The Experts below are selected from a list of 306 Experts worldwide ranked by ideXlab platform

Chung-yu Tsai - One of the best experts on this subject based on the ideXlab platform.

  • Optimized solar thermal Concentrator System based on free-form trough reflector
    Solar Energy, 2016
    Co-Authors: Chung-yu Tsai
    Abstract:

    Abstract A solar thermal Concentrator System is proposed comprising a free-form-trough (FFT) reflector and a cylindrical heat-pipe receiver. The profile of the reflector is designed using a free-form surface creation (FFSC) method such that each incident ray is directed to a certain user-specified point on the heat-pipe surface. The light ray paths within the Concentrator System are analyzed using a skew-ray tracing approach. A method is then proposed for optimizing the geometry of the Concentrator System in such a way as to achieve a uniform irradiance distribution on the heat-pipe surface. The validity of the proposed optimization approach is demonstrated by means of ZEMAX/SolidWorks-Flow simulations. The results show that the proposed FFT Concentrator yields a significant improvement in both the irradiance uniformity and the heating efficiency compared to conventional cylindrical-trough and parabolic-trough Concentrators.

  • Optimized variable-focus-parabolic-trough reflector for solar thermal Concentrator System
    Solar Energy, 2012
    Co-Authors: Chung-yu Tsai, Psang Dain Lin
    Abstract:

    Abstract A solar thermal Concentrator System is proposed comprising a cylindrical heat-pipe receiver and a variable-focus-parabolic-trough (VFPT) reflector in which the focal length varies as a function of the vertical displacement of the incidence point relative to the horizontal centerline of the receiver. The light ray paths within the Concentrator System are analyzed using a skew-ray tracing approach. A method is then proposed for optimizing the geometry of the Concentrator System in such a way as to optimize the uniformity of the irradiance distribution on the heat-pipe surface. The validity of the proposed optimization method is demonstrated by means of ZEMAX/SolidWorks-Flow simulations. It is shown that the optimized VFPT Concentrator yields a significant improvement in both the irradiance uniformity and the heating efficiency compared to conventional cylindrical-trough and parabolic-trough Concentrators.

Sarah Kurtz - One of the best experts on this subject based on the ideXlab platform.

  • Fill factor as a probe of current‐matching for GaInP2/GaAs tandem cells in a Concentrator System during outdoor operation
    Progress in Photovoltaics, 2008
    Co-Authors: William E. Mcmahon, Keith Emery, Daniel J. Friedman, L. Ottoson, Michelle Young, J. Scott Ward, Anna Duda, C. Kramer, Sarah Kurtz
    Abstract:

    Designing a tandem solar cell for use in a Concentrator System is challenging because: (a) the conditions are variable, so solar cells rarely operate under optimal conditions, and (b) the conditions are not controlled, so any design problems are difficult to characterize. Here, we show how the fill factor can be used as a diagnostic tool to either verify correct System design and operation or to help identify a problem. We give particular attention to the detection of spectral skewing by the Concentrator optics, as this can reduce the performance of GaInP2/GaAs tandem cells and is difficult to characterize. The conclusions are equally valid for GaInP2/GaAs/Ge triple-junction cells. Copyright © 2007 John Wiley & Sons, Ltd.

  • fill factor as a probe of current matching for gainp2 gaas tandem cells in a Concentrator System during outdoor operation
    Progress in Photovoltaics, 2008
    Co-Authors: William E. Mcmahon, Keith Emery, Daniel J. Friedman, L. Ottoson, Michelle Young, J. Scott Ward, Anna Duda, C. Kramer, Sarah Kurtz
    Abstract:

    Designing a tandem solar cell for use in a Concentrator System is challenging because: (a) the conditions are variable, so solar cells rarely operate under optimal conditions, and (b) the conditions are not controlled, so any design problems are difficult to characterize. Here, we show how the fill factor can be used as a diagnostic tool to either verify correct System design and operation or to help identify a problem. We give particular attention to the detection of spectral skewing by the Concentrator optics, as this can reduce the performance of GaInP2/GaAs tandem cells and is difficult to characterize. The conclusions are equally valid for GaInP2/GaAs/Ge triple-junction cells. Copyright © 2007 John Wiley & Sons, Ltd.

