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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 739 records · Page 41
All sourcesNASA NTRSDOE OSTI
NASA NTRS1975

A measurement of abundances of VVH nuclei above 0.6 GeV per nucleon

The abundance distribution of very very heavy (VVH) nuclei just beyond the iron group has been measured with a balloon-borne counter telescope flown in 1971 and 1972. While the statistical accuracy of these observations is limited, they are of considerable interest since very little work has so far been done to determine the abundance of nuclei with charge between 27 and 36. It is found that the element distribution in the cosmic rays arriving at the top of the atmosphere is quite similar to the solar-system abundance distribution in this interval.

Juliusson, E.↗
NASA NTRS1980

Solar panel thermal cycling testing by solar simulation and infrared radiation methods

For the solar panels of the European Space Agency (ESA) satellites OTS/MAROTS and ECS/MARECS the thermal cycling tests were performed by using solar simulation methods. The performance data of two different solar simulators used and the thermal test results are described. The solar simulation thermal cycling tests for the ECS/MARECS solar panels were carried out with the aid of a rotatable multipanel test rig by which simultaneous testing of three solar panels was possible. As an alternative thermal test method, the capability of an infrared radiation method was studied and infrared simulation tests for the ultralight panel and the INTELSAT 5 solar panels were performed. The setup and the characteristics of the infrared radiation unit using a quartz lamp array of approx. 15 sq and LN2-cooled shutter and the thermal test results are presented. The irradiation uniformity, the solar panel temperature distribution, temperature changing rates for both test methods are compared. Results indicate the infrared simulation is an effective solar panel thermal testing method.

Nuss, H. E.↗
NASA NTRS1989

The heliospheric neutral hydrogen density profile in the presence of a solar wind shock

The effect of a postulated nearby solar wind shock on the radial density profile of the cold inflowing neutral hydrogen atoms is studied. It is found that a nearby solar wind shock strongly affects the neutral hydrogen breeze. Model calculation reveals that the strongly perturbed hydrogen atom distribution beyond a solar wind shock can be remotely detected by observation of the radial dependence of the backscattered UV glow from the deep space probes Pioneer 10/11 and Voyager 1/2.

Gangopadhyay, P.↗
DOE OSTI2021

An Overview of Issues Related to IEEE Std 1547-2018 Requirements Regarding Voltage and Reactive Power Control

The revised Institute of Electrical and Electronics Engineers (IEEE) 1547 Standard for Interconnection and Interoperability of Distributed Energy Resources with Associated Electric Power Systems Interfaces (IEEE Std 1547-2018) was published in April 2018. This standard is one of the foundational documents in the United States needed for integrating distributed energy resources (DERs), including solar energy systems, with the electric distribution grid. The revised standard contains 11 chapters (clauses) and 8 annexes that comprise 136 pages. The revision is significantly different from the 2003 version, and it contains new concepts and new technical requirements. Each clause specifies information or requirements that apply to certain aspects important to the interconnection of DERs to the electric power system. Implementing the requirements necessitates a careful study of the underlying technical concept and requires the appropriate information required to calculate relevant settings and configurations. Various stakeholders have different roles in implementing the standard, and portions of the standard are directed toward a specific audience who must possess specialized information and technical training to use and apply the requirements. This document aims to (1) summarize a specific portion of the standard as concisely as possible and (2) provide the reader with introductory knowledge and information to support the utilization of the requirements.

14 SOLAR ENERGY↗
DOE OSTI2023

Voltage Support With PV Inverters in Low-Voltage Distribution Networks: An Overview

Large solar photovoltaic (PV) penetration using inverters in low voltage (LV) distribution networks may pose several challenges, such as reverse power flow and voltage rise situations. These challenges will eventually force grid operators to carry out grid reinforcement to ensure continued safe and reliable operations. However, smart inverters with reactive power control capability enable PV systems to support voltage quality in the distribution network better. Here, this paper gives an overview of the current state-of-the-art control strategies for handling voltage problems through PV inverters and other devices. In addition, the (control) technical issues of PV systems integrated into the LV distribution network are considered from a control point of view. By comparing the control issues of PV integration into the grid, the paper aims to help distribution system operators to expand the volume of PV generation in the distribution system in an efficient and safe manner. Additionally, it will help control engineers and researchers select proper control strategies for PV systems as well as other distributed renewable sources.

