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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 613 records · Page 34
All sourcesNASA NTRSDOE OSTI
DOE OSTI2022

LaNi x Fe 1–x O 3 as flexible oxygen or carbon carriers for tunable syngas production and CO 2 utilization

The current study reports LaFe 1–x Ni x O 3–δ redox catalysts as flexible oxygen or carbon carriers for CO2 utilization and tunable production of syngas at relatively low temperatures (~700 °C), in the context of a hybrid redox process. Specifically, perovskite-structured LaFe 1–x Ni x O 3–δ with seven different compositions (x = 0.4–1) were prepared and investigated. Cyclic experiments under alternating methane and CO 2 flows indicated that all the samples exhibited favorable reactive performance: CH 4 and CO 2 conversions varied between 85% and 98% and 70–88%, respectively. While H 2 /CO ratio from Fe-rich redox catalysts was ~2.3:1 in the methane conversion step, Ni-rich catalysts produced a concentrated (~ 93.7 vol%) hydrogen stream via methane cracking. The flexibility of LaFe 1–x Ni x O 3–δ to produce syngas (or hydrogen) with tunable compositions was found to be governed by the iron/nickel (Fe/Ni) ratio. Redox catalysts with higher Fe contents act as a lattice oxygen carrier via chemical looping partial oxidation (CLPOx) of methane whereas those with higher Ni contents function as a carbon carrier via chemical looping methane cracking (CLMC) scheme. XRD analysis and temperature-programmed reactions revealed that both types of catalysts involve the formation of La 2 O 3 and Ni 0 /Ni-Fe phases under the methane environment. The ability to re-incorporate La 2 O 3 and Ni/Fe into a perovskite structure gives rise to oxygen-carrying capacity whereas stable Ni 0 or Ni/Fe phases would catalyze methane cracking without lattice oxygen exchange in the reaction cycles. Here, temperature programmed oxidation and Raman spectroscopy indicated the presence of graphitic and amorphous carbon species, which were effectively gasified by CO 2 to produce concentrated CO. Stability tests over LaFe 0.5 Ni 0.5 O 3 and LaNiO 3 revealed that the redox performance was stable over a span of 50 cycles.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2013

Geomechanical effects on CO 2 leakage through fault zones during large-scale underground injection

The importance of geomechanics—including the potential for faults to reactivate during large-scale geologic carbon sequestration operations—has recently become more widely recognized. However, notwithstanding the potential for triggering notable (felt) seismic events, the potential for buoyancy-driven CO 2 to reach potable groundwater and the ground surface is actually more important from public safety and storage-efficiency perspectives. In this context, this paper extends the previous studies on the geomechanical modeling of fault responses during underground carbon dioxide injection, focusing on the short-term integrity of the sealing caprock, and hence on the potential for leakage of either brine or CO 2 to reach the shallow groundwater aquifers during active injection. We consider stress/strain-dependent permeability and study the leakage through the fault zone as its permeability changes during a reactivation, also causing seismicity. We analyze several scenarios related to the volume of CO 2 injected (and hence as a function of the overpressure), involving both minor and major faults, and analyze the profile risks of leakage for different stress/strain-permeability coupling functions. We conclude that whereas it is very difficult to predict how much fault permeability could change upon reactivation, this process can have a significant impact on the leakage rate. Moreover, our analysis shows that induced seismicity associated with fault reactivation may not necessarily open up a new flow path for leakage. Results show a poor correlation between magnitude and amount of fluid leakage, meaning that a single event is generally not enough to substantially change the permeability along the entire fault length. Finally, and consequently, even if some changes in permeability occur, this does not mean that the CO 2 will migrate up along the entire fault, breaking through the caprock to enter the overlying aquifer.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2020

Investigation of structural effects of aromatic compounds on sooting tendency with mechanistic insight into ethylphenol isomers

