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An Air Concentrator for Very Low Grade Colorado Plateau Uranium Ores

Description: Report discussing the use of an air concentrator on uraniferous sandstones for producing concentrates with over ten times the amount of uranium as original sandstone. A description of the concentrator, information regarding its operation, results of the concentration, information on the concentrator's applications, and a general summary are included.
Date: January 1953
Creator: Stieff, L. R. & Erickson, E. S., Jr.
Partner: UNT Libraries Government Documents Department

Optimal Heat Collection Element Shapes for Parabolic Trough Concentrators

Description: For nearly 150 years, the cross section of the heat collection tubes used at the focus of parabolic trough solar concentrators has been circular. This type of tube is obviously simple and easily fabricated, but it is not optimal. It is shown in this article that the optimal shape, assuming a perfect parabolic figure for the concentrating mirror, is instead oblong, and is approximately given by a pair of facing parabolic segments.
Date: November 15, 2007
Creator: Bennett, C
Partner: UNT Libraries Government Documents Department

Method and apparatus for aligning a solar concentrator using two lasers

Description: A method and apparatus are provided for aligning the facets of a solar concentrator. A first laser directs a first laser beam onto a selected facet of the concentrator such that a target board positioned adjacent to the first laser at approximately one focal length behind the focal point of the concentrator is illuminated by the beam after reflection thereof off of the selected facet. A second laser, located adjacent to the vertex of the optical axis of the concentrator, is used to direct a second laser beam onto the target board at a target point thereon. By adjusting the selected facet to cause the first beam to illuminate the target point on the target board produced by the second beam, the selected facet can be brought into alignment with the target point. These steps are repeated for other selected facets of the concentrator, as necessary, to provide overall alignment of the concentrator.
Date: October 5, 2000
Creator: Diver, Richard Boyer Jr.
Partner: UNT Libraries Government Documents Department

Advanced reflector materials for solar concentrators

Description: This paper describes the research and development program at the U.S. National Renewable Energy Laboratory (NREL) in advanced reflector materials for solar concentrators. NREL's research thrust is to develop solar reflector materials that maintain high specular reflectance for extended lifetimes under outdoor service conditions and whose cost is significantly lower than existing products. Much of this work has been in collaboration with private-sector companies that have extensive expertise in vacuum-coating and polymer-film technologies. Significant progress and other promising developments will be discussed. These are expected to lead to additional improvements needed to commercialize solar thermal concentration systems and make them economically attractive to the solar manufacturing industry. To explicitly demonstrate the optical durability of candidate reflector materials in real-world service conditions, a network of instrumented outdoor exposure sites has been activated.
Date: October 1, 1994
Creator: Jorgensen, G.; Williams, T. & Wendelin, T.
Partner: UNT Libraries Government Documents Department

Concentrator and Space Applications of High-Efficiency Solar Cells-Recent Developments

Description: GaInP/GaAs cells invented and developed at NREL have achieved world-record efficiencies. We estimate that their production for space applications has grown to > $100 million/yr. Approximately 300 MW/yr of 1000X terrestrial concentrator cells could be fabricated with the existing manufacturing capacity at a cost of about 21{cents}/Wp. A resurgence of interest in terrestrial PV concentrators, together with the strength of the III-V space-solar-cell industry, indicate that III-V cells are also attractive for terrestrial applications.
Date: October 26, 1998
Creator: Kurtz, S. R. & Friedman, D. J.
Partner: UNT Libraries Government Documents Department