42 ENGINEERING↗
NASA NTRS1973

Effect of energetic oxygen atoms on neutral density models.

The dissociative recombination of O2(+) and NO(+) in the F region results in the production of atomic oxygen and atomic nitrogen with substantially greater kinetic energy than the ambient atoms. In the exosphere these energetic atoms have long free paths. They can ascend to altitudes of several thousand kilometers and can travel horizontally to distances of the order of the earth's radius. The distribution of energetic oxygen atoms is derived by means of models of the ion and neutral densities for quiet and disturbed solar conditions. A distribution technique is used to study the motion of the atoms in the collision-dominated region. Ballistic trajectories are calculated in the spherical gravitational field of the earth. The present calculations show that the number densities of energetic oxygen atoms predominate over the ambient atomic oxygen densities above 1000 km under quiet solar conditions and above 1600 km under disturbed solar conditions.

Rohrbaugh, R. P.↗
DOE OSTI2018

Penumbra: A spatially distributed, mechanistic model for simulating ground-level incident solar energy across heterogeneous landscapes

Landscape solar energy is a significant environmental driver, yet it remains complicated to model well. Several solar radiation models simplify the complexity of light by estimating it at discrete point locations or by averaging values over larger areas. These modeling approaches may be useful in certain cases, but they are unable to provide spatially distributed and temporally dynamic representations of solar energy across entire landscapes. We created a landscape-scale ground-level shade and solar energy model called Penumbra to address this deficiency. Penumbra simulates spatially distributed ground-level shade and incident solar energy at user-defined timescales by modeling local and distant topographic shading and vegetative shading. Spatially resolved inputs of a digital elevation model, a normalized digital surface model, and landscape object transmittance are used to estimate spatial variations in solar energy at user-defined temporal timesteps. The research goals for Penumbra included: 1) simulations of spatiotemporal variations of shade and solar energy caused by both objects and topographic features, 2) minimal user burden and parameterization, 3) flexible user defined temporal parameters, and 4) flexible external model coupling. We test Penumbra’s predictive skill by comparing the model’s predictions with monitored open and forested sites, and achieve calibrated mean errors ranging from -17.3 to 148.1 μmoles/m 2 /s. Penumbra is a dynamic model that can produce spatial and temporal representations of shade percentage and ground-level solar energy. Outputs from Penumbra can be used with other ecological models to better understand the health and resilience of aquatic, near stream terrestrial, and upland ecosystems.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2017

Evolving Distributed Generation Support Mechanisms: Case Studies from United States, Germany, United Kingdom, and Australia (Chinese translation)

This is the Chinese translation of NREL/TP-6A20-67613. This report expands on a previous National Renewable Energy Laboratory (NREL) technical report (Lowder et al. 2015) that focused on the United States' unique approach to distributed generation photovoltaics (DGPV) support policies and business models. While the focus of that report was largely historical (i.e., detailing the policies and market developments that led to the growth of DGPV in the United States), this report looks forward, narrating recent changes to laws and regulations as well as the ongoing dialogues over how to incorporate distributed generation (DG) resources onto the electric grid. This report also broadens the scope of Lowder et al. (2015) to include additional countries and technologies. DGPV and storage are the principal technologies under consideration (owing to market readiness and deployment volumes), but the report also contemplates any generation resource that is (1) on the customer side of the meter, (2) used to, at least partly, offset a host's energy consumption, and/or (3) potentially available to provide grid support (e.g., through peak shaving and load shifting, ancillary services, and other means).

