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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 199 records · Page 11
All sourcesNASA NTRSDOE OSTI
DOE OSTI2023

Photochemical Decomposition of Y‐Series Non‐Fullerene Acceptors Is Responsible for Degradation of High‐Efficiency Organic Solar Cells

Abstract Organic photovoltaic cells that employ Y‐series non‐fullerene acceptors (NFAs) have recently achieved impressive power‐conversion efficiencies (>18%). To fulfill their commercial promise, it is important to quantify their operational lifetimes and understand their degradation mechanisms. In this work, the spectral‐dependent photostability of films and solar cells comprising several Y‐series acceptors and the donor polymer PM6 is investigated systematically. By applying longpass filters during aging, it is shown that UV/near‐UV photons are responsible for the photochemical decomposition of Y‐series acceptors; this degradation is the primary driver of early solar cell performance losses. Using mass spectrometry, the vinylene linkage between the core and electron‐accepting moieties of Y‐series acceptors is identified as the weak point susceptible to cleavage under UV‐illumination. Employing a series of device characterization, along with numerical simulations, the efficiency losses in organic photovoltaic cells are attributed to the formation of traps, which reduces charge extraction efficiency and facilitates non‐radiative recombination as the Y‐series acceptors degrade. This study provides new insights for molecular degradation of organic photovoltaic absorber materials and highlights the importance of future molecular design and strategies for improved solar cell stability.

14 SOLAR ENERGY↗
DOE OSTI2024

Monolithic Bifacial Halide Perovskite-Cadmium Selenide Telluride (CST) Tandem Thin-Film Solar Cells (Final Technical Report)

In this project, we develop a bifacial tandem design for monolithic metal halide perovskite-cadmium selenide telluride (CST) tandem solar cells. The bifacial tandem design not only enables the monolithic integration of perovskite-CST tandems but also delivers high efficiency by harvesting the albedo light. It also allows better current match and thus enables higher power output of the tandem devices than conventional tandem cells. We worked on understanding the critical factors limiting bifacial CST cells and developing strategies to improve their bifaciality. We also developed efficient wide-bandgap perovskite subcells and interconnecting layers that enable the monolithic perovskite-CST tandem solar cells. We successfully demonstrated prototype monolithic bifacial perovskite-CST tandem solar cells with bifacial equivalent efficiencies of more than 25% under an albedo of 0.4. Additionally, we optimized the wide-bandgap perovskite to realize four-terminal perovskite-CST tandem devices with efficiencies of 25.5% under monofacial illumination. The team disseminated these results to stakeholders in the PV academic and industry and discussed the challenges and major technical barriers for their market entry. The technologies developed in the project are promising but are not yet ready for immediate commercialization. Future fundamental study and R&D work are needed to advance these promising technologies.

14 SOLAR ENERGY↗
NASA NTRS1996

Effects of plasmaspheric ion heating due to ionospheric and magnetospheric sources

In an initial study, the He(+) observations from the Retarding Ion Mass Spectrometer on Dynamics Explorer 1 (RIMS/DE 1) was examined for more than 120 transits of the plasmasphere in the fall of 1981. The He(+) to H(+) ratio was determined as it varied spatially over portions of the DE 1 orbit, and its variation with solar and magnetic activities and with local time, focusing specifically on the inner plasmasphere. These variations were compared along the L = 2 field line with calculations made by the Field Line Interhemispheric Plasma (FLIP) code. In a recently submitted paper, the He(+) to H(+) density ratio was examined for all the available data from 1981 to 1984 from the RIMS on DE 1. There are two basic characteristics of the ratio: one is that the ratio decreases with radial distance in the plasmasphere, and the other is the strong dependence of the density ratio on solar activity. In addition to the He(+)/H(+) ratio research, a phenomenon has been studied in the topside ionosphere which relates to the thermal coupling of the ionosphere to the plasmasphere. There is little or no correlation with magnetic and solar activity here. Another study has been directed toward the relation of plasma properties to the density gradients forming the plasmapause. The study has followed a two-pronged approach. First, the observations have been analyzed to determine what happens to the plasma properties across these boundary layers (density gradients). Second, comparisons were made with FLIP model calculations to determine how well the model is able to treat these conditions. Among the significant lessons learned in these studies are two that bear directly on the direction of future investigations in this area. First, composition cannot be viewed independently of thermal structure. Second, solar and magnetic activity effects are real; but the causal relationship between activity and effects is frequently quite complicated because several different processes appear to be operating in different ways and on different time scales. Under these circumstances, large correlation coefficients should not be expected and are not generally found.

