Search NASA⌕ Search

SEARCH · Search NASA

Results for “Solar array”

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.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 775 records · Page 43
All sourcesNASA NTRSDOE OSTI
DOE OSTI2015

Spatial Resolution Versus Data Acquisition Efficiency in Mapping an Inhomogeneous System with Species Diffusion

Traditionally, spatially-resolved photoluminescence (PL) has been performed using a point-by-point scan mode with both excitation and detection occurring at the same spatial location. But with the availability of high quality detector arrays like CCDs, an imaging mode has become popular for performing spatially-resolved PL. By illuminating the entire area of interest and collecting the data simultaneously from all spatial locations, the measurement efficiency can be greatly improved. However, this new approach has proceeded under the implicit assumption of comparable spatial resolution. We show here that when carrier diffusion is present, the spatial resolution can actually differ substantially between the two modes, with the less efficient scan mode being far superior. We apply both techniques in investigation of defects in a GaAs epilayer – where isolated singlet and doublet dislocations can be identified. A superposition principle is developed for solving the diffusion equation to extract the intrinsic carrier diffusion length, which can be applied to a system with arbitrarily distributed defects. The understanding derived from this work is significant for a broad range of problems in physics and beyond (for instance biology) – whenever the dynamics of generation, diffusion, and annihilation of species can be probed with either measurement mode.

14 SOLAR ENERGY↗
DOE OSTI2019

Effect of Torque-Tube Parameters on Rear-Irradiance and Rear-Shading Loss for Bifacial PV Performance on 1-Axis Tracking Systems

The emergence of cost-competitive bifacial PV modules has raised the question of the additional value of bifacial modules in 1-axis tracking arrays, in particular when considering rear-irradiance losses from the tracker system itself. In this work, the effect of different geometries and materials of torque tubes is evaluated and found to reduce rear-irradiance averages without any torque-tube shading by 0.1 to 12% for metallic and black absorptive torque tubes respectively for a clear-sky day. This paper will compare modeled to measured rear-irradiance profiles, and propose a recommended range of rear-shading loss factors for different geometry conditions. The effect of rear-irradiance distribution into electrical mismatch loss will also be explored. shading by 0.1 to 12% for metallic and black absorptive torque tubes respectively for a clear-sky day. This paper will compare modeled to measured rear-irradiance profiles, and propose a recommended range of rear-shading loss factors for different geometry conditions. The effect of rear-irradiance distribution into electrical mismatch loss will also be explored.

14 SOLAR ENERGY↗
DOE OSTI2019

Fundamental Piezotronic and Piezo-phototronic Effects in Nanowires

The piezo-phototronic effect is about the use of the piezoelectric potential created inside some materials for enhancing the charge carrier generation or separation at the metal-semiconductor contact or p-n junction. We demonstrate the impact of the piezo-phototronic effect on the photon sensitivity for a ZnO-CdS core-shell micro/nanowire based visible and UVsensor. CdS nanowire arrays were grown on the surface of a ZnO micro/nanowire to form a ZnO-CdS core-shell nanostructure by a facile hydrothermal method. With the two ends of a ZnO-CdS wire bonded on a polymer substrate, a flexible photodetector was fabricated, which is sensitive simultaneously to both green light (548 nm) and UV light (372 nm). The photocurrent and sensitivity of the ZnO_CdS wire photodetector is 103 times higher than that of CdS nanoribbon, and the responsivity (11 A W -1 , 548 nm, at 2 V bias) is nearly 100 times higher than that of ZnSe-nanobelt-based blue/UV-light sensor (0.12 AW -1 , 400 nm, at 30 V bias). Moreover, the performance of the ZnO-CdS wire photodetector upon illumination of visible and UV light can be both further enhanced for more than 10 times with the participation of the piezo-phototronic effect when the device is subjected to a -0.31% compressive strain. This investigation extends the application of the piezo-phototronic effect in a wide spectrum photon detector.

