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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 1,045 records · Page 58
All sourcesNASA NTRSDOE OSTI
NASA NTRS1980

Preliminary study of a solar selective coating system using black cobalt oxide for high temperature solar collectors

Black cobalt oxide coatings (high solar absorptance layer) were deposited on thin layers of silver or gold (low emittance layer) which had been previously deposited on oxidized (diffusion barrier layer) stainless steel substrates. The reflectance properties of these coatings were measured at various thicknesses of cobalt for integrated values of the solar and infrared spectrum. The values of absorptance and emittance were calculated from the measured reflectance values, before and after exposure in air at 650 C for approximately 1000 hours. Absorptance and emittance were interdependent functions of the weight of cobalt oxide. Also, these cobalt oxide/noble metal/oxide diffusion barrier coatings have absorptances greater than 0.90 and emittances of approximately 0.20 even after about 1000 hours at 650 C.

Mcdonald, G.↗
NASA NTRS1979

Automated Array Assembly, Phase 2

The solar cell module process development activities in the areas of surface preparation are presented. The process step development was carried out on texture etching including the evolution of a conceptual process model for the texturing process; plasma etching; and diffusion studies that focused on doped polymer diffusion sources. Cell processing was carried out to test process steps and a simplified diode solar cell process was developed. Cell processing was also run to fabricate square cells to populate sample minimodules. Module fabrication featured the demonstration of a porcelainized steel glass structure that should exceed the 20 year life goal of the low cost silicon array program. High efficiency cell development was carried out in the development of the tandem junction cell and a modification of the TJC called the front surface field cell. Cell efficiencies in excess of 16 percent at AM1 have been attained with only modest fill factors. The transistor-like model was proposed that fits the cell performance and provides a guideline for future improvements in cell performance.

Carbajal, B. G.↗
NASA NTRS2014

Observational Signatures of Magnetic Reconnection

Magnetic reconnection is often referred to as the primary source of energy release during solar flares. Directly observing reconnection occurring in the solar atmosphere, however, is not trivial considering that the scale size of the diffusion region is magnitudes smaller than the observational capabilities of current instrumentation, and coronal magnetic field measurements are not currently sufficient to capture the process. Therefore, predicting and studying observationally feasible signatures of the precursors and consequences of reconnection is necessary for guiding and verifying the simulations that dominate our understanding. I will present a set of such observations, particularly in connection with long-duration solar events, and compare them with recent simulations and theoretical predictions.

Savage, Sabrina↗
DOE OSTI2018

The dye-sensitized solar cells based on the interconnected ternary cobalt diindium sulfide nanosheet array counter electrode

Highlights: • The ternary CoIn{sub 2}S{sub 4} CE was fabricated by in situ solvothermal synthesis. • The CoIn{sub 2}S{sub 4} CE displays an interconnected nanosheet array structure. • The solvent and In{sub 2.77}S{sub 4} intermediate play key roles on the formation of CoIn{sub 2}S{sub 4}. • DSSC based on the CoIn{sub 2}S{sub 4} CE gives an efficiency of 8.83%. - Abstract: The ternary cobalt diindium sulfide (CoIn{sub 2}S{sub 4}) counter electrode (CE) with interconnected nanosheet array structure is fabricated on the fluorine-doped tin oxide (FTO) substrate by in situ ethanol solvothermal synthesis. The ethanol solvent and In{sub 2.77}S{sub 4} intermediate play important roles on the formation of the interconnected nanosheet array structure. The dye-sensitized solar cell (DSSC) with the optimized ternary CoIn{sub 2}S{sub 4} CE gives an energy conversion efficiency of 8.83%, which is much higher than that of DSSCs based on the binary CoS{sub 2} (6.47%), and In{sub 2.77}S{sub 4} (0.46%) CEs and can be comparable with that of Pt CE (8.19%) under full sunlight illumination (100 mW cm{sup −2}, AM 1.5 G). Except for the intrinsically electrocatalytic activity from the CoIn{sub 2}S{sub 4}, the higher conversion efficiency of CoIn{sub 2}S{sub 4} based DSSC can be attributed to that the interconnected nanosheet array structure provides plentiful catalytic active sites, abundant electron transport channels, and fast electrolyte diffusion.

