The Experts below are selected from a list of 105 Experts worldwide ranked by ideXlab platform

Roland Winston - One of the best experts on this subject based on the ideXlab platform.

  • Wide-angle Nonimaging Concentrators principles and applications
    2015 Conference on Lasers and Electro-Optics (CLEO), 2015
    Co-Authors: Roland Winston
    Abstract:

    Nonimaging optics departs from the methods of traditional optical design by instead developing techniques for maximizing the collecting power of illumination elements and systems. Nonimaging designs exceed the concentration attainable with focusing techniques by factors of four or more and approach the theoretical limit (ideal Concentrators) allowing non-tracking solar Concentrators to attain high temperature operation. Of special interest to the optics community is the deep connection between the “Hottel strings” introduced by MIT professor Hoyt C. Hottel and the flow-line algorithm of Nonimaging optics design. We developed the XCPCs, which generate thermal energy by gathering and concentrating sunlight onto specially made collector tubes at the UC Solar Lab at UC Merced.

  • thermodynamic efficiency of Nonimaging Concentrators
    Proceedings of SPIE, 2009
    Co-Authors: Narkis Shatz, John C Bortz, Roland Winston
    Abstract:

    The purpose of a Nonimaging concentrator is to transfer maximal flux from the phase space of a source to that of a target. A concentrator's performance can be expressed relative to a thermodynamic reference. We discuss consequences of Fermat's principle of geometrical optics. We review etendue dilution and optical loss mechanisms associated with Nonimaging Concentrators, especially for the photovoltaic (PV) role. We introduce the concept of optical thermodynamic efficiency which is a performance metric combining the first and second laws of thermodynamics. The optical thermodynamic efficiency is a comprehensive metric that takes into account all loss mechanisms associated with transferring flux from the source to the target phase space, which may include losses due to inadequate design, non-ideal materials, fabrication errors, and less than maximal concentration. As such, this metric is a gold standard for evaluating the performance of Nonimaging Concentrators. Examples are provided to illustrate the use of this new metric. In particular we discuss concentrating PV systems for solar power applications.

  • high concentration two stage optics for parabolic trough solar collectors with tubular absorber and large rim angle
    Solar Energy, 1991
    Co-Authors: Manuel Collarespereira, Ari Rabl, Jeffrey M. Gordon, Roland Winston
    Abstract:

    Abstract A new two-stage optical design is proposed for parabolic trough solar collectors with tubular absorbers. It can boost the concentration ratio by a factor of 2.5 relative to the conventional design, while maintaining the large rim angles (i.e., low nominal ƒ-numbers) that are desirable for practical and economical reasons. The second stage involves asymmetric Nonimaging Concentrators of the CPC type, facing segments of the parabolic first stage. The second stage can be accommodated inside an evacuated receiver, allowing the use of first-surface silvered reflectors. The low heat loss of this design opens the possibility of producing steam at temperatures and pressures of conventional power plants, using only one-axis tracking. The improvement in conversion efficiency would be substantial.

Robert F Boehm - One of the best experts on this subject based on the ideXlab platform.

  • a review of Nonimaging solar Concentrators for stationary and passive tracking applications
    Renewable & Sustainable Energy Reviews, 2017
    Co-Authors: Srikanth Madala, Robert F Boehm
    Abstract:

    The solar energy research community has realized the redundancy of image-forming while collecting/concentrating solar energy with the discovery of the Nonimaging type radiation collection mechanism in 1965. Since then, various Nonimaging concentration mechanisms have proven their superior collection efficiency over their imaging counter-parts. The feasibility of using Nonimaging Concentrators successfully for stationary applications has rekindled interest in them. The economic benefits are appealing owing to the elimination of tracking costs (installation, operation & maintenance and auxiliary energy). This paper is an exhaustive review of the available Nonimaging concentrating mechanisms with stationary applications in mind. This paper also explores the idea of coupling Nonimaging Concentrators with passive solar tracking mechanism.

