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All sourcesNASA NTRSDOE OSTI
DOE OSTI2018

Cobalt and Yttrium Modified TiO{sub 2} Nanotubes Based Dye-Sensitized Solar Cells for Solar-Energy Conversion

The solar-energy conversion in eosin-sensitized solar cells based on cobalt and yttrium modified TiO2 nanotubes has been studied.It is established that the doping with metal ions shifts the absorption edge for Co and Y doped titanium dioxide samples to longer and shorter wavelengths, respectively. The efficiency of solar energy conversion depends on the wide bandgap of the semiconductor anode and reaches a maximum (4.4%) for yttrium-doped TiO{sub 2} in comparison to that (4.1%) for pure titanium dioxide.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2021

Method—Practices and Pitfalls in Voltage Breakdown Analysis of Electrochemical Energy-Conversion Systems

Many electrochemical energy-conversion systems are evaluated by polarization curves, which report the cell voltage across a range of current densities and are a global measure of operation and state of health. Mathematical models can be used to deconstruct the measured overall voltage and identify and quantify the voltage-loss sources, such as kinetic, ohmic, and mass-transport effects. These results elucidate the best pathways for improved performance. In this work, we discuss several voltage-breakdown methods and provide examples across different low-temperature, membrane-based electrochemical systems including electrolyzers, fuel cells, and related electrochemical energy-conversion devices. We present best practices to guide experimentalists and theorists in polarization-curve breakdown analysis.

30 DIRECT ENERGY CONVERSION↗
DOE OSTI2015

Mixed polyanion glass cathodes: Glass-state conversion reactions

Mixed polyanion (MP) glasses can undergo glass-state conversion (GSC) reactions to provide an alternate class of high-capacity cathode materials. GSC reactions have been demonstrated in phosphate/vanadate glasses with Ag, Co, Cu, Fe, and Ni cations. These MP glasses provided high capacity and good high power performance, but suffer from moderate voltages, large voltage hysteresis, and significant capacity fade with cycling. Details of the GSC reaction have been revealed by x-ray absorption spectroscopy, electron microscopy, and energy dispersive x-ray spectroscopy of ex situ cathodes at key states of charge. Using the Open Quantum Materials Database (OQMD), a computational thermodynamic model has been developed to predict the near-equilibrium voltages of glass-state conversion reactions in MP glasses.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Utilization of lignocellulosic biofuel conversion residue by diverse microorganisms

Lignocellulosic conversion residue (LCR) is the material remaining after deconstructed lignocellulosic biomass is subjected to microbial fermentation and treated to remove the biofuel. Technoeconomic analyses of biofuel refineries have shown that further microbial processing of this LCR into other bioproducts may help offset the costs of biofuel generation. Identifying organisms able to metabolize LCR is an important first step for harnessing the full chemical and economic potential of this material. In this study, we investigated the aerobic LCR utilization capabilities of 71 Streptomyces and 163 yeast species that could be engineered to produce valuable bioproducts. The LCR utilization by these individual microbes was compared to that of an aerobic mixed microbial consortium derived from a wastewater treatment plant as representative of a consortium with the highest potential for degrading the LCR components and a source of genetic material for future engineering efforts. We analyzed several batches of a model LCR by chemical oxygen demand (COD) and chromatography-based assays and determined that the major components of LCR were oligomeric and monomeric sugars and other organic compounds. Many of the Streptomyces and yeast species tested were able to grow in LCR, with some individual microbes capable of utilizing over 40% of the soluble COD. For comparison, the maximum total soluble COD utilized by the mixed microbial consortium was about 70%. This represents an upper limit on how much of the LCR could be valorized by engineered Streptomyces or yeasts into bioproducts. To investigate the utilization of specific components in LCR and have a defined media for future experiments, we developed a synthetic conversion residue (SynCR) to mimic our model LCR and used it to show lignocellulose-derived inhibitors (LDIs) had little effect on the ability of the Streptomyces species to metabolize SynCR. We found that LCR is rich in carbon sources for microbial utilization and has vitamins, minerals, amino acids and other trace metabolites necessary to support growth. Testing diverse collections of Streptomyces and yeast species confirmed that these microorganisms were capable of growth on LCR and revealed a phylogenetic correlation between those able to best utilize LCR. Identification and quantification of the components of LCR enabled us to develop a synthetic LCR (SynCR) that will be a useful tool for examining how individual components of LCR contribute to microbial growth and as a substrate for future engineering efforts to use these microorganisms to generate valuable bioproducts.

