Solar energy comes from the Sun to the Earth in the form of light and heat. It can be converted into electricity by solar cells. Today, scientists are engaged in developing new techniques for the benefit of mankind.

           Experiments have shown that when sunlight falls on certain metals like potassium and silicon, electrons are emitted from their surfaces. These electrons are known as photoelectrons and this phenomenon is called photoelectric effect. Photoelectrons so emitted can be used to produce electric current.

           Photoelectric effect has been used for the making of solar cells. A solar cell, in fact, is a device that directly converts solar energy into electric energy. These wafers of silicon element are used for making solar cells. Generally, a four centimetre long and two centimetre broad and 0.14 millimetre thick silicon wafer is used for one solar cell. When sunlight falls on this wafer it gets converted into electric energy. Each solar cell is capable of producing about a half volt of electricity.

           To produce useful quantities of electric current, it is necessary to join together a great number of solar cells. The cells are joined together in big panels and are placed in the sunlight. A panel of about 20,000 solar cells can produce 500 watts of electric power. The electricity produced thus can be used either immediately or can be used to charge electric storage batteries for later use. Materials like cadmium sulphide and gallium arsenide are also being used for making solar cells.

           Solar cells have several different uses. In sunny places, solar panels are used to provide boost power to telephone signals. In space where the supply of solar energy is plenty, solar cells are particularly useful. Spacecrafts, space-laboratories and satellites have a number of solar panels to provide power for their equipments.

          The biggest solar energy furnace of the world is in California, USA. It uses almost 2000 mirrors, which focus the sun rays on to a boiler unit on top of a tower. This produces steam which is used to drive electricity generating turbines. In India, The Bharat Heavy Electricals Ltd. (BHEL) and Central Electronics Ltd. (CEL) are making cells that have found many applications.