THE SOLAR ENERGY

Solar energy is a term that encompasses a broad range of energy forms. The sun's energy profoundly affects the world's wind patterns, causes ocean water to evaporate as part of the hydraulic cycle and is essential for plant growth. The winds may be used to turn windmills, the hydraulic cycle makes hydroelectric power possible. Vegetation, which grows in the presence of sunlight, may be burned directly for instance, as wood in a stove or fireplace. Solar energy also makes it possible to harness ocean thermal energy, which uses the temperature difference between sun-warmed surface water and cold water from the ocean depths to produce power.

Although all these indirect means of using energy from the sun are considered solar technologies, the solar energy most commonly refers to direct use of the sun's energy: by means of photovoltaic sollar cells, which convert sunlight into electricity. It includes the use of various devices to convert solar radiation to heat the may be used for heating and cooling buildings, providing hot water for homes, business, industry and generating electricity by thermal means.

Besides the direct conversion of sunlight into electricity by means of photovoltaic cells, sunlight may be used to generate steam, which can then be used to power a turbine for producing electricity. One solar-thermal design, called a power tower, consists of a field of movable mirrors that surround a tower, at the top of which is a boiler. The mirrors, called heliostats, track the sun so as to constantly focus its light on the boiler. At the bottom of the tower is a building that houses a turbine generator. Some scientists heve suggested building huge photovoltaic arrays in earth orbit for producing large amounts of power. Such arrays, called solar space power satellites, would beam collected energy to earth by way of microwaves.