14 SOLAR ENERGY↗
DOE OSTI2017

Observation of the Crab Nebula with the HAWC Gamma-Ray Observatory

The Crab Nebula is the brightest TeV gamma-ray source in the sky and has been used for the past 25 years as a reference source in TeV astronomy, for calibration and verification of new TeV instruments. The High Altitude Water Cherenkov Observatory (HAWC), completed in early 2015, has been used to observe the Crab Nebula at high significance across nearly the full spectrum of energies to which HAWC is sensitive. HAWC is unique for its wide field of view, nearly 2 sr at any instant, and its high-energy reach, up to 100 TeV. HAWC’s sensitivity improves with the gamma-ray energy. Above ∼1 TeV the sensitivity is driven by the best background rejection and angular resolution ever achieved for a wide-field ground array. We present a time-integrated analysis of the Crab using 507 live days of HAWC data from 2014 November to 2016 June. The spectrum of the Crab is fit to a function of the form ϕ(E)=ϕ{sub 0}(E/E{sub 0}){sup −α−β⋅ln(E/E{sub 0})}. The data is well fitted with values of α = 2.63 ± 0.03, β = 0.15 ± 0.03, and log{sub 10}(ϕ{sub 0} cm{sup 2} s TeV)=−12.60±0.02 when E {sub 0} is fixed at 7 TeV and the fit applies between 1 and 37 TeV. Study of the systematic errors in this HAWC measurement is discussed and estimated to be ±50% in the photon flux between 1 and 37 TeV. Confirmation of the Crab flux serves to establish the HAWC instrument’s sensitivity for surveys of the sky. The HAWC all-sky survey will be the deepest survey of the northern sky ever conducted in the multi-TeV band.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2015

Degradation of transparent conductive oxides: Interfacial engineering and mechanistic insights

Transparent conductive oxides (TCOs) are a known failure mode in a variety of thin film photovoltaic (PV) devices, through mechanisms such as resistivity increase and delamination. Degradation science studies of these materials, as well as most PV systems, have primarily utilized industry standard qualification protocols, which are not designed to be used as lifetime prediction tests. Here, this work applies a data science approach to this engineering challenge, utilizing commercially available TCOs and subjecting them to an array of stressors, including environmental and material stressors. Optical, electrical and surface sensitive TCO property metrics were monitored and analyzed en mass. Different degradation mechanisms and modes were observed when different stressor combinations were applied; TCO surfaces are sensitive to the proportion of water and light in an exposure, yellowing of the TCO only occurs when humidity and UV light are combined, and PEDOT:PSS (poly(3,4-ethylenedioxythiophene) poly(styrenesulfonate)) application results in hazing and roughening of aluminum-doped zinc oxide (AZO). Using multi-variate analytics and plotting critical material properties against one another in a mechanistic plot, trade-offs between properties and the activation of different degradation mechanisms become readily apparent. In addition to a survey of failure modes of TCOs, a possible solution to the degradation of AZO was examined: the application of an organofunctional silane layer. The application of a thin APTES (3-aminopropyltriethoxysilane) film nearly eliminated the observed edge effects and greatly reduced the resistivity increase caused by damp heat exposure of AZO.

14 SOLAR ENERGY↗
DOE OSTI2021

An in-depth field validation of “DUSST”: A novel low-maintenance soiling measurement device

This study presents indoor and field validation results for two versions of the “DUSST” optical soiling sensor, intended to be a low-cost and low-maintenance device for measuring photovoltaic soiling losses. Indoor testing covers irradiance calibration and temperature dependencies, which are necessary to achieve high accuracy, low uncertainty field measurements. Field testing includes an array of different environments including Saudi Arabia, California, Utah, and Colorado. DUSST versions include a configuration with a 530-nm light emitting diode (LED) (discussed in previous work) and a unit with seven white LEDs and a polycarbonate collimating optic. The new design increases light intensity fivefold and demonstrates a single linear calibration coefficient is effective to measure soiling losses as high as 75%. Field data from Utah and California demonstrate that daily soiling loss measurements and soiling rate calculations closely match both reference cell and full-size module measurements of soiling losses and soiling rates. Corrective methods employed on the Utah DUSST sensor suggest that it is possible to achieve measurement errors as low as ±0.1% at two standard deviations. Field data from both Colorado and Saudi Arabia demonstrate that LED lens soiling can occur and that further design optimizations are needed. The lesson learned from all the field deployment locations suggests directions for future design improvements.

