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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 541 records · Page 30
All sourcesNASA NTRSDOE OSTI
NASA NTRS1995

Monolithically interconnected GaAs solar cells: A new interconnection technology for high voltage solar cell output

Photovoltaic linear concentrator arrays can benefit from high performance solar cell technologies being developed at AstroPower. Specifically, these are the integration of thin GaAs solar cell and epitaxial lateral overgrowth technologies with the application of monolithically interconnected solar cell (MISC) techniques. This MISC array has several advantages which make it ideal for space concentrator systems. These are high system voltage, reliable low cost monolithically formed interconnections, design flexibility, costs that are independent of array voltage, and low power loss from shorts, opens, and impact damage. This concentrator solar cell will incorporate the benefits of light trapping by growing the device active layers over a low-cost, simple, PECVD deposited silicon/silicon dioxide Bragg reflector. The high voltage-low current output results in minimal 12R losses while properly designing the device allows for minimal shading and resistance losses. It is possible to obtain open circuit voltages as high as 67 volts/cm of solar cell length with existing technology. The projected power density for the high performance device is 5 kW/m for an AMO efficiency of 26% at 1 5X. Concentrator solar cell arrays are necessary to meet the power requirements of specific mission platforms and can supply high voltage power for electric propulsion systems. It is anticipated that the high efficiency, GaAs monolithically interconnected linear concentrator solar cell array will enjoy widespread application for space based solar power needs. Additional applications include remote man-portable or ultra-light unmanned air vehicle (UAV) power supplies where high power per area, high radiation hardness and a high bus voltage or low bus current are important. The monolithic approach has a number of inherent advantages, including reduced cost per interconnect and increased reliability of array connections. There is also a high potential for a large number of consumer products. Dual-use applications can include battery chargers and remote power supplies for consumer electronics products such as portable telephones/beepers, portable radios, CD players, dashboard radar detectors, remote walkway lighting, etc.

Dinetta, L. C.↗
DOE OSTI2022

Paving Pathways Toward Long–Life Graphite/LiNi 0.5 Mn 1.5 O 4 Full Cells: Electrochemical and Interphasial Points of View

The high-voltage spinel cathode LiNi 0.5 Mn 1.5 O 4 (LNMO) with no cobalt and low nickel content is promising for lithium-ion batteries due to its high energy and power densities, good thermal stability, and low cost. However, its high operating voltage (≈4.7 V) results in a decomposition of the electrolyte, severe chemical crossover, and deterioration of electrode-electrolyte interphases (EEIs), hindering its practical viability. It is demonstrated here that by electrochemically pre-cycling the graphite in an electrolyte containing 30 wt.% fluoroethylene carbonate, a robust LiF-rich artificial solid electrolyte interphase can be constructed for surface protection; on the other hand, an electrochemical pre-lithiation of Fe-doped LNMO serves as a lithium source for graphite at a full-cell voltage of 2.6 V. As a result, the full cells with the as-modified electrodes deliver a high capacity of 129 mA h g –1 with an excellent capacity retention of 93% after 200 cycles, vastly outperforming the full cells with fresh electrodes (120 mA h g –1 initial capacity with 78% retention). Lastly, pathways toward long-life graphite||LNMO full cells are pictured based on the inspirations from the electrochemical modifications and in-depth analyses of the EEIs in this study.

36 MATERIALS SCIENCE↗
NASA NTRS1993

High temperature co-axial winding transformers

The analysis and design of co-axial winding transformers is presented. The design equations are derived and the different design approaches are discussed. One of the most important features of co-axial winding transformers is the fact that the leakage inductance is well controlled and can be made low. This is not the case in conventional winding transformers. In addition, the power density of co-axial winding transformers is higher than conventional ones. Hence, using co-axial winding transformers in a certain converter topology improves the power density of the converter. The design methodology used in meeting the proposed specifications of the co-axial winding transformer specifications are presented and discussed. The final transformer design was constructed in the lab. Co-axial winding transformers proved to be a good choice for high power density and high frequency applications. They have a more predictable performance compared with conventional transformers. In addition, the leakage inductance of the transformer can be controlled easily to suit a specific application. For space applications, one major concern is the extraction of heat from power apparatus to prevent excessive heating and hence damaging of these units. Because of the vacuum environment, the only way to extract heat is by using a cold plate. One advantage of co-axial winding transformers is that the surface area available to extract heat from is very large compared to conventional transformers. This stems from the unique structure of the co-axial transformer where the whole core surface area is exposed and can be utilized for cooling effectively. This is a crucial issue here since most of the losses are core losses.

