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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 37 records · Page 2
All sourcesNASA NTRSDOE OSTI
NASA NTRS2003

Sensitivity Studies for Space-based Measurement of Atmospheric Total Column Carbon Dioxide Using Reflected Sunlight

A series of sensitivity studies is carried out to explore the feasibility of space-based global carbon dioxide (CO2) measurements for global and regional carbon cycle studies. The detection method uses absorption of reflected sunlight in the CO2 vibration-rotation band at 1.58 microns. The sensitivities of the detected radiances are calculated using the line-by-line model (LBLRTM), implemented with the DISORT (Discrete Ordinates Radiative Transfer) model to include atmospheric scattering in this band. The results indicate that (a) the small (approx.1%) changes in CO2 near the Earth's surface are detectable in this CO2 band provided adequate sensor signal-to-noise ratio and spectral resolution are achievable; (b) the radiance signal or sensitivity to CO2 change near the surface is not significantly diminished even in the presence of aerosols and/or thin cirrus clouds in the atmosphere; (c) the modification of sunlight path length by scattering of aerosols and cirrus clouds could lead to large systematic errors in the retrieval; therefore, ancillary aerosol/cirrus cloud data are important to reduce retrieval errors; (d) CO2 retrieval requires good knowledge of the atmospheric temperature profile, e.g. approximately 1K RMS error in layer temperature; (e) the atmospheric path length, over which the CO2 absorption occurs, must be known in order to correctly interpret horizontal gradients of CO2 from the total column CO2 measurement; thus an additional sensor for surface pressure measurement needs to be attached for a complete measurement package.

Mao, Jianping↗
NASA NTRS1990

Reflected Sunlight Reduction and Characterization for a Deep-Space Optical Receiver Antenna (DSORA)

A baffle system for the elimination of first-order specular and diffuse reflection of sunlight from the sunshade of a deep-space optical receiver telescope is presented. This baffle system consists of rings of 0.5cm blades spaced 2.5 cm apart on the walls of GO hexagonal sunshade tubes that combine to form the telescope sunshade. The shadow cast by the blades, walls, and rims of the tubes prevent all first-order reflections of direct sunlight from reaching the primary mirror of the telescope. A reflection model of the sunshade without baffles is also presented for comparison. Since manufacturers of absorbing surfaces do not measure data near grazing incidence, the reflection properties at anticipated angles of incidence must be characterized. A description of reflection from matte surfaces in term of bidirectional reflection distribution function (BRDF) is presented along with a discussion of measuring BRDF near grazing incidence.

Clymer, B. D.↗
DOE OSTI2020

THE CASE FOR MULTICRITERIA ANNUAL SUNLIGHT EXPOSURE GUIDELINES

This paper explored the effects of the current Annual Sunlight Exposure (ASE1000 lux, 250 hours) requirements on energy consumption and thermal comfort of an office space in five cities representing different U.S. climates. Specifically, the goal was to quantify the extent to which the current ASE metric requirements may be adjusted allowing for more/ less annual sunlight exposure to address climatic differences, energy, and thermal comfort criteria. A south-facing perimeter office space was simulated in the five climates to assess differences in energy and thermal comfort between the current ASE requirements and best-case scenarios. The results highlight the need to incorporate thermal comfort and energy as primary criteria informing target ASE requirements and guidelines. Lastly, the paper discusses research pathways to help develop multi-criteria ASE guidelines.

Abboushi, Belal K.↗
DOE OSTI2023

Thermally Responsive Hydrogels for Passive Temperature Regulation under Direct Sunlight

By spontaneously emitting midinfrared radiation to outer space through the atmospheric window and reflecting sunlight, daytime radiative coolers achieve notable passive cooling performance. However, existing daytime radiative cooling systems generally lack the ability to adaptively switch between heating and cooling states based on ambient conditions. Herein a passive thermal regulation system that features a temperature‐dependent switchable solar reflectance from 0.05 (low temperature) to 0.8 (high temperature) is presented. This, along with a ≈0.95 midinfrared emittance, it enables automatic switching between radiative cooling and solar heating. Switchablity is enabled using a poly( N ‐isopropylacrylamide) (PNIPAM) hydrogel which exhibits high solar scattering above its tunable lower critical solution temperature (LCST) and transparency below its LCST. The lower part of the hydrogel is loaded with graphite to absorb solar energy in the heating state. In testing under sunny and partly cloudy outside conditions, this system maintains a temperature close to the set LCST.

Xie, Dajie↗
DOE OSTI2021

Storing sunlight at low temperatures?

Here, artificial leaves that convert sunlight to fuels could provide a sustainable energy future. But several challenges must be overcome to improve their economic viability. Publishing in Energy & Environmental Science, Kölbach, Rehfeld, and May describe the potential of decentralized hydrogen production using thermally integrated architectures that operate under sub-freezing temperatures.