Small aromatic molecules with oxygen-containing functional groups are a promising class of fuel additives, as they can be readily sourced from depolymerized lignin. These oxygenated aromatic compounds (OACs) show a lower sooting tendency than aromatic hydrocarbons, but OACs having alkyl groups such as ethylphenol show a higher sooting tendency than other OACs such as phenol and anisole, despite the oxygen moiety. In this study, we investigate the relationship between chemical structure and soot precursor formation to explain observed differences in the sooting tendency of OACs and to gain insight into how alkyl or oxygenated substituents on the aromatic ring affect soot precursor formation. The weakest bond for 15 aromatic compounds was identified and cleavage of these bonds was shown to generate either benzyl or phenoxy radicals. A linear relationship between standard enthalpy of formation (ΔH f o ) of these radicals and the yield sooting index (YSI) was found, and thus ΔH f ° can be applied as a metric to estimate YSIs of various aromatic compounds; higher ΔH f o of a radical indicates an increase in the radical reactivity and leads to more soot precursor formation. Flow reactor experiments were performed for 2-ethylphenol and 3-ethylphenol to elucidate how ortho and meta substitution effects the sooting tendency. Soot precursors were identified from the experiment and their formation pathways were investigated computationally. 2-ethylphenol produces more oxygenated products than 3-ethylphenol since the ortho position has increased resonance stabilization of radical intermediates, which leads to lower YSI. Overall, these results further inform the selection of potential biomass-derived fuel blendstocks that have favorable sooting tendencies.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2014

Super-Resolution Mapping of Photogenerated Electron and Hole Separation in Single Metal-Semiconductor Nanocatalysts

Metal–semiconductor heterostructures are promising visible light photocatalysts for many chemical reactions. Here, we use high-resolution superlocalization imaging to reveal the nature and photocatalytic properties of the surface reactive sites on single Au–CdS hybrid nanocatalysts. We experimentally reveal two distinct, incident energy-dependent charge separation mechanisms that result in completely opposite photogenerated reactive sites (e– and h+) and divergent energy flows on the hybrid nanocatalysts. We find that plasmon-induced hot electrons in Au are injected into the conduction band of the CdS semiconductor nanorod. The specifically designed Au-tipped CdS heterostructures with a unique geometry (two Au nanoparticles at both ends of each CdS nanorod) provide more convincing high-resolution single-turnover mapping results and clearly prove the two charge separation mechanisms. Engineering the direction of energy flow at the nanoscale can provide an efficient way to overcome important challenges in photocatalysis, such as controlling catalytic activity and selectivity. These results bear enormous potential impact on the development of better visible light photocatalysts for solar-to-chemical energy conversion.

36 MATERIALS SCIENCE↗
DOE OSTI2022

A Geo‐Structurally Based Correction Factor for Apparent Dissolution Rates in Fractured Media

Abstract Field measurements of apparent geochemical weathering reaction rates in subsurface fractured porous media are known to deviate from laboratory measurements by multiple orders of magnitude. To date, there is no geologically based explanation for this discrepancy that can be used to predict reaction rates in field systems. Proposed correction factors are typically based on ad hoc characterizations related to geochemical kinetic models. Through a series of high‐fidelity reactive transport simulations of mineral dissolution within explicit 3D discrete fracture networks, we are able to link the geo‐structural attributes with reactive transport observations. We develop a correction factor to linear transition state theory for the prediction of the apparent dissolution rate based on measurable geological properties. The modified rate law shows excellent agreement with numerical simulations, indicating that geological structure could be a primary reason for the discrepancy between laboratory and field observations of apparent dissolution rates in fractured media.

58 GEOSCIENCES↗
DOE OSTI2019

N2O5 Reactive Uptake Kinetics and Chlorine Activation on Authentic Biomass-Burning Aerosol

