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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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All sourcesNASA NTRSDOE OSTI
DOE OSTI2025

Chemical Reactor Network Modeling of Ammonia Rich-Quench-Lean Combustion Using a Partially Stirred Reactor Approach

Ammonia is a promising alternative fuel, but its use is challenging due to low flammability and high nitrogen oxide (NOx) emissions. Two-stage rich-quench-lean (RQL) combustion strategies have shown promise in reducing NOx emissions. This approach involves two stages: a rich stage that oxidizes part of the fuel and decomposes ammonia into hydrogen, and a lean stage that burns out the hydrogen and residual ammonia. Researchers used a chemical reactor network model to study the effects of heat loss and mixing on emissions performance. They found that heat loss and reduced mixing rates can lead to increased NOx emissions and N2O formation. The results will inform the development of optimized two-stage RQL combustors for ammonia, with a focus on minimizing NOx emissions and improving overall efficiency.

ammonia combustion↗
DOE OSTI2021

Effect of temperature on capacity fade in silicon-rich anodes

Coin half-cells containing 80 wt% silicon electrodes are assembled and cycled at the similar to C/10 rate in the temperature range of 25-55 degrees C. To the best of our knowledge, this is the first time that the effect of temperature is reported for such high-silicon-containing cells. Two different electrolytes are used in this study, a baseline electrolyte and the baseline electrolyte +10 wt% fluoroethylene carbonate (FEC). Analysis of the capacity vs. cycle count data by curve fitting reveals that the addition of FEC markedly affects the capacity loss mechanism. Without FEC, the kinetic rate law for the capacity loss mechanism can be described as the sum of two logistic growth models. With the addition of FEC, the rate law depends on ln(t). Clearly, the addition of FEC has a profound effect on the mechanism of capacity loss. Interestingly, X-ray photoelectron spectroscopy (XPS) shows that the composition of the solid electrolyte interphase (SEI) layer changes markedly from mostly organic to mostly inorganic in the presence of FEC and how it varies at the different temperatures tested, especially in the absence of FEC.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2022

Compositionally Tuning Electron Transfer from Photoexcited Core/Shell Quantum Dots via Cation Exchange

It is critical to find methods to control the thermodynamic driving force for photoexcited charge transfer from quantum dots (QDs) and explore how this affects charge transfer rates, since the efficiency of QD-based photovoltaic and photocatalysis technologies depends on both this rate and the associated energetic losses. In this work, we introduce a single-pot shell growth and Cu-catalyzed cation exchange method to synthesize Cd x Zn 1-x Se/Cd y Zn 1-y S QDs with tunable driving forces for electron transfer. Functionalizing them with two molecular electron acceptors—naphthalenediimide (NDI) and anthraquinone (AQ)—allowed us to probe nearly 1 eV of driving forces. For AQ, at lower driving forces, we find that higher Zn content results in a 130-fold increase of electron transfer rate constants. However, at higher driving forces electron transfer dynamics are unaltered. Here, the data are understood using an Auger-assisted electron transfer model and analyzed with computational work to determine approximate binding geometries of these electron acceptors. Our work provides a method to tune QD reducing power and produces useful metrics for optimizing QD charge transfer systems that maximize rates of electron transfer while minimizing energetic losses.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2022

Newly developed sugarbeet lines with altered postharvest respiration rates differ in transcription factor and glycolytic enzyme expression

Respiration is the principal cause for postharvest sucrose loss in sugarbeet (Beta vulgaris L.) roots. Although reductions in respiration rate could mitigate these losses, developing sugarbeet cultivars and storage procedures that reduce respiration are hindered by a lack of knowledge of the genetic and metabolic factors that control storage respiration rate. Research was conducted to identify genes and gene products that affect storage respiration rate by creating two sugarbeet lines that differ in respiration rate and characterizing gene expression differences between these lines. Sugarbeet lines F1056 and F1057, which differ by up to 42% in respiration rate, were created by divergent selection of a sugarbeet population using root respiration rate after 30 d in storage as the principal selection criterion. RNA sequencing identified 287 differentially expressed genes (DEGs) between these lines on the day of harvest and after 28-d storage. Of these DEGs, nine encoded transcription factors and five encoded enzymes involved in the respiratory pathway. Other DEGs contributed to a variety of biological and molecular functions based on gene ontology classifications. Of respiratory pathway DEGS, genes for NAD+- and NADP+-dependent forms of glyceraldehyde-3-phosphate dehydrogenase were of note due to their high upregulation in the high respiring line and for their established role in glycolysis, a pathway identified as a likely bottleneck in respiratory substrate production. Overall, lines F1056 and F1057 provide new tools for investigating genetic and physiological differences in storage respiration rate, and their DEGs identify candidates for genes affecting sugarbeet root respiration rate.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2023

