Solar powerSolar power describes a number of methods of harnessing energy from the light of the sun. It has been present in many traditional building methods for centuries but has become of increasing interest in developed countries as other power sources such as fossil fuels become more scarce and expensive both in financial and environmental terms. It is often employed where other supplies of power are absent such as in remote locations and in space. As the earth orbits the sun, it receives 1,410 W / m2 of energy, as measured upon a surface kept normal (at a right angle) to the sun. Of this, approximately 19% of the energy is absorbed by the atmosphere, while clouds on average reflect a further 35% of the total energy. After passing through the Earth's atmosphere, most of the sun's energy is in the form of visible and ultraviolet light. Plants use solar energy to create chemical energy through photosynthesis. We use this energy when we burn wood or fossil fuels.
Classifications of solar powerDirect or indirectSolar power can be classified as direct or indirect. Direct solar power involves only one transformation into a usable form.
Indirect solar power involves more than one transformation to reach a usable form.
Many other types of power generation are indirectly solar-powered. Plants use photosynthesis to convert solar energy to chemical energy, which can later be burned as fuel to generate electricity; oil and coal originated as plants. Hydroelectric dams and wind turbines are indirectly powered by the sun.
Passive or activeSolar power can also be classified as passive or active: Passive solar systems are systems that do not involve the input of any other forms of energy apart from the incoming sunlight. Active solar This usually refers to system which use additional mechanisms such as circulation pumps, air blowers or automatic systems which aim collectors at the sun. Types of solar power applicationsMost solar energy used today is harnessed as heat or electricity.
Solar design in architectureSolar design is the use of architectural features to replace the use of grid electricity and fossil fuels with the use of solar energy and decrease the energy needed in a home or building with insulation and efficient lighting and appliances.
Solar hot waterSolar hot water systems are quite common in some countries where a small flat panel collector is mounted on the roof and able to meet most of a household's hot water needs. Cheaper flat panel collectors are also often used to heat swimming pools, thereby extending their swimming seasons. Solar cookingA solar box cooker traps the sun's power in an insulated box; these have been successfully used for cooking, pasteurization and fruit canning. Solar cooking is helping many developing countries, both reducing the demands for local firewood and maintaining a cleaner environment for the cooks. The first known western solar oven is attributed to Horace de Saussure, a Swiss naturalist experimenting as early as 1767. Photovoltaic cellsSolar cells (also referred to as photovoltaic cells) are devices or banks of devices that use the photoelectric effect of semiconductors to generate electricity directly from the sunlight. As their manufacturing costs have remained high during the twentieth century, their use has been limited to very low power devices such as calculators with LCD displays or to generate electricity for isolated locations which could afford the technology. The most important use to date has been to power orbiting satellites and other spacecraft. As manufacturing costs decreased in the last decade of the twentieth century, solar power has become cost-effective for many remote low power applications such as roadside emergency telephones, remote sensing, and limited "off grid" home power applications. Though their cost is not yet competitive with conventional power and hydroelectricity, it has been declining steadily and is now within a factor of 2 in many areas. Solar power plantsSolar power plants generally use reflectors to concentrate sunlight into a heat absorber.
Solar chemicalThere have been experiments to harness energy by absorbing sunlight in a chemical reaction in a way similar to photosynthesis without using living organisms but no practical process has yet emerged. Energy StorageFor a stand-alone system, some means must be employed to store the collected energy for use during hours of darkness or cloud cover - either as electrochemically in batteries, or in some other form such as hydrogen (produced by electrolysis of water), flywheels in vacuum, or superconductors. Storage always has an extra stage of energy conversion, with consequent energy losses, greatly increasing capital costs. One way around this is to export excess power to the power grid, drawing it back when needed. This effectively uses the power grid as a battery.
Deployment of Solar PowerDeployment of solar power depends largely upon local conditions and requirements. But as all industrialised nations share a need for electricity, it is clear that solar power will increasingly be used to supply a cheap, reliable electricity supply. North AmericaIn some areas of the U.S., solar electric systems are already competitive with utility systems. As of 2002, there is a list of technical conditions: There must be many sunny days. The systems must sell power to the grid, avoiding battery costs. The solar systems must be inexpensively mass-purchased, which usually means they must be installed at the time of construction. Finally, the region must have high power prices. For example, Southern California has about 260 sunny days a year, making it an excellent venue. It yields about 9%/yr returns of investment when systems are installed at $9/watt (not cheap, but feasible), and utility prices are at $0.095 per kilowatt-hour (the current base rate). On-grid solar power can be especially feasible when combined with time-of-use net metering, since the time of maximum production is largely coincident with the time of highest pricing.
Europe & JapanSeveral experimental photovoltaic (PV) power plants of 300 - 500 kW capacity are connected to electricity grids in Europe and the U.S. Japan has 150 MWe installed. A large solar PV plant is planned for the island of Crete. Research continues into ways to make the actual solar collecting cells less expensive and more efficient. Other major research is investigating economic ways to store the energy which is collected from the sun's rays during the day. A large parabolic reflector solar furnace is located in the Pyrenees at Odeillo, France. It is used for various research purposes. See alsoMain Renewable resource, Renewable energy, Sustainable design Solar: Solar box cooker, Solar thermal energy, Sun, Solar power satellite, Current solar income Energy crisis: 1973 energy crisis, 1979 energy crisis Electricity: Electricity generation, Electricity retailing, Energy storage, Green electricity, Direct current, Photoelectric effect, Power station, Power supply, Microwave power transmission, Solar cell, Power plant, Solar chimney Lists: List of conservation topics, List of physics topics People: Leonardo da Vinci, Charles Eames, Charles Kettering, Menachem Mendel Schneerson Other: Autonomous building, Solar-Club/CERN-Geneva-Switzerland, Electric vehicle, Mass driver, Clock of the Long Now, Tidal power, Smart 1, Science in the United States, Slope Point, Back to the land, Architectural engineering, Ecology, List of conservation topics, Nine Nations of North America External links
cy:Egni solar da:Solenergi de:Sonnenenergie nl:zonne-energie es:energía solar sv:Solenergi fr:Énergie solaire Categories: HVAC | Renewable energy | Sun |
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