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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 307 records · Page 17
All sourcesNASA NTRSDOE OSTI
NASA NTRS1980

Performance of silicon solar cells fabricated from multiple Czochralski ingots grown by using a single crucible

Results on the performance of solar cells fabricated on wafers from multiple silicon ingots of large diameter, grown by using a single crucible and a sequential melt replenishment Czochralski (CZO) technique are presented. Samples were analyzed for resistivity, dislocation density and impurity content. Solar cells were fabricated from the seed, center and tang end of each ingot to evaluate the growth reproducibility and material quality. The cell efficiency within a given wafer varies by no more than plus or minus 5% of the average value. A small but consistent decrease in the cell efficiency is observed from the first to the fourth ingot grown from a single crucible. This decrease may be related to an increase in impurity content or dislocation density or a combination of both. The efficiency of the cells fabricated from the tang end of the fourth ingot is about 10% lower than that of the control cell. An impurity effects model is employed to correlate this decrease in efficiency with the impurity build-up in the residual melt.

Kachare, A. H.↗
NASA NTRS1980

Nutritional criteria for closed-loop space food systems

The nutritional requirements for Skylab crews are summarized as a data base for long duration spaceflight nutrient requirements. Statistically significant increases in energy consumption were detected after three months, along with CO2/O2 exhalation during exercise and thyroxine level increases. Linoleic acid amounting to 3-4 g/day was found to fulfill all fat requirements, and carbohydrate and protein (amino acid) necessities are discussed, noting that vigorous exercise programs avoid deconditioning which enhances nitrogen loss. Urinary calcium losses continued at a rate 100% above a baseline figure, a condition which ingestion of vitamin D2 did not correct. Projections are given that spaceflights lasting more than eight years will necessitate recycling of human waste for nutrient growth, which can be processed into highly efficient space food with a variety of tastes.

Rambaut, P. C.↗
NASA NTRS1984

Proceedings of the Flat-plate Solar Array Project Research Forum on the High-speed Growth and Characterization of Crystals for Solar Cells

The High-Speed Growth and Characterization of Crystals for Solar Cells Research Forum was held on July 25-27, 1983, at the Sandpiper Bay Hotel in ort St. Lucie, Florida. The Research Forum was arranged into eight interactive sessions and addressed theoretical and experimental phenomena, applications, and characterization including stress/strain and other problem areas that limit the rate of growth of crystals suitable for processing into efficient, cost-effective solar cells. The Flat-Plate Solar Array Project of the Jet Propulsion Laboratory sponsored the meeting: Thirty-five invited papers were presented. Discussion periods followed each presentation. These Proceedings are a record of the papers and the discussions.

Katherine A. Dumas↗
NASA NTRS1986

Overview of NASA Lewis Research Center free-piston Stirling engine technology activities applicable to space power systems

Free piston Stirling technology is applicable for both solar and nuclear powered systems. As such, the Lewis Research Center serves as the project office to manage the newly initiated SP-100 Advanced Technology Program. This five year program provides the technology push for providing significant component and subsystem options for increased efficiency, reliability and survivability, and power output growth at reduced specific mass. One of the major elements of the program is the development of advanced power conversion concepts of which the Stirling cycle is a viable candidate. Under this program the research findings of the 25 kWe opposed piston Space Power Demonstrator Engine (SPDE) are presented. Included in the SPDE discussions are initial differences between predicted and experimental power outputs and power output influenced by variations in regenerators. Projections are made for future space power requirements over the next few decades. And a cursory comparison is presented showing the mass benefits that a Stirling system has over a Brayton system for the same peak temperature and output power.

Slaby, J. G.↗
NASA NTRS1991

Small Business Innovations (Crystal Components)

Scientific Materials Corporation, Bozeman, MT developed the SciMax line of improved Nd:Yag crystals under an Small Business Innovation Research (SBIR) contract with Langley Research Center. They reduced the amount of water trapped in the crystals during growth to improve the optical quality and efficiency. Applications of the crystals include fiber optics, telecommunications, welding, drilling, eye surgery and medical instrumentation.

Source record↗
NASA NTRS2013

Inclusion of Linearized Moist Physics in Nasa's Goddard Earth Observing System Data Assimilation Tools