14 SOLAR ENERGY↗
DOE OSTI2021

Strong Local Evaporative Cooling Over Land Due to Atmospheric Aerosols

Abstract Aerosols can enhance terrestrial productivity through increased absorption of solar radiation by the shaded portion of the plant canopy—the diffuse radiation fertilization effect. Although this process can, in principle, alter surface evaporation due to the coupling between plant water loss and carbon uptake, with the potential to change the surface temperature, aerosol‐climate interactions have been traditionally viewed in light of the radiative effects within the atmosphere. Here, we develop a modeling framework that combines global atmosphere and land model simulations with a conceptual diagnostic tool to investigate these interactions from a surface energy budget perspective. Aerosols increase the terrestrial evaporative fraction, or the portion of net incoming energy consumed by evaporation, by over 4% globally and as much as ∼40% regionally. The main mechanism for this is the increase in energy allocation from sensible to latent heat due to global dimming (reduction in global shortwave radiation) and slightly augmented by diffuse radiation fertilization. In regions with moderately dense vegetation (leaf area index >2), the local surface cooling response to aerosols is dominated by this evaporative pathway, not the reduction in incident radiation. Diffuse radiation fertilization alone has a stronger impact on gross primary productivity (+2.18 Pg C y −1 or +1.8%) than on land evaporation (+0.18 W m −2 or +0.48%) and surface temperature (−0.01 K). Our results suggest that it is important for land surface models to distinguish between quantity (change in total magnitude) and quality (change in diffuse fraction) of radiative forcing for properly simulating surface climate.

Chakraborty, TC↗
NASA NTRS1963

Low energy proton damage to solar cells.

Changes in silicon solar cells subjected to low energy proton bombardment, covering degradation of diffusion length, spectral response and efficiency under sun-like illumination

RADIATION EFFECT↗
NASA NTRS1972

A reliable all-silver front contact for silicon solar cells.

Methods have been found to apply an adherent and humidity resistant silver-only front contact to n on p silicon solar cells. The critical processing step was the removal of the diffused oxide layer. Humidity resistance is superior to present day commercial titanium-silver contacts and the electrical characteristics of the cells are excellent. Titanium, which is degraded by humidity and which is a source of heavy metal poisoning, has been eliminated from the contact.

Lamneck, J. H., Jr.↗
NASA NTRS1973

Radiation belts of Jupiter

The results of a theoretical study of the radiation belts of Jupiter are presented. The model of the electron radiation belt is based on the assumption that electrons from the solar wind are transported into the region near Jupiter by radial diffusion. The diffusion is driven by electric fields caused by an upper atmospheric dynamo in Jupiter's ionosphere. A proton radiation belt at Jupiter is predicted.

Stansberry, K. G.↗
NASA NTRS1974

Interplanetary diffusion coefficients for cosmic rays

Information on the cosmic-ray diffusion coefficient, kappa, derived from near-earth observations of the solar modulation of galactic electron fluxes and from the near-earth power spectra of the interplanetary magnetic field, has been used to study the heliocentric radial dependence of kappa, and to derive limits on the spatial extent of the solar modulation region. Representing kappa, as a separable function of radius r and rigidity, and assumming kappa(r) proportional to r to the n-th power, we can place a limit on the power law exponent, n not greater than 1.2. The distance of the modulation boundary is a function of n, and, e.g., for n = 0, falls into the range of 6-25 AU.

Cummings, A. C.↗
NASA NTRS1974

Corotating particle fluxes observed with the Pioneer 7 and IMP 4 spacecraft

Observations are reported of the time development of 17-MeV proton fluxes in four corotating particle streams during the five days required for corotation from Pioneer 7, about 70 E of earth in 1968, to IMP-4 at earth. The azimuthal width of the particle streams was observed to remain constant over the five days. Assuming either continuous or impulsive injection of particles at the sun, this observation is shown to imply that the azimuthal diffusion coefficient was significantly less than the value derived from recent solar flare observations (McKibben, 1972).

Mckibben, R. B.↗
NASA NTRS1977

Wave-particle interaction phenomena associated with shocks in the solar wind

Microscopic wave-particle interaction phenomena must generally affect the evolution of a traveling interplanetary discontinuity such as a collisionless shock, and solar wind plasma instabilities should also be associated with interplanetary acceleration, diffusion, and dissipation. Recent local measurements from diagnostics on widely separated spacecraft illustrate some examples of these interaction phenomena, and two bounding cases are considered in detail here. It is shown that the interplanetary shock of September 14, 1974 (detected on IMP-7, 8, Hawkeye-1, and Pioneer 11) was associated with intense local electrostatic noise and ion acceleration, while the shock of January 6, 1975 (detected on IMP-7 and Helios-1) had no detectable electrostatic turbulence.

