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Low-Cost Photovoltaic Cell Mount Study

Description: From abstract: This report is a technical and economic evaluation of five representative cell laydown techniques with the final goal being a determination of which was most promising from a cost performance basis.
Date: March 1980
Creator: Motorola, Inc. Government Electronics Division.
Partner: UNT Libraries Government Documents Department

RECORDING EQUIPMENT FOR INTERNAL FRICTION MEASUREMENTS

Description: An apparatus was developed for recording internal friction data in such a manner as to circumvent many of the laborious and time-consuming observations and calculations usually associated with these measurements. An optical lever is used and the passage of the beam across the scale is detected by photoconductive cells. The cells are strategically located so that, when their signals are fed through a multichannel switching circuit to the pens of an operation recorder, a plot of the logarithm of the vibrational amplitude versus the number of cycles is recorded on the chart. From the definitmon of the logarithmic decrement, ( delta ), it can be shown that the slope of this curve is - delta . The apparatus is inexpensive and requires a minimum of maintenance. It has been used for accurate determinations of values of delta from below 0.0001 up to 0.3. (auth)
Date: October 31, 1961
Creator: Stephenson, R.L. & McCoy, H.E. Jr.
Partner: UNT Libraries Government Documents Department

The Status of Thermophotovoltaic Energy Conversion Technology at Lockheed Martin Corporation

Description: In a thermophotovoltaic (TPV) energy conversion system, a heated surface radiates in the mid-infrared range onto photocells which are sensitive at these energies. Part of the absorbed energy is converted into electric output. Conversion efficiency is maximized by reducing the absorption of non-convertible energy with some form of spectral control. In a TPV system, many technology options exist. Our development efforts have concentrated on flat-plate geometries with greybody radiators, front surface tandem filters and a multi-chip module (MCM) approach that allows selective fabrication processes to match cell performance. Recently, we discontinued development of GaInAsSb quaternary cell semiconductor material in favor of ternary GaInAs material. In our last publication (Ref. 1), the authors reported conversion efficiencies of about 20% (radiator 950 C, cells 22 C) for small modules (1-4 cm{sup 2}) tested in a prototypic cavity test environment. Recently, we have achieved measured conversion efficiencies of about 12.5% in larger ({approx}100 cm{sup 2}) test arrays. The efficiency reduction in the larger arrays was probably due to quality and variation of the cells as well as non-uniform illumination from the hot radiator to the cold plate. Modules in these tests used GaInAsSb cells with 0.52 eV bandgap and front surface filters for spectral control. This paper provides details of the individual system components and the rationale for our technical decisions. It also describes the measurement techniques used to record these efficiencies.
Date: July 29, 2004
Creator: Brown, EJ; Baldasaro, PF; Burger, SR; Danielson, LR; DePoy, DM; Dolatowski, JM et al.
Partner: UNT Libraries Government Documents Department

Improving the performance of photo-electrically controlled lighting systems

Description: The ability of a photo-electrically controlled lighting system to maintain a constant total light level on a task surface by responding to changing daylight levels is affected by the control algorithm used to relate the photosensor signal to the supplied electric light level and by the placement and geometry of the photosensor. We describe the major components of a typical control system, discuss the operation of three different control algorithms, and derive expressions for each algorithm that express the total illuminance at the task as a function of the control photosensor signal. Using a specially-designed scale model, we measured the relationship between the signal generated by various ceiling-mounted control photosensors and workplane illuminance for two room geometries under real sky conditions. The measured data were used to determine the performance of systems obeying the three control algorithms under varying daylight conditions. Control systems employing the commonly-used integral reset algorithm supplied less electric light than required, failing to satisfy the control objective regardless of the control photosensor used. Systems employing an alternative, closed-loop proportional control algorithm achieved the control objective under virtually all tested conditions when operated by a ceiling-mounted photosensor shielded from direct window light.
Date: August 1, 1988
Creator: Rubinstein, F.; Ward, G. & Verderber, R.
Partner: UNT Libraries Government Documents Department

Reduction of photovoltaic cell reverse breakdown by a peripheral bypass diode

Description: A photovoltaic cell in a series-connected string can be forced to operate in a power-dissipation mode when the cell's short-circuit current is reduced below the string current as a result of cracking or shadowing. New techniques for significantly reducing the power dissipated are reported based on locating protection for the cell around its periphery. One approach uses a standard diode, thereby requiring processing; the other approach uses a backward diode, which requires one additional doping step. Theoretical considerations and experimental results are presented. Initial devices yield a power-dissipation reduction of more than a factor of 10 with the backward diode and over 30 for the standard diode. It is found that the standard diode requires a slight increase in cell-interconnect complexity while the backward diodes uses conventional interconnections.
Date: January 1, 1982
Creator: Cox, III, C H; Silversmith, D J & Mountain, R W
Partner: UNT Libraries Government Documents Department