Inclusion of moist physics in the linearized version of a weather forecast model is beneficial in terms of variational data assimilation. Further, it improves the capability of important tools, such as adjoint-based observation impacts and sensitivity studies. A linearized version of the relaxed Arakawa-Schubert (RAS) convection scheme has been developed and tested in NASA's Goddard Earth Observing System data assimilation tools. A previous study of the RAS scheme showed it to exhibit reasonable linearity and stability. This motivates the development of a linearization of a near-exact version of the RAS scheme. Linearized large-scale condensation is included through simple conversion of supersaturation into precipitation. The linearization of moist physics is validated against the full nonlinear model for 6- and 24-h intervals, relevant to variational data assimilation and observation impacts, respectively. For a small number of profiles, sudden large growth in the perturbation trajectory is encountered. Efficient filtering of these profiles is achieved by diagnosis of steep gradients in a reduced version of the operator of the tangent linear model. With filtering turned on, the inclusion of linearized moist physics increases the correlation between the nonlinear perturbation trajectory and the linear approximation of the perturbation trajectory. A month-long observation impact experiment is performed and the effect of including moist physics on the impacts is discussed. Impacts from moist-sensitive instruments and channels are increased. The effect of including moist physics is examined for adjoint sensitivity studies. A case study examining an intensifying Northern Hemisphere Atlantic storm is presented. The results show a significant sensitivity with respect to moisture.

Convection↗
DOE OSTI2023

GaAs solar cells grown on acoustically spalled GaAs substrates with 27% efficiency

Acoustic spalling presents a potentially low-cost reuse pathway for III–V epitaxial growth substrates via exfoliation of device layers with recovery and reuse of the substrate. However, surface features formed during spalling can reduce the performance of subsequently grown devices. Here, we develop an understanding of how the surface morphology of acoustically spalled substrates affects GaAs solar cell performance and develop strategies to mitigate these impacts. We demonstrate that minor planarization of the surface by wet chemical etching and/or epitaxial growth, or the redesign of the device structure to thicken critical layers, prevents performance degradation. Using these strategies, we demonstrate a 0.25 cm 2 single-junction GaAs device with 26.9% ± 0.2% photovoltaic conversion efficiency under the AM1.5G spectrum grown on an acoustically spalled substrate. These results enable the growth of high-performance III–V devices on non-traditional substrates with the potential for significantly reduced device costs.

14 SOLAR ENERGY↗
DOE OSTI2020

Adaptive laboratory evolution of methylotrophic Escherichia coli enables synthesis of all amino acids from methanol-derived carbon

Recent attempts to create synthetic Escherichia coli methylotrophs identified that de novo biosynthesis of amino acids, in the presence of methanol, presents significant challenges in achieving autonomous methylotrophic growth. Previously engineered methanol-dependent strains required co-utilization of stoichiometric amounts of co-substrates and methanol. As such, these strains could not be evolved to grow on methanol alone. In this work, we have explored an alternative approach to enable biosynthesis of all amino acids from methanol-derived carbon in minimal media without stoichiometric coupling. First, we identified that biosynthesis of threonine was limiting the growth of our methylotrophic E. coli. To address this, we performed adaptive laboratory evolution to generate a strain that grew efficiently in minimal medium with methanol and threonine. Methanol assimilation and growth of the evolved strain were analyzed and, interestingly, we found that the evolved strain synthesized all amino acids, including threonine, from methanol-derived carbon. Here, the evolved strain was then further engineered through overexpression of an optimized threonine biosynthetic pathway. We show that the resulting methylotrophic E. coli strain has a methanol-dependent growth phenotype with homoserine as co-substrate. In contrast to previous methanol-dependent strains, co-utilization of homoserine is not stoichiometrically linked to methanol assimilation. As such, future engineering of this strain and successive adaptive evolution could enable autonomous growth on methanol as the sole carbon source.

13C-labeling analysis↗
DOE OSTI2024

Elucidating the formation mechanisms of zeolites using data-driven modelling and in-situ characterization

Zeolites are the main solid catalysts used by the chemical industry. The use of zeolites in separations and as shape selective catalysts requires control of the width and connectivity of their pores. 235 distinct zeolite frameworks have been synthesized to date, of over 2 million that have been proposed. Recent work indicates that the limitation is in large part kinetic: new synthetic pathways are required to access new zeolites. Organic cations are used to direct the synthesis towards specific zeolites. However, the molecular mechanisms by which cations direct the nucleation towards specific zeolites is not known. Elucidating these mechanisms is key to realize new zeolites for catalysis and separations, and is the focus of this project. This project developed and implemented a synergistic, data-driven computational and experimental approach to resolve the molecular pathways of nucleation, growth, and polymorph selection of zeolites and the role of organic cations in directing their formation. The project developed computationally efficient and accurate models for the study of the nucleation and growth of pure silica zeolites in molecular simulations, using machine learning with data from experiments. Simulations with these models were integrated with scanning tunneling electron microscopy, computer vision, and deep learning to unveil the molecular pathways of formation of a zeolite. Of particular interest in this project was to elucidate the role of amorphous precursors in the nucleation of the zeolite. Previous experiments indicate that zeolites are born within non-crystalline aggregates in which the silicates and organic cations have local and medium range order similar to that of the zeolite. The organic cations that direct the formation of zeolites and those that direct the formation of ordered mesoporous silicas are similar. We hypothesized that the frustrated attraction that for large organic cations leads to the formation of stable mesophases that direct the synthesis of mesoporous silicas, could promote the formation of metastable mesophases that can assist in the nucleation and polymorph selection of zeolites. The simulations resolved how structure directing agents build crystalline order and showed that mesoscopic pre-ordering occurs is not required to facilitate the nucleation of zeolites, because the synthesis occurs at high driving forces, where the barriers for nucleation are negligible. This project unveiled that polymorph selection in zeolite synthesis occurs after nucleation, opening a distinct area of control through the kinetics of growth and not through nucleation barriers.