We examined the reactive uptake of dinitrogen pentoxide (N2O5) to authentic biomass-burning aerosol (BBA) using a small chamber reservoir in combination with an entrained aerosol flow tube. BBA was generated from four different fuel types and the reactivity of N2O5 was probed from 30 to 70% relative humidity (RH). The N2O5 reactive uptake coefficient, ?(N2O5), depended upon RH, fuel type, and to a lesser degree on aerosol chloride mass fractions. The ?(N2O5) ranged from 2.0 (±0.4) x10-3 on black needlerush derived BBA at 30% RH to 6.0 (±0.6) x10-3 on wiregrass derived BBA at 65% RH. Major N2O5 reaction products were observed including gaseous ClNO2 and HNO3 and particulate nitrate, and used to create a reactive nitrogen budget. Black needlerush BBA had the most particulate chloride, and the only measured ClNO2 yield > 1%. The ClNO2 yield on black needlerush decayed from an initial value of ~100% to ~ 30% over the course of the burn experiment, suggesting a depletion of BBA chloride over time. Black needlerush was also the only fuel for which the reactive nitrogen budget indicated other N-containing products were generated. Generally, the results suggest limited chloride availability for heterogeneous reaction for BBA in the RH range probed here, including BBA with chloride mass fractions on the higher end of reported values (~17-34%)(1,2). though less than sea spray aerosol, ~50%(3). We use these measured quantities to discuss the implications for nocturnal aerosol nitrate formation, the chemical fate of N2O5 (g), and the availability of particulate chloride for activation in biomass burning plumes.

Goldberger, Lexie A.↗
DOE OSTI2015

Activation of cyclic electron flow by hydrogen peroxide in vivo

Significance Cyclic electron flow around photosystem I (CEF) is critical for balancing the energy budget of photosynthesis, but its regulation is not well understood. Our results provide evidence that hydrogen peroxide, which is produced as a result of imbalances in chloroplast redox state, acts as a signaling agent to activate CEF in higher plants in vivo.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2019

Chance Constraints for Improving the Security of AC Optimal Power Flow

This paper introduces a scalable method for improving the solutions of ac optimal power flow (AC OPF) with respect to deviations in predicted power injections from wind and other uncertain generation resources. The aim of this paper is on providing solutions that are more robust to short-term deviations, and that optimize both the initial operating point and a parametrized response policy for control during fluctuations. We formulate this as a chance-constrained optimization problem. To obtain a tractable representation of the chance constraints, we introduce a number of modeling assumptions and leverage recent theoretical results to reformulate the problem as a convex, second-order cone program, which is efficiently solvable even for large instances. Our experiments demonstrate that the proposed procedure improves the feasibility and cost performance of the OPF solution, while the additional computation time is on the same magnitude as a single deterministic AC OPF calculation.

24 POWER TRANSMISSION AND DISTRIBUTION↗
DOE OSTI2016

Simulation of Hydraulic and Natural Fracture Interaction Using a Coupled DFN-DEM Model

The presence of natural fractures will usually result in a complex fracture network due to the interactions between hydraulic and natural fracture. The reactivation of natural fractures can generally provide additional flow paths from formation to wellbore which play a crucial role in improving the hydrocarbon recovery in these ultra-low permeability reservoir. Thus, accurate description of the geometry of discrete fractures and bedding is highly desired for accurate flow and production predictions. Compared to conventional continuum models that implicitly represent the discrete feature, Discrete Fracture Network (DFN) models could realistically model the connectivity of discontinuities at both reservoir scale and well scale. In this work, a new hybrid numerical model that couples Discrete Fracture Network (DFN) and Dual-Lattice Discrete Element Method (DL-DEM) is proposed to investigate the interaction between hydraulic fracture and natural fractures. Based on the proposed model, the effects of natural fracture orientation, density and injection properties on hydraulic-natural fractures interaction are investigated.

Discrete Fracture Network↗
DOE OSTI2017

A VISCOELASTIC MODEL FOR EVALUATING EXTRUSION-BASED PRINT CONDITIONS

Extrusion-based printing systems have improved significantly over the past several years, allowing for higher throughput, higher temperatures, and larger components. At the same time, advanced materials are being introduced on the market that can provide improved performance over a range of operating conditions. Often these materials incorporate fiber reinforcements, reactive resins, and additives to control reaction kinetics, flow rheology, or thermal stability. This study presents a general framework for evaluating the printability of various candidate materials based on a basic viscoelastic model. The model addresses fundamental requirements for extrusion-based printing, including pressure-driven flow, bead formation, bead functionality, and component-level functionality. The effectiveness of this model for evaluating the impact of compositional variations and identifying appropriate processing conditions has been demonstrated for specific materials on direct write, fused filament fabrication, and large-scale extrusion platforms.

