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Results for “energy conversion efficiency”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 109 records · Page 6
All sourcesNASA NTRSDOE OSTI
NASA NTRS1976

Energy Conversion Alternatives Study (ECAS), Westinghouse phase 1. Volume 5: Combined gas-steam turbine cycles

The energy conversion efficiency of gas-steam turbine cycles was investigated for selected combined cycle power plants. Results indicate that it is possible for combined cycle gas-steam turbine power plants to have efficiencies several point higher than conventional steam plants. Induction of low pressure steam into the steam turbine is shown to improve the plant efficiency. Post firing of the boiler of a high temperature combined cycle plant is found to increase net power but to worsen efficiency. A gas turbine pressure ratio of 12 to 1 was found to be close to optimum at all gas turbine inlet temperatures that were studied. The coal using combined cycle plant with an integrated low-Btu gasifier was calculated to have a plant efficiency of 43.6%, a capitalization of $497/kW, and a cost of electricity of 6.75 mills/MJ (24.3 mills/kwh). This combined cycle plant should be considered for base load power generation.

Amos, D. J.↗
NASA NTRS1976

Studies of silicon p-n junction solar cells

Single crystal silicon p-n junction solar cells made with low resistivity substrates show poorer solar energy conversion efficiency than traditional theory predicts. The physical mechanisms responsible for this discrepancy are identified and characterized. The open circuit voltage in shallow junction cells of about 0.1 ohm/cm substrate resistivity is investigated under AMO (one sun) conditions.

Lindholm, F. A.↗
NASA NTRS1976

Asymptotic residual pump transmission characteristics in laser-induced stimulated Brillouin scattering

The considered asymptotic relationship is investigated and an expression is sought for the slope of the curve representing the relation between the residual fractional transmitted pump and the pump excitation in backward-traveling-wave amplification. It is found that the characteristic -2 slope of the oscillation curve is a unique property. Rapid exponential decay may very well constitute an inherent limiting factor for efficient energy conversion.

Hsu, H.↗
NASA NTRS1977

Proceedings of the conference on Coal Feeding Systems

Development of coal feed systems for coal gasification, fluidized bed combustion, and magnetohydrodynamic applications is discussed. Process operations experience, energy conversion efficiency, and environment effects are among the factors considered.

Source record↗
NASA NTRS1977

Solar power satellite system definition study. Part 2, volume 4: Microwave power transmission systems

A slotted waveguide planar array was established as the baseline design for the spaceborne transmitter antenna. Key aspects of efficient energy conversion at both ends of the power transfer link were analyzed and optimized alternate approaches in the areas of antenna and tube design are discussed. An integrated design concept was developed which meets design requirements, observes structural and thermal constraints, exhibits good performance and was developed in adequate depth to permit cost estimating at the subsystem/component level.

Source record↗
NASA NTRS1979

Techno-economic projections for advanced small solar thermal electric power plants to years 1990-2000

Advanced technologies applicable to solar thermal electric power systems in the 1990-200 time-frame are delineated for power applications that fulfill a wide spectrum of small power needs with primary emphasis on power ratings less than 10MWe. Projections of power system characteristics (energy and capital costs as a function of capacity factor) are made based on development of identified promising technologies and are used as the basis for comparing technology development options and combinations of these options to determine developmental directions offering potential for significant improvements. Stirling engines, Brayton/Rankine combined cycles and storage/transport concepts encompassing liquid metals, and reversible-reaction chemical systems are considered for two-axis tracking systems such as the central receiver or power tower concept and distributed parabolic dish receivers which can provide efficient low-cost solar energy collection while achieving high temperatures for efficient energy conversion. Pursuit of advanced technology across a broad front can result in post-1985 solar thermal systems having the potential of approaching the goal of competitiveness with conventional power systems.

Fujita, T.↗
NASA NTRS1979

Automated Array Assembly Task In-depth Study of Silicon Wafer Surface Texturizing

A low cost wafer surface texturizing process was studied. An investigation of low cost cleaning operations to clean residual wax and organics from the surface of silicon wafers was made. The feasibility of replacing dry nitrogen with clean dry air for drying silicon wafers was examined. The two stage texturizing process was studied for the purpose of characterizing relevant parameters in large volume applications. The effect of gettering solar cells on photovoltaic energy conversion efficiency is described.

Jones, G. T.↗
NASA NTRS1979

Computer modeling of a two-junction, monolithic cascade solar cell

The theory and design criteria for monolithic, two-junction cascade solar cells are described. The departure from the conventional solar cell analytical method and the reasons for using the integral form of the continuity equations are briefly discussed. The results of design optimization are presented. The energy conversion efficiency that is predicted for the optimized structure is greater than 30% at 300 K, AMO and one sun. The analytical method predicts device performance characteristics as a function of temperature. The range is restricted to 300 to 600 K. While the analysis is capable of determining most of the physical processes occurring in each of the individual layers, only the more significant device performance characteristics are presented.

Lamorte, M. F.↗
NASA NTRS1977

Optimum antireflection coating for Antireflection-coated Metal-Oxide-Semiconductor /AMOS/ solar cells

Consideration is given to the design of a single-layer optimum antireflection coating for AMOS (antireflection-coated metal-oxide-semiconductor) solar cells to match the entire sunlight spectrum. The energy conversion efficiency is maximized by maximizing the open-circuit voltage and the short-circuit current. The former is maximized by oxidation techniques and the latter is maximized by the light-coupling into the solar cell. With reference to the effective index of refraction as obtained by ellipsometry, examples of optimum antireflection coatings for 60-A Au-GaAs solar cells are presented.

