The Experts below are selected from a list of 618 Experts worldwide ranked by ideXlab platform
Jeffrey M. Gordon - One of the best experts on this subject based on the ideXlab platform.
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New high-flux two-stage optical designs for parabolic solar concentrators
Solar Energy, 2004Co-Authors: Robert P. Friedman, Jeffrey M. Gordon, Harald RiesAbstract:Abstract We present a new two-stage optical design for parabolic dish concentrators that can realistically attain close to 90% of the thermodynamic limit to concentration with practical, compact designs (e.g., at parabola Rim half-Angles of around 45°). For comparison, the parabolic dish-plus-compound parabolic concentrator secondary design, at this Rim Angle, achieves no more than 50% of the thermodynamic limit. Our new secondary concentrator is tailored to accept edge rays from the parabolic pRimary, and incurs less than one reflection on average. It necessitates displacing the absorber from the parabola's focal plane, along the concentrator's optic axis, toward the pRimary reflector, and constructing the secondary between the absorber and the pRimary. The secondary tailored edge-ray concentrators described here create new possibilities for building compact, extremely high flux solar furnaces and/or commercial parabolic dish systems.
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Tailored edge-ray concentrators for solar energy applications: approaching the thermodynamic limit to concentration
8th Meeting on Optical Engineering in Israel: Optical Engineering and Remote Sensing, 1993Co-Authors: Jeffrey M. Gordon, Harald RiesAbstract:We present a new type of ideal non-imaging secondary concentrator, the tailored edge-ray concentrator (TERC), that can closely approach the thermodynamic limit of concentration, and illustrate it for both linear and point-focus Fresnel reflectors. For large Rim-Angle heliostat fields, practical-sized secondaries with shapes that should be relatively easy to fabricate can achieve concentrations substantially above those of compound parabolic concentrators (CPCs). This superiority stems from designing so as to accommodate the particular flux from the heliostat field. The edge-ray principle used for generating the new secondary dictates a heliostat tracking strategy different from the conventional one, but equally easy to implement.
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Tailored edge-ray concentrators as ideal second stages for Fresnel reflectors
Applied Optics, 1993Co-Authors: Jeffrey M. Gordon, Harald RiesAbstract:For both linear and point-focus Fresnel reflectors, we present a new type of ideal nonimaging secondary concentrator, the tailored edge-ray concentrator, that can closely approach the thermodynamic limit of concentration. For large Rim-Angle heliostat fields, practical-sized secondaries with shapes that should be relatively easy to fabricate can achieve concentrations substantially above those of compound parabolic concentrators. This superiority stems from designing so as to accommodate the particular flux from the heliostat field. The edge-ray principle used for generating the new secondary dictates a heliostat tracking strategy that is different from the conventional one but is equally easy to implement.
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Recent developments in nonimaging secondary concentrators for linear receiver solar collectors
Proceedings of SPIE, 1991Co-Authors: Jeffrey M. GordonAbstract:The energetic and economic attractiveness of linear solar concentrators can be significantly improved by the use of properly secondary non-imaging (CPC-type) concentrators. Two specific illustrative cases are analyzed. One is the optical re-design of a commercial two-stage solar concentrator which generates process steam at 150 degree(s)C. The pRimary is a linear Fresnel reflector with one-axis horizontal tracking. The receiver is a stationary, non- evacuated, glazed tubular receiver with secondary CPC. We have re-designed the initial, manufacturer-designed secondary so as to noticeably improve collector thermal output. Details of secondary design and system performance are presented. The other is a new concept in secondary CPC-type concentrators for parabolic trough collectors with tubular receivers and large Rim Angles (typically 80 degree(s)-120 degree(s)). It had been though that such large-Rim- Angle concentrators could not benefit from secondary concentrators, since the second-stage concentration boost goes as 1/sin(Rim Angle). However, by introducing multiple asymmetric CPC-type devices, we can increase the geometric concentration of a 90 degree(s) Rim Angle parabolic trough by roughly a factor of 3. Furthermore, certain secondary designs can be accommodated within the annulus of currently-manufactured evacuated receiver tubes, and still offer a flux concentration improvement of about a factor of 2.5. Examples of the new secondary designs, and achievable concentration gains, are presented.
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high concentration two stage optics for parabolic trough solar collectors with tubular absorber and large Rim Angle
Solar Energy, 1991Co-Authors: Manuel Collarespereira, Ari Rabl, Jeffrey M. Gordon, R WinstonAbstract: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.
