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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 865 records · Page 48
All sourcesNASA NTRSDOE OSTI
DOE OSTI2024

Solid State Quantum Refrigeration Superconducting, Absorption and Measurement Based (Final Technical Report)

During this DOE grant, DE-SC0017890, in place for the past six years, all proposed research was carried out and published in peer-reviewed papers, as well as other projects that emerged during the research. In that effort the research team accomplished all proposed research, as well as many closely related research projects discovered and conceived of during the grant. These works included “Efficient Quantum Measurement Engines”, a work published in Physical Review Letters, giving a theory of quantum measurement-based engines, which uses quantum measurement as a resource. These engines are designed to efficiently convert energy from the stochastic quantum measurement process into useful work. Further publications include “Experimental Realization of a Quantum Dot Energy Harvester”, a joint theory and experimental work in collaboration with the group of Charles Smith in Cambridge, UK, as well as long time theoretical collaborators, Rafael Sánchez and Björn Sothmann. This work, featured as an Editor’s Suggestion in Physical Review Letters, realized an earlier theoretical proposal of ours, whereby two resonant tunneling quantum dots are connected to a central electronic cavity that is heated by a hot energy source. We also published “Superconducting Quantum Refrigerator: Breaking and Rejoining Cooper Pairs with Magnetic Field Cycles” a work done in collaboration with experimentalist Francesco Giazotto from ENS Pisa, Italy, which also resulted in a patent. This paper, published in Phys. Rev. Applied, advanced the concept of a cyclic fridge based on the normal/superconducting phase transition together with layered materials separated by tunnel junctions. We also completed the proposed research on a heat transistor, publishing “Thermal transistor and thermometer based on Coulomb-coupled conductors”, carried out as a collaboration between my group and theorists Splettstoesser (Lund U., Sweden), Sothmann (U. Duisburg-Essen, Germany), and Sánchez (U. Autónoma de Madrid, Spain). We carried out an analysis of a quantum coupled to a quantum point contact as a sensitive thermometer and heat transistor. We found the optimal statistical estimator for the temperature and compared it with experiments on the same type of devices. We also investigated autonomous quantum absorption refrigerators using quantum dots to cool by using a very hot thermal reservoir to drive heat between two other reservoirs. In the article “Quantifying the quantum heat contribution from a driven superconducting circuit”, we demonstrated that for a driven superconducting circuit, we showed heat flow provided by a hot source to the qubit can be switched on and off by varying external parameters, the frequency and the intensity of the driving. In the work “Stochastic thermodynamic cycles of a mesoscopic thermoelectric engine”, we reconsidered the autonomous thermoelectric heat engine in terms of underlying cycles. Rather than periodic behavior, the cycles were stochastic in nature. Nevertheless, by undertaking a graph theoretical analysis of the elementary transport processed, great quantitative and qualitative insight could be found. We also considered the quantum measurement process and showed that a quantum version of Maxwell’s demon could be related to the work extraction of a quantum system, closely related to arrow-of-time measures for quantum measurement, as described in our article “Thermodynamics of quantum measurement and Maxwell's demon's arrow of time”. This work was selected in Phys. Rev. A as an Editor’s Suggestion. A recent preprint titled “Cyclic Superconducting Quantum Refrigerators Using Guided Fluxon Propagation” accomplished an important piece of this grant: to propose a new kind of quantum refrigerator using the dynamics of fluxons in a type II superconductor. This invention envisioned a race-track type geometry where fluxons are confined. By applying a gradient of magnetic field together with electric current in a Corbino geometry, the circulating fluxons can actively cool a cold reservoir, realizing a new type of cyclic superconducting refrigerator. We also investigated the possibility of thermal control from different points of view. The application of quantum measurement to the system gives a new kind of control on the system of interest – we have pioneered this approach and shown that measurement can boost the thermal power of quantum engines as described in “Continuous measurement boosted adiabatic quantum thermal machines”. The ability to have heat flows on demand is an outstanding challenge, and we have provided new solutions to this problem in Thermal control across a chain of electronic nanocavities” for a chain of electron cavities using gating voltage control. The control methods using qubit/qubit coupling to create absorption fridges at their most fundamental level have also been developed.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
NASA NTRS1987