Comfort, Richard H.↗
DOE OSTI2024

Integrated multimodel analysis reveals achievable pathways toward reliable, 100% renewable electricity for Los Angeles

Climate change has prompted many communities to set targets for carbon-free power supplies, but they often lack data-driven strategies to achieve them. We present a comprehensive analysis of an entirely renewable electric power system that can maintain operating reliability and resource adequacy using detailed models of the city of Los Angeles power grid. In consultation with the operating utility, the Los Angeles Department of Water and Power (LADWP), and the local community, we develop four supply scenarios across three demand projections to analyze which types of infrastructure and operational changes would achieve reliable electricity at least cost. We find that a reliable, 100%-renewable power system yielding more than $1 billion annually in health and climate co-benefits is achievable. Solar can supply most future energy needs, while combustion turbines that use renewable, storable carbon-neutral fuels are key to maintaining reliability. This study provides a replicable methodology that other jurisdictions globally can follow.

14 SOLAR ENERGY↗
NASA NTRS1997

Distributions and motions of nearby stars defined by objective prism surveys and Hipparcos data

Material and objective prism spectral classification work is used to determine the space density distribution of nearby common stars to the limits of objective prism spectral surveys. The aim is to extend the knowledge of the local densities of specific spectral types from a radius of 25 pc from the sun, as limited in the Gliese catalog of nearby stars, to 50 pc or more. Future plans for the application of these results to studies of the kinematic and dynamical properties of stars in the solar neighborhood as a function of their physical properties and ages are described.

Hemenway, P. D.↗
NASA NTRS2012

Experimental Investigation of a Direct-drive Hall Thruster and Solar Array System at Power Levels up to 10 kW

As NASA considers future exploration missions, high-power solar-electric propulsion (SEP) plays a prominent role in achieving many mission goals. Studies of high-power SEP systems (i.e. tens to hundreds of kilowatts) suggest that significant mass savings may be realized by implementing a direct-drive power system, so NASA recently established the National Direct-Drive Testbed to examine technical issues identified by previous investigations. The testbed includes a 12-kW solar array and power control station designed to power single and multiple Hall thrusters over a wide range of voltages and currents. In this paper, single Hall thruster operation directly from solar array output at discharge voltages of 200 to 450 V and discharge powers of 1 to 10 kW is reported. Hall thruster control and operation is shown to be simple and no different than for operation on conventional power supplies. Thruster and power system electrical oscillations were investigated over a large range of operating conditions and with different filter capacitances. Thruster oscillations were the same as for conventional power supplies, did not adversely affect solar array operation, and were independent of filter capacitance from 8 to 80 ?F. Solar array current and voltage oscillations were very small compared to their mean values and showed a modest dependence on capacitor size. No instabilities or anomalous behavior were observed in the thruster or power system at any operating condition investigated, including near and at the array peak power point. Thruster startup using the anode propellant flow as the power 'switch' was shown to be simple and reliable with system transients mitigated by the proper selection of filter capacitance size. Shutdown via cutoff of propellant flow was also demonstrated. A simple electrical circuit model was developed and is shown to have good agreement with the experimental data.

