DIRECT UTILIZATION OF SOLAR ENERGY
Burning fossil fuels or recently grown biomass, or harnessing the wind or running water are indirect ways of using the sun's energy. (The burning of fossil fuels is using energy taken from the sun millions of years ago.) It is possible to use the direct or the diffuse rays of the sun to supply the hot water needs of a home or to heat it. If one wished to use the sun's energy directly to generate electricity, it would be necessary to concentrate its rays on some working fluid of an engine and have the fluid research a very high temperature so the engine would operate efficiently.
One of the first written accounts of a high temperature achieved using the sun was related by the Roman historian, Galen. He described the burning of a Roman fleet by Archimedes in 212 B.C. by means of solar rays reflecting off mirrors. The story may be apocryphal but Archimedes did write a book entitled On Burning Mirrors.
Little more is recorded about the uses of solar energy for the next 20 centuries. By the 18th century, there is a record of a solar stove being invented for the cooking of food. This is an area of development that persists to this day. There is some hope that solar stoves could be introduced in parts of the world where the major accessible fuel is the wood of nearby trees. The denuding of an area of trees is a serious environmental danger that pollutes the air and degrades the quality of the soil. In addition, in the parts of the world where wood is the principal fuel, deforestation has already greatly reduced