14 SOLAR ENERGY↗
DOE OSTI2020

Voltage positioning using co-optimization of controllable grid assets in radial networks

With increasing penetration of solar PV, some distribution feeders are experiencing highly variable net-load flows and even reverse flows. To optimize distribution systems under such conditions, the scheduling of mechanical devices, such as OLTCs and capacitor banks, needs to take into account forecasted solar PV and actual grid conditions. However, these legacy switching assets are operated on a daily or hourly timescale, due to the wear and tear associated with mechanical switching, which makes them unsuitable for real-time control. Therefore, there is a natural timescale- separation between these slower mechanical assets and the responsive nature of inverter-based resources. In this paper, we present a network admissible convex formulation for holistically scheduling controllable grid assets to position voltage optimally against solar PV. An optimal hourly schedule is presented that utilizes mechanical resources to position the predicted voltages close to nominal values, while minimizing the use of inverter-based resources (i.e., DERs), making them available for control at a faster time-scale (after the uncertainty reveals itself). A convex, inner approximation of the OPF problem is adapted to a mixed-integer linear program that minimizes voltage deviations from nominal (i.e., maximizes voltage margins). Here, the resulting OPF solution respects all the network constraints and is, hence, robust against modeling simplifications. Simulation based analysis on IEEE distribution feeders validates the approach.

24 POWER TRANSMISSION AND DISTRIBUTION↗
NASA NTRS1975

A correlative study of simultaneously measured He(++) fluxes in the solar wind and in the magnetosphere utilizing Imp-1 and 1971-089A satellite data

Simultaneously measured He(++) fluxes in the solar wind and in the magnetosphere were studied using data from the plasma spectrometer on the Imp I satellite and the energetic ion mass spectrometer on the low altitude polar orbiting satellite 1971-89A. A detailed comparison of the He(++) energy spectra measured simultaneously in the solar wind and in the low altitude dayside polar cusp on March 7, 1972 was made. The energy-per-unit-charge range of the energetic ion mass spectrometer on board the polar orbiting satellite was 700 eV to 12 keV. Within this range there was a clear maximum in the He(++) energy spectrum at approximately 1.5 keV/nucleon. There was not a clearly defined maximum in the H(+) spectrum, but the data were consistent with a peak between 0.7 and 1.0 keV/nucleon. Both spectra could be reasonably well fit with a convecting Maxwellian plus a high energy tail; however, the mean velocity for He(++) distribution was significantly greater than that for the H(+) distribution. The simultaneous solar wind measurements showed the mean velocities for both ion species to be approximately 600 km/sec. The discrepancies between the relative velocity distributions in the low altitude cusp and those in the solar wind are consistent with a potential difference of approximately 1.4 kV along their flow direction between the two points of observation.

Shelley, E. G.↗
NASA NTRS2000

Solar UV Radiation and the Origin of Life on Earth

We have started a comprehensive, interdisciplinary study of the influence of solar ultraviolet radiation on the atmosphere of of the early Earth. We plan to model the chemistry of the Earth atmosphere during its evolution, using observed UV flux distributions of early solar analogs as boundary conditions in photochemical models of the Earth's atmosphere. The study has four distinct but interlinked parts: (1) Establishing the radiation of the early Sun; (2) Determining the photochemistry of the early Earth's atmosphere; (3) Estimating the rates of H2 loss from the atmosphere; and (4) Ascertaining how sensitive is the photochemistry to the metallicity of the Sun. We are currently using STIS and EUVE to obtain high-quality far-UV and extreme-UV observations of three early-solar analogs. We will perform a detailed non-LTE study of each stars, and construct theoretical model photosphere, and an empirical model chromospheres, which can be used to extrapolate the continuum to the Lyman continuum region. Given a realistic flux distribution of the early Sun, we will perform photochemical modeling of weakly reducing primitive atmospheres to determine the lifetime and photochemistry of CH4. In particular, we will make estimates of the amount of CH4 present in the prebiotic atmosphere, and estimate the atmospheric CH4 concentration during the Late Archean (2.5-3.0 b.y. ago) and determine whether it would have been sufficiently abundant to help offset reduced solar luminosity at that time. Having obtained a photochemical model, we will solve for the concentrations of greenhouse gasses and important pre-biotic molecules, and perform a detailed radiative transfer calculations to compute the UV flux reaching the surface.