Harald Ries - One of the best experts on this subject based on the ideXlab platform.
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New high-flux two-stage optical designs for parabolic solar concentrators
Solar Energy, 2004Co-Authors: Robert P. Friedman, Jeffrey M. Gordon, Harald RiesAbstract:Abstract We present a new two-stage optical design for parabolic dish concentrators that can realistically attain close to 90% of the thermodynamic limit to concentration with practical, compact designs (e.g., at parabola Rim half-Angles of around 45°). For comparison, the parabolic dish-plus-compound parabolic concentrator secondary design, at this Rim Angle, achieves no more than 50% of the thermodynamic limit. Our new secondary concentrator is tailored to accept edge rays from the parabolic pRimary, and incurs less than one reflection on average. It necessitates displacing the absorber from the parabola's focal plane, along the concentrator's optic axis, toward the pRimary reflector, and constructing the secondary between the absorber and the pRimary. The secondary tailored edge-ray concentrators described here create new possibilities for building compact, extremely high flux solar furnaces and/or commercial parabolic dish systems.
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nonimaging secondary concentrators for large Rim Angle parabolic troughs with tubular absorbers
Applied Optics, 1996Co-Authors: Harald Ries, W SpirklAbstract:For parabolic trough solar collectors with tubular absorbers, we design new tailored secondary concentrators. The design is applicable for any Rim Angle of a parabolic reflector. With the secondary, the concentration can be increased by a factor of more than 2 with a compact secondary reflector consisting of a single piece, even for the important case of a Rim Angle of 90 deg. The parabolic reflector can be used without changes; the reduced absorber is still tubular but smaller than the original absorber and slightly displaced toward the pRimary.
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Caustic and its use in designing optimal absorber shapes for 2D concentrators
Nonimaging Optics: Maximum Efficiency Light Transfer III, 1995Co-Authors: Harald Ries, W SpirklAbstract:The caustic of a set of edge rays is defined as the set of intersection points of adjacent edge rays. For a body having a smooth differentiable contour, the caustic of its edge rays coincides with the contour of the body. Therefore one would assume that by calculating the caustic of the edge rays as they are produced by a 2D concentrator such as a trough, the optimal shape for the absorber, e.g. the minimal surface absorber capable of intercepting all rays, should also coincide with the shape of the caustic. We show that this conjecture is not valid in general, but only if the caustic indeed forms a closed smooth curve. For parabolic trough systems, the caustic intersects and forms closed domains for half Rim Angles of around 60 degrees and 120 degrees. In both cases the contour is not smooth. Therefore the optimal shape is not given by the domain enclosed by the caustic. We present a general recipe of how to construct minimum surface absorbers for given caustics in 2D and apply this to the case of trough parabolic concentrators. We show practical absorber shapes for parabolic troughs with various Rim Angles. The optimal contour depends discontinuously on the Rim Angle. The area of the optimum shape for a Rim Angle of 90 degrees is 0.72 of the area of the smallest cylindric absorber capable of intersecting all rays.© (1995) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.
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Tailored edge-ray concentrators for solar energy applications: approaching the thermodynamic limit to concentration
8th Meeting on Optical Engineering in Israel: Optical Engineering and Remote Sensing, 1993Co-Authors: Jeffrey M. Gordon, Harald RiesAbstract:We present a new type of ideal non-imaging secondary concentrator, the tailored edge-ray concentrator (TERC), that can closely approach the thermodynamic limit of concentration, and illustrate it for both linear and point-focus Fresnel reflectors. For large Rim-Angle heliostat fields, practical-sized secondaries with shapes that should be relatively easy to fabricate can achieve concentrations substantially above those of compound parabolic concentrators (CPCs). This superiority stems from designing so as to accommodate the particular flux from the heliostat field. The edge-ray principle used for generating the new secondary dictates a heliostat tracking strategy different from the conventional one, but equally easy to implement.
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Tailored edge-ray concentrators as ideal second stages for Fresnel reflectors
Applied Optics, 1993Co-Authors: Jeffrey M. Gordon, Harald RiesAbstract:For both linear and point-focus Fresnel reflectors, we present a new type of ideal nonimaging secondary concentrator, the tailored edge-ray concentrator, that can closely approach the thermodynamic limit of concentration. For large Rim-Angle heliostat fields, practical-sized secondaries with shapes that should be relatively easy to fabricate can achieve concentrations substantially above those of compound parabolic concentrators. This superiority stems from designing so as to accommodate the particular flux from the heliostat field. The edge-ray principle used for generating the new secondary dictates a heliostat tracking strategy that is different from the conventional one but is equally easy to implement.
