14/12/2013 Solar power - Wikipedia, the free encyclopedia Solar power From Wikipedia, the free encyclopedia Solar power is the conversion of sunlight into electricity, either directly using photovoltaics (PV), or indirectly using concentrated solar power (CSP). Concentrated solar power systems use lenses or mirrors and tracking systems to focus a large area of sunlight into a small beam. Photovoltaics convert light into electric current using the photoelectric effect.[2] Photovoltaics were initially, and still are, used to power small and medium-sized applications, from the calculator powered by a single solar cell to off-grid homes powered by a photovoltaic array. They The 150 MW Andasol solar power are an important and relatively inexpensive source of electrical energy station is a commercial parabolic where grid power is inconvenient, unreasonably expensive to connect, trough solar thermal power plant, or simply unavailable. However, as the cost of solar electricity is located in Spain. The Andasol plant falling, solar power is also increasingly being used even in grid- uses tanks of molten salt to store connected situations as a way to feed low-carbon energy into the solar energy so that it can continue grid. generating electricity even when the sun isn't shining.[1] Commercial concentrated solar power plants were first developed in the 1980s. The 354 MW SEGS CSP installation is the largest solar power plant in the world, located in the Mojave Desert of California. Other large CSP plants include the Solnova Solar Power Station (150 MW) and the Andasol solar power station (150 MW), both in Spain. The 250+ MW Agua Caliente Solar Project in the United States, and the 221 MW Charanka Solar Park in India, are the world’s largest photovoltaic power stations. Average insolation showing land area Contents (small black dots) required to replace the world primary energy supply with 1 Concentrating solar power solar electricity (18 TW or 568 2 Photovoltaics Exajoule, EJ, per year). Insolation for 2.1 Photovoltaic power systems most people is from 150 to 300 W/m2 3 Development and deployment or 3.5 to 7.0 kWh/(m2day). 3.1 Photovoltaic power stations 3.2 Concentrating solar thermal power 4 Economics 4.1 Energy cost 4.2 Grid parity 4.3 Self Consumption 4.4 Energy pricing and incentives 5 Environmental impacts 5.1 Greenhouse gases 5.2 Energy payback 5.3 Cadmium 6 Energy storage methods 7 Experimental solar power en.wikipedia.org/wiki/Solar_power 1/22 14/12/2013 Solar power - Wikipedia, the free encyclopedia 8 See also 9 References 10 Sources 11 External links The first three units of Solnova in the foreground, with the two towers of the PS10 and PS20 solar power stations in the background. Concentrating solar power Further information: Solar thermal energy and Concentrated solar power Concentrating Solar Power (CSP) systems use lenses or mirrors and tracking systems to focus a large area of sunlight into a small beam. The concentrated heat is then used as a heat source for a conventional power plant. A wide range of concentrating technologies exists: the most developed are the parabolic trough , the concentrating linear fresnel reflector, the Stirling dish and the solar power tower. Various techniques are used to track the sun and focus light. In all of these systems a working fluid is heated by the concentrated sunlight, and is then used for power generation or energy storage.[3] Thermal storage efficiently allows up to 24 hour electricity generation.[4] A parabolic trough consists of a linear parabolic reflector that concentrates light onto a receiver positioned along the reflector's focal line. The receiver is a tube positioned right above the middle of the parabolic mirror and is filled with a working fluid. The reflector is made to follow the sun during daylight hours by tracking along a single axis. Parabolic trough systems provide the best land-use factor of any solar technology.[5] The SEGS plants in California and Acciona's Nevada Solar One near Boulder City, Nevada are representatives of this technology.[6][7] Compact Linear Fresnel Reflectors are CSP-plants which use many thin mirror strips instead of parabolic mirrors to concentrate sunlight onto two tubes with working fluid. This has the advantage that flat mirrors can be used which are much cheaper than parabolic mirrors, and that more reflectors can be placed in the same amount of space, allowing more of the available sunlight to be used. Concentrating linear fresnel reflectors can be used in either large or more compact plants.[8][9] The Stirling solar dish combines a parabolic concentrating dish with a Stirling engine which normally drives an electric generator. The advantages of Stirling solar over photovoltaic cells are higher efficiency of converting sunlight into electricity and longer lifetime. Parabolic dish systems give the highest efficiency among CSP technologies.[10] The 50 kW Big Dish in Canberra, Australia is an example of this technology.