Heap, Sara R.↗
NASA NTRS1990

Distributions of He(+) at middle and equatorial latitudes during solar maximum

The properties of the plasma composition in the topside ionosphere between 15 and 35 deg magnetic latitude are examined. Calculations are used to show that the distribution of neutral species at solar maximum, together with the appropriate ionization rates, can readily account for the dominance of He(+) at midlatitudes. The relative abundance of the atmospheric species is a sensitive function of local time and the associated evolution of the topside O(+) concentration profile. The existence of an ExB drift motion of the plasma is needed to explain the He(+) minimum at the dip equator. While the He(+) concentration there is produced in one day against the chemical loss process, at midlatitudes a large flux tube volume provides a reservoir in which the He(+) can accumulate each day.

Heelis, R. A.↗
NASA NTRS1975

Selected Theoretical Studies Group contributions to the 14th International Cosmic Ray conference

The galactic distribution of H2 was studied through gamma radiation and through X-ray, optical, and infrared absorption measurements from SAS-2 and other sources. A comparison of the latitude distribution of gamma-ray intensity with reddening data shows reddening data to give the best estimate of interstellar gas in the solar vicinity. The distribution of galactic cosmic ray nucleons was determined and appears to be identical to the supernova remnant distribution. Interactions between ultrahigh energy cosmic-ray nuclei and intergalactic photon radiation fields were calculated, using the Monte Carlo method.

Source record↗
NASA NTRS1991

The Oort cloud

Views of the large-scale structure of the solar system, consisting of the Sun, the nine planets and their satellites, changed when Oort demonstrated that a gigantic cloud of comets (the Oort cloud) is located on the periphery of the solar system. The following subject areas are covered: (1) the Oort cloud's mass; (2) Hill's cloud mass; (3) angular momentum distribution in the solar system; and (4) the cometary cloud around other stars.

Marochnik, Leonid S.↗
DOE OSTI2021

Stability of superthermal strahl electrons in the solar wind

We present a kinetic stability analysis of the solar wind electron distribution function consisting of the Maxwellian core and the magnetic-field aligned strahl, a superthermal electron beam propagating away from the sun. We use an electron strahl distribution function obtained as a solution of a weakly collisional drift-kinetic equation, representative of a strahl affected by Coulomb collisions but unadulterated by possible broadening from turbulence. This distribution function is essentially non-Maxwellian and varies with the heliospheric distance. The stability analysis is performed with the Vlasov–Maxwell linear solver leopard. We find that depending on the heliospheric distance, the core-strahl electron distribution becomes unstable with respect to sunward-propagating kinetic-Alfvén, magnetosonic, and whistler modes, in a broad range of propagation angles. The wavenumbers of the unstable modes are close to the ion inertial scales, and the radial distances at which the instabilities first appear are on the order of 1 au. However, we have not detected any instabilities driven by resonant wave interactions with the superthermal strahl electrons. Instead, the observed instabilities are triggered by a relative drift between the electron and ion cores necessary to maintain zero electric current in the solar wind frame (ion frame). Contrary to strahl distributions modelled by shifted Maxwellians, the electron strahl obtained as a solution of the kinetic equation is stable. Our results are consistent with the previous studies based on a more restricted solution for the electron strahl.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2017

Plug and Play Solar Power: Simplifying the Integration of Solar Energy in Hybrid Applications; Cooperative Research and Development Final Report, CRADA Number CRD-13-523

The Commonwealth Scientific and Industrial Research Organisation (CSIRO) is Australia's national science agency. CSIRO received funding from the Australian Solar Institute (ASI) for the United States-Australia Solar Energy Collaboration (USASEC) project 1-USO032 Plug and Play Solar Power: Simplifying the Integration of Solar Energy in Hybrid Applications (Broader Project). The Australian Solar Institute (ASI) operated from August 2009 to December 2012 before being merged into the Australian Renewable Energy Agency (ARENA). The Broader Project sought to simplify the integration, accelerate the deployment, and lower the cost of solar energy in hybrid distributed generation applications by creating plug and play solar technology. CSIRO worked with the National Renewable Energy Laboratory (NREL) as set out in a Joint Work Statement to review communications protocols relevant to plug-and-play technology and perform prototype testing in its Energy System Integration Facility (ESIF). For the avoidance of doubt, this CRADA did not cover the whole of the Broader Project and only related to the work described in the Joint Work Statement, which was carried out by NREL.

14 SOLAR ENERGY↗