Duty, Chad↗
DOE OSTI2019

System for the highly autonomous operation of a modular liquid-metal reactor with steam cycle

The invention relates to a nuclear plant in which the power of a nuclear reactor is controlled via demand of a connected electric grid. A naturally circulating nuclear reactor coolant loop is linked to a water/steam loop by means of a steam generator. The water/steam loop consists of an electric power generating unit and a water recirculating and steam control system. The generator is coupled to an external power grid. As power requirements of the grid change, a controller linked to the generator and a three way valve divides steam flow between the expansion turbine and a feedwater heater to boost or retard the power output. Altering the steam flow changes the pressure and temperature in the water/steam system and thus the coolant flow rate. The change in coolant flow allows the reactor core to regulate its reactivity to reach a state of equilibrium to the demand for electric power.

Vilim, Richard B.↗
DOE OSTI2022

Rapid manufacturing of tailored preforms

A method for rapid manufacturing of three dimensional discontinuous fiber preforms is provided. The method includes the deposition of a polymeric material containing fibers on a surface to form a tailored charge for compression molding. The reinforced polymeric material may be a thermoplastic or a reactive polymer with viscosity low enough to allow flow through an orifice during deposition, yet high enough zero shear viscosity to retain the approximate shape of the deposited charge. The material can be deposited in a predetermined pattern to induce the desired mechanical properties through alignment of the fibers. This deposition can be performed in a single layer or in multiple layers. The alignment is achieved passively by shear alignment of the fibers or actively through fiber orientation control or mixing. The fibers can be of the desired material, length, and morphology, including short and long filaments.

Kunc, Vlastimil↗
DOE OSTI2016

Artificial Neural Network Representation of Dynamic Criticality Excursion Experiment Data

This paper outlines time dependent considerations in applying the artificial neural network (ANN) paradigm to dynamic nuclear criticality excursion experiment data. The ANN amongst a variety of uses, can apply to function fitting of multiple input-multiple output data sets, pattern recognition, cluster analysis, and time series prediction. The ANN is a component of Machine Learning (ML) data analysis. The practical application of ML to criticality safety has been funded through the Y-12 Plant Directed Research and Demonstration (PDRD) program to support criticality safety and emergency planning efforts. The initial effort considered function fitting of criticality excursion data. Recent efforts successfully extended the ANN to criticality safety code validation. The initial ANN work applied to criticality excursions centered around multivariate function fitting of static (tabular) data taken from the French Consequences Radiologiques d'un Accident de Criticite (CRAC) and SILENE reactor campaigns. The former report (LeCorche) summarized important tabular data for the first 44 CRAC experiments. The initial ANN was trained to specific time-independent inputs, then applied to predict peak fission rate and total fissions for a wide variety of fissile solutions process conditions. This work extends that effort to apply the ANN paradigm to dynamic prediction of time-dependent criticality excursion experiment data. A dynamic criticality excursion in fissile solution represents a complex multiphysics phenomenon. Factors include among other things, coupled neutronic, multiphase fluid flow, temperature, pressure, acoustic shock, boiling heat transfer, reactivity feedback, and radiolytic gas considerations. There have been many efforts to model (over time) as coupled ordinary and (space) as partial differential equations (ODE, PDE). The ANN representation noted here does not rely on solving explicit ODE or PDEs. Rather the intent is to demonstrate that as a time series, the criticality excursion can be predicted by training specific ANN architectures to experimental input and output time series exclusively. The rationale for extending this work to the time-dependent regime is important in developing a 'criticality excursion emulator' solely on the basis of learning characteristics from experiment dynamic data. An emulator is different than a computer code simulator driven by the solution of ODEs and PDEs given select 'tuning parameters' that match outputs to experiments. A criticality excursion emulator, derived exclusively from an ANN or ML, could predict most likely excursion characteristics, trained from historic dynamic experiment data, presented with input values within the range of those experiments. The work noted shows that generic time-series ANN architectures can be satisfactorily applied to the prediction of dynamic, extremely chaotic criticality excursion power given an initial time dependent input series. In reality, an excursion emulator could be driven by user-supplied initial (t=0), time independent or constant values to generate time dependent outputs. Thus ongoing work includes developing a custom ANN such that initial dynamic conditions would be predicted. Those results then serve as inputs to a customized ANN architecture currently in development. (author)