14 SOLAR ENERGY↗
DOE OSTI2021

Initial Characterization of Active Transitioning Centaur, P/2019 LD{sub 2} (ATLAS), Using Hubble, Spitzer, ZTF, Keck, Apache Point Observatory, and GROWTH Visible and Infrared Imaging and Spectroscopy

We present visible and mid-infrared imagery and photometry of temporary Jovian co-orbital comet P/2019 LD{sub 2} taken with Hubble Space Telescope/Wide Field Camera 3 (HST/WFC3), Spitzer Space Telescope/Infrared Array Camera (Spitzer/IRAC), and the GROWTH telescope network, visible spectroscopy from Keck/Low-Resolution Imaging Spectrometer (LRIS), and archival Zwicky Transient Facility observations taken between 2019 April and 2020 August. Our observations indicate that the nucleus of LD{sub 2} has a radius between 0.2 and 1.8 km assuming a 0.08 albedo and a coma dominated by ∼100 μm-scale dust ejected at ∼1 m s{sup −1} speeds with a ∼1′ jet pointing in the southwest direction. LD{sub 2} experienced a total dust mass loss of ∼10{sup 8} kg at a loss rate of ∼6 kg s{sup −1} with Afρ/cross section varying between ∼85 cm/125 km{sup 2} and ∼200 cm/310 km{sup 2} from 2019 April 9 to 2019 November 8. If the increase in Afρ/cross section remained constant, it implies LD{sub 2}'s activity began ∼2018 November when within 4.8 au of the Sun, implying the onset of H{sub 2}O sublimation. We measure CO/CO{sub 2} gas production of ≲10{sup 27} mol s{sup −1}/≲10{sup 26} mol s{sup −1} from our 4.5 μm Spitzer observations; g–r = 0.59 ± 0.03, r–i = 0.18 ± 0.05, and i–z = 0.01 ± 0.07 from GROWTH observations; and H{sub 2}O gas production of ≲80 kg s{sup −1} scaling from our estimated C {sub 2} production of Q{sub C{sub 2}}≲7.5×10{sup 24} mol s{sup −1} from Keck/LRIS spectroscopy. We determine that the long-term orbit of LD{sub 2} is similar to Jupiter-family comets having close encounters with Jupiter within ∼0.5 Hill radius in the last ∼3 y and within 0.8 Hill radius in ∼9 y. Additionally, 78.8% of our orbital clones are ejected from the solar system within 1 × 10{sup 6} yr, having a dynamical half-life of 3.4 × 10{sup 5} yr.

47 OTHER INSTRUMENTATION↗
DOE OSTI2016

Shortwave Array Spectroradiometer–Zenith (SASZe) Instrument Handbook

The Shortwave Array Spectroradiometer – Zenith (SASZe) provides measurements of zenith spectral shortwave radiance at 1Hz over a continuous spectral range from approximately 300 nm to 1700 nm. The SASZe design connects an optical collector located outdoors to a pair of spectrometers and data collections system located indoors within a climate-controlled building via an umbilical cable of fiber optic and electrical cables. The light collector incorporates a collimator yielding a 1-degree Full Width at Half Maximum (FWHM) field of view. The data-acquisition electronics and spectrometers include an in-line fiber optic shutter and two Avantes fiber-coupled grating spectroradiometers within a temperature-controlled container. The Avantes Avaspec ULS 2048 charge-coupled device (CCD) spectrometer covers the wavelength range from about 300-1100 nm with a pixel spacing of less than 0.6 nm and a spectral resolution of about 2.4 nm FWHM. The Avantes Avaspec NIR256-1.7 spectrometer covers the wavelength range from about 950 nm to 1700 nm with a pixel spacing of less than 4 nm and a spectral resolution of about 6 nm FWHM.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2025

hls4ml: A Flexible, Open-Source Platform for Deep Learning Acceleration on Reconfigurable Hardware

We present hls4ml, a free and open-source platform that translates machine learning (ML) models from modern deep learning frameworks into high-level synthesis (HLS) code that can be integrated into full designs for field-programmable gate arrays (FPGAs) or application-specific integrated circuits (ASICs). With its flexible and modular design, hls4ml supports a large number of deep learning frameworks and can target HLS compilers from several vendors, including Vitis HLS, Intel oneAPI and Catapult HLS. Together with a wider eco-system for software-hardware co-design, hls4ml has enabled the acceleration of ML inference in a wide range of commercial and scientific applications where low latency, resource usage, and power consumption are critical. In this paper, we describe the structure and functionality of the hls4ml platform. The overarching design considerations for the generated HLS code are discussed, together with selected performance results.

