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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 559 records · Page 31
All sourcesNASA NTRSDOE OSTI
DOE OSTI2024

DISH-STARS™ Commercialization (Abstract)

The goal of this project is to aggressively support the near-term commercialization of a new technology platform – based on the integration of solar concentrators and micro- and meso-channel process technology (MMPT) – that was evaluated and identified as a strong candidate for near-term commercialization at EERE’s inaugural Lab-Corps program during early FY2016. Known as STARS, for Solar Thermochemical Advanced Reactor System, or Dish-STARS™ when paired with parabolic dish concentrators, STARS is a promising energy-related technology developed at the Pacific Northwest National Laboratory (PNNL) that efficiently converts solar energy into chemical energy. Combined with economies through hardware mass production, the efficiency of Dish-STARS™ provides a near-term opportunity for the production of renewable electricity, fuels and chemicals. This proposed CRADA project supports the commercialization of Dish-STARS™ in these important ways: The project will support the cooperative development of Dish-STARS™ by the DOE national laboratory and private partners, including the startup company, STARS Corporation, that is being established by the PNNL Lab-Corps team that evaluated STARS on behalf of EERE. The project will provide important transition funding at the time that the previous DOE SunShot project, which has supported Dish-STARS™ development from Technology Readiness Level 3 (TRL 3) to TRL 6, is scheduled to end.

14 SOLAR ENERGY↗
DOE OSTI2023

Fuel Salt Qualification and Associated Fuel Cycle Opportunities & Issues

NRC staff have defined fuel qualification as a process which provides high confidence that the physical and chemical behavior of fuel is sufficiently understood so that it can be adequately modeled for both normal and accident conditions, reflecting the role of the fuel design in the overall safety of the facility. Uncertainties are defined so that calculated fission product releases include the appropriate margins to ensure conservative calculation of radiological dose consequences. The Advisory Committee on Reactor Safeguards (ACRS) has accepted the methodology described in NUREG/CR-7299 as an acceptable method for fuel qualification for molten salt reactors. The fuel salt qualification process described in NUREG/CR-7299 is based upon understanding the role that the fuel salt plays in achieving the fundamental safety functions, which in-turn is based on the fuel salt thermophysical and thermochemical properties.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
NASA NTRS1993

Issues and approach to develop validated analysis tools for hypersonic flows: One perspective

Critical issues concerning the modeling of low density hypervelocity flows where thermochemical nonequilibrium effects are pronounced are discussed. Emphasis is on the development of validated analysis tools, and the activity in the NASA Ames Research Center's Aerothermodynamics Branch is described. Inherent in the process is a strong synergism between ground test and real gas computational fluid dynamics (CFD). Approaches to develop and/or enhance phenomenological models and incorporate them into computational flowfield simulation codes are discussed. These models were partially validated with experimental data for flows where the gas temperature is raised (compressive flows). Expanding flows, where temperatures drop, however, exhibit somewhat different behavior. Experimental data for these expanding flow conditions is sparse and reliance must be made on intuition and guidance from computational chemistry to model transport processes under these conditions. Ground based experimental studies used to provide necessary data for model development and validation are described. Included are the performance characteristics of high enthalpy flow facilities, such as shock tubes and ballistic ranges.

Deiwert, George S.↗
DOE OSTI2013

Combined Theoretical and Experimental Analysis of Processes Determining Cathode Performance in Solid Oxide Fuel Cells

Solid oxide fuel cells (SOFC) are under intensive investigation since the 1980’s as these devices open the way for ecologically clean direct conversion of the chemical energy into electricity, avoiding the efficiency limitation by Carnot’s cycle for thermochemical conversion. However, the practical development of SOFC faces a number of unresolved fundamental problems, in particular concerning the kinetics of the electrode reactions, especially oxygen reduction reaction. We review recent experimental and theoretical achievements in the current understanding of the cathode performance by exploring and comparing mostly three materials: (La,Sr)MnO3 (LSM), (La,Sr)(Co,Fe)O3 (LSCF) and (Ba,Sr)(Co,Fe)O3 (BSCF). Special attention is paid to a critical evaluation of advantages and disadvantages of BSCF, which shows the best cathode kinetics known so far for oxides. We demonstrate that it is the combined experimental and theoretical analysis of all major elementary steps of the oxygen reduction reaction which allows us to predict the rate determining steps for a given material under specific operational conditions and thus control and improve SOFC performance.