[6] A solar power tower uses an array of tracking reflectors (heliostats) to concentrate light on a central receiver atop a tower. Power towers are more cost effective, offer higher efficiency and better energy storage capability among CSP technologies.[6] The PS10 Solar Power Plant and PS20 solar power plant are examples of this technology. Photovoltaics Main article: Photovoltaics en.wikipedia.org/wiki/Solar_power 2/22 14/12/2013 Solar power - Wikipedia, the free encyclopedia A solar cell, or photovoltaic cell (PV), is a device that converts light into electric current using the photoelectric effect. The first solar cell was constructed by Charles Fritts in the 1880s.[11] The German industrialist Ernst Werner von Siemens was among those who recognized the importance of this discovery.[12] In 1931, the German engineer Bruno Lange developed a photo cell using silver selenide in place of copper oxide,[13] although the prototype selenium cells converted less than 1% of incident light into electricity. Following the work of Russell Ohl in the 1940s, researchers Gerald Pearson, Calvin Fuller and Daryl Chapin created the silicon solar cell in 1954.[14] These early solar cells cost 286 USD/watt and reached efficiencies of 4.5–6%.[15] Photovoltaic power systems Main article: Photovoltaic system Solar cells produce direct current (DC) power which fluctuates with the sunlight's intensity. For practical use this usually requires conversion to certain desired voltages or alternating current (AC), through the use of inverters.[16] Multiple solar cells are connected inside modules. Modules are wired together to form arrays, then tied to an inverter, which produces power at the desired voltage, and for [16] AC, the desired frequency/phase. A diagram of a parabolic trough solar farm (top), and an end view of how a Many residential systems are connected to the grid wherever parabolic collector focuses sunlight [17] available, especially in developed countries with large markets. In onto its focal point. these grid-connected PV systems, use of energy storage is optional. In certain applications such as satellites, lighthouses, or in developing countries, batteries or additional power generators are often added as back-ups. Such stand-alone power systems permit operations at night and at other times of limited sunlight. Development and deployment See also: Solar power by country and Growth of photovoltaics The 71.8 MW Lieberose Photovoltaic Park in Germany. The early development of solar technologies starting in the 1860s was driven by an expectation that coal would soon become scarce. However, development of solar technologies stagnated in the early 20th century in the face of the increasing availability, economy, and utility of coal and petroleum.[18] In 1974 it was estimated that only six private homes in all of North America were entirely heated or cooled by functional solar power systems.[19] The 1973 oil embargo and 1979 energy crisis caused a reorganization of energy policies around the world and brought renewed attention to developing solar technologies.[20][21] Deployment strategies focused on incentive programs such as the Federal Photovoltaic Utilization Program in the US and the Sunshine Program in Japan. Other efforts included the formation of research facilities in the US (SERI, now NREL), Japan (NEDO), and Germany (Fraunhofer Institute for Solar Energy Systems ISE).[22] en.wikipedia.org/wiki/Solar_power 3/22 14/12/2013 Solar power - Wikipedia, the free encyclopedia Between 1970 and 1983 photovoltaic installations grew rapidly, but falling oil prices in the early 1980s moderated the growth of PV from 1984 to 1996. Since 1997, PV development has accelerated due to supply Simplified schematics of a grid- issues with oil and natural connected residential PV power Nellis Solar Power Plant, 14 MW [16] gas, global warming system power plant installed 2007 in Nevada, concerns, and the USA improving economic position of PV relative to other energy technologies.[23] Photovoltaic production growth has averaged 40% per year since 2000 and installed capacity reached 39.8 GW at the end of 2010,[24] of them 17.4 GW in Germany. As of October 2011, the largest photovoltaic (PV) power plants in the world are the Sarnia Photovoltaic Power Plant (Canada, 97 MW), Montalto di Castro Photovoltaic Power Station (Italy, 84.2 MW) and Finsterwalde Solar Park (Germany, 80.7 MW).[25] Solar photovoltaic installation in Germany (MW) plotted against 58% There are also many large plants under construction. The Desert growth curve Sunlight Solar Farm is a 550 MW solar power plant under construction in Riverside County, California, that will use thin-film solar photovoltaic modules made by First Solar.[26] The Topaz Solar Farm is a 550 MW photovoltaic power plant, being built in San Luis Obispo County, California.[27] The Blythe Solar Power Project is a 500 MW photovoltaic station under construction in Riverside County, California.