Anomaly Detection in Liquid Sodium Cold Trap Operation with Multisensory Data Fusion Using Long Short-Term Memory Autoencoder

Sodium-cooled fast reactors (SFR), which use high temperature fluid near ambient pressure as coolant, are one of the most promising types of GEN IV reactors. One of the unique challenges of SFR operation is purification of high temperature liquid sodium with a cold trap to prevent corrosion and obstructing small orifices. We have developed a deep learning long short-term memory (LSTM) autoencoder for continuous monitoring of a cold trap and detection of operational anomaly. Transient data were obtained from the Mechanisms Engineering Test Loop (METL) liquid sodium facility at Argonne National Laboratory. The cold trap purification at METL is monitored with 31 variables, which are sensors measuring fluid temperatures, pressures and flow rates, and controller signals. Loss-of-coolant type anomaly in the cold trap operation was generated by temporarily choking one of the blowers, which resulted in temperature and flow rate spikes. The input layer of the autoencoder consisted of all the variables involved in monitoring the cold trap. The LSTM autoencoder was trained on the data corresponding to cold trap startup and normal operation regime, with the loss function calculated as the mean absolute error (MAE). The loss during training was determined to follow log-normal density distribution. During monitoring, we investigated a performance of the LSTM autoencoder for different loss threshold values, set at a progressively increasing number of standard deviations from the mean. The anomaly signal in the data was gradually attenuated, while preserving the noise of the original time series, so that the signal-to-noise ratio (SNR) averaged across all sensors decreased below unity. Results demonstrate detection of anomalies with sensor-averaged SNR < 1.

21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS↗
DOE OSTI2021

Effect of dehydroepiandrosterone administration before in vitro fertilization on the live birth rate in poor ovarian responders according to the Bologna criteria: A randomised controlled trial

Abstract Objective To evaluate the effect of dehydroepiandrosterone (DHEA) pre‐treatment before in vitro fertilization and embryo transfer (IVF‐ET) on the live birth rate in infertile women with poor ovarian response (POR) defined according to the Bologna criteria. Design A randomized, double‐blind, placebo‐controlled trial. Setting Nine reproductive medical centers in China. Population A total of 821 participants with POR defined according to the Bologna criteria were enrolled in the study between April 2016 and December 2018. Methods Eligible participants were randomly assigned to receive either DHEA ( n = 410) or placebo ( n = 411) treatments for 4–12 weeks prior to IVF‐ET, in a 1:1 ratio. Main outcome measures Live birth rate after the first embryo transfer. Results Thirty‐six (8.8%) of 410 women in the DHEA group and 37 (9.0%) of 411 women in the placebo group had a live birth, with no significant difference observed between groups (relative risk, 0.98, 95% CI, 0.63–1.51; p = 0.911). There were no significant differences in the number of retrieved oocytes, and the rates of clinical pregnancy, pregnancy loss, and cumulative live births between the two groups. Conclusions DHEA administration prior to IVF‐ET had no beneficial effect on the live birth rate relative to placebo in women with POR defined according to the Bologna criteria. Tweetable Abstract No benefit was found in poor ovarian responders who received DHEA administration prior to IVF.

Wang, Ze↗
DOE OSTI2021

Hydraulic architecture explains species moisture dependency but not mortality rates across a tropical rainfall gradient

Aim Intensified droughts are affecting tropical forests across the globe. However, the underlying mechanisms of tree drought response and mortality are poorly understood. Hydraulic traits and especially hydraulic safety margins (HSMs), i.e. the extent to which plants buffer themselves from thresholds of water stress, provide insights into species-specific drought vulnerability. Methods We investigated hydraulic traits during an intense drought triggered by the 2015-2016 El Niño on 27 canopy trees across three tropical forest sites with differing precipitation. We capitalized on the drought event as a time when plant water status might approach or exceed thresholds of water stress. We investigated the degree to which these traits varied across the rainfall gradient, as well as relationships amongst hydraulic traits and species-specific optimal moisture and mortality rates. Results There were no differences among sites for any measured trait. There was strong coordination among traits, with a network analysis revealing two major groups of coordinated traits. In one group there were water potentials, turgor loss point, sapwood capacitance and density, HSMs, and mortality rate. In the second group there was leaf mass per area, leaf dry matter content, hydraulic architecture (leaf area to sapwood area ratio), and species-specific optimal moisture. Conclusion These results demonstrated that while species with greater safety from turgor loss had lower mortality rates, hydraulic architecture was the only trait that explained species’ moisture dependency. Species with a greater leaf area to sapwood area ratio were associated with drier sites and reduced their transpirational demand during the dry season via deciduousness.