Mirror alignment and focus of point-focus solar concentrators

Description: Distributed point-focusing solar concentrators are being developed for dish-Stirling systems and other applications. Many of these concentrators make use of faceted mirrors that have to be accurately aligned. Some of the solar concentrator designs use stretched-membrane facets that also require focusing. Accurate mirror alignment and focus of faceted solar concentrators have two benefits. First, the concentration ratio of the concentrator/receiver (collector) system is improved with accurate alignment and focus. The receiver aperture diameter can therefore be smaller, thereby reducing thermal losses from the receiver and improving the overall efficiency of the collector. Second, and perhaps more importantly, flux intensities on the receiver can be sensitive to facet alignment and focus. In this paper, the theory and practical application of an alignment and focusing technique are presented. In the technique, light from an artificial source is reflected from the concentrator`s facets to a target. From basic geometric principles, the shape and location of the reflected light on the target can be predicted. Alignment is accomplished by adjusting the facets aim so that the reflected image falls on the predetermined location. To focus a stretched-membrane facet, the reflected image size is adjusted to match that of the target. The governing equations used to draw the alignment targets are developed and the practical application of the technique to the alignment and focus of the Cummins Power Generation, Inc. CPG-460 are presented. Alignment uncertainty associated with this technique on the CPG-460 is also discussed.
Date: November 1, 1994
Creator: Diver, R. B.
Partner: UNT Libraries Government Documents Department

Development of a 2f optical performance measurement system

Description: Commercialization of faceted stretched-membrane concentrators has created the need for quality control measurements for facet optical performance. High-volume production scenarios require a test method that is quick, can be performed on the production floor, and does not require laboratory-grade equipment. At Sandia, we are developing an optical test method that can be done in a relatively short period of time, requires little space, uses ``off the shelf`` test equipment, and provides a quantitative measure adequate to address quality control requirements. The test method is based on common ray trace calculations for targets and images at the radius of curvature for spherical and parabolic (f/D > 3) concentrators. The initial development work was done using a monochrome television camera and the beam characterization system. Twenty-four 3-meter facets built for a faceted stretched-membrane dish were characterized using this system. Other smaller facets have also been tested with the system to help establish a correlation with this method and other optical characterization tests. Current work involves adapting a color camera to the system and developing custom software to reduce analysis time and make the system viable for the production floor. This paper discusses the development of the monochrome system, reviews the results of testing, and presents plans for the development of a color system.
Date: December 1, 1993
Creator: Grossman, J. W.
Partner: UNT Libraries Government Documents Department

Novel Scanning Lens Instrument for Evaluating Fresnel Lens Performance: Equipment Development and Initial Results

Description: A system dedicated to the optical transmittance characterization of Fresnel lenses has been developed at NREL, in collaboration with the UPM. The system quantifies the optical efficiency of the lens by generating a performance map. The shape of the focused spot may also be analyzed to understand change in the lens performance. The primary instrument components (lasers and CCD detector) have been characterized to confirm their capability for performing optical transmittance measurements. Measurements performed on SoG and PMMA lenses subject to a variety of indoor conditions (e.g., UV and damp heat) identified differences in the optical efficiency of the evaluated lenses, demonstrating the ability of the Scanning Lens Instrument (SLI) to distinguish between the aged lenses.
Date: July 1, 2013
Creator: Herrero, R.; Miller, D. C.; Kurtz, S. R.; Anton, I. & Sala, G.
Partner: UNT Libraries Government Documents Department

Photovoltaic Manufacturing Technology report, Phase 1. Final technical report, 9 January 1991--14 April 1991

Description: This report describes subcontracted research by Spectrolab, Inc., to address tasks outlined in the National Renewable Energy Laboratory's (NREL) Letter of solicitation RC-0-10057. These tasks include the potential of making photovoltaics (PV) a more affordable energy source, as set forth in the goal of the PVMaT project. Spectrolab believes that the DOE cost goals can be met using three different types of cells: (1) silicon concentrator cells, (2) high efficiency GaAs concentrator cells, and (3) mechanically stacked multijunction cells.
Date: October 1, 1992
Creator: Mason, A. V. & Lillington, D. R.
Partner: UNT Libraries Government Documents Department

Luminescent solar concentrator development: Final subcontract report, 1 June 1982-31 December 1984

