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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 685 records · Page 38
All sourcesNASA NTRSDOE OSTI
DOE OSTI2023

Simulation and Sensitivity Analysis of a Cryogenic Carbon Capture System for the Cement Industry

The talk will describe modeling and analysis of cryogenic systems for carbon capture from industrial point sources, thermodynamic and process simulation requirements to predict capture from typical flue gases, quantification of temperature and flow profiles for a range of gas feed compositions and capture levels, and impacts of process conditions and heat transfer on energy requirements for heat integration.

Paul, Brandon↗
DOE OSTI2024

Impedance Scan of Inverter-Based Resources and Diesel Generator for Stability Analysis: Preprint

Impedance-based methods are widely used for power system stability analysis with inverter-based resources (IBRs), e.g., assessing dynamic interactions between the power grid and an IBR, control interactions between multiple IBRs, and the sub-synchronous oscillation and damping phenomenon. Since it is difficult to get a numerical model 100% matching with the hardware IBR, using the hardware inverter directly to obtain its output impedance has become a prominent approach nowadays. Therefore, this article presents the impedance scan using hardware IBRs, and also a hardware diesel generator as it still stays with the grid before the grid completely goes to renewable. The devices under test (DuTs) for the impedance scan includes two 3-..phi.., 480 V, 60 Hz commercial grid-forming IBRs (one of 250 kVA and another of 125 kVA rating) in series with ..delta..-Y transformers, one 3-..phi.., 480 V, 60 Hz commercial grid-following IBR (of 125 kVA rating), and a 3-..phi.., 480 V, 60 Hz commercial diesel generator (of 187.5 kVA rating). Using voltage signals perturbed with sub-, inter-, and higher harmonic components, and measuring the current response, the positive-sequence impedances are computed via an offline- based post-analysis. Moreover, best-fit transfer functions are estimated that closely resemble the measured data points of the positive-sequence impedances. Based on the observations from various outcomes of the hardware experiments, this article also provides some fundamental insights on the equivalent positive- sequence impedance of a combination of multiple hardware components by comparing the estimated and the empirically computed impedances. A comparative insight on the damping capability of the DuTs using the positive-sequence impedances of the hardware is also discussed.

grid following inverter↗
DOE OSTI2024

Exploring the Tl 2H 2 potential energy surface: A comparative analysis with group 13 systems and experiment

Abstract Thallium chemistry is experiencing unprecedented importance. Therefore, it is valuable to characterize some of the simplest thallium compounds. Stationary points along the singlet and triplet TlH potential energy surface have been characterized. Stationary point geometries were optimized with the CCSD(T)/aug‐cc‐pwCVQZ‐PP method. Harmonic vibrational frequencies were computed at the same level of theory while anharmonic vibrational frequencies were computed at the CCSD(T)/aug‐cc‐pwCVTZ‐PP level of theory. Final energetics were obtained with the CCSDT(Q) method. Basis sets up to augmented quintuple‐zeta cardinality (aug‐cc‐pwCV5Z‐PP) were employed to obtain energetics in order to extrapolate to the complete basis set limits using the focal point approach. Zero‐point vibrational energy corrections were appended to the extrapolated energies in order to determine relative energies at 0 K. It was found that the planar dibridged isomer lies lowest in energy while the linear structure lies highest in energy. The results were compared to other group 13 MH (M = B, Al, Ga, In, and Tl) theoretical studies and some interesting variations are found. With respect to experiment, incompatibilities exist.

Chemistry↗
DOE OSTI2020

Prenatal Ultrasound Analysis of Umbilical‐Portal‐Systemic Venous Shunts Concurrent With Trisomy 21

Objectives A classification termed umbilical‐portal‐systemic venous shunt (UPSVS) for an abnormal umbilical vein (UV), portal vein (PV), and ductus venosus (DV) was proposed recently. According to this classification, there are 3 types of UPSVSs: types I, II, and III. Trisomy 21 associated with UV‐PV‐DV anomalies has been described, but the incidence of trisomy 21 in UPSVS cases, the relationship between UPSVS types and trisomy 21, and the pregnancy outcome are poorly documented. This study aimed to address these issues. Methods All UPSVS cases diagnosed at our department from 2016 to 2019 were retrospectively studied. The English literature describing UV‐PV‐DV anomalies and trisomy 21 from 2000 to 2019 was searched, and the retrieved cases were analyzed. Results Four of 20 UPSVS cases identified by us also had trisomy 21, with 2 type I and 2 type II UPSVSs. Ultrasound markers of Down syndrome were observed in all 4 cases that underwent termination of pregnancy (TOP). The literature search retrieved 12 reports including 279 patients, with 29 also having trisomy 21, giving a pooled trisomy 21 incidence rate of 10.4%. Of the 29 cases, 16 had type I, and 9 had type II, whereas UPSVS types in 4 were undeterminable, and 22 cases underwent TOP. Conclusions There is a high incidence of trisomy 21 in UPSVS cases. Trisomy 21 is associated with a type I or II UPSVS. Most cases with the combined defect underwent TOP. These findings may be used to direct prenatal counseling and management of the combined condition.