Snyder, John S.↗
NASA NTRS2018

Next-Generation Radioisotope Thermoelectric Generator Study

Radioisotope Thermoelectric Generators (RTGs) have been used to power NASA missions of various types throughout the past five decades. The most recent RTG iteration, used for NASA’s Mars Science Laboratory, is the Multi-Mission RTG (MMRTG), which is currently the only spaceflight-qualified system available. The U.S. planetary science community has expressed a desire for more power system options to be available to accommodate a range of ambitious future mission concepts across the solar system. Recent advancements in thermoelectric (TE) materials technology have raised a potential for significantly increased efficiency in future RTGs, which helped spur a recent in-depth NASA study of options for future systems. A “next-generation” RTG study was conducted to develop new RTG concepts that could meet the needs of planetary science missions through the 2030s and beyond. A Next-Generation RTG would aim to extend the types of potential NASA missions able to be supported, while fulfilling requirements related to technical risk and schedule. In this study, 21 potential thermoelectric couple configurations were analyzed by considering various high-performance, high-temperature TE materials and segmentation techniques that maximize convertor efficiency and power density. System modularity was explored, and found to be a promising means to offer improved flexibility for NASA mission concepts with varying scope and power requirements. This paper presents the results of the study, demonstrating the viability of developing an updated RTG system design, and defining conceptual system approaches for a new, potentially revolutionary RTG.

Matthes, Christopher S. R.↗
NASA NTRS2002

Selection and Prioritization of Advanced Propulsion Technologies for Future Space Missions

The exploration of our solar system will require spacecraft with much greater capability than spacecraft which have been launched in the past. This is particularly true for exploration of the outer planets. Outer planet exploration requires shorter trip times, increased payload mass, and ability to orbit or land on outer planets. Increased capability requires better propulsion systems, including increased specific impulse. Chemical propulsion systems are not capable of delivering the performance required for exploration of the solar system. Future propulsion systems will be applied to a wide variety of missions with a diverse set of mission requirements. Many candidate propulsion technologies have been proposed but NASA resources do not permit development of a] of them. Therefore, we need to rationally select a few propulsion technologies for advancement, for application to future space missions. An effort was initiated to select and prioritize candidate propulsion technologies for development investment. The results of the study identified Aerocapture, 5 - 10 KW Solar Electric Ion, and Nuclear Electric Propulsion as high priority technologies. Solar Sails, 100 Kw Solar Electric Hall Thrusters, Electric Propulsion, and Advanced Chemical were identified as medium priority technologies. Plasma sails, momentum exchange tethers, and low density solar sails were identified as high risk/high payoff technologies.

Eberle, Bill↗
NASA NTRSDate not supplied

The HERMES Payload for Gateway: Heliophysics Enabled by Lunar Exploration

At launch, the first two modules of the Gateway space station will carry external payloads from NASA and ESA designed to observe the space environment. The NASA payload is the Heliophysics Environmental and Radiation Measurement Experiment Suite (HERMES). The HERMES instrumentation includes an ion mass spectrometer, an electron electrostatic analyzer, a proton and electron telescope for energetic particles, and a set of magnetometers. After an approximately one year transit to the Moon, HERMES will begin a science campaign that addresses heliophysics and space-weather objectives. Analyses of the in-situ measurements from HERMES will leverage observations from other Heliophysics spacecraft missions to enable multipoint studies of structure in the solar wind and in the magnetotail. Gateway’s polar lunar orbit is advantageous for this purpose. HERMES also is a pathfinder for future payloads on human-exploration vessels, for which there will be pragmatic interest in the variable radiation environment. Thus, with observations enabled by the ARTEMIS Program, HERMES is expected to be enabling of future exploration missions. Additionally, although HERMES objectives have a space-weather focus, the measurements also can be useful for studies of the Moon. Data, algorithms, calibrations, and related software produced by the project will be fully open and accessible through a Science Operations Center. In this presentation we provide an overview of science plans, including expectations for collaboration with other HSO missions and with international partners. Plain-Language Summary: The HERMES scientific payload will be attached to the HALO module of the Artemis Program's Gateway lunar outpost. HERMES will observe space weather conditions from lunar orbit. The data will be freely available for studies of the Moon and its space environment.

