Alternative Energy, Solar

Active Solar Energy

Active solar energy can be converted to electricity and used directly, as in the case of solar heating applications and solar photovoltaic (PV) applications. In a PV cell, sunlight strikes a layer of semiconductors, which in turn creates an electrical current. [Page 38]By 2005, this proven technology was being used to provide heat and power to well over 650,000 homes, primarily in the United States, Germany, and Japan. Electricity can be produced from solar power by placing solar panels on roofs. These panels consist of PV cells that can convert sunlight directly into electricity. Moreover, electricity produced as solar power during the day may be stored in batteries for use at night.

Another method of electric generation employs the use of turbines. In turbines, the sun's heat can be used to convert water into steam and then this steam is used to run turbines. The turbines, in turn, run generators, which produce electricity. Solar PV applications have found many uses in rural areas for multiple activities besides home lighting. Remote villages deprived of grid power can be easily powered using solar photovoltaic technology. The economics of rural electrification can be attractive considering the high cost of power transmission and erratic power supply in rural areas. From portable indoor uses such as calculators, to generating plants alongside railways and roads, PVs are adaptable. They easily function across most areas in both the Northern and Southern Hemispheres.

Passive Solar Energy

Passive solar thermal technology is employed for collecting and converting the sun's energy to heating applications such as water and air heating, cooking and drying, steam generation, and distillation. To accomplish this, a solar thermal collector device absorbs and stores heat. Solar thermal technology requires good heat conducting materials, insulation, and reflectors. Solar geysers, solar concentrators, and solar cookers are some examples of devices based on solar thermal technology.

Also, solar energy can be put into use by incorporating appropriate designs in buildings to maximize utilization of solar energy for various purposes such as lighting, air conditioning, and water and space heating/cooling and thereby reduce external energy inputs. PV cells require high exposure to direct sunlight. To assure maximum exposure to the sun throughout the day, a phyrheliometer is used to calculate how much sun exposure a location experiences. This information is useful in determining whether or not a specific location is suitable for solar energy, as well as what direction the cells should face. In many cases, these cells are placed on rooftops.

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