Environmental Molecular Sciences Laboratory↗
DOE OSTI2017

Structures and energetics of hydrated deprotonated cis-pinonic acid anion clusters and their atmospheric relevance

Pinonic acid, a C10-monocarboxylic acid with a hydrophilic –CO 2 H group and a hydrophobic hydrocarbon backbone, is a key intermediate oxidation product of α-pinene – an important monoterpene compound in biogenic emission processes that influences the atmosphere. Molecular interaction between cis-pinonic acid and water is essential for understanding its role in the formation and growth of pinene-derived secondary organic aerosols. In this work, we studied the structures, energetics, and optical properties of hydrated clusters of cis-pinonate anion (cPA–), the deprotonated form of cis-pinonic acid, by negative ion photoelectron spectroscopy and ab initio theoretical calculations. Our results show that cPA– can adopt two different structural configurations – open and folded. In the absence of waters, the open configuration has the lowest energy and provides the best agreement with the experiment. The addition waters, which mainly interact with the negatively charged -CO 2 – group, gradually stabilize the folded configuration and lower its energy difference relative to the most stable open-configured structure. Thermochemical and equilibrium hydrate distribution analysis suggests that the mono- and di- hydrates are likely to exist in humid atmospheric environment with high populations. The detailed molecular description of cPA– hydrated clusters unraveled in this study provides a valuable reference for understanding the initial nucleation process and aerosol formation involving organics containing both hydrophilic and hydrophobic groups, as well as for analyzing the optical properties of those organic aerosols.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2018

Proton-Coupled Electron Transfer to a Molybdenum Ethylene Complex Yields a β-Agostic Ethyl: Structure, Dynamics and Mechanism

In this paper, the interconversion of molybdenum ethylene and ethyl complexes by proton-coupled electron transfer (PCET) is described, an unusual transformation in organometallic chemistry. The cationic molybdenum ethylene complex [( Ph Tpy)(PPh 2 Me) 2 Mo(C 2 H 4 )][BArF 24 ] ([1-C 2 H 4 ] + ; Ph Tpy = 4'-Ph-2,2',6',2"-terpyridine, ArF 24 = [C 6 H 3 -3,5-(CF 3 ) 2 ] 4 ) was synthesized, structurally characterized, and its electronic structure established by a combination of spectroscopic and computational methods. The overall electronic structure is best described as a molybdenum(III) complex with a metallacyclopropane and a redox neutral terpyridine ligand. Addition of the nonclassical ammine complex [( Ph Tpy)(PPh 2 Me) 2 Mo(NH 3 )][BArF 24 ] ([1-NH 3 ] + ) to [1-C 2 H 4 ] + resulted in a net C–H bond-forming PCET reaction to yield the molybdenum ethyl [( Ph Tpy)(PPh 2 Me) 2 Mo(CH 2 CH 3 )][BArF 24 ] ([1-CH 2 CH 3 ] + ) and amido [( Ph Tpy)(PPh 2 Me) 2 Mo(NH 2 )][BArF 24 ] ([1-NH 2 ] + ) compounds. The reaction was reversed by addition of 2,4,6-tritert-butylphenoxyl radical to [1-CH 2 CH 3 ] + . The solid-state structure of [1-CH 2 CH 3 ] + established a β-agostic ethyl ligand that is maintained in solution as judged by variable temperature 1 H and 13 C NMR experiments. A combination of variable-temperature NMR experiments and isotopic labeling studies were used to probe the dynamics of [1-CH 2 CH 3 ] + and established restricted β-agostic -CH 3 rotation at low temperature (ΔG ‡ = 9.8 kcal mol –1 at -86 °C) as well as ethyl isomerization by β-hydride elimination-olefin rotation-reinsertion (ΔH ‡ = 19.3 ± 0.6 kcal mol –1 ; ΔS ‡ = 3.4 ± 1.7 cal mol –1 K –1 ). The β-(C–H) bond-dissociation free energy (BDFE) in [1-CH 2 CH 3 ] + was determined experimentally as 57 kcal mol –1 (THF) supported by a DFT-computed value of 52 kcal/mol –1 (gas phase). Comparison of pK a and electrochemical data for the complexes [1-C 2 H 4 ] + and [1-NH 3 ] + in combination with a deuterium kinetic isotope effect (k H /k D ) of 3.5(2) at 23 °C support a PCET process involving initial electron transfer followed by protonation leading to the formation of [1-CH 2 CH 3 ] + and [1-NH 2 ] + or a concerted pathway. Lastly, the data presented herein provides a structural, thermochemical and mechanistic foundation for understanding the PCET reactivity of organometallic complexes with alkene and alkyl ligands.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS1991