Development of High Resolution Scintillator Systems Based on Photocell Technology

Description: Inorganic scintillator/photomultiplier-based spectrometers are the systems of choice for a multitude of X-ray and gamma radiation measurement applications. Despite widespread use, they have numerous shortcomings. The most serious shortcoming is the relatively poor energy resolution that makes isotope identification problematic, particularly in the case of trace quantities. Energy resolution in scintillator/photomultiplier tube (PMT) spectrometers is governed by a combination of the crystal intrinsic resolution that includes non-linearity effects, photomultiplier statistics, and the variability in the probability of a scintillation photon generating a photoelectron at the photocathode. It is evident that energy resolution in these systems is linked to both the physics of light generation in the scintillator and the characteristics of the PMT. PMTs also present design problems, especially in the case of handheld and portable instruments, due to their considerable weight and volume. Additionally, PMTs require well-regulated high voltage, and are vulnerable to magnetic fields. The objective of this work is to provide instrument designers of scintillation-based gamma-ray spectrometers with superior energy resolution and greatly reduced weight and volume. It is planned to achieve this advancement by optimizing the performance of a new class of inorganic scintillators by matching their emission spectra with the enhanced quantum efficiency of certain photocells.
Date: January 1, 2006
Creator: Kernan, W. J.; Franks, L. A.; Groza, M. & Burger, A.
Partner: UNT Libraries Government Documents Department

AUTOMATIC DOSE COMPUTER FOR RADIATION FILM BADGES

Description: A combination densitomer and analog computer is described which determines radiation exposure of photographic film used in personnel badges. The range of the instrument is 0to 300 mr gamma and 0 to 300 mrad BETA plus gamma . A novel phototube circuit is used to obtain logarithms directly. (auth)
Date: April 1, 1960
Creator: Davis, J.E.
Partner: UNT Libraries Government Documents Department

Silicon ribbon growth by a capillary action shaping technique. Quarterly progress report No. 3, March 15, 1976

Description: Objectives of the program are the technological assessment of ribbon growth of silicon by a capillary action shaping technique and economic evaluation of ribbon silicon grown by a capillary action shaping technique as low-cost silicon. The program of study included crystal growth of silicon ribbons, characterization of silicon ribbons, and economic evaluations and computer-aided simulation of ribbon growth. (WDM)
Date: January 1, 1976
Creator: Schwuttke, G. H.; Ciszek, T. F. & Kran, A.
Partner: UNT Libraries Government Documents Department

Development of methods and procedures for high rate low energy expenditure fabrication of solar cells. Final report

Description: A one year program to develop a new concept for silicon solar cell production based upon the use of pulsed electron beam processes combined with ion implantation has been completed. Feasibility of producing solar cells at high speed by a simplified vacuum-room temperature processing sequence has been demonstrated. The method has many advantages, particularly for large scale production at lowest possible cost.
Date: November 1, 1976
Creator: Kirkpatrick, A. R.; Minnucci, J. A. & Greenwald, A. C.
Partner: UNT Libraries Government Documents Department

Development of methods and procedures for high rate low energy expenditure fabrication of solar cells. Quarterly progress report No. 3

Description: Solar cells are being fabricated by ion implantation and pulsed electron beam techniques which eliminate much of the complexity and energy consumption associated with conventional processing methods. Development continues to progress toward achievement of program objectives.
Date: July 1, 1976
Creator: Kirkpatrick, A. R. & Minnucci, J. A.
Partner: UNT Libraries Government Documents Department

Heat exchanger-ingot casting/slicing process. Silicon sheet growth development for the large area silicon sheet task of the low cost Silicon Solar Array Project. Third quarterly progress report, April 1, 1976--June 18, 1976

Description: The object of this program is to demonstrate that large single-crystal ingots, 6-inch diameter by 4 inches tall, can be economically cast by the Heat Exchanger Method (HEM) and economically sliced into thin sheets, 0.008-inches thick, with a multi-wafer slicer. The thrust of the experimental work during this quarter was to establish the proper seed meltback and to nucleate single-crystal growth off the seed. Slicing tests were begun on the multi-blade wafering machine, using a newly fabricated sensitive feed mechanism and associated components. (WDM)
Date: June 21, 1976
Creator: Schmid, F. & Reynolds, B.
Partner: UNT Libraries Government Documents Department

Silicon ribbon growth by a capillary action shaping technique. Quarterly technical progress report No. 1