Dong, Xiangyi↗
DOE OSTI2023

Life cycle analysis of a hydrogen production system based on solid oxide electrolysis cells integrated with different energy and wastewater sources

Hydrogen production via water electrolysis is a promising and evolving technology. The solid oxide electrolysis cell (SOEC) is one of the several technologies for this purpose. They are alternatives to the traditional hydrogen production from fossil fuels to enhance global energy decarbonization. However, in the bid for sustainability and a green economy, these technologies are not free from causing some environmental burdens. Using life cycle assessment (LCA), the greenhouse gas emission and degree of environmental impacts by these technologies can be identified and measured throughout their lifespan. This study addresses how to quantify these CO 2 emission impacts for an electrolytic system with different energy sources. The LCA of a novel integrated hydrogen production SOEC system with energy from solar photovoltaic and bituminous powerplant is performed using simaPro, the leading global LCA solution software. Measuring the environmental impact of the electrolytic operation in terms of weight, the bituminous powerplant poses damage which is, on average 700% more than solar PV. The thermal-to-hydrogen efficiency of the SOEC system is 56%, and a probable 28% reduction in carbon footprint with heat integration. The steam generation and the manufacturing of the SOEC have a very high environmental impact potential on the system. Here, we recommend LCA and net energy analysis is carried out for every new hydrogen technology and adequate comparison to enhance sustainable and green economy.

08 HYDROGEN↗
DOE OSTI2023

Concepts Relevant for the Kinetic Analysis of Reversible Reaction Systems

The net rate of a reversible chemical reaction is the difference between unidirectional rates of traversal along forward and reverse reaction paths. In a multistep reaction sequence, the forward and reverse trajectories, in general, are not the microscopic reverse of one another; rather, each unidirectional route is comprised of distinct rate-controlling steps, intermediates, and transition states. Consequently, traditional descriptors of rate (e.g., reaction orders) do not reflect intrinsic kinetic information but instead conflate unidirectional contributions determined by (i) the microscopic occurrence of forward/reverse reactions (i.e., unidirectional kinetics) and (ii) the reversibility of reaction (i.e., nonequilibrium thermodynamics). This review aims to provide a comprehensive resource of analytical and conceptual tools which deconvolute the contributions of reaction kinetics and thermodynamics to disambiguate unidirectional reaction trajectories and precisely identify rate- and reversibility-controlling molecular species and steps in reversible reaction systems. The extrication of mechanistic and kinetic information from bidirectional reactions is accomplished through equation-based formalisms (e.g., De Donder relations) grounded in principles of thermodynamics and interpreted in the context of theories of chemical kinetics developed in the past 25 years. Here, the aggregate of mathematical formalisms detailed herein is general to thermochemical and electrochemical reactions and encapsulates a diverse body of scientific literature encompassing chemical physics, thermodynamics, chemical kinetics, catalysis, and kinetic modeling.

42 ENGINEERING↗
DOE OSTI2025

Analytical Identification Method of Generalized Short‐Circuit Ratio Using Phasor Measurement Units

This paper introduces a novel analytical approach for the identification of the admittance matrix and the generalized short-circuit ratio (gSCR) in power systems integrated with renewable energy sources. The proposed method leverages voltage and current measurements from phasor measurement units (PMUs) to construct a least squares objective function, which is then solved using matrix calculus and partial derivatives. Unlike conventional optimization algorithms, this approach provides an analytical solution that substantially reduces data requirements, enabling the efficient and accurate identification of the gSCR with smaller datasets. Additionally, its fixed computational complexity allows for real-time updates as new data are collected, ensuring continuous refinement of the system of equations and enabling rapid, precise gSCR calculations. The method also exhibits strong robustness against measurement noise, making it well-suited for practical applications in dynamic power systems. The combination of reduced data requirements, real-time adaptability, noise robustness and fixed computational load establishes this method as a highly efficient and reliable tool for real-time power system stability analysis. Case studies on an EPRI 36-bus system demonstrate the method's effectiveness, highlighting its accuracy in closely matching true gSCR values, even under diverse disturbances and noisy conditions.

