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Thermodynamic cycles for a small particle heat exchange receiver used in concentrating solar power plants / Kyle Kitzmiller in Transactions of the ASME. Journal of solar energy engineering, Vol. 133 N° 3 (N° Spécial) (Août 2011) 

Public ISBD [article]  in Transactions of the ASME. Journal of solar energy engineering > Vol. 133 N° 3 (N° Spécial) (Août 2011) . - 08 p. Titre : Thermodynamic cycles for a small particle heat exchange receiver used in concentrating solar power plants Type de document : texte imprimé Auteurs : Kyle Kitzmiller, Auteur ; Fletcher Miller, Auteur Année de publication : 2012 Article en page(s) : 08 p. Note générale : Solar energy Langues : Anglais (eng) Mots-clés : Brayton  cycle  Convection  Fossil  fuels  Heat  exchangers  Hybrid  power  systems  Solar  energy  concentrators  Solar  power  Solar  power  stations Index. décimale : 621.47 Résumé : Gas-cooled solar receivers for concentrating solar power plants are capable of providing high temperature, pressurized gas for electrical power generation via a Brayton cycle. This can be accomplished by expanding hot, pressurized gas directly through a turbine, or through using a heat exchanger to indirectly heat pressurized air. Gas-cooled receivers can be divided into two basic technologies. In tube based solar receivers, thermal energy is transferred to air through convection with the heated tube wall. This limits receiver efficiency since the tube wall needs to be substantially hotter than the gas inside due to the relatively poor gas heat transfer coefficient. In volumetric receivers, solar energy is absorbed within a volume, rather than on a surface. The absorption volume can be filled with ceramic foam, wires, or particles to act as the absorbing medium. In a small particle heat exchange receiver, for example, submicron sized particles absorb solar radiation and transfer this energy as heat to a surrounding fluid. This effectively eliminates any thermal resistance, allowing for higher receiver efficiencies. However, mechanical considerations limit the size of volumetric, pressurized gas-cooled receivers.In order to solve this problem, several thermodynamic cycles have been investigated, each of which is motivated by key physical considerations in volumetric receivers. The cyclic efficiencies are determined by a new MATLAB code based on previous Brayton cycle modeling conducted by Sandia National Laboratories. The modeling accounts for pressure drops and temperature losses in various components, and parameters such as the turbine inlet temperature and pressure ratio are easily modified to run parametric cases.The performance of a gas-cooled solar receiver is largely a function of its ability to provide process gas at a consistent temperature or pressure, regardless of variations in solar flux, which can vary due to cloud transients or apparent sun motion throughout the day. Consistent output can be ensured by combusting fuel within the cycle, effectively making a solar/fossil fuel hybrid system. Several schemes for hybridization with natural gas are considered here, including externally fired concepts and combined receiver/combustor units. Because the efficiency of hybridized cycles is a function of the solar thermal input, the part load behavior of the recuperated cycle is examined. However, off-design models are simplistic in this research, as the goal of the work is an introductory evaluation of different potential cycles. DEWEY : 621.47 ISSN : 0199-6231 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JSEEDO000133000003 [...] [article] Thermodynamic cycles for a small particle heat exchange receiver used in concentrating solar power plants [texte imprimé] / Kyle Kitzmiller, Auteur ; Fletcher Miller, Auteur . - 2012 . - 08 p. Solar energy Langues : Anglais (eng) in Transactions of the ASME. Journal of solar energy engineering > Vol. 133 N° 3 (N° Spécial) (Août 2011) . - 08 p. Mots-clés : Brayton  cycle  Convection  Fossil  fuels  Heat  exchangers  Hybrid  power  systems  Solar  energy  concentrators  Solar  power  Solar  power  stations Index. décimale : 621.47 Résumé : Gas-cooled solar receivers for concentrating solar power plants are capable of providing high temperature, pressurized gas for electrical power generation via a Brayton cycle. This can be accomplished by expanding hot, pressurized gas directly through a turbine, or through using a heat exchanger to indirectly heat pressurized air. Gas-cooled receivers can be divided into two basic technologies. In tube based solar receivers, thermal energy is transferred to air through convection with the heated tube wall. This limits receiver efficiency since the tube wall needs to be substantially hotter than the gas inside due to the relatively poor gas heat transfer coefficient. In volumetric receivers, solar energy is absorbed within a volume, rather than on a surface. The absorption volume can be filled with ceramic foam, wires, or particles to act as the absorbing medium. In a small particle heat exchange receiver, for example, submicron sized particles absorb solar radiation and transfer this energy as heat to a surrounding fluid. This effectively eliminates any thermal resistance, allowing for higher receiver efficiencies. However, mechanical considerations limit the size of volumetric, pressurized gas-cooled receivers.In order to solve this problem, several thermodynamic cycles have been investigated, each of which is motivated by key physical considerations in volumetric receivers. The cyclic efficiencies are determined by a new MATLAB code based on previous Brayton cycle modeling conducted by Sandia National Laboratories. The modeling accounts for pressure drops and temperature losses in various components, and parameters such as the turbine inlet temperature and pressure ratio are easily modified to run parametric cases.The performance of a gas-cooled solar receiver is largely a function of its ability to provide process gas at a consistent temperature or pressure, regardless of variations in solar flux, which can vary due to cloud transients or apparent sun motion throughout the day. Consistent output can be ensured by combusting fuel within the cycle, effectively making a solar/fossil fuel hybrid system. Several schemes for hybridization with natural gas are considered here, including externally fired concepts and combined receiver/combustor units. Because the efficiency of hybridized cycles is a function of the solar thermal input, the part load behavior of the recuperated cycle is examined. However, off-design models are simplistic in this research, as the goal of the work is an introductory evaluation of different potential cycles. DEWEY : 621.47 ISSN : 0199-6231 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JSEEDO000133000003 [...]