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  • 1
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    The 25 percent-efficient GaAs Cassegrainian concentrator cell (1989)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: Very high-efficiency GaAs Cassegrainian solar cells have been fabricated in both the n-p and p-n configurations. The n-p configuration exhibits the highest efficiency at concentration, the best cells having an efficiency eta of 24.5 percent (100X, AM0, temperature T = 28 C). Although the cells are designed for operation at this concentration, peak efficiency is observed near 300 suns (eta = 25.1 percent). To our knowledge, this is the highest reported solar cell efficiency for space applications. The improvement in efficiency over that reported at the previous SPRAT conference is attributed primarily to lower series resistance and improved grid-line plating procedures. Using previously measured temperature coefficients, researchers estimate that the n-p GaAs cells should deliver approximately 22.5 percent efficiency at the operating conditions of 100 suns and T = 80 C. This performance exceeds the NASA program goal of 22 percent for the Cassegrainian cell. One hundred Cassegrainian cells have been sent to NASA as deliverables, sixty-eight in the n-p configuration and thirty-two in the p-n configuration.
    Keywords: ENERGY PRODUCTION AND CONVERSION
    Type: NASA, Lewis Research Center, Space Photovoltaic Research and Technology, 1988. High Efficiency. Space Environment, and Array Technology; p 292-297
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  • 2
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    Working group report on advanced high-voltage high-power and energy-storage space systems (1986)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: Space systems in the future will probably include high-voltage, high-power energy-storage and -production systems. Two such technologies are high-voltage ac and dc systems and high-power electrodynamic tethers. The working group identified several plasma interaction phenomena that will occur in the operation of these power systems. The working group felt that building an understanding of these critical interaction issues meant that several gaps in our knowledge had to be filled, and that certain aspects of dc power systems have become fairly well understood. Examples of these current collection are in quiescent plasmas and snap over effects. However, high-voltage dc and almost all ac phenomena are, at best, inadequately understood. In addition, there is major uncertainty in the knowledge of coupling between plasmas and large scale current flows in space plasmas. These gaps in the knowledge are addressed.
    Keywords: ENERGY PRODUCTION AND CONVERSION
    Type: Space Technology Plasma Issues in 2001; p 12-15
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  • 3
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    Measurement of the heat produced internally during discharge by the 6V Eveready Energizer Battery, no. 528 (1986)
    In:  CASI
    Details
    Publication Date: 2006-06-12
    Description: When a 6V Eveready Energizer Battery, 528, is discharged, heat is produced internally within the battery itself. Detailed measurements of this battery heat were made for a five day discharge period using a load resistance of 20 ohms and an ambient temperature of 10 C. The battery heat produced per quarter day varied considerably, ranging from 1.08 watt-hrs to 2.63 watt-hrs. The total battery heat produced, using a 3.0 volt cutoff, is significant (37 watt-hrs) when compared to the total load heat produced (70 watt-hrs).
    Keywords: ENERGY PRODUCTION AND CONVERSION
    Type: NASA. Goddard Space Flight Center The 1985 Get Away Special Experimenter's Symposium; p 177-184
    Format: text
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    NASA TECHNICAL REPORTS
  • 4
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    The application of electrochemical impedance spectroscopy for characterizing the degradation of Ni(OH)2/NiOOH electrodes (1989)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: Electrochemical impedance spectra of rolled and bonded and sintered porous nickel battery electrodes were recorded periodically during charge/discharge cycling in concentrated KOH solution at various temperatures. A transmission line model (TLM) was adopted to represent the impedance of the porous electrodes, and various model parameters were adjusted in a curve fitting routine to reproduce the experimental impedances. Degradation processes for rolled and bonded electrodes were deduced from changes in model parameters with electrode cycling time. In developing the TLM, impedance spectra of planar (non-porous) electrodes were used to represent the pore wall and backing plate interfacial impedances. These data were measured over a range of potentials and temperatures, and an equivalent circuit model was adopted to represent the planar electrode data. Cyclic voltammetry was used to study the characteristics of the oxygen evolution reaction on planar nickel electrodes during charging, since oxygen evolution can affect battery electrode charging efficiency and ultimately electrode cycle life if the overpotential for oxygen evolution is sufficiently low. Transmission line modeling results suggest that porous rolled and bonded nickel electrodes undergo restructuring during charge/discharge cycling prior to failure.