Han, Zelei [Hohai University, Nanjing (China)] (OR↗
DOE OSTI2021

Concept Design and Analysis of the Magnet System of the Sustained High Power Density Tokamak Facility

A recent National Academy study recommended a next-step sustained high power density (SHPD) facility for the United States that can be a bridge to a compact fusion pilot plant. A design has been initiated to investigate a possible SHPD non-deuterium-tritium device that builds upon recent low aspect ratio tokamak studies. Here, a 1.2-m device with a 2.4 aspect ratio has been chosen to evaluate physics performance goals within a double-null plasma machine arrangement centered on three component features: high current density toroidal field (TF) and central ohmic heating/poloidal field (PF) coils, liquid metal divertor/first wall systems, and the integration of a limited set of outboard dual-coolant lead lithium test blankets that can be maintained within a vertical maintenance approach.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2021

Energy performance analysis of smart wall system with switchable insulation and thermal storage capacity

The ever-increasing global energy demand and the issues caused by population growth and unsustainable energy resource usages have several environmental and economic impacts. The on-demand capability of dynamic wall systems with switchable insulation systems can contribute toward energy efficiency and reduced electric cost using "building-as-a-battery." In this paper, the performance of an exterior envelope system that employs a switchable insulation system is investigated. A COMSOL simulation was used to study the envelope performance under three switchable insulation locations in the wall system. The on and off switching cycle included insulating or conducting the exterior, interior, or both sides of the mass wall system. To validate the simulation work, an experimental test was conducted in climate chamber on a 4 × 8 in. wall system with identical wall components used in the COMSOL simulation. Results show a good agreement between the experiment and simulation results. The wall system with switchable insulation placed on the exterior side provided the highest interior inward heat flux when compared with the interior or split insulation. Also, an exterior switchable insulation system in addition to a thermal mass maintained a positive heat flow for more hours when the outdoor temperature was lower than the interior temperature.

Iffa, Emishaw↗
DOE OSTI2023

Principled Schedulability Analysis for Distributed Storage Systems Using Thread Architecture Models

In this article, we present an approach to systematically examine the schedulability of distributed storage systems, identify their scheduling problems, and enable effective scheduling in these systems. We use Thread Architecture Models (TAMs) to describe the behavior and interactions of different threads in a system, and show both how to construct TAMs for existing systems and utilize TAMs to identify critical scheduling problems. We specify three schedulability conditions that a schedulable TAM should satisfy: completeness, local enforceability, and independence; meeting these conditions enables a system to easily support different scheduling policies. We identify five common problems that prevent a system from satisfying the schedulability conditions, and show that these problems arise in existing systems such as HBase, Cassandra, MongoDB, and Riak, making it difficult or impossible to realize various scheduling disciplines. We demonstrate how to address these schedulability problems using both direct and indirect solutions, with different trade-offs. To show how to apply our approach to enable scheduling in realistic systems, we develop Tamed-HBase and Muzzled-HBase, sets of modifications to HBase that can realize the desired scheduling disciplines, including fairness and priority scheduling, even when presented with challenging workloads.

Computer Science↗
DOE OSTI2023

Many-Body Effects in Aqueous Systems: Synergies Between Interaction Analysis Techniques and Force Field Development

Interaction analysis techniques, including the many-body expansion (MBE), symmetry-adapted perturbation theory, and energy decomposition analysis, allow for an intuitive understanding of complex molecular interactions. We review these methods by first providing a historical context for the study of many-body interactions and discussing how nonadditivities emerge from Hamiltonians containing strictly pairwise-additive interactions. We then elaborate on the synergy between these interaction analysis techniques and the development of advanced force fields aimed at accurately reproducing the Born–Oppenheimer potential energy surface. In particular, we focus on ab initio–based force fields that aim to explicitly reproduce many-body terms and are fitted to high-level electronic structure results. These force fields generally incorporate many-body effects through ( a) parameterization of distributed multipoles, ( b) explicit fitting of the MBE, ( c) inclusion of many-atom features in a neural network, and ( d) coarse-graining of many-body terms into an effective two-body term. We also discuss the emerging use of the MBE to improve the accuracy and speed of ab initio molecular dynamics.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2021

Watermarks in stream processing systems: semantics and comparative analysis of Apache Flink and Google cloud dataflow

Streaming data processing is an exercise in taming disorder: from oftentimes huge torrents of information, we hope to extract powerful and timely analyses. But when dealing with streaming data, the unbounded and temporally disordered nature of real-world streams introduces a critical challenge: how does one reason about the completeness of a stream that never ends? In this paper, we present a comprehensive definition and analysis of watermarks, a key tool for reasoning about temporal completeness in infinite streams.First, we describe what watermarks are and why they are important, highlighting how they address a suite of stream processing needs that are poorly served by eventually-consistent approaches:• Computing a single correct answer, as in notifications.• Reasoning about a lack of data, as in dip detection.• Performing non-incremental processing over temporal subsets of an infinite stream, as in statistical anomaly detection with cubic spline models.• Safely and punctually garbage collecting obsolete inputs and intermediate state.• Surfacing a reliable signal of overall pipeline health.Second, we describe, evaluate, and compare the semantically equivalent, but starkly different, watermark implementations in two modern stream processing engines: Apache Flink and Google Cloud Dataflow.

Akidau, Tyler↗