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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 145 records · Page 8
All sourcesNASA NTRSDOE OSTI
DOE OSTI2018

Fundamental Operator-Valued Functions of Singular Integrodifferential Operators in Banach Spaces

In this paper, using methods of the theory of generalized functions in Banach spaces, we examine the Cauchy problem for an abstract integrodifferential equation of a specific type. Under the assumption that there exist the complete Jordan structure of the differential part of the equation and the order of the zero of the kernel of the integral part, the fundamental operator-valued function (the fundamental solution) is constructed for the corresponding integrodifferential operator, which is used for further investigation of the problem.

97 MATHEMATICS AND COMPUTING↗
DOE OSTI2024

In-Situ Blade Strain Measurements and Fatigue Analysis of a Cross-Flow Turbine Operating in a Tidal Flow

Cross-flow turbines (CFTs) are inherently unsteady devices with regards to operating principle and loading. By improving our understanding of the dynamic loading on these turbines, we hope to better inform CFT design, improve survivability, and reduce overall costs. The University of New Hampshire (UNH) and the National Renewable Energy Laboratory (NREL) collaborated on a project to instrument and test a four-bladed New Energy Corp. vertical axis cross-flow turbine in a real tidal flow. One blade from the 3.2 m diameter x 1.7 m height turbine was instrumented with eight full-bridge strain gauges along the span of the blade. The turbine was then deployed at the UNH-Atlantic Marine Energy Center (AMEC) Tidal Energy Test Site in Portsmouth, NH. Time-synchronized measurements of blade strain, inflow, thrust, rotational speed, and electrical output were obtained to characterize blade loading under various conditions. The blade strain was examined to assess the dynamic loading and conduct a fatigue analysis on the device.

blade strain↗
DOE OSTI2016

Wholesale Electricity Market Design with Increasing Levels of Renewable Generation: Incentivizing Flexibility in System Operations

This paper discusses the importance and challenges of incentivizing flexibility during short-term operations of the bulk power system due to the increasing variability and uncertainty from growing penetrations of variable generation (VG). Operational flexibility can refer to many aspects of a resource's capability to support the power system, such as the speed, range, and duration of power output, as well as the ability to autonomously respond to frequency or voltage changes. Inefficient utilization of existing flexibility, or unwillingness of resources to provide flexibility, can compromise system reliability by not meeting the changing net load, and it can also lead to higher costs when an inefficient use of flexibility resources occurs. There are many existing characteristics of market design that incentivize flexibility in some manner. How they incentivize the provision of flexibility as well as the level of flexibility is still debated. We explore some of these existing market designs, as well as new market mechanisms, such as pay-for-performance regulating reserve and flexible ramping products, that aim to explicitly incentivize the provision of more flexibility to the system, particularly as a result of increasing VG penetration levels.

24 POWER TRANSMISSION AND DISTRIBUTION↗
DOE OSTI2021

Performance and Durability of Pure-Water-Fed Anion Exchange Membrane Electrolyzers Using Baseline Materials and Operation

Water electrolysis powered by renewable electricity produces green hydrogen and oxygen gas, which can be used for energy, fertilizer, and industrial applications and thus displace fossil fuels. Pure-water anion-exchange-membrane (AEM) electrolyzers in principle offer the advantages of commercialized proton-exchange-membrane systems (high current density, low cross over, output gas compression, etc.) while enabling the use of less-expensive steel components and nonprecious metal catalysts. AEM electrolyzer research and development, however, has been limited by the lack of broadly accessible materials that provide consistent cell performance, making it difficult to compare results across studies. Further, even when the same materials are used, different pretreatments and electrochemical analysis techniques can produce different results. Here, we report an AEM electrolyzer comprising commercially available catalysts, membrane, ionomer, and gas-diffusion layers operating near 1.9 V at 1 A cm –2 in pure water. After the initial break in, the performance degraded by 0.67 mV h –1 at 0.5 A cm –2 at 55 °C. We detail the key preparation, assembly, and operation techniques employed and show further performance improvements using advanced materials as a proof-of-concept for future AEM-electrolyzer development. Here, the data thus provide an easily reproducible and comparatively high-performance baseline that can be used by other laboratories to calibrate the performance of improved cell components, nonprecious metal oxygen evolution, and hydrogen evolution catalysts and learn how to mitigate degradation pathways.