FOS: Computer and information sciences↗
DOE OSTI2019

Stabilization of a monolayer tellurene phase at CdTe interfaces

Two-dimensional (2D) materials provide a plethora of novel condensed matter physics and are the new playground in materials science, offering potentially vast applications. One of the critical hurdles for many 2D systems is the synthesis of these low-dimensional systems as well as the prediction and identification of new candidates. Herein, a self-assembly of a monolayer tellurene by bonding CdTe wafers is demonstrated for the first time. The conventional applications of wafer-bonding range from the production of microelectromechanical systems to the synthesis of lattice-mismatched multi-junction photovoltaics. Due to the heterogeneous materials that are typically employed, the bond-interface usually contains a thin amorphous layer or arrays of dislocations. Such an interface is thus itself inactive and in many cases has detrimental effects on the device. The new material phase stabilized in this work consists of an undulating monolayer of tellurium atoms covalently bonded to {111} Cd-terminated CdTe wafer surfaces. First-principles calculations and experimentally observed changes in the localized plasmon excitation energy indicate the clear rearrangement of the underlying band-structure suggesting a metallic character, bands showing linear dispersion, and a significant asymmetric spin-band splitting. The I–V characteristics show the presence of a highly conductive pathway that lowers the resistivity by three orders of magnitude, as compared to bulk CdTe, which can be attributed to the tellurium monolayer. The findings indicate that suitably chosen crystallographic wafer surfaces can act as structural templates allowing the production of exotic phases. Furthermore, the presently stabilized monolayer is an addition to the family of tellurene variants, providing new insights into the fundamental properties of this and other emerging 2D materials, while attracting attention to the unusual side of the wafer-bonding technology exemplified in this study.

14 SOLAR ENERGY↗
DOE OSTI2020

Connector system for photovoltaic array

A photovoltaic assembly comprising; (a) at least two photovoltaic components that are adjacent to each other in a first direction, each photovoltaic component comprising (i) a partial recess in communication with the partial recess in an adjacent photovoltaic component and (ii) one or more connector receptors aligned in a second direction which is non-parallel to the first direction; (b) a connector located at feast partially in the partial recess of the photovoltaic component and at least partially in the partial recess of the adjacent photovoltaic component so that the connector connects the photovoltaic component to the adjacent photovoltaic component, the connector comprising: (i) a flexible housing having a first end and a second end; (ii) one or more connection ports at the first end; (iii) one or more connection ports at the second end; and (iv) one more flexible electrical conductors that extend from the one or more connection ports at the first end to the one or more connection ports at the second end; wherein the connector is flexible so that the first end and the second end are movable relative to each other in a plane, out of the plane, or both; wherein the one or more connection ports at the first end and the one or more connection ports at the second end form a connection with the one or more connector receptors of the photovoltaic component and the adjacent photovoltaic component so that the connector electrically connects the photovoltaic component to the adjacent photovoltaic component.

14 SOLAR ENERGY↗
DOE OSTI2015

Effect of shape in near-field thermal transfer for periodic structures

In this paper, the effect of the geometrical shape on the radiative thermal transfer between a periodic array of beams and a planar substrate is investigated. Specifically, we analyze the changes in the thermal transfer that occur when the cross-sectional shape of SiC beams is modified from rectangular to ellipsoidal and finally triangular. Numerical calculations are done based on the rigorous coupled wave analysis. These exact results from this analysis are compared to modified proximity and far-field approximations, which become valid for small and large spacings, respectively. Moreover, these results are also compared to effective medium theory, which becomes increasingly accurate in the limit of small periodicities. We show that a reduction in the periodicity will lead to a reduced thermal transfer for triangular and ellipsoidal shaped beams. Even though, in the limit of very small periodicity, thermal transfer for the case of rectangular shaped beams also decreases by decreasing the periodicity, this decrease is slower as compared to other cross-sectional shapes. Lastly, we show that even though changing periodicity will change the magnitude of thermal transfer, the scaling law for its variation with the beam to substrate spacing is primarily determined by the cross-sectional shape rather than the periodicity. We analytically prove this fact by investigating the large and small periodicity regimes.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2017

