Modern ways for concentrating solar power(CSP) ABSTRACT Advanced and This essay is a summary of modern ways for concentrating alternative solar power, within this essay all types of CSP will be discussed. Things like their main components, costs and energy performance will be discussed. Finally, a little forecast and systems conclusions about it will be implied. (302.064) Eric Martínez Lara 1228149 302.064 - Advanced and alternative energy systems Modern ways for concentrat ing solar energy Contents Introduction .................................................................................................................................. 3 Different types of CSP (concentrating solar power) ..................................................................... 5 parabolic trough collector technology ...................................................................................... 5 linear fresnel plants ................................................................................................................. 10 solar dish systems ................................................................................................................... 13 power tower solar plants ........................................................................................................ 18 Thermal Storage Systems for Concentrating Solar Power ...................................................... 22 forecast and conclusions ............................................................................................................. 26 Figure list ..................................................................................................................................... 31 References list ............................................................................................................................. 32 Eric Martinez Lara 2 302.064 - Advanced and alternative energy systems Modern ways for concentrat ing solar energy Introduction The origin of this kind of power production comes from a legend, this legend explain that Archimedes using a "burning glass" concentrated sunlight on the invading Roman fleet and repelled them from Syracuse. Then, in 1973 a Greek scientist, Dr. Ioannis Sakkas, which was curious about whether Archimedes could have destroyed the Roman fleet in 212 BC, put near of 60 Greek sailors holding oblong mirrors tipped to catch the sun's rays and direct them at a target plywood silhouette 160 feet away. This ship caught fire after few minutes. Figure 1: Ioannis Sakkas experiment On the other hand, in 1866, Auguste Mouchout used a parabolic trough to produce steam for the first solar steam engine. Then, the first patent for solar collector was obtained by the Italian Alessandro Battaglia, in the same year. Over the following years, inventors such as John Ericsson and Frank Shuman developed concentrating solar-powered devices for irrigation, refrigeration and locomotion. Then, in 1968, Professor Giovanni Francia designed and built the first concentrated- solar plant. This plant had the architecture of today's concentrated-solar plants with a solar receiver in the center of a field of solar collectors. This plant was able to produce 1 MW with a superheated steam of 100 bar and 500 degrees Celsius. The next development came in 1981, in Southern California, it was a Solar One power tower of 10MW. But the parabolic-trough technology of the nearby Solar Energy Generating Systems, begun in 1984, which was more workable. Concentrated solar power (also called concentrating solar power, concentrated solar thermal, and CSP) are systems which use mirrors or lenses to concentrate a large area onto a small area. This concentrated light is converted to heat, which drives a heat Eric Martinez Lara 3 302.064 - Advanced and alternative energy systems Modern ways for concentrat ing solar energy engine (usually a steam turbine) connected to an electrical power generator, in order to produce electrical power. Figure 2: CSP example The innovative aspect of CSP is that it captures and concentrates the sun’s energy to provide the heat required to generate electricity, rather than using fossil fuels or nuclear reactions. Another attribute of CSP plants is that they can be equipped with a heat storage system in order to generate electricity even when the sky is cloudy or after sunset. This significantly increases the CSP capacity factor compared with solar photovoltaics and, more importantly, enables the production of dispatchable electricity, which can facilitate both grid integration and economic competitiveness. CSP technologies therefore benefit from advances in solar concentrator and thermal storage technologies, while other components of the CSP plants are based on rather mature technologies and cannot expect to see rapid cost reductions. Eric Martinez Lara 4 302.064 - Advanced and alternative energy systems Modern ways for concentrat ing solar energy Different types of CSP (concentrating solar power) CSP plants can be divided into two different groups, based on whether the solar collectors concentrate the sun rays along a focal line or on a single focal point (with much higher concentration factors). Line-focusing systems include parabolic trough and linear Fresnel plants and have single-axis tracking systems. Point-focusing systems include solar dish systems and solar tower plants and include two-axis tracking systems to concentrate the power of the sun. The next step will be to intensely present, one by one, all systems that I have mentioned above. Line-focusing systems parabolic trough collector technology The parabolic trough collectors (PTC) consist of solar collectors (mirrors), heat receivers and support structures. The parabolic-shaped mirrors are constructed by forming a sheet of reflective material into a parabolic shape that concentrates incoming sunlight onto a central receiver tube at the focal line of the collector. The arrays of mirrors can be 100 metres (m) long or more, with the curved aperture of 5 m to 6 m. A single-axis tracking mechanism is used to orient both solar collectors and heat receivers toward the sun (A.T. Kearney and ESTELA, 2010). PTC are usually aligned North-South and track the sun as it moves from East to West to maximize the collection of energy. The receiver comprises the absorber tube (usually metal) inside an evacuated glass envelope. The absorber tube is generally a coated stainless steel tube, with a spectrally selective coating that absorbs the solar (short wave) irradiation well, but emits very little infrared (long wave) radiation. This helps to reduce heat loss. Evacuated glass tubes are used because they help to reduce heat losses. Eric Martinez Lara 5 302.064 - Advanced and alternative energy systems Modern ways for concentrat ing solar energy Figure 3: Solar/Rankine parabolic trough system schematic Components of a Parabolic trough solar collector The basic component of a parabolic trough solar field is the solar collector assembly or SCA. A solar field consists of hundreds or potentially thousands of solar collector assemblies. Each solar collector assembly is an independently tracking, parabolic trough solar collector composed of the following subsystems: Concentrator Structure Mirrors or reflectors Linear receiver or heat collection element Collector balance of system Also, each parabolic trough solar collector assembly consists of multiple, torque-tube or truss assemblies (often referred to as solar collector elements or modules). Eric Martinez Lara 6 302.064 - Advanced and alternative energy systems Modern ways for concentrat ing solar energy Concentrator Structure The structural skeleton of the parabolic trough solar collector is the concentrator structure. The concentrator structure: Supports the mirrors and receivers, maintaining them in optical alignment Withstands external forces, such as wind Allows the collector to rotate, so the mirrors and receiver can track the sun. Mirrors or Reflectors The most obvious object within the parabolic trough solar collector are its parabolic- shaped mirrors or reflectors. Those mirrors are curved in the shape of a parabola, which allows them to concentrate the sun's direct beam radiation on the linear receiver. All current parabolic trough power plants use glass mirror panels manufactured by Flabeg. The mirrors are second-surface silvered glass mirrors (which means that the reflective silver layer is on the backside of the glass). The glass is a 4-milimeter-thick, special low iron or white glass with a high transmittance. The mirrors have a solar- weighted specular reflectivity of about 93.5%. A special multilayer paint coating protects the silver on the back of the mirror. And each mirror panel is approximately 2 square meters in area. The glass mirror panels have performed very well during the operation of the SEGS (solar electric generating system) power plants. They've maintained high reflectivity and suffer low annual breakage rates. However, mirror breakage does occur and replacements have been relatively expensive. A number of alternative mirror concepts have been under development to reduce cost, improve reliability, or increase performance. Linear Receiver or Heat Collection Element The parabolic trough linear receiver, also called a heat collection element (HCE), is one of the primary reasons for the high efficiency of the original Luz parabolic trough collector design. Eric Martinez Lara 7 302.064 - Advanced and alternative energy systems Modern ways for concentrat ing solar energy The receiver is a