William R Paterson↗
NASA NTRSDate not supplied

The HERMES Payload for Gateway: Heliophysics Enabled by Lunar Exploration

At launch, the first two modules of the Gateway space station will carry external payloads from NASA and ESA designed to observe the space environment. The NASA payload is the Heliophysics Environmental and Radiation Measurement Experiment Suite (HERMES). The HERMES instrumentation includes an ion mass spectrometer, an electron electrostatic analyzer, a proton and electron telescope for energetic particles, and a set of magnetometers. After an approximately one year transit to the Moon, HERMES will begin a science campaign that addresses heliophysics and space-weather objectives. Analyses of the in-situ measurements from HERMES will leverage observations from other Heliophysics spacecraft missions to enable multipoint studies of structure in the solar wind and in the magnetotail. Gateway’s polar lunar orbit is advantageous for this purpose. HERMES also is a pathfinder for future payloads on human-exploration vessels, for which there will be pragmatic interest in the variable radiation environment. Thus, with observations enabled by the ARTEMIS Program, HERMES is expected to be enabling of future exploration missions. Additionally, although HERMES objectives have a space-weather focus, the measurements also can be useful for studies of the Moon. Data, algorithms, calibrations, and related software produced by the project will be fully open and accessible through a Science Operations Center. In this presentation we provide an overview of science plans, including expectations for collaboration with other HSO missions and with international partners.

W.R. Paterson↗
NASA NTRS1992

Phase change energy storage for solar dynamic power systems

This paper presents the results of a transient computer simulation that was developed to study phase change energy storage techniques for Space Station Freedom (SSF) solar dynamic (SD) power systems. Such SD systems may be used in future growth SSF configurations. Two solar dynamic options are considered in this paper: Brayton and Rankine. Model elements consist of a single node receiver and concentrator, and takes into account overall heat engine efficiency and power distribution characteristics. The simulation not only computes the energy stored in the receiver phase change material (PCM), but also the amount of the PCM required for various combinations of load demands and power system mission constraints. For a solar dynamic power system in low earth orbit, the amount of stored PCM energy is calculated by balancing the solar energy input and the energy consumed by the loads corrected by an overall system efficiency. The model assumes an average 75 kW SD power system load profile which is connected to user loads via dedicated power distribution channels. The model then calculates the stored energy in the receiver and subsequently estimates the quantity of PCM necessary to meet peaking and contingency requirements. The model can also be used to conduct trade studies on the performance of SD power systems using different storage materials.

Chiaramonte, F. P.↗
DOE OSTI2021

Tailoring the Surface of Metal Halide Perovskites to Enable the Atomic Layer Deposition of Metal Oxide Contacts

Replacing organic contact layers with inorganic counterparts, such as metal oxides, is one strategy for improving long-term device stability in metal halide perovskite solar cells. Often, the methods used to deposit metal oxide thin films are incompatible with metal halide perovskites, creating challenges for the fabrication of contacts above the perovskite absorber layer. In this study, we utilize a one-step, solution treatment of the top surface of Cs 0.25 FA 0.75 Pb(Br 0.20 I 0.80 ) 3 to create a thin (~1 nm) overlayer of lead sulfide (PbS) to protect the underlying perovskite during subsequent deposition. X-ray characterization of the surface region shows that the PbS overlayer limits undesirable changes to the perovskite structure and stoichiometry during atomic layer deposition (ALD) of SnO 2 . This protection enables ALD growth of SnO 2 electron contacts on top of the perovskite without an organic transport layer (e.g., C 60 ), resulting in a solar cell with a power conversion efficiency of 5.8%. This result is a marked improvement over devices with ALD SnO 2 grown directly on the perovskite without a PbS overlayer, which produce no power output. Furthermore, the interface characterization and device results in this study highlight some of the key challenges associated with ALD metal oxide growth on perovskite materials and can help inform the future design of inorganic contact layer deposition in solar photovoltaic technologies.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Automatic Crack Segmentation and Feature Extraction in Electroluminescence Images of Solar Modules

The effect of cracks in solar cells on the long-term degradation of photovoltaic (PV) modules remains to be determined. To investigate this effect in future studies, it is necessary to quantitatively describe the crack features (e.g., length) and correlate them with module power loss. Electroluminescence (EL) imaging is a common technique for identifying cracks. However, it is currently challenging and time-consuming to identify cracks in a large number of EL images and quantify complex crack features by human inspection. This article introduces a fast semantic segmentation method (~0.18 s/cell) to automatically segment cracks from EL images and algorithms to extract crack features. Here we fine-tuned a UNet neural network model using pretrained VGG16 as the encoder and obtained an average F1 score of 0.875 and an intersection over union score of 0.782 on the testing set. With cracks and busbars segmented, we developed algorithms for extracting crack features, including the crack-isolated area, the brightness inside the isolated area, and the crack length. We also developed an automatic preprocessing tool for cropping individual cell images from EL images of PV modules (~0.72 s/module). Our codes are published as open-source an software, and our annotated dataset composed of various types of cells is published as a benchmark for crack segmentation in EL images.