Spacecraft external heating variations in orbit

The results of an evaluation of variations in on-orbit external heating of spacecraft surfaces are presented. The analyzed time-varying components are the direct solar, the latitude-dependent shortwave reflected, and the latitude-dependent longwave planetary-emitted radiation. Differences in instantaneous heating rates at a given latitude among the different model environments are found to be much larger than are differences in orbital mean heating rates. The discrepancies are found to increase with the orbit inclination angle. The ratio of Northern Hemisphere winter-to-summer orbital mean heating rates for a nadir-facing node is near unity and shows only a slight dependence on large variations in node absorptance. Mean orbital albedo and emission values for low-inclination orbits are found to differ significantly from global values obtained in meteorological studies. Algorithms relating mean orbital albedos and emissions to orbit inclination are developed. The relative importance of more realistic nondiffuse over diffuse reflections is evaluated for spacecraft heating and found to be negligible. The sun-spacecraft-earth angular configuration is such that, for reception of the peak intensities in the nondiffuse reflectance angular distribution, the albedo heating rate is more than adequately suppressed by an extremely small view factor from the spacecraft to the sunlit 'crescent' earth.

Leffler, J. M.↗
DOE OSTI2025

Setup for Optical Absorption Measurements of Molten Salt Mixtures

In this work we describe the setup of a spectrophotometer to take absorbance measurements of a heated sample in an inert atmosphere. By using fiber optics to bring light into and out of a glovebox we are able to use a pitch-catch optical setup to observe samples in a cuvette heated up to 400℃. The functionality of the setup is demonstrated by observing the signal produced by Li 2 S in a eutectic mixture of LiCl/LiBr/KBr at elevated temperature overtime.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2021

Direct Measurement of the Selective Microwave-Induced Heating of Agglomerates of Dipolar Molecules: The Origin of and Parameters Controlling a Microwave Specific Superheating Effect

Agglomerates of polar molecules in nonpolar solvents are selectively heated by microwave radiation. The magnitude of the selective heating was directly measured by using the temperature dependence of the intensities of the Stokes and anti-Stokes bands in the Raman spectra of p-nitroanisole (pNA) and mesitylene. Under dynamic heating conditions, a large apparent temperature difference (ΔT) of over 100 °C was observed between the polar pNA solute and the nonpolar mesitylene solvent. This represents the first direct measurement of the selective microwave heating process. The magnitude of the selective microwave heating was affected by the properties of the agglomerated pNA. As the concentration of the pNA increases, the magnitude of the selective heating of the pNA was observed to decrease. This is explained by the tendency of the pNA dipoles to orient in an antiparallel fashion in the aggregates as measured by the Kirkwood g value, which decreased with increasing concentration. This effect reduces the net dipole moment of the agglomerates, which decreases the microwave absorption. After the radiation was terminated, the effective temperature of the dipolar molecules returned slowly to that of the medium. The slow heat transfer was modeled successfully by treating the solutions as a biphasic solvent/solute system. Based on modeling and the fact that the agglomerate can be heated above the boiling temperature of the solvent, an insulating layer of solvent vapor is suggested to form around the heated agglomerate, slowing convective heat transfer out of the agglomerate. Furthermore, this is an effect unique to microwave heating.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2021

Measurements of Non-Maxwellian Electron Distribution Functions and Their Effect on Laser Heating

Electron velocity distribution functions driven by inverse bremsstrahlung heating are measured to be non-Maxwellian using a novel angularly resolved Thomson-scattering instrument and the corresponding reduction of electrons at slow velocities results in a ~40% measured reduction in inverse bremsstrahlung absorption. The distribution functions are measured to be super-Gaussian in the bulk (v/v th < 3) and Maxwellian in the tail (v/v th > 3) when the laser heating rate dominates over the electron-electron thermalization rate. Furthermore, simulations with the particle code quartz show the shape of the tail is dictated by the uniformity of the laser heating.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
NASA NTRS1992