36 MATERIALS SCIENCE↗
DOE OSTI2020

The Effect of Size on Postrelease Survival of Head-Started Mojave Desert Tortoises

Abstract Captive-rearing conservation programs focus primarily on maximizing postrelease survival. Survival increases with size in a variety of taxa, often leading to the use of enhanced size as a means to minimize postrelease losses. Head-starting is a specific captive-rearing approach used to accelerate growth in captivity prior to release in the wild. We explored the effect of size at release, among other potential factors, on postrelease survival in head-started Mojave desert tortoises Gopherus agassizii. Juvenile tortoises were reared for different durations of captivity (2–7 y) and under varying husbandry protocols, resulting in a wide range of juvenile sizes (68–145 mm midline carapace length) at release. We released all animals (n = 78) in the Mojave National Preserve, California, United States, on 25 September 2018. Release size and surface activity were the only significant predictors of fate during the first year postrelease. Larger sized head-starts had higher predicted survival rates when compared with smaller individuals. This trend was also observed in animals of the same age but reared under different protocols, suggesting that accelerating the growth of head-started tortoises may increase efficiency of head-starting programs without decreasing postrelease success. Excluding five missing animals, released head-starts had 82.2% survival in their first year postrelease (September 2018–September 2019), with all mortalities resulting from predation. No animals with >90-mm midline carapace length were predated by ravens. Our findings suggest the utility of head-starting may be substantially improved by incorporating indoor rearing to accelerate growth. Target release size for head-started chelonians will vary among head-start programs based on release site conditions and project-specific constraints.

Biodiversity & Conservation↗
NASA NTRS2002

Sensitivities of Tropical Cyclones to Surface Friction and the Coriolis Parameter in a 2-D Cloud-Resolving Model

The sensitivities to surface friction and the Coriolis parameter in tropical cyclogenesis are studied using an axisymmetric version of the Goddard cloud ensemble model. Our experiments demonstrate that tropical cyclogenesis can still occur without surface friction. However, the resulting tropical cyclone has very unrealistic structure. Surface friction plays an important role of giving the tropical cyclones their observed smaller size and diminished intensity. Sensitivity of the cyclogenesis process to surface friction. in terms of kinetic energy growth, has different signs in different phases of the tropical cyclone. Contrary to the notion of Ekman pumping efficiency, which implies a preference for the highest Coriolis parameter in the growth rate if all other parameters are unchanged, our experiments show no such preference.

Chao, Winston C.↗
NASA NTRS1986

Space station 20-kHz power management and distribution system

During the conceptual design phase a 20-kHz power distribution system was selected as the reference for the space station. The system is single-phase 400 VRMS, with a sinusoidal wave form. The initial user power level will be 75 kW with growth to 300 kW. The high-frequency system selection was based upon considerations of efficiency, weight, safety, ease of control, interface with computers, and ease of paralleling for growth. Each of these aspects will be discussed as well as the associated trade-offs involved. An advanced development program has been instituted to accelerate the maturation of the high-frequency system. Some technical aspects of the advanced development will be discussed.

Hansen, I. G.↗
NASA NTRS1986

Space Station 20-kHz power management and distribution system

During the conceptual design phase a 20-kHz power distribution system was selected as the reference for the Space Station. The system is single-phase 400 VRMS, with a sinusoidal wave form. The initial user power level will be 75 kW with growth to 300 kW. The high-frequency system selection was based upon considerations of efficiency, weight, safety, ease of control, interface with computers, and ease of paralleling for growth. Each of these aspects will be discussed as well as the associated trade-offs involved. An advanced development program has been instituted to accelerate the maturation of the high-frequency system. Some technical aspects of the advanced development will be discussed.