  • effect of reflection losses on stationary dielectric filled Nonimaging Concentrators
    Journal of Photonics for Energy, 2016
    Co-Authors: Srikanth Madala, Robert F Boehm
    Abstract:

    The effect of Fresnel reflection and total internal reflection (TIR) losses on the performance parameters in refractive solar Concentrators has often been downplayed because most refractive solar Concentrators are traditionally the imaging type, yielding a line or point image on the absorber surface when solely interacted with paraxial etendue ensured by solar tracking. Whereas, with refractive-type Nonimaging solar Concentrators that achieve two-dimensional (rectangular strip) focus or three-dimensional (circular or elliptical) focus through interaction with both paraxial and nonparaxial etendue within the acceptance angle, the Fresnel reflection and TIR losses are significant as they will affect the performance parameters and, thereby, energy collection. A raytracing analysis has been carried out to illustrate the effects of Fresnel reflection and TIR losses on four different types of stationary dielectric-filled Nonimaging Concentrators, namely V-trough, compound parabolic concentrator, compound elliptical concentrator, and compound hyperbolic concentrator. The refractive index (RI) of a dielectric fill material determines the acceptance angle of a solid Nonimaging collector. Larger refractive indices yield larger acceptance angles and, thereby, larger energy collection. However, they also increase the Fresnel reflection losses. This paper also assesses the relative benefit of increasing RI from an energy collection standpoint.

Srikanth Madala - One of the best experts on this subject based on the ideXlab platform.

  • a review of Nonimaging solar Concentrators for stationary and passive tracking applications
    Renewable & Sustainable Energy Reviews, 2017
    Co-Authors: Srikanth Madala, Robert F Boehm
    Abstract:

    The solar energy research community has realized the redundancy of image-forming while collecting/concentrating solar energy with the discovery of the Nonimaging type radiation collection mechanism in 1965. Since then, various Nonimaging concentration mechanisms have proven their superior collection efficiency over their imaging counter-parts. The feasibility of using Nonimaging Concentrators successfully for stationary applications has rekindled interest in them. The economic benefits are appealing owing to the elimination of tracking costs (installation, operation & maintenance and auxiliary energy). This paper is an exhaustive review of the available Nonimaging concentrating mechanisms with stationary applications in mind. This paper also explores the idea of coupling Nonimaging Concentrators with passive solar tracking mechanism.

  • effect of reflection losses on stationary dielectric filled Nonimaging Concentrators
    Journal of Photonics for Energy, 2016
    Co-Authors: Srikanth Madala, Robert F Boehm
    Abstract:

    The effect of Fresnel reflection and total internal reflection (TIR) losses on the performance parameters in refractive solar Concentrators has often been downplayed because most refractive solar Concentrators are traditionally the imaging type, yielding a line or point image on the absorber surface when solely interacted with paraxial etendue ensured by solar tracking. Whereas, with refractive-type Nonimaging solar Concentrators that achieve two-dimensional (rectangular strip) focus or three-dimensional (circular or elliptical) focus through interaction with both paraxial and nonparaxial etendue within the acceptance angle, the Fresnel reflection and TIR losses are significant as they will affect the performance parameters and, thereby, energy collection. A raytracing analysis has been carried out to illustrate the effects of Fresnel reflection and TIR losses on four different types of stationary dielectric-filled Nonimaging Concentrators, namely V-trough, compound parabolic concentrator, compound elliptical concentrator, and compound hyperbolic concentrator. The refractive index (RI) of a dielectric fill material determines the acceptance angle of a solid Nonimaging collector. Larger refractive indices yield larger acceptance angles and, thereby, larger energy collection. However, they also increase the Fresnel reflection losses. This paper also assesses the relative benefit of increasing RI from an energy collection standpoint.

Noel C. Giebink - One of the best experts on this subject based on the ideXlab platform.

  • Nonimaging Optical Gain in Luminescent Concentration through Photonic Control of Emission Étendue
    2015
    Co-Authors: Yufei Shen, Yufei Jia, Xing Sheng, Ling Shen, John A. Rogers, Noel C. Giebink
    Abstract:

    ABSTRACT: Luminescent and Nonimaging optical concen-tration constitute two fundamentally different ways of collecting and intensifying light. Whereas Nonimaging Concentrators based on reflective, refractive, or diffractive optics operate most effectively for collimated light, lumines-cent Concentrators (LCs) rely on absorption, re-emission, and waveguiding to concentrate diffuse light incident from any direction. LCs have been explored in many different shapes and sizes but have so far been unable to exploit the power of Nonimaging optics to further increase their concentration ratio because their emission is angularly isotropic. Here, we use a luminescent thin film bilayer to create sharply directed conical emission in an LC and derive a Nonimaging optical solution to leverage this directionality for secondary geometric gain ranging up to an order of magnitude or higher. We demonstrate this concept experimentally using a custom compound parabolic optical element index-matched to the LC surface and show that it delivers three times more luminescent power to an opposing GaAs photovoltaic cell when the emission profile is conically directed than when it is isotropic or the Nonimaging optic is absent. These results open up a significant and general opportunity to improve LC performance for a variety of applications including photovoltaics, photobioreactors, and scintillator-based radiation detection