09 BIOMASS FUELS↗
DOE OSTI2018

Data from Increasing Ethanol Yield through Fiber Conversion in Corn Dry Grind Process

Conversion of corn fiber to ethanol in the dry grind process could increase ethanol yields, reduce downstream processing costs and improve overall process profitability. This work investigates the in-situ conversion of corn fiber into ethanol (cellulase addition during simultaneous saccharification and fermentation) during dry grind process. Addition of 30 FPU/g fiber cellulase resulted in 4.6% increase in ethanol yield compared to the conventional process. Use of excess cellulase (120 FPU/g fiber) resulted in incomplete fermentation and lower ethanol yield compared to the conventional process. Multiple factors including high concentrations of ethanol and phenolic compounds were responsible for yeast stress and incomplete fermentation in excess cellulase experiments.

Conversion↗
DOE OSTI2015

DOE-EFRC Center on Nanostructuring for Efficient Energy Conversion (CNEEC)

CNEEC’s mission has been to understand how nanostructuring of materials can enhance efficiency for solar energy conversion to produce hydrogen fuel and to solve fundamental cross-cutting problems. The overarching hypothesis underlying CNEEC research was that controlling, synthesizing and modifying materials at the nanometer scale increases the efficiency of energy conversion and storage devices and systems. In this pursuit, we emphasized the development of functional nanostructures that are based primarily on earth abundant and inexpensive materials.

08 HYDROGEN↗
DOE OSTI2016

A reload and startup plan for conversion of the NIST research reactor

The National Institute of Standards and Technology operates a 20 MW research reactor for neutron-based research. The heavy-water moderated and cooled reactor is fueled with high-enriched uranium (HEU) but a program to convert the reactor to low-enriched uranium (LEU) fuel is underway. Among other requirements, a reload and startup test plan must be submitted to the U.S. Nuclear Regulatory Commission (NRC) for their approval. The NRC provides guidance for what should be in the plan to ensure that the licensee has sufficient information to operate the reactor safely. Hence, a plan has been generated consisting of two parts. The reload portion of the plan specifies the fuel management whereby initially only two LEU fuel elements are in the core for eight fuel cycles. This is repeated until a point when the optimum approach is to place four fresh LEU elements into the reactor each cycle. This final transition is repeated and after eight cycles the reactor is completely fueled with LEU. By only adding two LEU fuel elements initially, the plan allows for the consumption of HEU fuel elements that are expected to be in storage at the time of conversion and provides additional qualification of production LEU fuel under actual operating conditions. Because the reload is to take place over many fuel cycles, startup tests will be done at different stages of the conversion. The tests, to be compared with calculations to show that the reactor will operate as planned, are the measurement of critical shim arm position and shim arm and regulating rod reactivity worths. An acceptance criterion for each test is specified based on technical specifications that relate to safe operation. Additional tests are being considered that have less safety significance but may be of interest to bolster the validation of analysis tools.