Divan, Deepakraj M.↗
NASA NTRS1975

Experimental evaluation of trailing edge and incidence fluctuation noise theories

Tests were conducted to evaluate conflicting theories for trailing edge noise and for incidence fluctuation noise. A flat-plate airfoil with flush-mounted surface pressure transducers was tested in an anechoic wind tunnel at velocities from 31.5 to 177 m/sec and nominal 4 and 6% grid-generated turbulence levels. In one series of runs, the airfoil was faired into the tunnel nozzle and extended beyond the nozzle lip for studies of trailing edge noise without a leading edge and with flow on only one side. Such noise was found to vary with velocity to the fifth power and turbulence level squared as predicted by Ffowcs Williams and Hall (1970) and by Chase (1972). Power spectral density at high frequencies decayed approximately inversely with frequency to the 10/3 power as predicted by Chase. The data were poorly predicted by Hayden's correlation (1969, 1972).

Fink, M. R.↗
DOE OSTI2023

Power Electronics Cooling Technology Research at NREL

This presentation describes power electronics thermal management technologies used for on-road EVs. Examples are provided and heat exchangers are described. Advanced cooling technologies developed are NREL to enable increased power density and enable high WBG temperature operation are then presented. The performance (e.g., thermal resistance, pumping power) of the advanced power electronics cooling technologies are compared to the performance of current, on-road technology.

DIRECT ENERGY CONVERSION↗
NASA NTRS1989

Parallel Optical Random Access Memory (PORAM)

It is shown that the need to minimize component count, power and size, and to maximize packing density require a parallel optical random access memory to be designed in a two-level hierarchy: a modular level and an interconnect level. Three module designs are proposed, in the order of research and development requirements. The first uses state-of-the-art components, including individually addressed laser diode arrays, acousto-optic (AO) deflectors and magneto-optic (MO) storage medium, aimed at moderate size, moderate power, and high packing density. The next design level uses an electron-trapping (ET) medium to reduce optical power requirements. The third design uses a beam-steering grating surface emitter (GSE) array to reduce size further and minimize the number of components.

Alphonse, G. A.↗
DOE OSTI2022

Self‐Assembly and Oriented Growth of Conductive Ni‐CAT‐1 Metal‐Organic Framework at Solid–Liquid Interfaces

Abstract Two‐dimensional (2D) conductive metal‐organic frameworks (MOF) represent a unique class of electrode materials with high capacity and power density. Understanding molecular mechanisms and pathways for heterogeneous nucleation of 2D π‐conjugated MOFs is highly desirable for controlling the structure and properties of conductive MOFs on solid substrates. Herein, a systematic study of nucleation and growth of 2D π‐conjugated Ni‐catecholate (Ni‐CAT‐1) MOFs on highly oriented pyrolytic graphite (HOPG) and copper substrates is reported. It is discovered that the nucleation density and growth kinetics of the MOF film can be controlled by varying substrate interactions with the organic linker. Specifically, π–π interactions between the linker and the HOPG dictate lower nucleation density, whereas π–metal interactions between the linker and the copper substrate dictate faster nucleation and higher nucleation densities. These studies reveal the key mechanism for Ni‐CAT‐1 nucleation on different surfaces and provide insights into interfacial control over the growth of other 2D π‐conjugated MOF films on solid substrates to inform synthesis of functional materials.

2D materials↗
NASA NTRS1977

Effect of microstructure on Na/+/ diffusion in beta alumina

The effect of microstructural features, such as grain size and orientation, on sodium ion diffusion in polycrystalline beta alumina is investigated; the ionic solid is suitable for use in high-energy and power density batteries. Two types of hot-pressed polycrystalline samples are studied, one with grains highly oriented in the direction normal to the pressing direction, the other with significantly less preferred orientation normal to the pressing direction. Results of the experimental assessments indicate that grain size and diffusion path tortuosity have little effect on diffusion kinetics, while grain boundary type and grain aspect ratio are important factors in determining the diffusion rate.

Sarian, S.↗
DOE OSTI2022

Automotive Power Electronics Cooling Technology Research at NREL

This presentation describes power electronics thermal management technologies used for on-road EVs. Examples are provided and heat exchangers are described. Advanced cooling technologies developed are NREL to enable increased power density and enable high WBG temperature operation are then presented. The performance (e.g., thermal resistance, pumping power) of the advanced power electronics cooling technologies are compared to the performance of current, on-road technology.