Description: Progress during the first quarter of the contractual effort is described. The work performed relates (a) to ribbon growth by a capillary action shaping technique, (b) to ribbon characterization, and (c) to economic evaluation and computer-aided simulation of ribbon growth. Actual progress includes growth of 12-mm and 25-mm-wide ribbon with individual lengths ranging from 0.12 to 1.06 meters. The growth of silicon tubes of 6-mm diameter, 1-mm wall thickness, and more than 100-cm length was also accomplished. The ''growth rate'' problem of melt-grown ribbon-shaped crystals was addressed. An expression for maximum growth rate of cylindrical (Czochralski geometry) crystals and ribbon-shaped crystals was derived. Some representative values at 7.5-cm diameter or width are 45 cm/hr or 2000 cm/sup 3//hr for a cylindrical Czochralski-grown crystal and 625 cm/hr or 95 cm/sup 3//hr for a 0.02-cm-thick ribbon. (auth)
Date: August 1, 1975
Creator: Schwuttke, G. H.; Ciszek, T. F. & Kran, A.
Partner: UNT Libraries Government Documents Department

Mercuric Iodide Photocell Technology for Room Temperature Readout of Scintillators

Description: Mercuric iodide (HgI2) is a well known material for the direct detection of gamma rays; however, the largest volume achievable is limited by thickness of the detector, which needs to be a small fraction of the average trapping length for electrons. We are reporting here preliminary results in using HgI2 crystals to fabricate photocells used in the readout of various scintillators. The optical spectral response and efficiency of these photocells were measured and will be reported. Preliminary nuclear response from a HgI2 photocell that was optically matched to a Ce3+ :LaBr3 scintillator will also be presented and discussed. Further improvements will be sought by optimizing the transparent contact technology.
Date: August 31, 2007
Creator: al., Warnick Kernan et
Partner: UNT Libraries Government Documents Department

Determination of a definition of solar grade silicon. Third quarterly report, 1 April--30 June 1976

Description: All scheduled experimental crystals have been grown. Analysis is about 75 percent complete; solar cell work is about 50 percent complete. Minority carrier life-time measurements are 90 percent done. From the results we conclude not only do solar cells tolerate certain impurities but cells built in silicon containing controlled amounts (up to one ppM) of magnesium, manganese and nickel, singly or combined, have actually higher-than-baseline performances. On the other hand, iron, chromium, vanadium and particularly titanium, reduce conversion efficiency from slightly to catastrophically. The influence of carbon is perhaps only marginal but no doubt is left about oxygen. Oxygen levels about 50 ppM, i.e., about 10/sup 18/ atoms/cc reduce device performance definitely.
Date: January 1, 1976
Creator: Christ, M. H.; Gupta, K. P.; Gutsche, H. W.; Hill, D. E.; Tucker, W. F. & Wang, M. S.
Partner: UNT Libraries Government Documents Department

Automatic lighting controls demonstration: Long-term results. Final report, July 1991

Description: An advanced electronically ballasted lighting control system was installed in a portion of an office building to measure the energy and demand savings. The lighting control system used an integrated lighting control scenario that included daylight following, lumen depreciation correction, and scheduling. The system reduced lighting energy on weekdays by 62% and 51% in the north and south daylit zones, respectively, compared to a reference zone that did not have controls. During the summer, over 75% energy savings were achieved on weekdays in the north daylit zone. Even in the south interior zone, which benefitted lime from daylight, correction strategies and adjustment of the aisleway lights to a low level resulted in energy use of only half that of the reference zone. Although, in general, the savings varied over the year due to changing daylight conditions, the energy reduction achieved with controls could be fit using a simple analytical model. Significant savings also occurred during core operating hours when it is more expensive to supply and use energy. Compared to the usage in the reference zone, energy reductions of 49%, 44%, and 62% were measured in the south daylight, south interior, and north daylight zones, respectively, during core operating hours throughout the year. Lighting energy usage on weekends decreased dramatically in the zones with controls, with the usage in the north daylit zone only 10% that of the reference zone. A simple survey developed to assess occupant response to the lighting control system showed that the occupants were satisfied with the light levels provided.
Date: October 18, 1991
Creator: Rubinstein, F.
Partner: UNT Libraries Government Documents Department

Improving the performance of photo-electrically controlled lighting systems

Description: The ability of a photo-electrically controlled lighting system to maintain a constant total light level on a task surface by responding to changing daylight levels is affected by the control algorithm used to relate the photosensor signal to the supplied electric light level and by the placement and geometry of the photosensor. We describe the major components of a typical control system, discuss the operation of three different control algorithms, and derive expressions for each algorithm that express the total illuminance at the task as a function of the control photosensor signal. Using a specially-designed scale model, we measured the relationship between the signal generated by various ceiling-mounted control photosensors and workplane illuminance for two room geometries under real sky conditions. The measured data were used to determine the performance of systems obeying the three control algorithms under varying daylight conditions. Control systems employing the commonly-used integral reset algorithm supplied less electric light than required, failing to satisfy the control objective regardless of the control photosensor used. Systems employing an alternative, closed-loop proportional control algorithm achieved the control objective under virtually all tested conditions when operated by a ceiling-mounted photosensor shielded from direct window light.
Date: August 1, 1988
Creator: Rubinstein, F.; Ward, G. & Verderber, R.
Partner: UNT Libraries Government Documents Department