22 GENERAL STUDIES OF NUCLEAR REACTORS↗
DOE OSTI2015

Research and Development of Multiphysics Models in Support of the Conversion of the High Flux Isotope Reactor to Low Enriched Uranium Fuel

The findings presented in this report are results of a five year effort led by the RRD Division of the ORNL, which is focused on research and development toward the conversion of the High Flux Isotope Reactor (HFIR) fuel from high-enriched uranium (HEU) to low-enriched uranium (LEU). This report focuses on the tasks accomplished by the University of Tennessee Knoxville (UTK) team from the Department of Mechanical, Aerospace, and Biomedical Engineering (MABE) that provided expert support in multiphysics modeling of complex problems associated with the LEU conversion of the HFIR reactor. The COMSOL software was used as the main computational modeling tool, whereas Solidworks was also used in support of computer-aided-design (CAD) modeling of the proposed LEU fuel design. The UTK research has been governed by a statement of work (SOW), which was updated annually to clearly define the specific tasks reported herein. Ph.D. student Isaac T. Bodey has focused on heat transfer and fluid flow modeling issues and has been aided by his major professor Dr. Rao V. Arimilli. Ph.D. student Franklin G. Curtis has been focusing on modeling the fluid-structure interaction (FSI) phenomena caused by the mechanical forces acting on the fuel plates, which in turn affect the fluid flow in between the fuel plates, and ultimately the heat transfer, is also affected by the FSI changes. Franklin Curtis has been aided by his major professor Dr. Kivanc Ekici. M.Sc. student Adam R. Travis has focused two major areas of research: (1) on accurate CAD modeling of the proposed LEU plate design, and (2) reduction of the model complexity and dimensionality through interdimensional coupling of the fluid flow and heat transfer for the HFIR plate geometry. Adam Travis is also aided by his major professor, Dr. Kivanc Ekici. We must note that the UTK team, and particularly the graduate students, have been in very close collaboration with Dr. James D. Freels (ORNL technical monitor and mentor) and have benefited greatly from his leadership and expertise in COMSOL modeling of complex physical phenomena. Both UTK and ORNL teams have used COMSOL releases 3.4 through 5.0 inclusive (with particular emphasis on 3.5a, 4.3a, 4.3b, and 4.4) for most of the work described in this report, except where stated otherwise. Just as in the performance of the research, each of the respective sections has been originally authored by respective authors. Therefore, the reader will observe a contrast in writing style throughout this document.

22 GENERAL STUDIES OF NUCLEAR REACTORS↗
DOE OSTI2017

Life-Cycle Analysis of Greenhouse Gas Emissions and Water Consumption – Effects of Coal and Biomass Conversion to Liquid Fuels as Analyzed with the GREET Model

The vast reserves of coal in the U.S. provide a significant incentive for the development of processes for coal conversion to liquid fuels (CTL). Also, CTL using domestic coal can help move the U.S. toward greater energy independence and security. However, current conversion technologies are less economically competitive and generate greater greenhouse gas (GHG) emissions than production of petroleum fuels. Altex Technologies Corporation (Altex, hereinafter) and Pennsylvania State University have developed a hybrid technology to produce jet fuel from a feedstock blend of coal and biomass. Collaborating with Altex, Argonne National Laboratory has expanded and used the Greenhouse gases, Regulated Emissions, and Energy use in Transportation (GREET®) model to assess the life-cycle GHG emissions and water consumption of this hybrid technology. Biomass feedstocks include corn stover, switchgrass, and wheat straw. The option of biomass densification (bales to pellets) is also evaluated in this study. The results show that the densification process generates additional GHG emissions as a result of additional biomass process energy demand. This process coproduces a large amount of char, and this study investigates two scenarios to treat char: landfill disposal (Char-LF) and combustion for combined heat and power (CHP). Since the CHP scenarios export excess heat and electricity as coproducts, two coproduct handling methods are used for well-to-wake (WTWa) analysis: displacement (Char-CHP-Disp) and energy allocation (Char-CHP-EnAllo). When the feedstock contains 15 wt% densified wheat straw and 85 wt% lignite coal, WTWa GHG emissions of the coal-and-biomass-to-liquid pathways are 116, 97, and 137 gCO2e per megajoule (MJ) under the Char-LF, Char-CHP-Disp, and Char-CHP-EnAllo scenarios, respectively, as compared to conventional jet fuel production at 84 gCO2e/MJ. WTWa water consumption values are 0.072, -0.046, and 0.044 gal/MJ for Char-LF, Char-CHP-Disp, and Char-CHP-EnAllo, respectively, as compared to conventional jet fuel production at 0.028 gal/MJ. To reach the break-even point of 84 gCO2e/MJ, under the assumptions of constant product yields and energy demands regardless of the share of biomass and coal feedstocks, 31 wt%, 23 wt%, and 53 wt% of the feedstock blend need to be biomass under the Char-LF, Char-CHP-Disp, and Char-CHP-EnAllo scenarios, respectively.