  • Daily fill factor variation as a diagnostic probe of multijunction Concentrator Systems during outdoor operation
    High and Low Concentration for Solar Electric Applications II, 2007
    Co-Authors: William E. Mcmahon, Keith Emery, Daniel J. Friedman, L. Ottoson, Michelle Young, J. Scott Ward, Charlene M. Kramer, Anna Duda, Sarah Kurtz
    Abstract:

    Optimizing a Concentrator System which uses multijunction solar cells is challenging because: (a) the conditions are variable, so the solar cells rarely operate under optimal conditions and (b) the conditions are not controlled, so any design problems are difficult to characterize. Any change in the spectral content of direct-beam sunlight as it passes through the Concentrator optics is of particular interest, as it can reduce the performance of multijunction cells and is difficult to characterize. Here we show how the fill factor can be used to detect and diagnose this sort of a "spectral skewing" by the Concentrator optics during outdoor operation. The work presented here is for GaInP 2 /GaAs tandem cells, but the conclusions are equally valid for GaInP 2 /GaAs/Ge triple-junction cells.

  • The effect of chromatic aberrations on two-junction, two-terminal, devices on a Concentrator System [solar cells]
    Proceedings of 1994 IEEE 1st World Conference on Photovoltaic Energy Conversion - WCPEC (A Joint Conference of PVSC PVSEC and PSEC), 1994
    Co-Authors: Sarah Kurtz, Daniel J. Friedman, J. M. Olson
    Abstract:

    Of the modules monitored in PVUSA (Photovoltaics for Utility-Scale Applications), the one with the highest efficiency has been the ENTECH Concentrator System. If the 18%-efficient Si solar cells in this module could be replaced by 26%-28% efficient two-terminal, two-junction (Ga/sub 0.5/In/sub 0.5/P/GaAs) devices, the efficiency of the System could be increased. However, two-junction, two-terminal devices present a special problem in that they must be current matched to retain their high efficiencies. This implies that variations in the spectrum caused by the focusing optics could be a potential problem. In this study, the authors undertake to assess the severity of this problem and find that, when properly aligned, ENTECH's current lens introduces spectral nonuniformities which cause about 4% loss in power output for two-terminal Ga/sub 0.5/In/sub 0.5/P/GaAs devices compared with similar four-terminal devices. The power loss increases significantly if the lens is not correctly aligned, and can be diminished somewhat by reducing the maximum refraction angle of the lens from 40/spl deg/ to 30/spl deg/. While the spectral nonuniformities reduce the power output, they also reduce the sensitivity of the System to variations in the spectrum. Thus, they conclude that, while care should be taken to minimize losses from chromatic aberrations, because of the variable spectrum, chromatic aberrations are unlikely to be a serious problem in any well designed Concentrator System.

  • E EFFECT OF CHROMATIC ABERRATIONS ON TWO-JUNCTION, TWO-TERMINAL DEVICES IN A Concentrator System
    1994
    Co-Authors: Sarah Kurtz, Daniel J. Friedman, J. M. Olson
    Abstract:

    Of the modules monitored in PVUSA (Photovoltaics for Iltiiity-Scale Applications), the one with the highest efficiency has been the ENTECH Concentrator System. If the 18%-efficient Si cells in this module could be replaced by 2 6 Yo-2 8 % efficient two - t e r m i n a I, two - j u n c t i o n (Gao.5 In0.5 P/GaAs) devices, the efficiency of the System could be increased. However, two-junction, two-terminal devices present a special problem in that they must be current matched to retain their high efficiencies. This implies that variations in the spectrum caused by the focusing optics could be a potential problem. In this study we undertake to assess the severity of this problem and find that, when properly aligned, ENTECH's current lens introduces spectral nonuniformities which cause about 4% loss in power output for two-terminal Gao.5 In0.5 P/GaAs devices compared with similar four-terminal devices. The power loss increases significantly if the lens is not correctly aligned, and can be diminished somewhat by reducing the maximum refraction angle of the lens from 40" to 30". While the spectral nonuniformities reduce the power output, they also reduce the sensitivity of the System to variations in the spectrum. Thus, we conclude that, while care should be taken to minimize losses from chromatic aberrations, because of the variable spectrum, chromatic aberrations are unlikely to be a serious problem in any well designed Concentrator System.

