In Vedic age peoples expected the sun as chief god. Now the whole world is praising the sun for its huge source of energy. In fact all the available energy on the earth is due to the sun. All the known sources of energy are being rapidly consumed, therefore as a source of energy is needed.
About 100 year ago it was known that with the help of a foil of Selenium Solar Energy can be converted into Electrical Energy. But only 0.6% Solar Energy can be converted into Electrical Energy. In 1954 a practical Solar cell was manufactured that can be converted 1% Solar Energy into Electrical Energy. The
efficiency of Selenium Solar cell is up to 25%.