09 BIOMASS FUELS↗
DOE OSTI2021

Algal Biomass Conversion to Fuels via Combined Algae Processing (CAP): 2020 State of Technology and Future Research

The annual State of Technology (SOT) assessment is an essential activity for platform research conducted under the Bioenergy Technologies Office. It allows for the impact of research progress to be quantified in terms of economic improvements in the overall biofuel production process for a particular biomass processing pathway, whether based on terrestrial or algal biomass feedstocks. As such, initial benchmarks can be established for currently demonstrated performance, and progress can be tracked towards out-year goals to ultimately demonstrate economically viable biofuel technologies. NREL's algae state of technology benchmarking efforts focus both on front-end algal biomass production and separately on back-end conversion to fuels through NREL's "combined algae processing" (CAP) pathway. The production model is based on outdoor long-term cultivation data, enabled by comprehensive algal biomass production trials conducted under the Development of Integrated Screening, Cultivar Optimization, and Verification Research consortium (DISCOVR) efforts, driven by data furnished by Arizona State University (ASU) at the Arizona Center for Algae Technology and Innovation (AzCATI) testbed site. The CAP model is based on experimental efforts conducted under NREL research and development projects. This report focuses on back-end conversion of algal biomass through the CAP pathway, highlighting the 2020 updates to minimum fuel selling price (MFSP). Notably, this analysis marks the first time that polyurethane (PU) is included as a value-added coproduct in the SOT case. Relative to prior 2019 benchmarks, the 2020 CAP SOT achieved further MFSP reductions of over $4/gallon gasoline equivalent, reflective of (a) the inclusion of PU co-production, (b) reduced SOT biomass production costs, and (c) higher pretreatment sugar yield data.

09 BIOMASS FUELS↗
DOE OSTI2022

Algal Biomass Conversion to Fuels via Combined Algae Processing (CAP) (2021 State of Technology and Future Research)

The annual State of Technology (SOT) assessment is an essential activity for platform research conducted under the Bioenergy Technologies Office. It allows for the impact of research progress to be quantified in terms of economic improvements in the overall biofuel production process for a particular biomass processing pathway, whether based on terrestrial or algal biomass feedstocks. As such, initial benchmarks can be established for currently demonstrated performance, and progress can be tracked towards out-year goals to ultimately demonstrate economically viable biofuel technologies. NREL's algae state of technology benchmarking efforts focus both on front-end algal biomass production and separately on back-end conversion to fuels through NREL's "combined algae processing" (CAP) pathway. The production model is based on outdoor long-term cultivation data, enabled by comprehensive algal biomass production trials conducted under the Development of Integrated Screening, Cultivar Optimization, and Verification Research consortium (DISCOVR) efforts, driven by data furnished by Arizona State University (ASU) at the Arizona Center for Algae Technology and Innovation (AzCATI) testbed site. The CAP model is based on experimental efforts conducted under NREL research and development projects. This report focuses on back-end conversion of algal biomass through the CAP pathway, highlighting the 2021 updates to minimum fuel selling price (MFSP). This update maintains an important recent inclusion of polyurethane (PU) previously incorporated in the 2020 SOT as a value-added coproduct. Relative to the 2020 SOT case, this indicates a minimal increase of $0.10-$0.14/GGE (roughly 2%) for both the acids and BDO pathways, attributed to minimal increases in upstream algal biomass costs from slightly lower demonstrated cultivation productivities in the 2021 SOT.