ADVANCED PROPULSION SYSTEMS↗
DOE OSTI2020

Non-uniform longitudinal current density induced power saturation in GaAs-based high power diode lasers

The output power of modern 975 nm GaAs-based broad area diode lasers is limited by increasing carrier and photon losses at high bias. Here, we use experiment and one-dimensional calculations on these devices to reveal that higher current densities (and hence higher local recombination rates and higher losses) arise near the front facet due to spatial hole burning and that the non-uniformity is strongly affected by laser geometry, which is more severe for longer resonators and less severe for higher front facet reflectivity. Specifically, we use devices with a segmented p-contact to directly measure the current distribution along the resonator and compare this with laser simulation. Devices with a 6 mm resonator show 29% more current at the front than back, twice as large as the 15% current non-uniformity in devices with a 3 mm resonator. In contrast, increased front facet reflectivity (20% rather than 0.8%) is shown to almost halve the current non-uniformity from 29% to 18% in devices with a 6 mm resonator and reduces power saturation. Although the magnitude of current non-uniformity in experiment and theory is broadly consistent, in experiment, an additional divergence is seen in current flow (and hence recombination rate) near the facets, and earlier power saturation occurs. Finally, we discuss the possible saturation mechanisms that are not included in the simulation.

47 OTHER INSTRUMENTATION↗
DOE OSTI2021

High Performance PEFC Electrode Structures

Raytheon Technologies Research Center (RTRC) in collaboration with Ion Power Inc. and the University of Arkansas at Little Rock and the FC-PAD consortium executed a project that: (1) developed comprehensive models of oxygen and proton transport in cathode catalyst layers that provided new insights about losses associated with reducing platinum loading to 0.1 mg/cm 2 , (2) designed, fabricated, characterized, and tested cells featuring carbon-supported catalyst layers with low platinum loadings that met efficiency and power density targets set forth by the Hydrogen and Fuel Cells Technology Office, and (3) designed, fabricated, characterized, and tested novel catalyst structures. The modeling efforts produced eight scientific publications that shared new descriptions of oxygen and proton transport in catalyst layers with the broader technical community. The key physical insights from the models are expressed in straightforward algebraic expressions, facilitating easy adoption by other researchers. The models developed during the project explain why resistance to oxygen transport is inversely proportional to interfacial area of platinum – an observation that eluded quantitative explanation for a decade. The models quantitatively predict polarization when measured morphological parameters and transport properties are input. Membrane-electrode assemblies made during the project met stated goals for current at high voltage and power density at rated voltage for transportation fuel cells at the end of budget period 2. High performance was achieved by developing a diffusion layer with low resistance to oxygen transport and a PtCo/C cathode catalyst layer capable of supporting rapid proton and oxygen transport. The project was subsequently directed to curtail experimental work and focus on modeling during budget period 3. Ion Power Inc. developed new expertise in fabricating catalyst layers containing platinum-cobalt catalysts, and processing very thin membranes. The University of Arkansas at Little Rock developed novel nanocolumnar self-supported thin film electrocatalysts that can be grown on carbon supports using a simple high pressure sputter deposition method. The nanocolumnar microstructure provides adequate surface-to-volume ratio for efficient platinum utilization, and the conformal platinum shell with larger crystal grain sizes covering the carbon support surface may eliminate durability issues associated with catalyst dissolution, agglomeration, and carbon corrosion.

08 HYDROGEN↗
NASA NTRS1982

Magnetoplasmadynamic thruster development

Current research on self-field MPD thrusters presents the possibility of developing high power/low cost electric propulsion. The interest generated in this propulsion concept within both NASA and the U.S. Air Force has led to a coordinated interagency effort, and the recent completion of several test sites are expected to speed thruster concept development. Efficiencies approaching 40% at 2200 sec have been experimentally demonstrated. Among the characteristics recommending development of MPD thrusters are high thrust density and power handling capability, simplicity, and a wide dynamic range of thrust and specific impulse. MPD thrusters can, moreover, operate either continuously, at high available power levels, or in a pulsed mode, to match lower power levels.