14 SOLAR ENERGY↗
DOE OSTI2023

Star-exoplanet interactions: A growing interdisciplinary field in heliophysics

Traditionally, heliophysics is characterized as the study of the near-Earth space environment, where plasmas and neutral gases originating from the Earth, the Sun, and other solar system bodies interact in ways that are detectable only through in-situ or close-range (usually within ~10 AU) remote sensing. As a result, heliophysics has data from the space environment around a handful of solar system objects, in particular the Sun and Earth. Comparatively, astrophysics has data from an extensive array of objects, but is more limited in temporal, spatial, and wavelength information from any individual object. Thus, our understanding of planetary space environments as a complex, multi-dimensional network of specific interacting systems may in the past have seemed to have little to do with the highly diverse space environments detected through astrophysical methods. Recent technological advances have begun to bridge this divide. Exoplanetary studies are opening up avenues to study planetary environments beyond our solar system, with missions like Kepler, TESS, and JWST, along with increasing capabilities of ground-based observations. At the same time, heliophysics studies are pushing beyond the boundaries of our heliosphere with Voyager, IBEX, and the future IMAP mission. The interdisciplinary field of star-exoplanet interactions is a critical, growing area of study that enriches heliophysics. A multidisciplinary approach to heliophysics enables us to better understand universal processes that operate in diverse environments, as well as the evolution of our solar system and extreme space weather. The expertise, data, theory, and modeling tools developed by heliophysicists are crucial in understanding the space environments of exoplanets, their host stars, and their potential habitability. The mutual benefit that heliophysics and exoplanetary studies offer each other depends on strong, continuing solar system-focused and Earth-focused heliophysics studies. The heliophysics discipline requires new targeted funding to support inter-divisional opportunities, including small multi-disciplinary research projects, large collaborative research teams, and observations targeting the heliophysics of planetary and exoplanet systems. Here we discuss areas of heliophysics-relevant exoplanetary research, observational opportunities and challenges, and ways to promote the inclusion of heliophysics within the wider exoplanetary community.

79 ASTRONOMY AND ASTROPHYSICS↗
NASA NTRS2011

Environmental Catastrophes in the Earth's History Due to Solar Systems Encounters with Giant Molecular Clouds

In its motion through the Milky Way galaxy, the solar system encounters an average density (>=330 H atoms/cubic cm) giant molecular cloud (GMC) approximately every 108 years, a dense (approx 2 x 103 H atoms/cubic cm) GMC every approx 109 years and will inevitably encounter them in the future. However, there have been no studies linking such events with severe (snowball) glaciations in Earth history. Here we show that dramatic climate change can be caused by interstellar dust accumulating in Earth's atmosphere during the solar system's immersion into a dense (approx ,2 x 103 H atoms/cubic cm) GMC. The stratospheric dust layer from such interstellar particles could provide enough radiative forcing to trigger the runaway ice-albedo feedback that results in global snowball glaciations. We also demonstrate that more frequent collisions with less dense GMCs could cause moderate ice ages.