Low-redshift Lyman-alpha absorption lines and the dark matter halos of disk galaxies

Ultraviolet observations of the low-redshift quasar 3C 273 using the Hubble Space Telescope have revealed many more Lyman-alpha absorption lines than would be expected from extrapolation of the absorption systems seen toward QSOs at z about 2. It is shown here that these absorption lines can plausibly be produced by gas at large radii in the disks of spiral and irregular galaxies; the gas is confined by the dark matter halos and ionized and heated by the extragalactic radiation field. This scenario does not require the extragalactic ionizing radiation field to decline as rapidly with decreasing z as the QSO emissivity. Observations of Ly-alpha absorption through the halos of known galaxies at low redshift will constrain both the extragalactic background and the properties of galactic halos.

Maloney, Philip↗
DOE OSTI2021

Implications of parasitic absorption of electron cyclotron waves on ITER operation around half-field

The ITER Research Plan envision operation around half of the nominal magnetic field (i.e. around B = 2.65 T) as a path to baseline operation. This work discusses constraints on the optimal range of magnetic field, which is bounded in the lower limit by the presence of the third-harmonic electron cyclotron resonance at half field, and on the upper limit by the loss of core heating and current drive. Additionally, it will be shown that increasing the magnetic field by only 3%, i.e. to 2.75 T, eliminates the third harmonic parasitic absorption without compromising demonstration of access to H-mode, while operating at a magnetic field of 3.0 T—previously proposed for optimal use of the ion cyclotron system—would impair the use of the electron cyclotron system for core-heating and current drive. Operation at 2.65 T would still be possible if the polarization of the equatorial launcher is changed from X-mode to O-mode in the current flattop phase.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2025

Multiphase computational fluid dynamics modeling of reacting flows in absorption columns for carbon capture

First-principles derived computational fluid dynamics (CFD) simulations have been proposed as a fundamental tool for investigating solvent-based CO 2 absorption in packed columns due to their ability to accurately represent the underlying nonlinear, multiscale dynamics. Numerous studies have previously utilized such CFD simulations to investigate hydrodynamics of columns with structured and random packings by assessing the key hydrodynamic metrics such as the interfacial and wetted areas. While mapping such metrics for different conditions is essential to the optimization of absorption columns, it is not sufficient, as the CO 2 capture rate depends also on the coupled, nonlinear dynamics from the underlying chemical reaction kinetics, thermodynamics, and heat-transfer rates. In this work, we present detailed CFD simulation results augmented by incorporating the effects of interfacial physical mass transfer of CO 2 , heat release from chemical reaction kinetics, and thermophysical property variations from resulting temperature gradients. We demonstrate the applicability of the proposed approach in numerically assessing the performance of packed columns by evaluating key hydrodynamic quantities, CO 2 absorption rates, and temperature rise in a reference column with packings that are structurally similar to the Sulzer Mellapak™ 250.Y packing, for different solvent inflow velocities and temperatures. Predictions from simulation results are found to be consistent with the trends in experimental observations from the literature, suggesting that the predictive capabilities of the simulation framework can be leveraged to guide the future development of absorber-column designs and optimized process flowsheets.