Near-field heat transfer between graphene/hBN multilayers

We study the radiative heat transfer between multilayer structures made by a periodic repetition of a graphene sheet and a hexagonal boron nitride (hBN) slab. Surface plasmons in a monolayer graphene can couple with a hyperbolic phonon polaritons in a single hBN lm to form hybrid polaritons that can assist photon tunneling. For periodic multilayer graphene/hBN structures, the stacked metallic/dielectric array can give rise to a further e ective hyperbolic behavior, in addition to the intrinsic natural hyperbolic behavior of hBN. The e ective hyperbolicity can enable more hyperbolic polaritons that enhance the photon tunneling and hence the near- eld heat transfer. However, the hybrid polaritons on the surface, i.e. surface plasmon-phonon polaritons, dominate the near- eld heat transfer between multilayer structures when the topmost layer is graphene. The e ective hyperbolic regions can be well predicted by the e ective medium theory (EMT), thought EMT fails to capture the hybrid surface polaritons and results in a heat transfer rate much lower compared to the exact calculation. The chemical potential of the graphene sheets can be tuned through electrical gating and results in an additional modulation of the heat transfer. We found that the near- eld heat transfer between multilayer structure does not increase monotonously with the number of layer in the stack, which provides a way to control the heat transfer rate by the number of graphene layers in the multilayer structure. The results may bene t the applications of near- eld energy harvesting and radiative cooling based on hybrid polaritons in two-dimensional materials.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Human Health Risk Assessment Methods for PV, Part 1: Fire Risks

The photovoltaic (PV) industry has experienced rapid growth in recent years due in part to the development of public policies to address climate change and energy security. Some industry stakeholders have expressed concerns regarding potential human inhalation exposure to hazardous materials should a PV module array be exposed to fire, particularly in a residential or commercial rooftop application. To evaluate these concerns, fire hazard analysis methods are presented that can estimate emissions that may occur when PV modules (hereafter mostly referred to simply as 'modules') are exposed to fire, estimate the associated chemical concentrations in ambient air downwind from the fire, and finally compare these exposure-point concentrations to health-protective screening levels. Specifically, this report presents an analysis of potential human health impacts associated with chemical release from modules during a building fire for three PV technologies, focusing on airborne release of the highest-prioritized chemical element for each: Pb content in crystalline-silicon (c-Si) modules, Cd content in thin film cadmium telluride (CdTe) modules, and Se content in thin film copper indium selenide (CIS) modules. The intent of this analysis is to demonstrate the application of the proposed methods for modules exposed to fire in a quantitative yet illustrative manner. In particular, this report quantifies what are expected to be the worst-case potential health impacts over a wide range of possible conditions, including building/fire size, downwind receptor location, exposure duration, and meteorological conditions, utilizing a Gaussian plume modeling approach that is typically used in regulatory contexts.

14 SOLAR ENERGY↗
DOE OSTI2022

Grassland productivity responds unexpectedly to dynamic light and soil water environments induced by photovoltaic arrays