Daniel J. Friedman - One of the best experts on this subject based on the ideXlab platform.

  • AlGaInP/GaAs tandem solar cells for power conversion at 400°C and high concentration
    2017
    Co-Authors: Myles A. Steiner, Daniel J. Friedman, Emmett E. Perl, John Simon, Nikhil Jain, Paul Sharps, Claiborne Mcpheeters, Minjoo Larry Lee
    Abstract:

    We demonstrate dual junction (Al)GaInP/GaAs solar cells that are designed to operate at 400°C and 1000X concentration in a hybrid photovoltaic-solar thermal Concentrator System. The cells have a front metallization and anti-reflection coating that are stable under 400°C operation. We show how the cell performance degrades with increasing aluminum compositions in the top cell. Our best cell is a GaInP/GaAs tandem that demonstrated 15±1% efficiency at 400°C over a concentration range of 300-1000 suns, with several pathways to improved performance.

  • Fill factor as a probe of current‐matching for GaInP2/GaAs tandem cells in a Concentrator System during outdoor operation
    Progress in Photovoltaics, 2008
    Co-Authors: William E. Mcmahon, Keith Emery, Daniel J. Friedman, L. Ottoson, Michelle Young, J. Scott Ward, Anna Duda, C. Kramer, Sarah Kurtz
    Abstract:

    Designing a tandem solar cell for use in a Concentrator System is challenging because: (a) the conditions are variable, so solar cells rarely operate under optimal conditions, and (b) the conditions are not controlled, so any design problems are difficult to characterize. Here, we show how the fill factor can be used as a diagnostic tool to either verify correct System design and operation or to help identify a problem. We give particular attention to the detection of spectral skewing by the Concentrator optics, as this can reduce the performance of GaInP2/GaAs tandem cells and is difficult to characterize. The conclusions are equally valid for GaInP2/GaAs/Ge triple-junction cells. Copyright © 2007 John Wiley & Sons, Ltd.

  • fill factor as a probe of current matching for gainp2 gaas tandem cells in a Concentrator System during outdoor operation
    Progress in Photovoltaics, 2008
    Co-Authors: William E. Mcmahon, Keith Emery, Daniel J. Friedman, L. Ottoson, Michelle Young, J. Scott Ward, Anna Duda, C. Kramer, Sarah Kurtz
    Abstract:

    Designing a tandem solar cell for use in a Concentrator System is challenging because: (a) the conditions are variable, so solar cells rarely operate under optimal conditions, and (b) the conditions are not controlled, so any design problems are difficult to characterize. Here, we show how the fill factor can be used as a diagnostic tool to either verify correct System design and operation or to help identify a problem. We give particular attention to the detection of spectral skewing by the Concentrator optics, as this can reduce the performance of GaInP2/GaAs tandem cells and is difficult to characterize. The conclusions are equally valid for GaInP2/GaAs/Ge triple-junction cells. Copyright © 2007 John Wiley & Sons, Ltd.

  • Daily fill factor variation as a diagnostic probe of multijunction Concentrator Systems during outdoor operation
    High and Low Concentration for Solar Electric Applications II, 2007
    Co-Authors: William E. Mcmahon, Keith Emery, Daniel J. Friedman, L. Ottoson, Michelle Young, J. Scott Ward, Charlene M. Kramer, Anna Duda, Sarah Kurtz
    Abstract:

    Optimizing a Concentrator System which uses multijunction solar cells is challenging because: (a) the conditions are variable, so the solar cells rarely operate under optimal conditions and (b) the conditions are not controlled, so any design problems are difficult to characterize. Any change in the spectral content of direct-beam sunlight as it passes through the Concentrator optics is of particular interest, as it can reduce the performance of multijunction cells and is difficult to characterize. Here we show how the fill factor can be used to detect and diagnose this sort of a "spectral skewing" by the Concentrator optics during outdoor operation. The work presented here is for GaInP 2 /GaAs tandem cells, but the conclusions are equally valid for GaInP 2 /GaAs/Ge triple-junction cells.