Particle simulation in a multiprocessor environment

A parallel implementation of a particle simulation method that is portable between a wide class of multiprocessor computers is presented. A fine grain spatial decomposition is utilized where several subdomains having a regular structure are computed at each processing node. This leads directly to an efficient and straightforward load balancing scheme if the number of subdomains at each processor is permitted to vary in an appropriate manner. Three dimensional simulations incorporating full thermochemical nonequilibrium are possible using the resulting code. Vectorizable algorithms are retained from earlier work allowing efficient use of deeply pipelined node processors where available. Performance results are presented from three different machine architectures demonstrating the portability of the code. On a 128-node Intel iPSC/860, performance is twice that of a single Cray-Y/MP CPU running a highly vectorized simulation code. Speedup is linear over the full range of number of processors on all target machines, indicating scalability of the method to higher degrees of parallelism.

Mcdonald, Jeffrey D.↗
DOE OSTI2013

Conversion of Methanol, Ethanol and Propanol over Zeolites

Renewable fuel from lignocellulosic biomass has recently attracted more attention due to its environmental and the potential economic benefits over the crude oil [1]. In particular the production of fuel range hydrocarbon (HC) from alcohol generated lots of interest since the alcohol can be produced from biomass via thermochemical [2] (mixed alcohol from gasification derived synthesis gas) as well as the biochemical routes [3] (alcohol fermentation). Along with the development of ZSM5 synthesis and the discovery of methanol-to-gasoline (MTG) process by Mobil in 1970’s triggered lots of interest in research and development arena to understand the reaction mechanisms of alcohols over zeolites in particular ZSM5 [4]. More detailed research on methanol conversion was extensively reported [5] and in recent times the research work can be found on ethanol [6] and other alcohols as well but comprehensive comparison of catalyst activity and the deactivation mechanism of the conversion of various alcohols over zeolites has not been reported. The experiments were conducted on smaller alcohols such as methanol, ethanol and 1-propanol over HZSM5. The experimental results on the catalyst activity and the catalyst deactivation mechanism will be discussed.

Alcohol↗
DOE OSTI2022

Sustainable Conversion of Carbon Dioxide and Shale Gas to Green Acetic Acid via a Thermochemical Cyclic Redox Scheme (Final Report)

The large-scale production of commodity chemicals relies heavily on the combustion of fossil fuels. As a result, enormous amounts of carbon dioxide (CO 2 ) are emitted which severely affects the global climate. The challenges for CO 2 utilization reside in the high stability of CO 2 molecules relative to the products, which requires the addition of significant external energy and overcoming slow and/or unfavorable reaction kinetics/thermodynamics. Chemical looping dry reforming of methane (CLDRM), also known as a hybrid redox process (HRP), is a promising alternative that allows the utilization of CO 2 and domestic shale gas resources to produce commodity chemicals. HRP works in two steps: In the first step, a redox catalyst reacts with methane to yield synthesis gas with a H 2 /CO ratio near 2:1, which is suitable for methanol and Fischer–Tropsch synthesis. The reduced redox catalyst then reacts with an oxidizing agent, such as CO 2 , to yield CO. In comparison to conventional thermochemical CO 2 splitting approaches, the use of methane as the reducing agent in HRP can significantly lower the operating temperature for CO 2 splitting.