09 BIOMASS FUELS↗
DOE OSTI2018

Radioisotope Power Systems: Considerations for use of Dynamic versus Static Conversion Technologies for NASA Missions

For more than five decades, Radioisotope Power Systems (RPS) have played a critical role in the exploration of space, enabling missions of scientific discovery to destinations across the solar system by providing electrical power to explore remote, challenging and extreme environments. In particular, RPS enable deep space missions where increased heliocentric distances reduce the ability of solar power to adequately meet spacecraft and instruments power requirements. Some previous notable missions that were enabled by RPS include Nimbus III, the Apollo Sur-face Experiments, the Pioneers 10 and 11, the Viking Mars Landers, Galileo, Ulysses, Cassini, New Horizons and Curiosity. The current operating set of missions that are enabled by RPS are Voyagers 1 and 2, Cassini, New Hori-zons, and Curiosity. The Multi-Mission Radioisotope Thermal Generator (MMRTG) is the current RPS used for mis-sions. An enhanced version of this generator outfitted with higher efficiency thermoelectrics is under development for potential use in the future. There are also current development efforts underway by NASA to explore dynamic power conversion systems such as Brayton and Stirling. This paper will compare and contrast the pros and cons of a generalized dynamic system with the current state-of-the-art thermoelectric static conversion system. The reason for this paper is to calmly analyze the pros and cons so that all the pertinent factors are placed under the same examination light with equal brightness. As with any purchase made the “newness” of certain items sometimes overrides a needed desire to fully vet all characteristics of the merchandise so that the best choice is made. The following areas will be specifically examined and discussed as they may impact the choice of radioisotope power system for a specific mission: • Projected power output to weight ratio (We/kg) • Amount of Pu-238 required per a fixed power output • Excess heat available to be rejected or used • Fueling operations during assembly by the Department of Energy (DOE) • Planetary protection protocol during fueling and testing of RPS • Transportation operations from DOE assembly site to Kennedy Space Center (KSC) • Remote operations at KSC prior to launch during Assembly Test and Launch Operations (ATLO) phase o Timing of the placement of the RPS onto spacecraft/rover o Off-normal operations at KSC

99 GENERAL AND MISCELLANEOUS↗
DOE OSTI2019

Conversion of Diesel Engines to a Gas and Gas–Diesel Cycle

The conversion of diesel engines to gas and gas–diesel cycles during the production process is analyzed. The requirements for conversion to natural-gas operation are presented. The power, efficiency, and environmental impact of diesel engines, natural-gas engines, and gas–diesel engines are compared.

42 ENGINEERING↗
DOE OSTI2023

Modeling of Liquid Hydrogen Tank Cooled with Para-Orthohydrogen Conversion

With the accelerating development of liquid-hydrogen storage facilities, the problem of boil-off hydrogen losses becomes very important. A promising method to reduce these losses is to utilize the endothermic para-orthohydrogen conversion of vented hydrogen, which can effectively decrease heat loads on a hydrogen tank. To model such a process, a hybrid computational model has been developed, based on the application of computational fluid dynamics for an ullage space, where knowledge of thermal stratification is important, and reduced-order models for other system elements. The simulation results for a spheroidal tank in selected conditions indicated a 10–25% reduction of boil-off losses due to cooling produced by vented hydrogen undergoing para-ortho-conversion.

