There are many possible ways of tapping solar energy. It may be intercepted space by a satellite beamed as an intense beam. simply, it can and to earth be collected as that are basically it reaches the earth's surface by collectors hot water radiators working in reverse. Such collectors can provide space heating in houses or can be used as the basis for air-conditioning systems. Solar energy can also be converted directly into electricity. at low efficiency, by solar cells similar to those used in satellites. Alternatively, it can be collected by using it to grow plants that are then used directly as fuei, or converted into a liquid fuel by chemical conver- sion or by the use of micro-organism. Finally, the heat stored in the sea can be used to provide energy by employing the temperature difference between water at the surface exposed to the sun and cold deep water.