(a) Heat radiated by the sun is effectively trapped by solar collectors to heat water. A wide variety of solar heating systems are now in use.
(b) Solar heating systems were initially used as a supplementary hot water source to a main hot water or steam boiler. But recent advances have made such systems more efficient and reliable, thus making them a primary source of hot water supplemented by other conventional sources.
(c) Buildings such as hotels, hospitals, hostels and manufacturing industries requiring hot water can usefully utilize solar hot water heating systems to save conventional fuels.
(d) To be effective and efficient the solar panels need to be oriented towards the south at an angle which depends on the latitude of the place. Solar panels require large surface areas on roof or at ground level with proper access for cleaning of the panels periodically and maintenance.