Hydraulic Saftey Margins, drought, tropical forest↗
DOE OSTI2025

Achievable Rates for Concatenated Square Gottesman-Kitaev-Preskill Codes

The Gottesman-Kitaev-Preskill (GKP) codes are known to achieve optimal rates under displacement noise and pure-loss channels, which establishes theoretical foundations for its optimality. However, such optimal rates are only known to be achieved at a discrete set of noise strengths with the current self-dual symplectic lattice construction. In this work, we develop a new coding strategy using concatenated continuous variable-discrete variable encodings to go beyond past results and establish GKP’s optimal rate over all noise strengths. In particular, for displacement noise, the rate is obtained through a constructive approach by concatenating GKP codes with a quantum polar code and analog decoding. For a pure-loss channel, we prove the existence of capacity-achieving GKP codes through a random coding approach. These results highlight the capability of concatenation-based GKP codes and provides new methods for constructing good GKP lattices.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2021

High Data Rate Detector for Neutron Reflectometer

Neutron reflectometers are a class of instruments that employ neutron diffraction for measuring the structure of thin films. The technique provides valuable information over a wide variety of scientific and technological applications including chemical aggregation, polymer and surfactant adsorption, structure of thin film magnetic systems, biological membranes, etc. Such instruments are considered to be one of the most important in the neutron science field. Newer facilities place growing demands on the count rate capability of the specialized neutron detectors required. Proportional Technologies completed the Phase I effort successfully with a fully operational prototype detector built at PTI and tested at the CG1A neutron beam of the High Flux Isotope Reactor (HFIR, Oak Ridge, TN). The prototype incorporated 3 panels of 14 copper-walled cells each (total of 42 cells), each lined with 1.3 μm of 10B4C. The detector was tested for efficiency, spatial resolution, count rate linearity, uniformity, overlap and scatter. Testing revealed stable operation, uniform response across cells, and successful resolution of individual cells. The maximum count rate tested in the 3 panels combined was 590 kHz, limited by a deadtime of about 1 μs in the digital electronics. The local rate measured in a single cell showed no deadtime losses up to 810 cps/mm2, indicating that a rate of 20 Mhz can be supported in the 308-cell detector planned for Phase II.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2024

Modeling the Moisture Content and Dry Matter Loss in Dynamic Woody Biomass Storage Piles with Variable Extraction

The urgent need to mitigate climate change has spurred significant interest in renewable energy sources. This paper explores the storage and processing of woody biomass for biofuel production, considering the dynamic nature of biomass piles in real-world scenarios. A model has been developed to analyze moisture content changes and dry matter loss in woody biomass stored in piles prior to processing, taking into account varying extraction methods and environmental conditions. Case studies that examine the effects of different unpiling methods (FIFO, LIFO, and homogeneous) on moisture content and dry matter loss under various feedstock arrival rates and weather conditions are presented. Results indicate that unpiling methods significantly impact moisture content, with LIFO typically resulting in higher moisture content due to the utilization of fresher feedstock. Dry matter loss increases with pile size and time, emphasizing the importance of accurate modeling for assessing carbon emissions and feedstock quality. Furthermore, the model highlights the importance of process loading order and extraction methods in biomass storage, suggesting potential cost benefits associated with decreased moisture content. The difference between different extraction methods could vary the moisture content in the feedstock reaching the biofuel process by as much as 37.6%, however dry matter loss varies minimally for realistic pile changes. Overall, this research contributes to a better understanding of biomass storage dynamics and informs sustainable biofuel production practices.