Module Utilization Committee. Final report

Description: Photovoltaic collector modules were declared surplus to the needs of the US Department of Energy. The Module Utilization Committee was formed to make appropriate disposition of the surplus modules. The final report of that committee accounts for that disposition. The membership and activities of the committee are set forth and the results of its activities are reported.
Date: March 1, 1984
Partner: UNT Libraries Government Documents Department

Development of pulsed processes for the manufacture of solar cells. Quarterly progress report No. 2

Description: The status of a program to develop ion implantation and specialized associated processes necessary to achieve automated production of silicon solar cells is reported. Implantation requirements for high efficiency solar cells are described, and a process specification for baseline 16% efficient cells is presented. Cell performance comparisons have been made in which junctions were prepared by diffusion and ion implantation. Design efforts for an ion implanter capable of implanting 100 MW/sub e/ of solar cell product per year are nearing completion.
Date: April 1, 1978
Creator: Minnucci, J.
Partner: UNT Libraries Government Documents Department

Maximally Concentrating Optics for Photovoltaic Solar Energy Conversion

Description: Use of a two-stage concentrator with a fresnel lens primary and a nonimaging dielectric totally internally reflecting secondary, has unique advantages for photovoltaic concentration. Some preliminary ray trace studies have shown that with planar lenses, an increase in angular acceptance for a given geometric concentration to about 2/3 of the maximum theoretical limit can be achieved. To demonstrate this, two preprototype concentrators, each having a geometric concentration of 248:1 for a 0.635cm (0.25 inch) diameter cell, have been designed, built, and tested. Measurements of the angular response show an acceptance of 8[degrees] (full angle) which is drastically better than the 1[degrees]--2[degrees] achievable without a secondary, and is in excellent agreement with the ray trace predictions. For these preprototypes, passive cooling was sufficient to prevent any thermal problems for both the cell and secondary. No problems associated with nouuniform cell illumination were found, as evidenced by the fill factor of 71%--73% measured under concentration. Initial measurements of the system electrical efficiency lie in the range 7.5%--9.9% for a variety of individual cells.
Date: March 7, 1985
Creator: O'Gallagher, J. J.
Partner: UNT Libraries Government Documents Department

Silicon Materials Task of the Low Cost Solar Array Project (Phase II). Effect of impurities and processing on silicon solar cells. Phase II. Summary and eleventh quarterly report

Description: The effects of various processes, metal contaminants and contaminant-process interactions on the performance of terrestrial silicon solar cells were investigated. A variety of aspects including thermal treatments, crystal growth rate, base doping concentration (low resistivity), base doping type (n vs. p), grain boundary structure, and carbon/oxygen-metal interactions (float zone vs Czochralski growth) were studied. The effects of various metallic impurities were studied, introduced singly or in combination into Czochralski, float zone and polycrystalline silicon ingots and into silicon ribbons grown by the dendritic web process. The totality of the solar cell data (comprising over 4000 cells) indicate that impurity-induced performance loss is primarily due to reduction in base diffusion length. Based on this assumption an analytical model has been developed which predicts cell performance as a function of metal impurity content. The model has now been verified for p-base material by correlating the projected and measured performance of solar cells made on 19 ingots bearing multiple impurities.
Date: July 1, 1978
Creator: Hopkins, R.H.; Davis, J.R.; Blais, P.D.; Rohatgi, A.; Rai-Choudhury, P.; Hanes, M.H. et al.
Partner: UNT Libraries Government Documents Department

Analysis and evaluation in the production process and equipment area of the Low-Cost Solar Array Project. Quarterly report, January-April 1980

Description: The analyses of the front metallization design methods and their impacts on solar cell performance, particularly for large area cells, have been continued and completed herein. The influence of line shape on the effective voltage drop, which was treated before for the uniform width lines and the fully tapered lines, has now been generalized to include any taper. The potential merits of an oblique arrangement of the grid lines with respect to the bus lines are investigated. It is found that the arrangement of the grid lines normal to the bus lines gives the best performance. However, the performance penalty for oblique arrangement at relatively small inclination angles against the normal to the bus line is rather small. Also, the ways of optimizing the front metallization pattern, consisting of grid and bus lines, with respect to lowest total performance loss, due both to shading by metal coverage and to voltage drops in the various elements of the current path, was re-investigated. It was determined that it is essential that each level in the hierarchy of conductors have a substantially lower sheet resistance, by at least an order of magnitude, than the preceding level. The findings of these analyses were combined into a set of Design Rules for the front metallization design for large area solar cells. (WHK)
Date: November 1, 1980
Creator: Wolf, M.
Partner: UNT Libraries Government Documents Department