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

Permutable SOS (symmetry operational similarity)

Abstract Based on symmetry consideration, quasi-one-dimensional (1D) objects, relevant to numerous observables or phenomena, can be classified into eight different types. We provide various examples of each 1D type and discuss their symmetry operational similarity (SOS) relationships, which are often permutable. A number of recent experimental observations, including current-induced magnetization in polar or chiral conductors, non-linear Hall effect in polar conductors, spin-polarization of tunneling current to chiral conductors, and ferro-rotational domain imaging with linear gyration are discussed in terms of (permutable) SOS. In addition, based on (permutable) SOS, we predict a large number of new phenomena in low symmetry materials that can be experimentally verified in the future.

Materials Science↗
DOE OSTI2019

Conditions for stable operation of solid oxide electrolysis cells: oxygen electrode effects

Solid oxide electrolysis cells (SOECs) convert renewable electricity to fuels with efficiency substantially higher than other electrolysis technologies. However, questions remain regarding degradation mechanisms that limit SOEC long-term stability. One of the key degradation mechanisms is oxygen electrode delamination; although prior studies have improved the understanding of this mechanism, it is still difficult to predict how degradation depends on SOEC materials and operating conditions, i.e., temperature, voltage, and current density. Here we present a study aimed at developing a quantitative understanding of oxygen electrode delamination. Experimentally, a life test study of symmetric and full cells with yttria-stabilized zirconia (YSZ) electrolytes and Gd-doped ceria (GDC) barrier layers was done with three different perovskite oxygen electrode materials. Fracture was observed at the perovskite–GDC interface above a critical current density and below a critical operating temperature. A theory is presented that combines a calculation of the effective oxygen pressure across the electrolyte with an estimation of the pressure required for fracture. Fracture is correctly predicted for a critical oxygen partial pressure of ~7200 atm and an associated electrode overpotential of ~0.2 V, occurring at the electrode/GDC interface because of the relatively low perovskite fracture toughness. As a result, damage at the GDC/YSZ interface was also observed in some cases and explained by a peak in the oxygen pressure at this interface.

30 DIRECT ENERGY CONVERSION↗
DOE OSTI2015

The NOνA experiment, the first 12 months of commissioning, operations and physics data

The NOνA experiment is a long baseline neutrino experiment designed to make precision measurements of the oscillation probabilities for ν{sub µ} → ν{sub e} and ν{sub µ} → ν{sub µ} for both neutrinos and anti-neutrinos. These measurements will provide new information on the neutrino mass hierarchy, improve our knowledge of whether θ{sub 23} is non-maximal and possibility provide information on the CP violating phase δ{sub CP} of the PMNS neutrino mixing matrix. We present the observations of the first neutrino event in the NOνA far and near detectors along with data obtained during the first year of detector commissioning and operations. We use the data to demonstrate the detector’s ability to identify electron and muon neutrino events and to reject cosmic ray induced backgrounds at a level of 4 × 10{sup 7}:1. New estimates for the signal and background sensitivities of the NOνA experiment during the first year of full detector running are presented.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2016

Fluid moments of the nonlinear Landau collision operator

An important problem in plasma physics is the lack of an accurate and complete description of Coulomb collisions in associated fluid models. To shed light on the problem, this Letter introduces an integral identity involving the multivariate Hermite tensor polynomials and presents a method for computing exact expressions for the fluid moments of the nonlinear Landau collision operator. The proposed methodology provides a systematic and rigorous means of extending the validity of fluid models that have an underlying inverse-square force particle dynamics to arbitrary collisionality and flow.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2018