Description: An investigation of luminescent solar concentrators (LSCs) was begun by the US Department of Energy (DOE) at Owens-Illinois, Inc., in 1978. Experimental and theoretical results of that investigation are summarized in this report. An assessment of the LSC technology was compiled to provide a concise description to guide future research in this field. Since 1978, tremendous progress was made in the development of this device as a practical nonimaging concentrator for achieving solar concentration ratios on the order of 10X. The two most important technical achievements appear to be first, the understanding that dye self-absorption of radiated energy is not as serious a problem as originally thought; and second, the demonstration that organic dyes in polymeric hosts are capable of surviving outdoors in bright sunlight for years without serious degradation. System efficiencies approaching 4% have been achieved for photovoltaic conversion and theoretical efficiencies on the order of 9% appear feasible for large-area devices.
Date: April 1, 1987
Creator: Friedman, P.S. & Parent, C.R.
Partner: UNT Libraries Government Documents Department

Conceptual design of a 5x CPC for solar total energy systems

Description: The results of a conceptual design of a nontracking collector for a solar total energy system are described. Sandia Laboratories has responsibility for the evaluation of concentrating collectors in a total energy test bed. A Rankine cycle turbine, generator, controls, thermal storage, and air conditioning equipment have been installed and checked out. The thermal energy for the facility is to be provided by a large (approximately 800 m/sup 2/) concentrating collector field. At present a portion of the area is installed as E-W oriented linear parabolic troughs. Three additional concepts for the remaining area have been selected--a fixed mirror-moving receiver system, fixed receiver-moving reflector slats, and a two-axis tracking parabolic dish. All four systems use diurnal tracking and have the reflecting surfaces exposed to the elements. Argonne National Laboratory has been working on the development of non-tracking concentrators for high temperature operation. The recent experimental results indicate that a 5x CPC collector with only 12 adjustments per year could effectively compete with the systems presently being considered. These collectors would be enclosed under a protective cover glass, eliminating many of the problems with dirt, etc. A conceptual design of a CPC collector system is presented.
Date: January 1, 1977
Creator: Cole, R; Schertz, W W & Teagan, W P
Partner: UNT Libraries Government Documents Department

Performance and testing of a stationary concentrating collector. [Compound parabolic concentrators coupled to tubular evacuated receivers]

Description: The development of nonimaging solar collectors for heating and cooling applications is reported. A totally stationary concentrating collector has been designed, built, and tested. The collectors employ compound parabolic concentrators coupled to tubular evacuated receivers. Performance of the collector is substantially better than flat plate collectors, and the collectors are suitable for powering mechanically driven air conditioning systems as well as conventional absorption cycle machines. This collector concept was awarded an IR-100 award by Industrial Research Magazine as one of the 100 most significant new developments in 1977.
Date: January 1, 1977
Creator: Cole, R L; Allen, J W; Levitz, N M; McIntire, W R & Schertz, W W
Partner: UNT Libraries Government Documents Department

Application of glass technology to novel solar energy collectors

Description: Various compound parabolic concentrator (CPC) configurations are discussed, and the application of glass technology to CPC designs is discussed. CPC designs with flat absorbers, cylindrical absorbers, evacuated receivers, and evacuated tube receivers are considered. Also a floodlamp collector concept and a fluorescent tube collector concept are discussed. (WHK)
Date: January 1, 1979
Creator: Reed, K A
Partner: UNT Libraries Government Documents Department

Development of lightweight compound parabolic concentrators for solar thermal electric and process heat applications

Description: The design and construction of a lightweight collector panel that uses the Compound Parabolic Concentrator (CPC) to achieve maximal concentration with minimal tracking requirements is described. The primary goal of the effort has been the development of methods of constructing the units with low cost materials that still allow high temperature (120 to 230/sup 0/C) operation. The use of thermoformed plastics for both the container box and the reflector substrate has been investigated for use in combination with an evacuated glass tube around the absorber plate. The predicted performance of the collector has been calculated, and the problem of keeping the reflectors cool has been addressed. Preliminary results on the reflector tests are presented.
Date: January 1, 1976
Creator: Allen, J.; Levitz, N.; Rabl, A.; Reed, K.; Schertz, W. & Winston, R.
Partner: UNT Libraries Government Documents Department

Software and codes for analysis of concentrating solar power technologies.