R Winston - One of the best experts on this subject based on the ideXlab platform.
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high concentration two stage optics for parabolic trough solar collectors with tubular absorber and large Rim Angle
Solar Energy, 1991Co-Authors: Manuel Collarespereira, Ari Rabl, Jeffrey M. Gordon, R WinstonAbstract: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.
Marc J Philippon - One of the best experts on this subject based on the ideXlab platform.
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Defining a safety margin for labral suture anchor insertion using the acetabular Rim Angle.
The American journal of sports medicine, 2020Co-Authors: Pisit Lertwanich, Leandro Ejnisman, Michael R Torry, J Erik Giphart, Marc J PhilipponAbstract:Suture anchors are commonly used to reattach a torn labrum to the acetabular Rim. The acetabular Rim anatomy is not uniform, and the safety margin for inserting suture anchors is unknown. The acetabular Rim Angle is an anatomic measurement that is indicative of the safety margin for inserting suture anchors. To investigate the acetabular Rim Angle as a function of clock position, to evaluate the effect of drill depth on the acetabular Rim Angle, and to evaluate the effect of Rim tRimming on the acetabular Rim Angle. Descriptive laboratory study. Three-dimensional acetabular models were reconstructed from computed tomography scans of 20 nonpaired cadaveric hip specimens, and the acetabular Rim Angle, which quantifies the Angle between the subchondral margin and the outer cortex of the acetabulum, was measured from the 8- to 4-o'clock positions. At each position, the acetabular Rim Angle was measured for 5 drill depths (10, 12.5, 15, 20, and 25 mm) to simulate different lengths of suture anchors or drill bit depths on the acetabular Rim Angle. To simulate Rim tRimming, the acetabular Rim Angle was measured at the points that would become the suture anchor insertion points after 2.5- and 5-mm Rim tRimming. Clock position, drill depth, and Rim tRimming all had significant effects on the acetabular Rim Angle (P < .0001). The acetabular Rim Angle was largest at the 2-o'clock and smallest at the 3-o'clock position. Greater drill depths provided smaller acetabular Rim Angles, whereas Rim tRimming provided larger acetabular Rim Angles. The acetabular Rim Angle varied significantly as a function of the location on the acetabular Rim. A shorter drill depth and a greater amount of Rim tRimming provided a larger acetabular Rim Angle. Surgeons should be aware of the acetabular Rim variations, especially in the anterosuperior quadrant, as well as the effects of drill depth and Rim tRimming, when selecting the optimal insertion Angle for suture anchor placement to avoid articular cartilage penetration. The acetabular safety Angle was smallest at the 3-o'clock position. Therefore, extra care must be taken when drilling or inserting anchors around the 3-o'clock position.
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defining a safety margin for labral suture anchor insertion using the acetabular Rim Angle
American Journal of Sports Medicine, 2011Co-Authors: Pisit Lertwanich, Leandro Ejnisman, Michael R Torry, Erik J Giphart, Marc J PhilipponAbstract:BackgroundSuture anchors are commonly used to reattach a torn labrum to the acetabular Rim. The acetabular Rim anatomy is not uniform, and the safety margin for inserting suture anchors is unknown. The acetabular Rim Angle is an anatomic measurement that is indicative of the safety margin for inserting suture anchors.PurposeTo investigate the acetabular Rim Angle as a function of clock position, to evaluate the effect of drill depth on the acetabular Rim Angle, and to evaluate the effect of Rim tRimming on the acetabular Rim Angle.Study DesignDescriptive laboratory study.MethodsThree-dimensional acetabular models were reconstructed from computed tomography scans of 20 nonpaired cadaveric hip specimens, and the acetabular Rim Angle, which quantifies the Angle between the subchondral margin and the outer cortex of the acetabulum, was measured from the 8- to 4-o'clock positions. At each position, the acetabular Rim Angle was measured for 5 drill depths (10, 12.5, 15, 20, and 25 mm) to simulate different leng...
Manuel Collarespereira - One of the best experts on this subject based on the ideXlab platform.
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high concentration two stage optics for parabolic trough solar collectors with tubular absorber and large Rim Angle
Solar Energy, 1991Co-Authors: Manuel Collarespereira, Ari Rabl, Jeffrey M. Gordon, R WinstonAbstract: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.
