Concentrated solar power largest CSP Project in the world has been installed in Abu Dhabi, by Masdar.[5] CSP growth is expected to continue at a fast pace. As of January 2014, Spain had a total capacity of 2,204 MW making this country the world leader in CSP. Interest is also notable in North Africa and the Middle East, as well as India and China. The global market has been domi- nated by parabolic-trough plants, which account for 90% of CSP plants.[4] CSP is not to be confused with concentrated photovoltaics (CPV). In CPV, the concentrated sunlight is converted The PS10 Solar Power Plant concentrates sunlight from a field directly to electricity via the photovoltaic effect. of heliostats onto a central solar power tower. 1 History A legend has it that Archimedes used a “burning glass” to concentrate sunlight on the invading Roman fleet and repel them from Syracuse. In 1973 a Greek scientist, Dr. Ioannis Sakkas, curious about whether Archimedes could really have destroyed the Roman fleet in 212 BC, lined up nearly 60 Greek sailors, each holding an oblong mirror tipped to catch the sun’s rays and direct them at a tar-covered plywood silhouette 160 feet away. The ship caught fire after a few minutes; however, historians con- tinue to doubt the Archimedes story.[6] Part of the 354 MW SEGS solar complex in northern San In 1866, Auguste Mouchout used a parabolic trough to Bernardino County, California. produce steam for the first solar steam engine. The first patent for a solar collector was obtained by the Italian Concentrated solar power (also called concentrating Alessandro Battaglia in Genoa, Italy, in 1886. Over solar power, concentrated solar thermal, and CSP) the following years, inventors such as John Ericsson and systems generate solar power by using mirrors or lenses Frank Shuman developed concentrating solar-powered to concentrate a large area of sunlight, or solar thermal devices for irrigation, refrigeration, and locomotion. In energy, onto a small area. Electricity is generated when 1913 Shuman finished a 55 HP parabolic solar thermal the concentrated light is converted to heat, which drives energy station in Maadi, Egypt for irrigation.[7][8][9][10] a heat engine (usually a steam turbine) connected to an The first solar-power system using a mirror dish was built electrical power generator or powers a thermochemical by Dr. R.H. Goddard, who was already well known for reaction (experimental as of 2013).[1][2][3] his research on liquid-fueled rockets and wrote an article in 1929 in which he asserted that all the previous obsta- CSP is being widely commercialized and the CSP mar- [11] ket has seen about 740 MW of generating capacity added cles had been addressed. between 2007 and the end of 2010. More than half of Professor Giovanni Francia (1911–1980) designed and this (about 478 MW) was installed during 2010, bring- built the first concentrated-solar plant, which entered into ing the global total to 1095 MW. Spain added 400 MW operation in Sant'Ilario, near Genoa, Italy in 1968. This in 2010, taking the global lead with a total of 632 MW, plant had the architecture of today’s concentrated-solar while the US ended the year with 509 MW after adding plants with a solar receiver in the center of a field of solar 78 MW, including two fossil–CSP hybrid plants.[4] The collectors. The plant was able to produce 1 MW with su- Middle East is also ramping up their plans to install CSP perheated steam at 100 bar and 500 °C.[12] The 10 MW based projects and as a part of that Plan, Shams-I the Solar One power tower was developed in Southern Cali- 1 2 2 CURRENT TECHNOLOGY fornia in 1981, but the parabolic-trough technology of the nearby Solar Energy Generating Systems (SEGS), begun in 1984, was more workable. The 354 MW SEGS is still the largest solar power plant in the world, and will remain so until the 390 MW Ivanpah power tower project comes online. 2 Current technology CSP is used to produce electricity (sometimes called so- lar thermoelectricity, usually generated through steam). Concentrated-solar technology systems use mirrors or lenses with tracking systems to focus a large area of sun- light onto a small area. The concentrated light is then Parabolic trough at a plant near Harper Lake, California used as heat or as a heat source for a conventional power plant (solar thermoelectricity). The solar concentrators used in CSP systems can often also be used to provide industrial process heating or cooling, such as in solar air- mercial parabolic trough plant are representative, along- conditioning. side with Plataforma Solar de Almería's SSPS-DCS test facilities in Spain.