Abstract Agrivoltaic (AV) systems are designed to coproduce photovoltaic (PV) energy on lands simultaneously supporting agriculture (food/forage production). PV infrastructure in agroecosystems alters resources critical for plant growth, and water‐limited agroecosystems such as grasslands are likely to be particularly sensitive to the unique spatial and temporal patterns of incident sunlight and soil water inherent within AV systems. However, the impact of resource alteration on forage production, the primary ecosystem service from managed grasslands, is poorly resolved. Here, we evaluated seasonal patterns of soil moisture (SM) and diurnal variation in incident sunlight (photosynthetic photon flux density [PPFD]) in a single‐axis‐tracking AV system established in a formerly managed semiarid C 3 grassland in Colorado. Our goals were to (1) quantify dynamic patterns of PPFD and SM within a 1.2 MW PV array in a perennial grassland, and (2) determine how aboveground net primary production (ANPP) and photosynthetic parameters responded to the resource patterns created by the PV array. We hypothesized that spatial variability in ANPP would be strongly related to SM patterns, typical of most grasslands. We measured significant reductions in ANPP directly beneath PV panels, where SM and PPFD were both low. However, in locations with significantly increased SM from the shedding and redistribution of precipitation by PV panels, ANPP was not increased. Instead, ANPP was greatest in locations where plants were shaded in the afternoon but received high levels of PPFD in the morning hours, when air temperatures and vapor pressure deficits were relatively low. Thus, contrary to expectations, we found relatively weak relationships between SM and ANPP despite significant spatial variability in both. Further, there was little evidence that light‐saturated photosynthesis ( A sat ) and quantum yield of CO 2 assimilation (ϕCO 2 ) differed for plants growing directly beneath (lowest PPFD) versus between (highest PPFD) PV panels. Overall, the AV system established in this semiarid managed grassland did not alter patterns of ANPP in ways predictable from past studies of controls of ANPP in open grasslands. However, our results suggest that the diurnal timing of low versus high periods of PPFD incident on plants is an important determinant of productivity patterns in grasslands.

14 SOLAR ENERGY↗
DOE OSTI2016

Analysis of Joist Masonry Moisture Content Monitoring

BSC TO5 Task 7.2 Analysis of Joist Masonry Moisture Content Monitoring House - Lawrence, MA 01840 This work involved the field monitoring of embedded wood joist ends in a solid brick building in zone 5A that was retrofitted with interior insulation. Eleven joists throughout the building (which have a variety of orientations, exposures, and masonry wall types) were monitored for wood MCs at the embedded joist ends and for temperatures and RHs within the joist pocket. Indoor and outdoor conditions were also recorded. Results were collected for 28 months (December 2012-April 2015). One limitation was that the renovation was still ongoing; limited wintertime construction heating and no permanent occupancy were factors. Much of the building experienced cold interior temperatures (e.g., construction heating) during the winters. These were not typical interior heating set points. Because the building was essentially unoccupied, no significant interior moisture was generated. These boundary conditions are not normal service conditions. Overall, the RHs and MCs measured in joist pockets were higher than recommended for longterm durability. Many of the joist pockets had sustained conditions of 100% RH, and many wood MCs were in the 25%-35% range for extended periods. Typical guidance includes: (1) MCs lower than 20% are safe, and (2) decay fungi become active at MCs higher than 28%. ASHRAE xi 160 analysis showed that high RH levels coincided with temperatures that were high enough to support mold growth for most of the monitoring period (60%-70% of the hours) in most joists. However, no damage was seen at the joist ends when the instrumentation was installed or when a joist end sample was removed. This suggests that dense, old-growth framing might be able to survive these MCs without damage. Orientation has a significant effect on RH and MC levels: solar heating and drying kept all southfacing joist MCs well within the safe range. The east and west orientations had mixed results: some were in the safe range, but others exceeded the 20% MC level. The north side joists consistently had the highest MCs. Almost all the joists showed seasonal rises and falls; MC and RH conditions were higher during the summer and lower during the winter. This indicates the temperature gradient caused moisture to be driven inward during the summer. MC plots with driving rain showed no discernable correlations. In the parts of the building that had significant wintertime heating, many joists showed a drop in MC that coincided with the addition of heat, even after insulation and air sealing were installed. The joist ends showed a repeated pattern of MC measurements at their upper and lower ends. The lower joist end was consistently wetter than the upper joist end, which can be attributed to contact with the masonry pocket, gravity drainage of bulk water to the bottom of the pocket, greater drying at the top of the beam or deeper embedment at the bottom of the beam, and a larger air pocket at the top of the beam. The north-facing insulated and uninsulated joist ends were compared; a significant or consistent MC or RH difference was not seen between these cases. All three joist pockets essentially remained at a constant 100% RH.

Array↗