  • The effect of chromatic aberrations on two-junction, two-terminal, devices on a Concentrator System [solar cells]
    Proceedings of 1994 IEEE 1st World Conference on Photovoltaic Energy Conversion - WCPEC (A Joint Conference of PVSC PVSEC and PSEC), 1994
    Co-Authors: Sarah Kurtz, Daniel J. Friedman, J. M. Olson
    Abstract:

    Of the modules monitored in PVUSA (Photovoltaics for Utility-Scale Applications), the one with the highest efficiency has been the ENTECH Concentrator System. If the 18%-efficient Si solar cells in this module could be replaced by 26%-28% efficient two-terminal, two-junction (Ga/sub 0.5/In/sub 0.5/P/GaAs) devices, the efficiency of the System could be increased. However, two-junction, two-terminal devices present a special problem in that they must be current matched to retain their high efficiencies. This implies that variations in the spectrum caused by the focusing optics could be a potential problem. In this study, the authors undertake to assess the severity of this problem and find that, when properly aligned, ENTECH's current lens introduces spectral nonuniformities which cause about 4% loss in power output for two-terminal Ga/sub 0.5/In/sub 0.5/P/GaAs devices compared with similar four-terminal devices. The power loss increases significantly if the lens is not correctly aligned, and can be diminished somewhat by reducing the maximum refraction angle of the lens from 40/spl deg/ to 30/spl deg/. While the spectral nonuniformities reduce the power output, they also reduce the sensitivity of the System to variations in the spectrum. Thus, they conclude that, while care should be taken to minimize losses from chromatic aberrations, because of the variable spectrum, chromatic aberrations are unlikely to be a serious problem in any well designed Concentrator System.

Andrew Blakers - One of the best experts on this subject based on the ideXlab platform.

  • Hybrid CPV-T micro-Concentrator System
    2011 37th IEEE Photovoltaic Specialists Conference, 2011
    Co-Authors: Vernie Everett, J. Harvey, Sachin Surve, Elizabeth Thomsen, Marta Vivar, M. Fuentes, Shakir Rahman, Y. Osorio Mayon, Andrew Blakers
    Abstract:

    A hybrid CPV-Thermal (CPV-T) micro-Concentrator (MCT) System has been constructed. The MCT is a fully sealed, light-weight structure with a low wind-load factor. It incorporates modified one-sun solar cells operating at around 15 suns optical concentration using a novel ultra-lightweight Fresnel array with closed loop tracking to produce electricity and thermal energy suitable for generating hot water or running absorption chillers. Preliminary electrical and thermal performance data will be presented.

  • A Linear Fresnel Hybrid PV/Thermal Micro-Concentrator System for Roof-top Integration
    2010
    Co-Authors: Andrew Tanner, Andrew Blakers, M. Greaves, J. Harvey, Sachin Surve, Marta Vivar, Daniel Walter, P. Le Lievre, Vernie Everett
    Abstract:

    An overview of the key design features and preliminary electrical performance is presented for a novel implementation of a roof-top friendly linear Fresnel mirror Concentrator photovoltaic-thermal (CPV-T) System operating at 15x concentration. This technology, referred to as the Chromasun Micro-Concentrator (MCT) is being co-developed by Chromasun Inc. and the Centre for Sustainable Energy Systems, at The Australian National University. Design decisions have been targeted at eliminating the added costs and complexities normally associated with conventional linear Concentrator Systems. Low-cost, reliable and massproducible components, leading technologies, and innovative processes have been adapted from related industries, which will significantly reduce cost and development time to market. The MCT is expected to be commercially available in 2011.