Pawlik, E. V.↗
DOE OSTI2022

Efficient and scalable GaInAs thermophotovoltaic devices

We report thermophotovoltaics are promising solid-state energy converters for a variety of applications such as grid-scale energy storage, concentrating solar-thermal power, and waste-heat recovery. Here, we report the design, fabrication, and testing of large area (0.8 cm 2 ), scalable, single-junction 0.75-eV GaInAs thermophotovoltaic devices reaching an efficiency of 38.8% +/- 2.0% and an electrical power density of 3.78 W/cm 2 at an emitter temperature of 1,850 °C. Reaching such a high emitter temperature and power density without sacrificing efficiency is a direct result of combining good spectral management with an optimized cell architecture, excellent material quality, and low series resistance. Importantly, fabrication of 12 high-performing devices on a 2-in wafer is shown to be repeatable, and the cell design can be readily transferred to commercial epitaxy on even larger wafers. Further improvements in efficiency can be obtained by using a multijunction architecture, illustrated by early results for a two-junction 0.84-eV GaInPAs/0.75-eV GaInAs device.

14 SOLAR ENERGY↗
NASA NTRS1992

Quantum well, beam deflecting surface emitting lasers

This invention relates to surface emitting semiconductor lasers (SELs), with integrated 45 deg. beam deflectors. A SEL is formed on a wafer including vertical mirrors and 45 deg. beam deflectors formed in grooves by tilted ion beam etching. A SEL is a lattice matched, or unstrained, AlGaAs/GaAs GRINSCH SQW SEL. An alternate embodiment is shown, in which a SEL is lattice mismatched, strained or pseudomorphic, or InGaAs/AlGaAs GRINSCH SQW SEL which emits radiation at a wavelength to which its substrate is transparent. Both SELs exhibit high output power, low threshold current density, and relatively high efficiency, and each are processing compatible with conventional large scale integration technology. Such SELs may be fabricated in large numbers from single wafers. The novel features of this invention include the use of tilted ion beam etching to form a pair of grooves each including vertical mirrors and 45 deg. beam deflectors. The embodiment provides substantial circuit design flexibility because radiation may be coupled both up and/or down through the substrate.

Kim, Jae H.↗
DOE OSTI2024

Battery Energy Storage Systems: A Review of Energy Management Systems and Health Metrics

With increasing concerns about climate change, there is a transition from high-carbon-emitting fuels to green energy resources in various applications including household, commercial, transportation, and electric grid applications. Even though renewable energy resources are receiving traction for being carbon-neutral, their availability is intermittent. To address this issue to achieve extensive application, the integration of energy storage systems in conjunction with these resources is becoming a recommended practice. Additionally, in the transportation sector, the increased demand for EVs requires the development of energy storage systems that can deliver energy for rigorous driving cycles, with lithium-ion-based batteries emerging as the superior choice for energy storage due to their high power and energy densities, length of their life cycle, low self-discharge rates, and reasonable cost. As a result, battery energy storage systems (BESSs) are becoming a primary energy storage system. The high-performance demand on these BESS can have severe negative effects on their internal operations such as heating and catching on fire when operating in overcharge or undercharge states. Reduced efficiency and poor charge storage result in the battery operating at higher temperatures. To mitigate early battery degradation, battery management systems (BMSs) have been devised to enhance battery life and ensure normal operation under safe operating conditions. Some BMSs are capable of determining precise state estimations to ensure safe battery operation and reduce hazards. Precise estimation of battery health is computed by evaluating several metrics and is a central factor in effective battery management systems. In this scenario, the accurate estimation of the health indicators (HIs) of the battery becomes even more important within the framework of a BMS. This paper provides a comprehensive review and discussion of battery management systems and different health indicators for BESSs, with suitable classification based on key characteristics.

Nazaralizadeh, Solmaz (ORCID:0009000737004039)↗
NASA NTRS1975

The solar flare iron line to continuum ratio and the coronal abundances of iron and helium

Narrow band Ross filter measurements of the Fe 25 line flux around 0.185 nm and simultaneous broadband measurements during a solar flare were used to determine the relationship between the solar coronal abundances of iron and helium. The Fe 25 ion population was also determined as a function of time. The proportional counter and the Ross filter on OSO-7 were utilized. The data were analyzed under the separate assumptions that (1) the electron density was high enough that a single temperature could characterize the continuum spectrum and the ionization equilibrium, and that (2) the electron density was low so that the ion populations trailed the electron temperature in time. It was found that the density was at least 5x10 to the 9th power, and that the high density assumption was valid. It was also found that the iron abundance is 0.000011 for a helium abundance of 0.2, relative to hydrogen.

Mckenzie, D. L.↗