Description: This report presents a review and evaluation of software and codes that have been used to support Sandia National Laboratories concentrating solar power (CSP) program. Additional software packages developed by other institutions and companies that can potentially improve Sandia's analysis capabilities in the CSP program are also evaluated. The software and codes are grouped according to specific CSP technologies: power tower systems, linear concentrator systems, and dish/engine systems. A description of each code is presented with regard to each specific CSP technology, along with details regarding availability, maintenance, and references. A summary of all the codes is then presented with recommendations regarding the use and retention of the codes. A description of probabilistic methods for uncertainty and sensitivity analyses of concentrating solar power technologies is also provided.
Date: December 1, 2008
Creator: Ho, Clifford Kuofei
Partner: UNT Libraries Government Documents Department

Performance of evacuated solar collectors with Compound Parabolic Concentrators

Description: Compound Parabolic Concentrators (CPC) achieve the highest possible concentration for a given acceptance angle, permitting geometric concentration ratios up to about 2 in fixed solar collectors and up to about 10 in collectors with day-to-day tilt adjustments. Design, construction and test results are reported for several CPC collectors with evacuated receivers supplied by Corning Glass, by General Electric and by Owens-Illinois. Efficiencies of 45 percent at ..delta..T = 150/sup 0/K above ambient have been reached with a fixed collector. This collector accepts more than half of the diffuse radiation in addition to all of the direct beam, for at least seven hours per day.
Date: January 1, 1978
Creator: Rabl, A.
Partner: UNT Libraries Government Documents Department

Markets for concentrating solar power

Description: The report describes the markets for concentrating solar power. As concentrating solar power technologies advance into the early stages of commercialization, their economic potential becomes more sharply defined and increasingly tangible.
Date: April 1, 1998
Partner: UNT Libraries Government Documents Department

Side-by-Side Comparisons of Evacuated Compound Parabolic Concentrator and Flat Plate Solar Collector Systems

Description: Three liquid-based solar heating systems employing different types of solar collectors were tested side by side near Chicago, Illinois for one year. The three different types of collectors were: (1) a flat plate collector with a black-chrome coated absorber plate and one low-iron glass cover; (2) an evacuated-tube compound parabolic concentrator (CPC) with a concentration ratio of 1.1, oriented with tubes and troughs along a north-south axis; and (3) an evacuated-tube CPC collector with a concentration ratio of 1.3 and one low-iron glass cover, with tubes and troughs oriented along an east-west axis. Results indicate that the flat plate collector system was the most efficient during warm weather, but the CPC systems were more efficient during cold weather, but the CPC systems were more efficient during cold weather, and the CPC systems operated under conditions too adverse for the flat plate collector. The computer simulation model ANSIM was validated by means of the side-by-side tests. The model uses analytical solutions to the storage energy balance. ANSIM is compared with the general simulation TRNSYS.
Date: October 1983
Creator: McGarity, Arthur E.; Allen, John W. & Schertz, William W.
Partner: UNT Libraries Government Documents Department

A Preliminary Low-Frequency Electromagnetic Analysis of a Flux Concentrator

Description: The objective of this investigation was to conduct a quick, preliminary transient magnetostatic analysis of a Brechna-type[1] flux concentrator to determine its feasibility for collecting positrons in the International Linear Collider. The magnetostatic transient module of Maxwell 3D, Version 10, from the Ansoft Corporation was used to model the flux concentrator.
Date: June 7, 2006
Creator: Mayhall, D J
Partner: UNT Libraries Government Documents Department

