H.P. Garg Centre of Energy Studies Indian Institute of Technology Hauz Khas, New Delhi 110 016 India Heating of water using solar energy is not new and by using a little science and technology in it, the solar energy can be utilized more effectively and economically for heating the water both for domestic and industrial applications. Solar Water Heaters are popular for the last three decades in countries like USA, Australia, Israel, Japan, India. This is the only solar energy application which is commercially, technic ally and economically viable and has been studied for more than 30 years in...