14 SOLAR ENERGY↗
DOE OSTI2021

Ruthenium Dye Excitations and Relaxations in Natural Sunlight

Solar harvesting devices using dyes convert the sun's energy to usable forms. The photophysics involved are generally investigated using time-resolved spectroscopic experiments with femtosecond to nanosecond resolution. We show that a kinetic framework constructed from transient and linear absorption measurements of metal-ligand charge transfer states for a set of ruthenium complexes in solution can be used to simulate the steady-state dynamics of dyes adsorbed on a substrate under diffuse solar radiation. Even though the intensity of sunlight is relatively low, double excitations to higher excited states can occur. The steady-state populations show that the dyes' triplet state is the main species present besides the ground state. While small, these persistent excited populations can influence reactivity over the extended periods of time that the systems operate. The results show that non-radiative and optical events (dye -1 s -1 ) within the singlet manifold and from the triplet state exhibit a dependence on ligand substituents.

14 SOLAR ENERGY↗
DOE OSTI2025

Maximizing sunlight absorption in narrow bandgap semiconducting copper(I) iodides for enhanced photocatalytic dye degradation

Photocatalytic dye degradation leverages sunlight to break down dyes and pigments into safer, simpler molecules. Using a material that can absorb a broad range of the solar spectrum optimizes the speed and efficiency of this process. In this study, we explore a series of new, narrow bandgap copper iodide semiconductors (1.5–1.7 eV) with various dimensionalities (0D to 3D) to evaluate their photocatalytic efficiency in dye degradation. The most effective material achieved 95% degradation within just 27 minutes. Mass spectrometry provided a detailed insight and in-depth understanding into the degradation mechanism. All materials demonstrated excellent stability under ambient conditions, highlighting their promise as eco-friendly candidates for dye degradation in water purification.

Carignan, Gia M. [Rutgers Univ., Piscataway, NJ (U↗
DOE OSTI2023

Canopy tree mortality depends on the proportion of crown exposed to sunlight, but this effect varies with species' wood density

Abstract Understanding what drives changes in tree mortality as well as the covariates influencing trees' response is a research priority to predict forest responses to global change. Here, we combined drone photogrammetry and ground‐based data to assess the influence of crown exposure to light (relative to total crown area), growth deviations (relative to conspecifics), tree size, and species' wood density (as a surrogate for light‐demanding and shade‐tolerant life‐history strategies) on the mortality of 984 canopy trees in an Amazonterra firmeforest. Trees with lower wood density were less prone to die when their proportion of crown was more exposed to sunlight, but this relationship with relative crown exposure weakened and slightly reversed as wood density increased. Trees growing less than their species average had higher mortality, especially when the species' wood density decreased. The role of wood density in determining the survival of canopy trees under varying light conditions indicates differential responses of light‐demanding versus shade‐tolerant species. Our results highlight the importance of accounting for life‐history strategies, via plant functional types, in vegetation dynamic models aiming to predict forest demography under a rapidly changing climate. Abstract in Spanish is available with online material.

Environmental Sciences & Ecology↗
DOE OSTI2021

Reflecting Sunlight: Recommendations for Solar Geoengineering Research and Research Governance

The National Academies of Sciences, Engineering, and Medicine (NASEM) report "Reflecting Sunlight: Recommendations for Solar Geoengineering Research and Research Governance" focused on three atmospheric-based Solar Geoengineering strategies: Stratospheric Aerosol Injection, Marine Cloud Brightening, Cirrus Cloud Thinning. The study recommends that a national (and internationally-coordinated) Solar Geoengineering research program be established and coordinated by the U.S. Global Change Research Program—with a focus on developing information needed by decision makers, not advancing a path to deployment. The study recommends a detailed framework for governance of this research, at both national and international levels. The study also recommends a detailed research agenda for this program, encompassing over a dozen transdisciplinary research topics that can be loosely grouped into the categories of (i) technical dimensions and impacts, (ii) social dimensions, and (iii) context and goals for solar geoengineering research itself.

54 ENVIRONMENTAL SCIENCES↗
NASA NTRS1972

Space Satellite Dynamics with Applications to Sunlight Pressure Attitude Control

A research program into three aspects of space satellite dynamics was carried out. First, a four-dimensional space-time formulation of Newtonian mechanics is developed. This theory allows a new physical interpretation of the conservation theorems of mechanics first derived rigorously by Noether. Second, a new concept for estimating the three angles which specify the orientation in space of a rigid body is presented. Two separate methods for implementing this concept are discussed, one based on direction cosines, the other on quaternions. Two examples are discussed: constant orientation in space, and constant rate of change of the three angles with time. Third, two synchronous equatorial orbit communication satellite designs which use sunlight pressure to control their attitude are analyzed. Each design is equipped with large reflecting surfaces, called solar sails, which can be canted in different directions to generate torques to correct pointing errors.

Stuck, B. W.↗