Absorption columns↗
NASA NTRS1990

Modeling of interactions between biosphere and atmosphere on the global scale

Simulations of weather and climate with general circulation models show that the circulation and rainfall are sensitive to the transfers of radiation, sensible heat, water vapor, and momentum across the atmosphere land surface interface. Because, in nature, these transfers depend in large measure on the morphological and physiological characteristics of the surface vegetation, an interactive biosphere is needed for GCM's. The simple model of the biosphere (SiB) that the authors have constructed is based on the recognized difference between ground cover vegetation (grasses and other herbaceous plants) and canopy vegetation (trees and shrubs), where the latter act like elevated blocks of porous material which efficiently extract momentum from the air that flows through them; by a large number of multiple reflections enhance the absorption of the incident solar radiation; when the canopy is wet, act like well ventilated psychrometers which extract sensible heat from the air and produce a negative Bowen ratio; and, in all of these ways, behave differently from ground cover vegetation. The complete set of governing equations of SiB, whereby the various allowable combinations of trees, ground covers, and bare ground, in interaction with the atmosphere, determine all of the vegetation dependent transfers at the land surface, have been presented and described.

Baer, Ferdinand↗
DOE OSTI2020

Solar-driven evaporators for water treatment: challenges and opportunities

Solar-driven evaporation is an emerging process to acquire freshwater from saline water or wastewater, in which photothermal materials play a crucial role. Additionally, significant effort has been devoted to promoting energy conversion efficiency by material and device design. In the current review, we discuss the major factors affecting evaporator efficiency and long-term performance, including selection of photothermal materials, promotion of evaporation efficiency, and solutions to the problem of scaling. Both the material components and structure will affect the absorption and reflection of the incident light, and the evaporation efficiency can be enhanced by reducing heat loss, enlarging surface area, and recycling latent heat. Scaling can be addressed by tailoring surface properties and structure.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2022

Optical bistability in PECVD silicon-rich nitride

We present a study of optical bi-stability in a 3.02 refractive index at 1550nm plasma enhanced chemical vapor deposition (PECVD) silicon-rich nitride (SRN) film, as it pertains to bi-stable switching, memory applications, and thermal sensing applications. In this work we utilize an SRN ring resonator device, which we first characterize at low-power and then compare thermo-optic coefficients, (2.12 ± 0.125) × 10 −4 /°C, obtained from thermal-heating induced resonance shifts to optically induced resonance shifts as well as estimated propagation loss and absorption. We then measure the time response of this nonlinearity demonstrating the relaxation time to be 18.7 us, indicating the mechanism to be thermal in nature. Finally, we demonstrate bi-stable optical switching.

42 ENGINEERING↗
DOE OSTI2023

Quantifying Optical Loss of High-Voltage Degradation Modes in PV Modules Using Spectral Analysis [Slides]

The direct current bias for photovoltaic (PV) modules interconnected in series-strings may include both high voltage negative ("HV-") and positive ("HV+") polarity with respect to the electrical ground. Multiple degradation modes, resulting in quantifiable optical loss, were found to occur during HV-/HV+ sequential stress, including: corrosion of the external glass surface, encapsulant delamination (at its interfaces with the glass and the PV cell), internal haze formation (resulting from a chemical interaction between the glass and the encapsulant), corrosion and migration of the gridlines, and corrosion of the silicon nitride (SixNy) antireflective coating on the cell. The effects of these separate modes were examined using monolithic (e.g., glass or PV cell) and laminated-coupon (glass/encapsulant/glass or glass/encapsulant/cell/encapsulant/backsheet) specimens. Characterizations during and after unbiased accelerated testing at 85 degrees C/85% relative humidity included: spectrophotometry, optical microscopy, electron microscopy, and ellipsometry. For some module components (i.e., the glass and the SixNy coating), the optical performance was determined through iterative analysis of empirical measurements. Concentrating on just their spectral effect, a novel model was then developed to estimate the transfer of light to the PV cell and the return of light from the PV module with simultaneous degradation mechanisms, which was compared to a mini-module previously subjected to HV-/HV+ stress. The model suggests one-third of the current loss observed for the mini-module can be attributed to the optical degradation of the packaging materials. The dominant degradation modes include encapsulant delamination and corrosion of the SixNy coating. Recommendations are given so that the optical model may be improved relative to accelerated testing and validated relative to field aging.