42 ENGINEERING↗
DOE OSTI2022

Coupled neutronic-thermal-hydraulic simulations of the European SFR core

Within the European SFR (Sodium-cooled Fast Reactor) - Safety Measures Assessment and Research Tools (ESFR-SMART) project, steady-state coupled simulation of the ESFR core has been performed using several core analysis packages, with the objective of quantifying the coupling effect. Focus is on the fuel Doppler effect and coolant expansion effect. Standalone neutronics calculations in TRACE/PARCS (PSI), DYN3D (HZDR) and WIMS (Jacobs) showed superb agreement with the reference Serpent power distribution (root mean square - rms discrepancies of 1.3%, 1.5% and 0.7% respectively). Results for COUNTHER (CIEMAT) were also in reasonable agreement, but with a somewhat higher discrepancy of 3.7%. Temperature distributions from thermal-hydraulic calculations were also compared and are found to be in good agreement. The effect of Doppler and coolant density feedback on core power distribution was predicted by TRACE/PARCS, DYN3D and WIMS to be between 0.4% and 0.8% rms difference in assembly powers. Reactivity coefficients for perturbations in the inlet temperature, flow rate and core power were shown to be negative for these three codes, with values of roughly -0.5 pcm/C. degree, -0.3 pcm/C. degree and -3.5 pcm/C. degree respectively. A preliminary investigation of differential thermal expansion effects indicates that this may have a significant effect on core power distribution of a few %, greater than anticipated a priori and may warrant inclusion in coupled core analysis to ensure the accurate calculation of power distributions. (authors)

21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS↗
DOE OSTI2023

Fairness-Aware Distributed Energy Coordination for Voltage Regulation in Power Distribution Systems

The accelerating deployment of solar photovoltaics into low-voltage distribution networks can cause reverse power flow and overvoltage problems. However, if coordinated properly, the real and reactive power flexibility of these resources enables distribution operators to manage their networks more efficiently. Existing literature is rich in droop-based control (Volt-Watt and Volt-VAr) and optimization-based distributed energy coordination for four-quadrant control of photovoltaics to prevent overvoltage issues. While optimal coordination can effectively mitigate overvoltage, it tends to treat resources at sensitive parts of the grid unfairly. Here, to address this concern, we propose a distributed optimal power flow formulation that incorporates fairness in curtailing photovoltaic generation and utilizes the reactive power capability of smart inverters. The proposed distributed formulation allows for scalable resource aggregation that can be leveraged to achieve fairness within a certain segment of the grid and/or fairness across the entire network. Fair curtailment of photovoltaic systems is demonstrated with aggregation at each of two layers in a distribution network: 1) area-level fairness and 2) feeder-level fairness. To explore the trade-off between fairness and optimal utilization, the fairness-aware control actions are compared against the performance of a centralized controller that aims to maximize the aggregate PV generation without incorporating fairness. Simulation results show that introducing area-level fairness increased curtailment by 0.0101 percentage points and feeder-level fairness increased curtailment by 0.0458 percentage points compared to a fairness-agnostic control.

Poudel, Shiva↗
DOE OSTI2023

Immune checkpoint analysis of T‐cell responses to pp65 and IE‐1 antigens in end‐stage lung diseases

Abstract Lung transplant (LTX) patients are at high risk of cytomegalovirus (CMV) infection, which is often associated with high mortality and morbidity. Reactivation of CMV causes cell injury due to the cytopathic effect of viral replication and triggering of T cell immunity. The aim of this study was to compare expression of immune checkpoints (ICs) (PD‐1, CTLA‐4, LAG‐3 and TIGIT) in CD4, CD8 and CD56 and activation markers CD137, CD154 and CD69 of end‐stage patients awaiting lung transplant. Eighteen pre‐LTX positive for anti‐CMV IgG titres and 18 healthy subjects were enrolled. IC and activation markers have been evaluated through flow cytometric analysis in HC and pre‐LTX patients. Reactive (QF+) and unreactive (QF−) patients were stratified according to QuantiFERON‐CMV assays. ICs' and activation markers' expression were determined before and after in vitro stimulation with pp‐65 and IE‐1 antigens. Lower expression of PD‐1 was observed in CD4 and CD8 cells of pre‐LTX patients than controls, whereas CTLA4 appeared upregulated in CD56 and CD8 cells. TIGIT is increased on the surface of CD4, CD8 and NK cells after peptide stimulation in QF‐negative patients and PD‐1 is only downregulated after stimulation in the QF‐positive patients. This study provides new evidence of immune dysregulation in patients with end‐stage lung disorders, particularly in relation to immune checkpoint cell biology. The change in QF+ mostly happens on cytotoxic cells NK and CD8, while the changes in QF− were observed in adaptive immune cells, including CD4 and CD8.