[20] Concentrating technologies exist in five common forms, namely parabolic trough, enclosed trough, dish Stir- lings, concentrating linear Fresnel reflector, and solar [13] power tower. Although simple, these solar concen- 2.1.1 Enclosed trough trators are quite far from the theoretical maximum concentration.[14][15] For example, the parabolic-trough concentration gives about 1/3 of the theoretical maxi- Enclosed trough systems are used to produce process mum for the design acceptance angle, that is, for the same heat. The design encapsulates the solar thermal system overall tolerances for the system. Approaching the theo- within a greenhouse-like glasshouse. The glasshouse cre- retical maximum may be achieved by using more elabo- ates a protected environment to withstand the elements rate concentrators based on nonimaging optics.[16] that can negatively impact reliability and efficiency of the solar thermal system.[21] Lightweight curved solar- Different types of concentrators produce different peak reflecting mirrors are suspended from the ceiling of the temperatures and correspondingly varying thermody- glasshouse by wires. A single-axis tracking system posi- namic efficiencies, due to differences in the way that they tions the mirrors to retrieve the optimal amount of sun- track the sun and focus light. New innovations in CSP light. The mirrors concentrate the sunlight and focus it on technology are leading systems to become more and more a network of stationary steel pipes, also suspended from [17] cost-effective. the glasshouse structure.[22] Water is carried throughout the length of the pipe, which is boiled to generate steam when intense solar radiation is applied. Sheltering the 2.1 Parabolic trough mirrors from the wind allows them to achieve higher tem- perature rates and prevents dust from building up on the Main article: Parabolic trough mirrors.[21] 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 di- 2.2 Fresnel reflectors rectly above the middle of the parabolic mirror and filled with a working fluid. The reflector follows the sun dur- ing the daylight hours by tracking along a single axis. A Main article: Compact Linear Fresnel Reflector working fluid (e.g. molten salt[18]) is heated to 150–350 °C (423–623 K (302–662 °F)) as it flows through the re- Fresnel reflectors are made of many thin, flat mirror strips ceiver and is then used as a heat source for a power gener- to concentrate sunlight onto tubes through which working ation system.[19] Trough systems are the most developed fluid is pumped. Flat mirrors allow more reflective sur- CSP technology. The Solar Energy Generating Systems face in the same amount of space as a parabolic reflector, (SEGS) plants in California, the world’s first commercial thus capturing more of the available sunlight, and they are parabolic trough plants, Acciona’s Nevada Solar One near much cheaper than parabolic reflectors. Fresnel reflectors Boulder City, Nevada, and Andasol, Europe’s first com- can be used in various size CSPs.[23][24] 3 but they offer higher efficiency and better energy stor- age capability. The Solar Two in Daggett, California and the CESA-1 in Plataforma Solar de Almeria Almeria, Spain, are the most representative demonstration plants. The Planta Solar 10 (PS10) in Sanlucar la Mayor, Spain, is the first commercial utility-scale solar power tower in the world. eSolar's 5 MW Sierra SunTower, located in Lancaster, California, is the only CSP tower facility op- erating in North America. The National Solar Thermal Test Facility, NSTTF located in Albuquerque, NM, is an experimental solar thermal test facility with a heliostat field capable of producing 6 MW. 3 Deployment around the world A dish Stirling Main articles: List of solar thermal power stations and Solar power by country 2.3 Dish Stirling 1,000 2,000 Main article: Dish Stirling 3,000 4,000 A dish Stirling or dish engine system consists of a stand- 1984 alone parabolic reflector that concentrates light onto a re- 1990 ceiver positioned at the reflector’s focal point. The reflec- 1995 tor tracks the Sun along two axes. The working fluid in 2000 the receiver is heated to 250–700 °C (523–973 K (482– 2005 1,292 °F)) and then used by a Stirling engine to gener- 2010 ate power.[19] Parabolic-dish systems provide high solar- Worldwide CSP capacity since 1984 in MW to-electric efficiency (between 31% and 32%), and their modular nature provides scalability. The Stirling Energy The commercial deployment of CSP plants started by Systems (SES), United Sun Systems (USS) and Science 1984 in the US with the SEGS plants until 1990 when Applications International Corporation (SAIC) dishes at the last SEGS plant was completed. From 1991 to 2005 UNLV, and Australian National University's Big Dish in no CSP plants were built anywhere in the world.