14 SOLAR ENERGY↗
DOE OSTI2025

Diagnosis of PV Cell Antireflective Coating Degradation Resulting from Hot-Humid, High Voltage Potential Aging

Corrosion of the antireflective coating on a photovoltaic cell ("ARc corrosion") has previously been observed in studies using hot-humid test conditions with external high-voltage (HV) bias. This study primarily focuses on known vulnerable, legacy aluminum back surface field (Al-BSF) cells in mini-modules (MiMos) put through comparative stepped stress tests. Each cell type had MiMos at +1500 V, -1500 V, or unbiased ("Voc") potential, which were sequentially subjected to test conditions of 60deg C/60% relative humidity (RH) for 96 h, as in International Electrotechnical Commission (IEC) Technical Specification 62804-1; 70 deg C/70% RH for 200 h; and 85 deg C/85% RH for 200 h. Characterizations at each step included visual camera and electroluminescence (EL) imaging, colorimetry, and current-voltage (I-V) curve tracing. Final characterizations included: Suns-Voc; spatial mapping of external quantum efficiency (EQE); high-resolution photoluminescence (PL), EL, and dark lock-in thermography (DLIT) imaging. Forensics were performed on extracted cores, including scanning electron microscopy (SEM) with energy-dispersive X-ray spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS), and scanning Auger microscopy (SAM). Forensics were also conducted on MiMos from previous studies that underwent stepped HV aging and separate outdoor aged full-sized modules. ARc corrosion was specifically seen for the glass/encapsulant/cell side of the +1500V (HV+) stressed MiMos and modules. Appearance, color, and reflectance were the most distinguishing characteristics relative to glass corrosion, gridline-corrosion and -delamination as well as other concurrent degradation modes. SEM/EDS and SAM identified conversion of silicon nitride to hydrated silica, hydrous silica, or hydrated amorphous silica, which preferentially occurred at the edges and tips of the pyramidal textured cell surface.

14 SOLAR ENERGY↗
DOE OSTI2022

Parametric Decay of Alfvénic Wave Packets in Nonperiodic Low-beta Plasmas

The parametric decay of finite-size Alfvén waves in nonperiodic low-beta plasmas is investigated using one-dimensional (1D) hybrid simulations. Compared with the usual small periodic system, a wave packet in a large system under the absorption boundary condition shows different decay dynamics, including reduced energy transfer, localized density cavitation, and ion heating. The resulting Alfvén wave dynamics are influenced by several factors relating to this instability, including the growth rate, central wave frequency, and unstable bandwidth. A final steady state of the wave packet may be achieved when the instability does not have enough time to develop within the residual packet, and the packet size shows well-defined scaling dependencies on the growth rate, wave amplitude, and plasma beta. Under the proper conditions, enhanced secondary decay can also be excited in the form of a narrow, amplified wave packet. These results may help to interpret laboratory and spacecraft observations of Alfvén waves, and to refine our understanding of the associated energy transport and ion heating.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
NASA NTRS1968

Precise doping of metals by small gas flows

Simple method was developed for doping refractory metals with oxygen. The metal specimens are heated in a dynamic high-vacuum system. The system can be used for other oxygen absorption processes /such as low-pressure oxidation measurements/ and for gases other than oxygen.

Barrett, C. A.↗
NASA NTRS1974

Recommended radiative property data for Venusian entry calculations

A compilation of experimental and calculated data on the radiative properties species important in Venusian entry is presented. Molecular band systems, atomic lines, free-bound, and free-free continua are considered for the principal radiating species of shock heated carbon dioxide. A limited amount of data pertinent to the species in the ablation layer is also included. The assumption is made that the Venus atmosphere so closely approximates pure CO2 that the inviscid layer radiation is due almost entirely to thermally excited CO2. The only exception is the inclusion of data on the Violet band system of CN. Recommendations are made as to best property values for radiative heating calculations. A review of the basic equations and the relationships of the various emission-absorption gas porperties is also included.

Jones, J. J.↗