03 NATURAL GAS↗
DOE OSTI2019

Equations of state for polyethylene and its shock-driven decomposition products

We construct new equations of state (EOS) for high density and ultrahigh molecular weight polyethylene and their chemical decomposition products under shock loading. The former were built using the SESAME framework, based in part on new specific heat and thermal expansion data reported here. The products EOS was based on thermochemical modeling under the assumption of full thermodynamic and chemical equilibrium. The products are represented as the ideal mixture of bulk carbon in the form of diamond, H 2 , H, and CH 4 . In the process of building a new EOS for the products, we recalibrated our exponential-6 pair potential for methane in order to better agree with data that have appeared since its original parameterization. The polyethylene EOS were calibrated to thermal, thermomechanical, and shock data, and their performance was evaluated in hydrodynamic modeling of deep release experiments reported previously.

36 MATERIALS SCIENCE↗
NASA NTRS1992

Issues and approach to develop validated analysis tools for hypersonic flows: One perspective

Critical issues concerning the modeling of low-density hypervelocity flows where thermochemical nonequilibrium effects are pronounced are discussed. Emphasis is on the development of validated analysis tools. A description of the activity in the Ames Research Center's Aerothermodynamics Branch is also given. Inherent in the process is a strong synergism between ground test and real-gas computational fluid dynamics (CFD). Approaches to develop and/or enhance phenomenological models and incorporate them into computational flow-field simulation codes are discussed. These models have been partially validated with experimental data for flows where the gas temperature is raised (compressive flows). Expanding flows, where temperatures drop, however, exhibit somewhat different behavior. Experimental data for these expanding flow conditions are sparse; reliance must be made on intuition and guidance from computational chemistry to model transport processes under these conditions. Ground-based experimental studies used to provide necessary data for model development and validation are described. Included are the performance characteristics of high-enthalpy flow facilities, such as shock tubes and ballistic ranges.

Deiwert, George S.↗
DOE OSTI2020

Ammonia Fiber Expansion (AFEX) Pretreatment of Lignocellulosic Biomass

Lignocellulosic materials are plant-derived feedstocks, such as crop residues (e.g., corn stover, rice straw, and sugar cane bagasse) and purpose-grown energy crops (e.g., miscanthus, and switchgrass) that are available in large quantities to produce biofuels, biochemicals, and animal feed. Plant polysaccharides (i.e., cellulose, hemicellulose, and pectin) embedded within cell walls are highly recalcitrant towards conversion into useful products. Ammonia fiber expansion (AFEX) is a thermochemical pretreatment that increases accessibility of polysaccharides to enzymes for hydrolysis into fermentable sugars. These released sugars can be converted into fuels and chemicals in a biorefinery. Here, we describe a laboratory-scale batch AFEX process to produce pretreated biomass on the gram-scale without any ammonia recycling. The laboratory-scale process can be used to identify optimal pretreatment conditions (e.g., ammonia loading, water loading, biomass loading, temperature, pressure, residence time, etc.) and generates sufficient quantities of pretreated samples for detailed physicochemical characterization and enzymatic/microbial analysis. The yield of fermentable sugars from enzymatic hydrolysis of corn stover pretreated using the laboratory-scale AFEX process is comparable to pilot-scale AFEX process under similar pretreatment conditions. This paper is intended to provide a detailed standard operating procedure for the safe and consistent operation of laboratory-scale reactors for performing AFEX pretreatment of lignocellulosic biomass.