Niska, Janel↗
DOE OSTI2025

Background Measurements and Simulations of the ComPair Balloon Flight

ComPair, a prototype of the All-sky Medium Energy Gamma-ray Observatory (AMEGO), completed a short-duration high-altitude balloon campaign on 27 August 2023 from Fort Sumner, New Mexico, USA. The goal of the balloon flight was to demonstrate ComPair as both a Compton and Pair telescope in flight, reject the charged particle background, and measure the background γ-ray spectrum. This analysis compares measurements from the balloon flight with Monte Carlo simulations to benchmark the instrument. The comparison finds good agreement between the measurements and simulations and supports the conclusion that ComPair accomplished its goals for the balloon campaign. Additionally, two charged particle background rejection schemes are discussed: a soft ACD veto that records a higher charged particle event rate but with less risk of event loss, and a hard ACD veto that limits the charged particle event rate on board. There was little difference in the measured spectra from the soft and hard ACD veto schemes, indicating that the hard ACD veto could be used for future flights. The successes of ComPair’s engineering flight will inform the development of the next generation of ComPair with upgraded detector technology and larger active area.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2023

Design, Optimization, and Validation of GaN-Based DAB Converter for Active Cell Balancing in BTMS Applications: Preprint

This paper focuses on the design of a bidirectional dual active bridge (DAB) DC/DC converter that utilizes Gallium Nitride (GaN) switches as active components. In the existing literature, MOSFET-based DAB for active cell balancing is available, but GaN-based DAB converter for active cell balancing is still new. The proposed modular isolated GaN-based DAB converter is designed as an individual module of active cell balancing for behind-the-meter storage (BTMS) applications, targeting high-power charging stations. Modular isolated converters are connected to each cell (low voltage bus), and each cell is connected in series to build up a battery module. According to the reference current command of supervisory control, each DAB converter can transfer power back and forth through the high voltage (HV) bus to balance the State of Charge (SoC) between the cells. Each module DAB converter is designed at a 50W power rating. Switch power and transformer losses are analyzed for different switching frequencies, showing the optimum switching frequency for minimum losses. Furthermore, the procedure to select the required gate driver and the PCB layout optimization are discussed. Finally, the DAB performance analysis of GaNbased DAB and Si-based DAB is provided for a battery module operating with a LiFeMnPO4 prismatic cell with 3.2V 20Ah rated values.

active cell balancing↗
DOE OSTI2023

Design, Optimization, and Validation of GaN-Based DAB Converter for Active Cell Balancing in BTMS Applications

This paper focuses on the design of a bidirectional dual active bridge (DAB) DC/DC converter that utilizes Gallium Nitride (GaN) switches as active components. In the existing literature, MOSFET-based DAB for active cell balancing is available, but GaN-based DAB converter for active cell balancing is still new. The proposed modular isolated GaN-based DAB converter is designed as an individual module of active cell balancing for behind-the-meter storage (BTMS) applications, targeting high-power charging stations. Modular isolated converters are connected to each cell (low voltage bus), and each cell is connected in series to build up a battery module. According to the reference current command of supervisory control, each DAB converter can transfer power back and forth through the high voltage (HV) bus to balance the State of Charge (SoC) between the cells. Each module DAB converter is designed at a 50 W power rating. Switch power and transformer losses are analyzed for different switching frequencies, showing the optimum switching frequency for minimum losses. Furthermore, the procedure to select the required gate driver and the PCB layout optimization are discussed. Finally, the DAB performance analysis of GaN-based DAB and Si-based DAB is provided for a battery module operating with a LiFeMnPO4 prismatic cell with 3.2V 20Ah rated values.

active cell balancing↗
DOE OSTI2020

Effects of charging rates on LiNi 0.6 Mn 0.2 Co 0.2 O 2 (NMC622)/graphite Li-ion cells

Enabling fast charging capability of lithium-ion battery is of great importance to widespread adoption of electric vehicles. Increasing the charging rates from state-of-the-art 2C (30 min) to 6C (10 min) requires deep understanding on the cell aging mechanism. Here, 400 mAh pouch cells are cycled at 1C, 4C and 6C charging rates with 1C discharging rate. Capacity fading, cathode structural changes, Li inventory loss, electrolyte composition changes and Li plating on graphite electrodes are thoroughly studied by various characterization techniques. The rapid capacity fading in cells at 6C charging rate is mainly due to Li inventory loss from cathode structure and metallic Li plating on graphite electrode at higher charging rate. Post-mortem analysis also revealed changes in electrolyte such as increased salt molarity and transesterification during fast charging.