Gyroaveraging operations using adaptive matrix operators

A new adaptive scheme to be used in particle-in-cell codes for carrying out gyroaveraging operations with matrices is presented. This new scheme uses an intermediate velocity grid whose resolution is adapted to the local thermal Larmor radius. The charge density is computed by projecting marker weights in a field-line following manner while preserving the adiabatic magnetic moment μ. These choices permit to improve the accuracy of the gyroaveraging operations performed with matrices even when strong spatial variation of temperature and magnetic field is present. Accuracy of the scheme in different geometries from simple 2D slab geometry to realistic 3D toroidal equilibrium has been studied. As a result, a successful implementation in the gyrokinetic code XGC is presented in the delta-f limit.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2021

Cryogenic operation of planar ultrananocrystalline diamond field emission source in SRF injector

Here, we report a demonstration of electron beam generation in a superconducting radio frequency (SRF) Teraelectronvolt Energy Superconducting Linear Accelerator 1.3 GHz gun equipped with a field emission cathode and operated at 2 K. The cathode is a submicrometer film of nitrogen-incorporated ultrananocrystalline diamond [(N)UNCD] deposited atop a Nb RRR300 cathode plug that is 4 mm in diameter. Measurements of the output current showed that it increased exponentially as a function of the gun gradient. Our results demonstrate a feasible path toward simplified fully cryogenic SRF injector technology. At a maximal gradient of 0.9 MV/m, a current density of 22 μA/cm2 was obtained [calculated as a 2.75 μA current over the total cathode surface area of π(2 mm)2]. One important finding is that the electron emitter made of (N)UNCD, a material long been known as a highly efficient field emission material, demonstrated a record low turn-on gradient of 0.6 MV/m. A hypothesis explaining this behavior is proposed.

43 PARTICLE ACCELERATORS↗
DOE OSTI2023

Geometric Optimization of an Electrochemical Purification Cell to Prevent Corrosion in CSP Plants During Operation

When exposed to moisture or oxygen, molten chloride salts produce corrosive impurities which degrade containment alloys. This can significantly decrease the lifetime and increase costs of molten-salt-based systems. To overcome this barrier, we designed and modeled an electrochemical purification cell to remove the corrosive impurity MgOH+. Various reactor architectures, including continuous stirred tank reactors (CSTRs) and plug flow reactors (PFRs) were investigated. Steady-state thermoelectric properties were evaluated using analytical methods, allowing assessment of the effects of structure and design parameters such as flow rate, cell length, and cross-sectional area of molten salt. The results suggest that our design could most effectively increase reliability and decrease costs of molten-chloride-salt-based systems by protecting them during continuous operation using an annular plug flow reactor.

analytical modeling↗
DOE OSTI2015

Enabling opportunistic resources for CMS Computing Operations

With the increased pressure on computing brought by the higher energy and luminosity from the LHC in Run 2, CMS Computing Operations expects to require the ability to utilize opportunistic resources resources not owned by, or a priori configured for CMS to meet peak demands. In addition to our dedicated resources we look to add computing resources from non CMS grids, cloud resources, and national supercomputing centers. CMS uses the HTCondor/glideinWMS job submission infrastructure for all its batch processing, so such resources will need to be transparently integrated into its glideinWMS pool. Bosco and parrot wrappers are used to enable access and bring the CMS environment into these non CMS resources. Finally, we describe our strategy to supplement our native capabilities with opportunistic resources and our experience so far using them.

97 MATHEMATICS AND COMPUTING↗
DOE OSTI2016

Astrophysical constraints on dark-matter Q -balls in the presence of baryon-violating operators

Supersymmetric extensions of the standard model predict the existence of non-topological solitons, Q-balls. Assuming the standard cosmological history preceded by inflation, Q-balls can form in the early universe and can make up the dark matter. The relatively large masses of such dark-matter particles imply a low number density, making direct detection very challenging. The strongest limits come from the existence of neutron stars because, if a baryonic Q-ball is captured by a neutron star, the Q-ball can absorb the baryon number releasing energy and eventually destroying a neutron star. Yet, in the presence of baryon number violating higher-dimension operators, the growth of a Q-ball inside a neutron star is hampered once the Q-ball reaches a certain size. We re-examine the limits and identify some classes of higher-dimensional operators for which supersymmetric Q-balls can account for dark matter. The current limits leave a wide range of parameters available for dark matter in the form of supersymmetric Q-balls.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