08 HYDROGEN↗
DOE OSTI2016

EXPLAINING INVERTED-TEMPERATURE LOOPS IN THE QUIET SOLAR CORONA WITH MAGNETOHYDRODYNAMIC WAVE-MODE CONVERSION

Coronal loops trace out bipolar, arch-like magnetic fields above the Sun’s surface. Recent measurements that combine rotational tomography, extreme-ultraviolet imaging, and potential-field extrapolation have shown the existence of large loops with inverted-temperature profiles, i.e., loops for which the apex temperature is a local minimum, not a maximum. These “down loops” appear to exist primarily in equatorial quiet regions near solar minimum. We simulate both these and the more prevalent large-scale “up loops” by modeling coronal heating as a time-steady superposition of (1) dissipation of incompressible Alfvén wave turbulence and (2) dissipation of compressive waves formed by mode conversion from the initial population of Alfvén waves. We found that when a large percentage (>99%) of the Alfvén waves undergo this conversion, heating is greatly concentrated at the footpoints and stable “down loops” are created. In some cases we found loops with three maxima that are also gravitationally stable. Models that agree with the tomographic temperature data exhibit higher gas pressures for “down loops” than for “up loops,” which is consistent with observations. These models also show a narrow range of Alfvén wave amplitudes: 3 to 6 km s{sup -1} at the coronal base. This is low in comparison to typical observed amplitudes of 20–30 km s{sup -1} in bright X-ray loops. However, the large-scale loops we model are believed to compose a weaker diffuse background that fills much of the volume of the corona. By constraining the physics of loops that underlie quiescent streamers, we hope to better understand the formation of the slow solar wind.

79 ASTRONOMY AND ASTROPHYSICS↗
NASA NTRS2007

Thermoelectric Energy Conversion: Future Directions and Technology Development Needs

This viewgraph presentation reviews the process of thermoelectric energy conversion along with key technology needs and challenges. The topics include: 1) The Case for Thermoelectrics; 2) Advances in Thermoelectrics: Investment Needed; 3) Current U.S. Investment (FY07); 4) Increasing Thermoelectric Materials Conversion Efficiency Key Science Needs and Challenges; 5) Developing Advanced TE Components & Systems Key Technology Needs and Challenges; 6) Thermoelectrics; 7) 200W Class Lightweight Portable Thermoelectric Generator; 8) Hybrid Absorption Cooling/TE Power Cogeneration System; 9) Major Opportunities in Energy Industry; 10) Automobile Waste Heat Recovery; 11) Thermoelectrics at JPL; 12) Recent Advances at JPL in Thermoelectric Converter Component Technologies; 13) Thermoelectrics Background on Power Generation and Cooling Operational Modes; 14) Thermoelectric Power Generation; and 15) Thermoelectric Cooling.

theromelectric↗
NASA NTRS2014

Gas Turbine Energy Conversion Systems for Nuclear Power Plants Applicable to LiFTR Liquid Fluoride Thorium Reactor Technology

This panel plans to cover thermal energy and electric power production issues facing our nation and the world over the next decades, with relevant technologies ranging from near term to mid-and far term.Although the main focus will be on ground based plants to provide baseload electric power, energy conversion systems (ECS) for space are also included, with solar- or nuclear energy sources for output power levels ranging tens of Watts to kilo-Watts for unmanned spacecraft, and eventual mega-Watts for lunar outposts and planetary surface colonies. Implications of these technologies on future terrestrial energy systems, combined with advanced fracking, are touched upon.Thorium based reactors, and nuclear fusion along with suitable gas turbine energy conversion systems (ECS) will also be considered by the panelists. The characteristics of the above mentioned ECS will be described, both in terms of their overall energy utilization effectiveness and also with regard to climactic effects due to exhaust emissions.

Energy Conversion↗
NASA NTRSDate not supplied

Brayton Cycle Power Conversion Model for MW-Class Nuclear Electric Propulsion Mars Missions

A Brayton cycle based power conversion system for a nuclear electric propulsion application was modeled in Simulink as part of NASA’s space nuclear program in order to explore the impact of technology assumptions on the power conversion system performance and capabilities. The thermodynamic processes and algorithms within the model are documented, including a higher fidelity reactor model. Assumptions are chosen based on literature and subject matter expert review, and example results and capabilities of the model are shown. The effects of the turbine inlet and compressor inlet temperature on radiator area and thermal efficiency are discussed. For a He-Xe closed Brayton cycle, radiator areas as low as 650 m2/MWe are shown, with corresponding thermal efficiences at roughly 20% for the minimal radiator area solutions.

Brayton↗