Reflective materials evaluation. Final report, Task III, July 1975--April 1977

Description: Research involved an investigation of specific reflective membrane composites and protective coatings which appeared capable of providing the economical, efficient, durable reflective surfaces required for use with solar concentrating systems. The main part of the work on this task was the exposure of candidate materials to an outside environment. This took place at Desert Sunshine Exposure Tests, Inc. (DSET), which is located near Phoenix, Arizona. All the materials and composites tested were selected from combinations which had previously performed satisfactorily under salt-spray and humidity/temperature cycling tests. Specular reflectance of specimens to be tested was measured using the Sheldahl specular photometer, both before and after exposure at DSET. A description of these tests and a discussion of the results are presented.
Date: April 1, 1977
Creator: Arden, W. M.
Partner: UNT Libraries Government Documents Department

Reflective coatings for solar applications

Description: Many applications of solar energy require large mirrors to provide high levels of concentrated sunlight. The success of such conversion systems hinges on the optical durability and economic viability of the reflector materials. A major effort at the National Renewable Energy Laboratory (NREL) has been to improve the existing reflector materials technology and to identify candidates that retain optical performance and durability criteria and offer potential for reduced cost. To attain the goals, it is desirable to maintain and increase the involvement of industrial organizations in reflective materials R&D related to the conversion of solar resources to useful energy. Toward this end, NREL has recently initiated several collaborative efforts with industry to develop advanced reflector materials.
Date: May 1, 1993
Creator: Jorgensen, G.
Partner: UNT Libraries Government Documents Department

Status of photovoltaic concentrator modules and systems

Description: Several leading line- and point-focus photovoltaic concentrator system development programs are reviewed, including those by ENTECH, SEA Corporation, AMONIX, and Alpha Solarco. Concentrating collectors and trackers are gaining maturity and reaching product status as designs are made more manufacturable and reliable. Utilities are starting to take notice of this emerging technology, and several privately-funded utility installations are underway. Several advantages are offered by concentrators, including low system and capital cost and rapid production ramp-up. These are discussed along with issues generally raised concerning concentrator technology.
Date: April 1, 1994
Creator: Maish, A. B.
Partner: UNT Libraries Government Documents Department

Felt-metal-wick heat-pipe solar receiver

Description: Reflux heat-pipe receivers have been identified as a desirable interface to couple a Stirling-cycle engine with a parabolic dish solar concentrator. The reflux receiver provides power nearly isothermally to the engine heater heads while decoupling the heater head design from the solar absorber surface design. The independent design of the receiver and engine heater head leads to higher system efficiency. Heat pipe reflux receivers have been demonstrated at approximately 65 kW{sub t} power throughput. Several 25 to 30-kW{sub e} Stirling-cycle engines are under development, and will soon be incorporated in commercial dish-Stirling systems. These engines will require reflux receivers with power throughput limits reaching 90-kW{sub t}. The extension of heat pipe technology from 60 kW{sub t} to 100 kW{sub t} is not trivial. Current heat pipe wick technology is pushed to its limits. It is necessary to develop and test advanced wick structure technologies to perform this task. Sandia has developed and begun testing a Bekaert Corporation felt metal wick structure fabricated by Porous Metal Products Inc. This wick is about 95% porous, and has liquid permeability a factor of 2 to 8 times higher than conventional technologies for a given maximum pore radius. The wick has been successfully demonstrated in a bench-scale heat pipe, and a full-scale on-sun receiver has been fabricated. This report details the wick design, characterization and installation into a heat pipe receiver, and the results of the bench-scale tests are presented. The wick performance is modeled, and the model results are compared to test results.
Date: December 31, 1994
Creator: Andraka, C. E.; Adkins, D. R.; Moss, T. A.; Cole, H. M. & Andreas, N. H.
Partner: UNT Libraries Government Documents Department