Pavlov, Alexander A.↗
NASA NTRS2023

Star-Exoplanet Interactions: A Growing Interdisciplinary Field in Heliophysics

Traditionally, heliophysics is characterized as the study of the near-Earth space environment, where plasmas and neutral gases originating from the Earth, the Sun, and other solar system bodies interact in ways that are detectable only through in-situ or close-range (usually within ∼10 AU) remote sensing. As a result, heliophysics has data from the space environment around a handful of solar system objects, in particular the Sun and Earth. Comparatively, astrophysics has data from an extensive array of objects, but is more limited in temporal, spatial, and wavelength information from any individual object. Thus, our understanding of planetary space environments as a complex, multi-dimensional network of specific interacting systems may in the past have seemed to have little to do with the highly diverse space environments detected through astrophysical methods. Recent technological advances have begun to bridge this divide. Exoplanetary studies are opening up avenues to study planetary environments beyond our solar system, with missions like Kepler, TESS, and JWST, along with increasing capabilities of ground-based observations. At the same time, heliophysics studies are pushing beyond the boundaries of our heliosphere with Voyager, IBEX, and the future IMAP mission. The interdisciplinary field of star-exoplanet interactions is a critical, growing area of study that enriches heliophysics. A multidisciplinary approach to heliophysics enables us to better understand universal processes that operate in diverse environments, as well as the evolution of our solar system and extreme space weather. The expertise, data, theory, and modeling tools developed by heliophysicists are crucial in understanding the space environments of exoplanets, their host stars, and their potential habitability. The mutual benefit that heliophysics and exoplanetary studies offer each other depends on strong, continuing solar system-focused and Earth-focused heliophysics studies. The heliophysics discipline requires new targeted funding to support inter-divisional opportunities, including small multi-disciplinary research projects, large collaborative research teams, and observations targeting the heliophysics of planetary and exoplanet systems. Here we discuss areas of heliophysics-relevant exoplanetary research, observational opportunities and challenges, and ways to promote the inclusion of heliophysics within the wider exoplanetary community.

heliophysics↗
NASA NTRS2002

The Solar Connections Observatory for Planetary Environments

The NASA Sun-Earth Connection theme roadmap calls for comparative study of how the planets, comets, and local interstellar medium (LISM) interact with the Sun and respond to solar variability. Through such a study we advance our understanding of basic physical plasma and gas dynamic processes, thus increasing our predictive capabilities for the terrestrial, planetary, and interplanetary environments where future remote and human exploration will occur. Because the other planets have lacked study initiatives comparable to the terrestrial ITM, LWS, and EOS programs, our understanding of the upper atmospheres and near space environments on these worlds is far less detailed than our knowledge of the Earth. To close this gap we propose a mission to study {\it all) of the solar interacting bodies in our planetary system out to the heliopause with a single remote sensing space observatory, the Solar Connections Observatory for Planetary Environments (SCOPE). SCOPE consists of a binocular EUV/FUV telescope operating from a remote, driftaway orbit that provides sub-arcsecond imaging and broadband medium resolution spectro-imaging over the 55-290 nm bandpass, and high (R>10$^{5}$ resolution H Ly-$\alpha$ emission line profile measurements of small scale planetary and wide field diffuse solar system structures. A key to the SCOPE approach is to include Earth as a primary science target. From its remote vantage point SCOPE will be able to observe auroral emission to and beyond the rotational pole. The other planets and comets will be monitored in long duration campaigns centered when possible on solar opposition when interleaved terrestrial-planet observations can be used to directly compare the response of both worlds to the same solar wind stream and UV radiation field. Using a combination of observations and MHD models, SCOPE will isolate the different controlling parameters in each planet system and gain insight into the underlying physical processes that define the solar connection.

Oliversen, Ronald J.↗
DOE OSTI2025

GODEEEP-hydro: Historical and projected power system ready hydropower data for the United States

Hydropower is a critical electricity resource in the United States which, in addition to low-cost electricity generation, provides valuable ancillary grid services, and supports the integration of nondispatchable weather-dependent resources (e.g., wind and solar). Despite its value to the grid, there are very few comprehensive datasets available from which to study both historical and future impacts of climate, weather driven energy droughts, and integration of other weather driven generation. In this paper, we present a hydropower generation dataset covering 1,452 hydroelectric plants in the contiguous U.S. The dataset contains monthly and weekly hydropower generation estimates for both historical (1982–2019) and future (2020–2099) periods which includes 4 future climate scenarios. In addition, this dataset provides weekly and monthly constraints such as minimum and maximum power which are particularly useful in power system models which are used to study grid reliability, transmission planning and capacity expansion.

13 HYDRO ENERGY↗