    Keywords: ENERGY PRODUCTION AND CONVERSION
    Type: NASA, Lewis Research Center, Space Electrochemical Research and Technology (SERT), 1989; p 311-24
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  • 5
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    Perovskite oxides: Oxygen electrocatalysis and bulk structure (1987)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: Perovskite type oxides were considered for use as oxygen reduction and generation electrocatalysts in alkaline electrolytes. Perovskite stability and electrocatalytic activity are studied along with possible relationships of the latter with the bulk solid state properties. A series of compounds of the type LaFe(x)Ni1(-x)O3 was used as a model system to gain information on the possible relationships between surface catalytic activity and bulk structure. Hydrogen peroxide decomposition rate constants were measured for these compounds. Ex situ Mossbauer effect spectroscopy (MES), and magnetic susceptibility measurements were used to study the solid state properties. X ray photoelectron spectroscopy (XPS) was used to examine the surface. MES has indicated the presence of a paramagnetic to magnetically ordered phase transition for values of x between 0.4 and 0.5. A correlation was found between the values of the MES isomer shift and the catalytic activity for peroxide decomposition. Thus, the catalytic activity can be correlated to the d-electron density for the transition metal cations.
    Keywords: ENERGY PRODUCTION AND CONVERSION
    Type: NASA-Lewis Research Center, Space Electrochemical Research and Technology (SERT); p 221-23
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  • 6
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    GaAs solar cells with V-grooved emitters (1989)
    In:  CASI
    Details
    Publication Date: 2013-08-29
    Description: A GaAs solar cell with a V-grooved front surface is described. It shows improved optical coupling and higher short-circuit current compared to planar cells. The GaAs homojunction cells, manufactured by OrganoMetallic Chemical Vapor Deposition (OMCVD), are described. The V-grooves were formed by anisotropic etching. Reflectivity measurements show significantly lower reflectance for the microgrooved cell compared to the planar structure. The short circuit current of the V-grooved solar cell is consistently higher than that of the planar controls.
    Keywords: ENERGY PRODUCTION AND CONVERSION
    Type: ESA, European Space Power, Volume 2; p 515-518
    Format: text
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  • 7
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    Radiation damage of gallium arsenide production cells (1987)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: High efficiency liquid phase epitaxy (LPE) gallium arsenide cells were irradiated with 1 Mev electrons up to fluences of 1 times 10 to the 16th power cm-2. Measurements of spectral response and dark and illuminated I-V data were made at each fluence and then, using computer codes, the experimental data was fitted to gallium arsenide cell models. In this way it was possible to determine the extent of the damage, and hence damage coefficients in both the emitter and base of the cell.
    Keywords: ENERGY PRODUCTION AND CONVERSION
    Type: NASA. Lewis Research Center, Space Photovoltaic Research and Technology 1986. High Efficiency, Space Environment and Array Technology; p 213-222
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  • 8
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    Increased voltage photovoltaic cell (1985)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: A photovoltaic cell, such as a solar cell, is provided which has a higher output voltage than prior cells. The improved cell includes a substrate of doped silicon, a first layer of silicon disposed on the substrate and having opposite doping, and a second layer of silicon carbide disposed on the first layer. The silicon carbide preferably has the same type of doping as the first layer.
    Keywords: ENERGY PRODUCTION AND CONVERSION
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  • 9
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    Effect of precipitation on wind turbine performance (1985)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The effects of precipitation on wind turbine power output was analyzed. The tests were conducted on the two bladed Mod-0 horizontal axis wind turbine with three different rotor configurations. Experimental data from these tests are presented which clearly indicate that the performance of the Mod-0 wind turbine is affected by rain. Light rainfall degraded performance by as much as 20 percent while heavy rainfall degraded performance by as much as 30 percent. Snow mixed with drizzle degraded performance by as much as 36 percent at low windspeeds. Also presented are the results of an analysis to predict the effect of rain on wind turbine performance. This analysis used a blade element/momentum code with modified airfoil characteristics to account for the effect of rain and predicted a loss in performance of 31 percent in high winds with moderate rainfall rates. These predicted results agreed well with experimental data.
    Keywords: ENERGY PRODUCTION AND CONVERSION
    Type: NASA-TM-86986 , E-2530 , DOE/NASA/20320-64 , NAS 1.15:86986
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  • 10
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    AC impedance study of degradation of porous nickel battery electrodes (1987)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: AC impedance spectra of porous nickel battery electrodes were recorded periodically during charge/discharge cycling in concentrated KOH solution at various temperatures. A transmission line model (TLM) was adopted to represent the impedance of the porous electrodes, and various model parameters were adjusted in a curve fitting routine to reproduce the experimental impedances. Degradation processes were deduced from changes in model parameters with electrode cycling time. In developing the TLM, impedance spectra of planar (nonporous) electrodes were used to represent the pore wall and backing plate interfacial impedances. These data were measured over a range of potentials and temperatures, and an equivalent circuit model was adopted to represent the planar electrode data. Cyclic voltammetry was used to study the characteristics of the oxygen evolution reaction on planar nickel electrodes during charging, since oxygen evolution can affect battery electrode charging efficiency and ultimately electrode cycle life if the overpotential for oxygen evolution is sufficiently low.
    Keywords: ENERGY PRODUCTION AND CONVERSION
    Type: NASA-Lewis Research Center, Space Electrochemical Research and Technology (SERT); p 257-28
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