Scarf, F. L.↗
NASA NTRS1980

Opto-electronic properties of cells made from various silicon forms

Opto-electronic properties of the various silicon forms were obtained from the solar cell performance. Performance parameters included the photovoltaic characteristics, minority carrier diffusion length, spectral response and small light spot scanning. Self consistent results were obtained from the various measurement techniques, which can provide useful information on sheet quality, as a potential for low cost terrestrial applications, and areas where the sheet formation methods can be improved.

Yoo, H.↗
NASA NTRS1981

Gamma Ray Astrophysics: New insight into the universe

Gamma ray observations of the solar system, the galaxy and extragalactic radiation are reported. Topics include: planets, comets, and asteroids; solar observations; interstellar medium and galactic structure; compact objects; cosmology; and diffuse radiation. The instrumentation used in gamma ray astronomy in covered along with techniques for the analysis of observational spectra.

Fichtel, C. E.↗
NASA NTRS1982

Importance of heterogeneous processes to tropospheric chemistry - Studies with a one-dimensional model

A one-dimensional, time-dependent model of tropospheric air composition is developed which incorporates several heterogeneous physical and chemical processes. The model includes the interaction of gases, aerosols, and hydrometeors through the physical mechanisms of nucleation, condensation, evaporation, coagulation, coalescence, and deliquescence. Precipitation, sedimentation, and dry deposition act to remove material from the atmosphere, while chemical transformations occur both in the vapor and the condensed phases. The model also incorporates the sources and vertical diffusion of gases and particles, as well as changes in the solar intensity caused by light-scattering from aerosols and clouds. Preliminary simulations made using this model indicate that rainout and washout processes strongly influence the distributions of tropospheric gases and aerosols under certain conditions.

Turco, R. P.↗
NASA NTRS1985

Telescoping Shield for Point-Focusing Solar Concentrators

Telescoping shield normally stowed around solar receiver protects heat engine and supporting structure from overheating when concentrator aimed few degrees away from line to Sun. When extended, shield intercepts off center concentrated solar radiation. Heat spread out over thermally conductive shield and reradiated diffusely not to cause structural damage.

Argoud, M.↗
NASA NTRS1984

Flat-plate solar array project process development area, process research of non-CZ silicon material

The program is designed to investigate the fabrication of solar cells on N-type base material by a simultaneous diffusion of N-type and P-type dopants to form an P(+)NN(+) structure. The results of simultaneous diffusion experiments are being compared to cells fabricated using sequential diffusion of dopants into N-base material in the same resistivity range. The process used for the fabrication of the simultaneously diffused P(+)NN(+) cells follows the standard Westinghouse baseline sequence for P-base material except that the two diffusion processes (boron and phosphorus) are replaced by a single diffusion step. All experiments are carried out on N-type dendritic web grown in the Westinghouse pre-pilot facility. The resistivities vary from 0.5 (UC OMEGA)cm to 5 (UC OMEGA)cm. The dopant sources used for both the simultaneous and sequential diffusion experiments are commercial metallorganic solutions with phosphorus or boron components. After these liquids are applied to the web surface, they are baked to form a hard glass which acts as a diffusion source at elevated temperatures. In experiments performed thus far, cells produced in sequential diffusion tests have properties essentially equal to the baseline N(+)PP(+) cells. However, the simultaneous diffusions have produced cells with much lower IV characteristics mainly due to cross-doping of the sources at the diffusion temperature. This cross-doping is due to the high vapor pressure phosphorus (applied as a metallorganic to the back surface) diffusion through the SiO2 mask and then acting as a diffusant source for the front surface.

Campbell, R. B.↗
NASA NTRS1985

Short-lived nuclides in the early solar system and general isotopic anomalies in meteorites

Evidence for short-lived nuclides in the early solar system is reviewed. The presence of these nuclides requires the addition to the interstellar medium, from which the solar system formed, of freshly synthesized materials just prior to the formation of the solar system. The best evidence is obtained for Al26. The time scale implied by the Al26 effects is equated with the free-fall time for the collapse of the protosolar cloud. From the observation of ratios of short-lived parent to stable isotopes for nuclides with different half-lives, it is apparent that addition of exotic material to the solar system occurred just prior to its formation. Evidence for a diffuse galactic gamma-ray line emission attributed to Al26 provides support for the existence of Al26 in the protosolar cloud. The time scale for isolation of the protosolar cloud would still be restricted on a timescale comparable to tau 1/2 (Al26).

Papanastassiou, D. A.↗