Hansen, Irving G.↗
NASA NTRSDate not supplied

Thermal Model of Ice Growth in Vacuum for Lunar Water Production

To support NASA’s goal of sustained lunar presence, the use of in-situ resource utilization will reduce launch weight and frequency of resupply missions. With the discovery of water in the permanently shadowed regions of the moon, the prospect of harvesting water has generated particular interest. A more fundamental understanding of water storage and capture in lunar conditions is necessary for effective and efficient water capture and transport. The present study derives a thermal model for ice height, heat flux, chamber pressure, and mass flow rate in sub-atmospheric pressures below the triple point. The thermal model compares ice layer height against the results of the experiment at two pressures (300 Pa and 500 Pa) and temperatures from -18°C to -3°C. The thermal model predicts the trends seen experimentally with an overall root mean square error of 0.1135 cm and coefficient of efficiency of 0.994, indicating the model predicts the experimental results. The thermal model can be utilized to examine the impacts of varying pressure, temperature, and cold plate area to determine the most effective ice growth conditions for efficient capture of water on the lunar surface. The thermal model will provide a useful tool for NASA in the design of the lunar ice tanker and shows the promise of effective capture water on the lunar surface.

Ice growth↗
NASA NTRSDate not supplied

Thermal Model of Ice Growth in Vacuum for Lunar Water Production

To support NASA’s goal of sustained lunar presence, the use of in-situ resource utilization will reduce launch weight and frequency of resupply missions. With the discovery of water in the permanently shadowed regions of the moon, the prospect of harvesting water has generated particular interest. A more fundamental understanding of water storage and capture in lunar conditions is necessary for effective and efficient water capture and transport. The present study derives a thermal model for ice height, heat flux, chamber pressure, and mass flow rate in sub-atmospheric pressures below the triple point. The thermal model compares ice layer height against the results of the experiment at two pressures (300 Pa and 500 Pa) and temperatures from -18°C to -3°C. The thermal model predicts the trends seen experimentally with an overall root mean square error of 0.1135 cm and coefficient of efficiency of 0.994, indicating the model predicts the experimental results. The thermal model can be utilized to examine the impacts of varying pressure, temperature, and cold plate area to determine the most effective ice growth conditions for efficient capture of water on the lunar surface. The thermal model will provide a useful tool for NASA in the design of the lunar ice tanker and shows the promise of effective capture water on the lunar surface.

Ice growth↗
NASA NTRS1990

Advanced avionics concepts: Autonomous spacecraft control

A large increase in space operations activities is expected because of Space Station Freedom (SSF) and long range Lunar base missions and Mars exploration. Space operations will also increase as a result of space commercialization (especially the increase in satellite networks). It is anticipated that the level of satellite servicing operations will grow tenfold from the current level within the next 20 years. This growth can be sustained only if the cost effectiveness of space operations is improved. Cost effectiveness is operational efficiency with proper effectiveness. A concept is presented of advanced avionics, autonomous spacecraft control, that will enable the desired growth, as well as maintain the cost effectiveness (operational efficiency) in satellite servicing operations. The concept of advanced avionics that allows autonomous spacecraft control is described along with a brief description of each component. Some of the benefits of autonomous operations are also described. A technology utilization breakdown is provided in terms of applications.

Source record↗
DOE OSTI2021

Pressure-tailored lithium deposition and dissolution in lithium metal batteries

Unregulated lithium (Li) growth is the major cause of low Coulombic efficiency, short cycle life and safety hazards for rechargeable Li metal batteries. Strategies that aim to achieve large granular Li deposits have been extensively explored, and yet it remains a challenge to achieve the ideal Li deposits, which consist of large Li particles that are seamlessly packed on the electrode and can be reversibly deposited and stripped. In this work, we report a dense Li deposition (99.49% electrode density) with an ideal columnar structure that is achieved by controlling the uniaxial stack pressure during battery operation. Using multiscale characterization and simulation, we elucidate the critical role of stack pressure on Li nucleation, growth and dissolution processes and propose a Li-reservoir-testing protocol to maintain the ideal Li morphology during extended cycling. The precise manipulation of Li deposition and dissolution is a critical step to enable fast charging and a low-temperature operation for Li metal batteries.

25 ENERGY STORAGE↗
DOE OSTI2020

The effects of outdoor air-side fouling on frost growth and heat transfer characteristics of a microchannel heat exchanger: An experimental study

Air source heat pumps have the potential to efficiently heat and cool buildings, but their effectiveness in many climates is limited by frost growth on the outdoor heat exchanger in heating mode. These heat exchanger coils are also subject to fouling from fibers and particulates outdoors. Frost and fouling have each independently been studied extensively, and newly available research on fouling provides a method to realistically foul the air-side of coils in the laboratory. The current paper uses this method to conduct the first laboratory study of the important interactions between fouling and frost growth for a heat pump outdoor coil. A microchannel heat exchanger is tested clean and fouled, with variations in fouling level, humidity, and initial face velocity of air. Air flow rate is allowed to vary with resistance, and a surprising result is that light fouling increases heat transfer and frost growth rates, even with a 3.5% reduction in initial airflow caused by the fouling. However, heavier fouling decreases both rates. When frost growth is normalized to heat transfer, it is found to be increased by fouling; i.e. the coil’s sensible heat ratio decreases.

42 ENGINEERING↗