Bergantini, Laura↗
DOE OSTI2023

Single-Well Push–Pull Tracer Test Analyses to Determine Aquifer Reactive Transport Parameters at a Former Uranium Mill Site (Grand Junction, Colorado)

At a former uranium mill site where tailings have been removed, prior work has determined several potential ongoing secondary uranium sources. These include locations with uranium sorbed to organic carbon, uranium in the unsaturated zone, and uranium associated with the presence of gypsum. To better understand uranium mobility controls at the site, four single-well push–pull tests (with a drift phase) were completed with the goal of deriving aquifer flow and contaminant transport parameters for inclusion in a future sitewide reactive transport model. This goes beyond the traditional use of a constant sorption distribution coefficient (K d ) and allows for the evaluation of alternative remedial injection fluids, which can produce variable K d values. Dispersion was first removed from the resulting data to determine possible reactions before conducting reactive transport simulations. These initial analyses indicated the potential need to include cation exchange, uranium sorption, and gypsum dissolution. A reactive transport model using multiple layers to account for partially penetrating wells was completed using the PHT-USG reactive transport modeling code and calibrated using PEST. The model results quantify the hydraulic conductivity and dispersion parameters using the injected tracer concentrations. Uranium sorption, cation exchange, and gypsum dissolution parameters were quantified by comparing the simulated versus observed geochemistry. All simulations required some cation exchange and calcite equilibrium, and one simulation required gypsum dissolution to improve the model fit for calcium and sulfate. Uranium sorption parameters were not strongly influenced by the other parameter values but were highly influenced by uranium concentrations during the drift phase, with possible kinetic rate limitations. Thus, a future recommendation for such push–pull tests is to collect more geochemical data during the drift phase. The final uranium sorption parameters were within the range of values determined from prior column testing. The flow and transport parameters derived from these single-well push–pull tests will provide initial parameters for any future sitewide reactive transport model.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2020

Seasonal mixing from intermittent flow drives concentration-discharge behaviour in a stream affected by coal mine drainage

Abandoned mining operations continue to severely degrade many ecosystems worldwide by releasing acidic water and/or heavy metals into surface and groundwater. Contaminant concentrations in affected streams vary with discharge in patterns that reflect both geochemical reactions and variable mixing of contaminated and non-contaminated waters. However, controls on concentration-discharge (C-Q) patterns remain unclear, particularly for constituents that experience changing solubility across redox and pH gradients. Understanding the C-Q behaviour of contaminants aids in predicting both downstream transport and effects on aquatic life under variable flow. Here, we examined the C-Q behaviours of non-reactive (Na, K, Ca, Mg, Cl - ) and reactive (Fe, Mn, Al, H + , SO 4 2- ) solutes in a stream contaminated with acid mine drainage in northeastern Ohio, USA. Concentration-discharge patterns at the watershed outlet primarily reflected mixing of contaminated baseflow with intermittent inputs of high pH water draining from a passive limestone treatment system into the stream. The treatment system acted as an ephemeral tributary that mitigated contamination in the stream by diluting solutes, raising pH, and driving metal precipitation, but only when flow was present during wet seasons. Consequently, AMD-derived reactive solutes (H + , Fe, Mn, Al) decreased with increasing stream discharge while relatively conservative solutes (e.g., Ca, Mg, K, Na) decreased only slightly or were chemostatic. This study highlights both the unique C-Q patterns of reactive solutes when compared to those of non-reactive solutes and the potential for intermittent streams to control C-Q behaviour in headwater catchments.

58 GEOSCIENCES↗