25 ENERGY STORAGE↗
DOE OSTI2026

The Impact of Operational Strategies and Load Fluctuations on Anion Exchange Membrane Water Electrolyzer Degradation

This study reports on the durability of anion exchange membrane water electrolyzers (AEMWEs) at the cell level in a supporting electrolyte (1 M) and the impact of operational profiles on cell degradation. While constant load shows significant voltage loss, including a current hold at 1 A cm −2 and a potential hold at 2 V, it generally occurs in the first 70 h of testing. These losses are likely due to passivation altering site reactivity and cell kinetics, and are largely recoverable upon load cycling and diagnostics at the end of test. Furthermore, square and triangular-wave cycling do not show cell degradation and indicate that AEMWEs are not vulnerable to load cycling. When operating outside of this potential window (1.45–2 V), cell voltage decay rates markedly increase and the losses are not recoverable. This includes a current density hold at 4.0 A cm −2 with high cell voltages (>2.4 V for test duration) and cycling between 0 and 2 V to simulate start–stop, where more than a 50% loss in current density occurs over 50 h. The findings presented here demonstrate the high durability of AEMWEs, particularly when operating with load fluctuations, and may allow for durability advantages compared to iridium and proton exchange membrane systems.

08 HYDROGEN↗
DOE OSTI2023

Electrochemical Characterization of Degradation Modes of High-Voltage Li x Ni 0.33 Mn 0.33 Co 0.33 O 2 Electrodes

While deeply charged high-voltage cathodes can improve battery energy density, understanding and preventing any accelerated cell degradation is crucial to practical success. Here, to analyze the degradation of LiNi x Mn y Co 1–x–y O 2 (NMC) type material charged to 4.3 and 4.5 V, a physics-based model is applied to cycling data to obtain parameter estimates indicative of degradation modes, which are validated by simple electrochemical measurements and further interpreted by materials characterization. Growth rates of interfacial impedance and active material loss are greater at 4.5 V, as might be expected. However, when charged to 4.5 V, degradation rates are initially lower at a cycling C-rate of 1.0 C than at 0.5 C. Once degradation mode changes are quantified, simulations evaluate the contribution of individual degradation mode to performance losses and provide estimates of the energy-power correlation (Ragone plots) of cells after cycling.

25 ENERGY STORAGE↗
DOE OSTI2022

Desorption characteristics of selenium and tellurium thin films

The temperature-dependent desorption behavior of selenium and tellurium is investigated using a heated quartz crystal microbalance. Prior to heating the quartz crystal microbalance, selenium and tellurium films with varying thickness were deposited using thermal effusion cells in a molecular beam epitaxy system for subsequent determination of temperature-dependent mass loss of the deposited films. The desorption rate for tellurium was found to exhibit one sharp peak around 190°C, indicating the loss of the entire film irrespective of film thickness within a temperature window of 20°C, which was completely evaporated at 200°C. Similar experiments for selenium revealed that the thermal desorption took place via a two-stage process with a smaller portion of the material desorbing within an even narrower temperature window of 5°C at a much lower peak temperature of 65°C, while most selenium desorbed within a temperature range of 10°C around 90°C. This two-stage behavior indicated the presence of at least two chemically distinct selenium species or binding states. The direct and quantitative determination of the chalcogen desorption process provides important insights into the kinetics of chalcogenide-based film growth and is in addition of applied benefit to the research community in the area of Se/Te capping and decapping of air sensitive materials as it provides temperature ranges and rates at which full desorption is achieved. Our work furthermore points toward the need for a more detailed understanding of the chemical composition state of atomic and molecular beams supplied from thermal evaporation sources during growth.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Impact of illumination and encapsulant resistivity on polarization-type potential-induced degradation on n-PERT cells

Power loss caused by polarization-type potential-induced degradation (PID-p) in a variety of high-performance photovoltaic cell types has been observed to be recoverable via subsequent illumination and in some cases preventable via simultaneous illumination. In this report, we describe the results of a study in which the front faces of n-PERT cells encapsulated in polymers with a broad range of electrical resistivity were exposed to varying and controlled irradiance during PID testing. For a low resistivity ethylene-vinyl acetate copolymer encapsulant, no reduction in the rate or extent of power loss was observed for irradiance as high as 1,000 W/m 2 , whereas for high and intermediate resistivity polyolefin encapsulants, 100 and 300 W/m 2 , respectively, prevented power loss. We introduce a simple model based on charge accumulation that facilitates interpretation of these results whereby degradation via charge accumulation under voltage stress and recovery due to light exposure are opposing and interdependent phenomena that describe the susceptibility of a module to power loss.

14 SOLAR ENERGY↗