  • a 20 sun hybrid pv thermal linear micro Concentrator System for urban rooftop applications
    Photovoltaic Specialists Conference, 2010
    Co-Authors: Daniel Walter, Andrew Blakers, Vernie Everett, J. Harvey, Sachin Surve, Marta Vivar, J Muricnesic, T Ratcliff, R Van Scheppingen, Le P Lievre
    Abstract:

    A unique, linear, low-concentration, hybrid ‘micro-Concentrator’ (MCT) System concept has been developed specifically for urban rooftop environments. The light-weight, low-profile form factor satisfies aesthetic demands for general rooftop solar technologies, and is a marked departure from conventional linear Concentrator Systems. Valuable thermal energy, normally of nuisance value only, and usually wasted by conventional CPV, is extracted via a heat transfer fluid. The recovered thermal energy can be used for applications ranging from domestic hot water through to space heating, ventilation, and air conditioning (HVAC), and process heat. The System can be modularly configured for hybrid concentrating PV-Thermal (CPV-T) or thermal-only operation to meet specific customer demands. At a 20x concentration ratio, System output of 500 W pe and 2 kW pt is expected, for a combined System efficiency of up to 75%. The MCT is constructed from mature, proven technologies and industry-standard processes. An installed System cost of less than US$2/W pe is targeted, and commercial availability is expected to commence in 2011.

  • 40kW PV Thermal Roof Mounted Concentrator System
    2006 IEEE 4th World Conference on Photovoltaic Energy Conference, 2006
    Co-Authors: John Smeltink, Andrew Blakers
    Abstract:

    The Australian National University (ANU) has installed a 300 m2 photovoltaic-thermal (PV-T) Concentrator System in a four-story building. The building is provided with eight CHAPS collectors, 6000 liters of hot water storage, hydronic in-slab floor heating, gas fired boosters and a 40 kW inverter. A CHAPS collector is a 38X, one axis tracking PV Concentrator that is 24 meters long. Heat is removed from the solar cells using a fluid, which is then passed through a heat exchanger to provide heat to an external circuit. The thermal component of the System currently is being commissioned and the PV-T receivers will be installed later. The projected annual generating capacity for the System is 50 MWhr of electricity and 360 GJ of hot water. This paper describes details of the installation, performance of the System and summarizes the lessons learnt

  • A 40Kw roof mounted PV thermal Concentrator System
    2006
    Co-Authors: John Smeltink, Joe Coventry, Andrew Blakers
    Abstract:

    The Australian National University, Centre for Sustainable Energy Systems (ANU-CSES) has developed a photovoltaic thermal (PV-T) Concentrator System. This System is based on its Combined Heat and Power Solar (CHAPS) collector technology. This paper describes a roof mounted 40 kW PV-T Concentrator System which was installed during 2003-4. The System comprises eight 24 metre long single axis tracking reflective solar collectors. Mirrors are used to focus light onto high efficiency monocrystalline silicon solar cells. The mirrors are constructed by laminating mirrored glass onto a metal backing, and provide a geometrical concentration ratio of 37x. Heat is removed from the solar cells using a fluid, which flows through a passage in the cell housings. The fluid is then passed through a heat exchanger to provide heat for domestic hot water and room heating. The collector movement is controlled by a microprocessor using an open loop time based algorithm. The annual output of the System is expected to be 50 MWHr of electricity and 100 MWHr of hot water.

Psang Dain Lin - One of the best experts on this subject based on the ideXlab platform.

  • Optimized variable-focus-parabolic-trough reflector for solar thermal Concentrator System
    Solar Energy, 2012
    Co-Authors: Chung-yu Tsai, Psang Dain Lin
    Abstract:

    Abstract A solar thermal Concentrator System is proposed comprising a cylindrical heat-pipe receiver and a variable-focus-parabolic-trough (VFPT) reflector in which the focal length varies as a function of the vertical displacement of the incidence point relative to the horizontal centerline of the receiver. The light ray paths within the Concentrator System are analyzed using a skew-ray tracing approach. A method is then proposed for optimizing the geometry of the Concentrator System in such a way as to optimize the uniformity of the irradiance distribution on the heat-pipe surface. The validity of the proposed optimization method is demonstrated by means of ZEMAX/SolidWorks-Flow simulations. It is shown that the optimized VFPT Concentrator yields a significant improvement in both the irradiance uniformity and the heating efficiency compared to conventional cylindrical-trough and parabolic-trough Concentrators.