09 BIOMASS FUELS↗
DOE OSTI2020

Nanoporous Catalysts for Biomass Conversion

Transforming plant biomass to biofuel and chemicals has become a global effort as results of increasing fuel demand but diminishing fossil-based energy preservation and rising concerns of climate and environmental impact. Various conversion routes involving thermochemical and biological conversions have been established and well-studied. Heterogeneous catalysis is playing a critical role in the biomass conversion and, with some unique catalytic properties, nanoporous catalysts have been extensively utilized in catalytic process of biomass conversion and exhibited exciting catalytic performance. This chapter will be devoted to nanoporous catalysts used in biomass conversion. It will start with a brief introduction of current biomass conversion technologies and then a detailed review of the application of various nanoporous materials in a large diversity of catalytic reactions in biomass conversion. The nanoporous materials include zeolites and zeotypes, metal-organic frameworks (MOFs), nanoporous carbons and carbon nitrides, nanoporous oxides, hydroxides and complex oxide forms, porous organic polymers (POPs), and porous metals.

Shi, Hui↗
DOE OSTI2018

Tritium Diffusion Pathways in y-LiAlO2 Pellets Used in TPBAR: A First-Principles Density Functional Theory Investigation

With superior thermophysical and thermochemical properties, gamma-LiAlO2 has high compatibility with other blanket materials and is used in the form of an annular pellet in tritium-producing burnable absorber rods (TPBARs) to produce tritium by thermal neutron irradiation of Li-6. In radiation damaged gamma-LiAlO2, different types of vacancies, defects of its constituent elements, and other trapping sites hinder the diffusion process of tritium. In this study, the first-principles density functional theory approach is used to study the diffusion mechanisms of tritium defect and its species, such as interstitial and substitutional tritium defects, oxygen-tritium vacancy defects, and interaction of tritium with oxygen vacancies in defective and nondefective gamma-LiAlO2. The obtained results provide an understanding of how such defects hamper the diffusivity and solubility of tritium. By calculating several different diffusion pathways, our results show that the smallest activation energy barrier is 0.63 eV for substitutional tritium diffusion with a diffusion coefficient of 3.25 X 10(-12) m(2)/s. The smallest oxygen-tritium diffusion barrier is found to be 2.17 eV, which is around 3.5 times higher than the tritium diffusion barrier alone.

Paudel, Hari↗
DOE OSTI2021

Opportunities and Challenges of Lignin Utilization

Lignin is the most abundant non-carbohydrate component of plant cell walls and the largest aromatic source on earth. It is gaining more attention due to its potentials for many industrial applications. Compared to the applications of carbohydrate components like cellulose and hemicellulose, the utilization of lignin is challenging due to its natural rigidity, heterogeneity, and complexity. On the other hand, the successful utilization of lignin can broaden the spectrum of renewable resources in producing chemicals, fuels, and materials. In addition, value-added lignin products can enhance the economic competitivity of many biofuels and biochemicals mainly produced from cellulose and hemicellulose. In the last few decades, there have been notable improvements in fundamental understandings of the plant cell wall, lignin chemistry, catalysis, and other engineering principles, as well as the development of diverse conversion and characterization technologies. Prior to the detailed discussions of recent lignin utilization strategies through decomposition approaches such as thermochemical, biological, photoelectrochemical and electrochemical depolymerization and material approaches including carbon materials, adsorbents, thermosets, thermoplastics, hydrogels and nanoparticles, this chapter briefly discusses the types of lignin and its potentials and limitations based on its characteristics and applied processes.

Geun yoo, Chang↗
NASA NTRS1972

Thermochemical nonequilibrium in atomic hydrogen at elevated temperatures

A numerical study of the nonequilibrium flow of atomic hydrogen in a cascade arc was performed to obtain insight into the physics of the hydrogen cascade arc. A rigorous mathematical model of the flow problem was formulated, incorporating the important nonequilibrium transport phenomena and atomic processes which occur in atomic hydrogen. Realistic boundary conditions, including consideration of the wall electrostatic sheath phenomenon, were included in the model. The governing equations of the asymptotic region of the cascade arc were obtained by writing conservation of mass and energy equations for the electron subgas, an energy conservation equation for heavy particles and an equation of state. Finite-difference operators for variable grid spacing were applied to the governing equations and the resulting system of strongly coupled, stiff equations were solved numerically by the Newton-Raphson method.

Scott, R. K.↗