Yeh, Y. C. M.↗
NASA NTRS1979

Isis 1 observations at the source of auroral kilometric radiation

Observations of auroral kilometric radiation (AKR) were made by Isis 1 in the source region. The radiation is found to be generated in the extraordinary mode just above the local cut-off frequency and to emanate nearly perpendicular to the magnetic field. It occurs within local depletions of electron density, where the ratio of plasma frequency to cyclotron frequency is less than 0.2. The density depletion is restricted to altitudes above about 2000 km, and the upper AKR frequency limit corresponds to the extraordinary cut-off frequency at this altitude. AKR is observed from Isis 1 above the nighttime auroral zone over a wider extent in longitude than in latitude with an intense source region observed most often near 2200 LMT and 70 deg invariant latitude. It is directly related to inverted V electron precipitation events with an electron-to-wave energy conversion efficiency of the order of 0.1 to 1%.

Benson, R. F.↗
NASA NTRS1980

Hydrogen fluoride and deuterium fluoride lasers. Citations from the International Aerospace Abstracts data base

Research cited from the international literature adresses various aspects of hydrogen fluoride and deuterium fluoride lasers. Topics covered include flows, laser outputs, molecular relaxation, molecular rotation, energy conversion efficiency, reaction kinetics, and laser materials. Continous wave and pulsed laser are considered. This updated bibliography contains 283 citations, 53 of which are new additions to the previous edition.

Mauk, S. C.↗
NASA NTRS1980

Neodymium YAG lasers. Citations from the International Aerospace Abstracts data base

Various aspects of neodymium yag lasers are discussed in approximately 267 citations. Laser materials and outputs, laser mode locking; crystal, fiber, and nonlinear optics, optical pumping communications, energy conversion efficiency, and laser applications are covered. Pulsed, continuous wave, solid state, Q switched, infrared, and dye lasers are included.

Mauk, S. C.↗
NASA NTRS1980

Recent progress in high-output-voltage silicon solar cells

The status of the technology associated with the development of high output voltage silicon solar cells is reported. The energy conversion efficiency of a double diffusion process is compared to that of a single diffusion process. The efficiency of a 0.1 ohm/cm solar cell is characterized both before and after covering.

Muelenberg, A.↗
NASA NTRS1981

Study of the effects of impurities on the properties of silicon materials and performance of silicon solar cell

The effect of silicon film thickness on the energy conversion efficiency of a back surface field solar cell is investigated. A computer-aided design study on the dependence of efficiency peaks on the concentrations of the recombination and dopant impurities is presented. The illuminated current voltage characteristics of over 100 cell designs were obtained using the transmission line circuit model to numerically solve the Shockley Equations. Using an AM1 efficiency of 17% as a target value, it is shown that the efficiency versus thickness dependence has a broad maximum which varies less than 1% over more than three-to-one range of cell thickness from 30 to 100 microns. Optical reflecting back surface will give only a slight improvement of AM1 efficiency, about 0.7%, in this thickness range. The sensitive dependence of efficiency on patchiness across the back surface field, low high junction in thin cells is noted.

Sah, C. T.↗
NASA NTRS1981

Unconventional processes for food regeneration in space - An overview

Alternatives to conventional plant agriculture for the regeneration of food during space missions of extended duration are examined. The options considered, which may be used in combination with conventional agriculture, include the production of food from plant wastes, the chemical synthesis of food from carbon dioxide and other simple molecules or the substitution of edible chemicals, and the use of microrganisms for food and oxygen regeneration, with suitable processing. A comparison of solar energy conversion efficiencies is presented for nonphotosynthetic bacteria grown on hydrogen and algal systems photosynthetically, and it is shown that hydrogen bacteria are potentially more attractive than photosynthetic algae using artificial light. Weight-volume requirements for the conventional plant, algae and hydrogen bacteria systems are also compared to demonstrate the advantages of microbial systems.

Stokes, B. O.↗
NASA NTRS1981

Photovoltage response to temperature change at oxide semiconductor electrodes

A study has been carried out on single crystal electrodes of TiO2, SrTiO3, and alpha-Fe2O3 and polycrystalline WO3 to investigate the effect of cell temperature on the onset potential of n-type oxide semiconductor electrodes. It is found that the change of the onset potential with temperature is due to the potential change across the Helmholtz layer. The amount of this change depends on the point of zero zeta potential (pzzp) of the semiconductor electrode. The possibility of increasing the solar-to-chemical energy conversion efficiency of a photochemical cell by increasing the cell temperature is discussed.

Reichman, B.↗
NASA NTRS1982

Gain-enhanced free-electron laser with an electromagnetic pump field

The feasibility of enhancing the gain for the free electron laser (FEL) with an electromagnetic (EM) pump field has been considered. The enhancement is provided by reacceleration of the electrons in the interaction region by means of a static, axial electric field. A FEL utilizing a low energy electron beam and a wiggler magnet with a periodicity on the order of 1 cm would produce far infared (FIR) radiation with wavelengths on the order of a few hundred microns. The use of the FIR radiation as the pump field in a two-stage FEL is envisioned to obtain visible radiation with a low energy electron beam. A summary is provided regarding the theory and equations of motion for the EM-pumped FEL. The derived relations are applied to the second stage of such a two-stage FEL. The obtained equations have been incorporated into a computer code which has been used to calculate laser gain and energy conversion efficiency.

Hiddleston, H. R.↗