The sun is the source of all energy either in the form of fossil fuels or wood. After all, these substances have been made from the energy of the sun and have stored its energy. However, the heat of the sun can be used directly in the form of solar energy. Solar cells and giant solar plants are used for generating electricity. It has been estimated that the solar energy reaching the Earth’s surface in one year is double than we will ever receive from all the Earth’s resources of coal, oil, natural gas, and uranium together.