heating or generating electricity. Solar energy research and applications have been receiving increasing attention throughout the world as solar energy must play a much greater role in the energy mix in upcoming years.