  • Nonimaging Optical Gain in Luminescent Concentration through Photonic Control of Emission Étendue
    2014
    Co-Authors: Yufei Shen, Yufei Jia, Xing Sheng, Ling Shen, John A. Rogers, Noel C. Giebink
    Abstract:

    Luminescent and Nonimaging optical concentration constitute two fundamentally different ways of collecting and intensifying light. Whereas Nonimaging Concentrators based on reflective, refractive, or diffractive optics operate most effectively for collimated light, luminescent Concentrators (LCs) rely on absorption, re-emission, and waveguiding to concentrate diffuse light incident from any direction. LCs have been explored in many different shapes and sizes but have so far been unable to exploit the power of Nonimaging optics to further increase their concentration ratio because their emission is angularly isotropic. Here, we use a luminescent thin film bilayer to create sharply directed conical emission in an LC and derive a Nonimaging optical solution to leverage this directionality for secondary geometric gain ranging up to an order of magnitude or higher. We demonstrate this concept experimentally using a custom compound parabolic optical element index-matched to the LC surface and show that it delivers three times more luminescent power to an opposing GaAs photovoltaic cell when the emission profile is conically directed than when it is isotropic or the Nonimaging optic is absent. These results open up a significant and general opportunity to improve LC performance for a variety of applications including photovoltaics, photobioreactors, and scintillator-based radiation detection

Jeffrey M. Gordon - One of the best experts on this subject based on the ideXlab platform.

  • Double-tailored dual-mirror Nonimaging Concentrators for maximum-performance solar concentration
    Nonimaging Optics: Efficient Design for Illumination and Solar Concentration VII, 2010
    Co-Authors: Alex Goldstein, Jeffrey M. Gordon
    Abstract:

    A Nonimaging strategy wherein two mirror contours are tailored for concentration near the etendue limit is explored, prompted by solar applications where a sizable gap between the optic and absorber is required. Subtle limitations of this simultaneous multiple surface method approach are derived, rooted in the manner in which phase space boundaries can be mapped according to the edge-ray principle. The fundamental categories of these optics are identified, only a minority of which can pragmatically offer maximum concentration at high collection efficiency. Illustrative examples confirm that acceptance half-angles as large as 30 mrad can be realized at a flux concentration of ~1000.

  • complementary construction of ideal Nonimaging Concentrators and its applications
    Applied Optics, 1996
    Co-Authors: Jeffrey M. Gordon
    Abstract:

    A construction principle for ideal Nonimaging Concentrators based on the complementary edge rays outside the nominal field of view is presented, with illustrations for the trumpet, compound parabolic concentrator, and compound hyperbolic concentrator. A simple string construction for the trumpet concentrator is shown to follow from this observation—the trumpet having been the one ideal concentrator for which no string-construction method had previously been noted. An application of these observations for solar concentrator design when nonisothermal receivers are advantageous is also presented.

  • high concentration two stage optics for parabolic trough solar collectors with tubular absorber and large rim angle
    Solar Energy, 1991
    Co-Authors: Manuel Collarespereira, Ari Rabl, Jeffrey M. Gordon, Roland Winston
    Abstract:

    Abstract A new two-stage optical design is proposed for parabolic trough solar collectors with tubular absorbers. It can boost the concentration ratio by a factor of 2.5 relative to the conventional design, while maintaining the large rim angles (i.e., low nominal ƒ-numbers) that are desirable for practical and economical reasons. The second stage involves asymmetric Nonimaging Concentrators of the CPC type, facing segments of the parabolic first stage. The second stage can be accommodated inside an evacuated receiver, allowing the use of first-surface silvered reflectors. The low heat loss of this design opens the possibility of producing steam at temperatures and pressures of conventional power plants, using only one-axis tracking. The improvement in conversion efficiency would be substantial.