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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 1,405 records · Page 78
All sourcesNASA NTRSDOE OSTI
DOE OSTI2014

Band-gap nonlinear optical generation: The structure of internal optical field and the structural light focusing

A novel approach for the enhancement of nonlinear optical effects inside globular photonic crystals (PCs) is proposed and systematically studied via numerical simulations. The enhanced optical harmonic generation is associated with two- and three-dimensional PC pumping with the wavelength corresponding to different PC band-gaps. The interactions between light and the PC are numerically simulated using the finite-difference time-domain technique for solving the Maxwell's equations. Both empty and infiltrated two-dimensional PC structures are considered. A significant enhancement of harmonic generation is predicted owing to the highly efficient PC pumping based on the structural light focusing effect inside the PC structure. It is shown that a highly efficient harmonic generation could be attained for both the empty and infiltrated two- and three-dimensional PCs. We are demonstrating the ability for two times enhancement of the parametric decay efficiency, one order enhancement of the second harmonic generation, and two order enhancement of the third harmonic generation in PC structures in comparison to the nonlinear generations in appropriate homogenous media. Obviously, the nonlinear processes should be allowed by the molecular symmetry. The criteria of the nonlinear process efficiency are specified and calculated as a function of pumping wavelength position towards the PC globule diameter. Obtained criterion curves exhibit oscillating characteristics, which indicates that the highly efficient generation corresponds to the various PC band-gap pumping. The highest efficiency of nonlinear conversions could be reached for PC pumping with femtosecond optical pulses; thus, the local peak intensity would be maximized. Possible applications of the observed phenomenon are also discussed.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2022

A flexible neutron spectrometer concept with a new ultra-high field steady-state vertical-bore magnet

The proposed facility explores materials under ultra-high magnetic fields. By combining the power of high fields to tune materials and of neutron scattering to probe the resulting changes down to the atomic scale, this facility will enable transformative progress in the study of quantum materials and is named for the “TITAN” subset of Greek gods to reflect this transformation. TITAN will offer DC magnetic fields up to at least 20 T. Exploiting the record brightness and bandwidth of the Second Target Station at the Spallation Neutron Source, TITAN will probe atomic-scale responses through high efficiency neutron spectroscopy up to 80 meV energy transfer, high resolution diffraction, and small angle neutron scattering. Focusing neutron optics will maximize flux on accurately positioned samples, while radial collimation and optimized shielding and detection strategies will minimize backgrounds.

47 OTHER INSTRUMENTATION↗
DOE OSTI2024

A Gaussian process based surrogate approach for the optimization of cylindrical targets

Simulating direct-drive inertial confinement experiments presents significant computational challenges, both due to the complexity of the codes required for such simulations and the substantial computational expense associated with target design studies. Machine learning models, and in particular, surrogate models, offer a solution by replacing simulation results with a simplified approximation. In this study, we apply surrogate modeling and optimization techniques that are well established in the existing literature to one-dimensional simulation data of a new cylindrical target design containing deuterium–tritium fuel. These models predict yields without the need for expensive simulations. We find that Bayesian optimization with Gaussian process surrogates enhances sampling efficiency in low-dimensional design spaces but becomes less efficient as dimensionality increases. Nonetheless, optimization routines within two-dimensional and five-dimensional design spaces can identify designs that maximize yield, while also aligning with established physical intuition. Optimization routines, which ignore constraints on hydrodynamic instability growth, are shown to lead to unstable designs in 2D, resulting in yield loss. However, routines that utilize 1D simulations and impose constraints on the in-flight aspect ratio converge on novel cylindrical target designs that are stable against hydrodynamic instability growth in 2D and achieve high yield.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2011

Photon-echo quantum memory with complete use of natural inhomogeneous broadening

The photon-echo quantum memory is based on a controlled rephasing of the atomic coherence excited by a signal light field in the inhomogeneously broadened resonant line. Here, we demonstrate an active mechanism of the atomic rephasing that provides a perfect retrieval of the stored light field in the photon-echo quantum memory based on the use of arbitrary initial inhomogeneous broadening of the resonant line. We show that the rephasing mechanism can exploit all resonant atoms, thereby maximally increasing an optical depth of the resonant transition, which is one of the critical parameters for the realization of highly efficient quantum memory. We also demonstrate that the rephasing mechanism can be used for various realizations of the photon-echo quantum memory, thereby creating many possibilities for its practical realization.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2016

Resolution recovery for Compton camera using origin ensemble algorithm

Purpose: Compton cameras (CCs) use electronic collimation to reconstruct the images of activity distribution. Although this approach can greatly improve imaging efficiency, due to complex geometry of the CC principle, image reconstruction with the standard iterative algorithms, such as ordered subset expectation maximization (OSEM), can be very time-consuming, even more so if resolution recovery (RR) is implemented. We have previously shown that the origin ensemble (OE) algorithm can be used for the reconstruction of the CC data. Here we propose a method of extending our OE algorithm to include RR. Methods: To validate the proposed algorithm we used Monte Carlo simulations of a CC composed of multiple layers of pixelated CZT detectors and designed for imaging small animals. A series of CC acquisitions of small hot spheres and the Derenzo phantom placed in air were simulated. Images obtained from (a) the exact data, (b) blurred data but reconstructed without resolution recovery, and (c) blurred and reconstructed with resolution recovery were compared. Furthermore, the reconstructed contrast-to-background ratios were investigated using the phantom with nine spheres placed in a hot background. Results: Our simulations demonstrate that the proposed method allows for the recovery of the resolution loss that is due to imperfect accuracy of event detection. Additionally, tests of camera sensitivity corresponding to different detector configurations demonstrate that the proposed CC design has sensitivity comparable to PET. When the same number of events were considered, the computation time per iteration increased only by a factor of 2 when OE reconstruction with the resolution recovery correction was performed relative to the original OE algorithm. We estimate that the addition of resolution recovery to the OSEM would increase reconstruction times by 2–3 orders of magnitude per iteration. Conclusions: The results of our tests demonstrate the improvement of image resolution provided by the OE reconstructions with resolution recovery. The quality of images and their contrast are similar to those obtained from the OE reconstructions from scans simulated with perfect energy and spatial resolutions.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2014

Measure Guideline: Guide to Attic Air Sealing

The Guide to Attic Air Sealing was completed in 2010 and although not in the standard Measure Guideline format, is intended to be a Measure Guideline on Attic Air Sealing. The guide was reviewed during two industry stakeholders meetings held on December 18th, 2009 and January 15th, 2010, and modified based on the comments received. Please do not make comments on the Building America format of this document. The purpose of the Guide to Attic Air Sealing is to provide information and recommendations for the preparation work necessary prior to adding attic insulation. Even though the purpose of this guide is to save energy - health, safety and durability should not be compromised by energy efficiency. Accordingly, combustion safety and ventilation for indoor air quality are addressed first. Durability and attic ventilation then follow. Finally, to maximize energy savings, air sealing is completed prior to insulating. The guide is intended for home remodelers, builders, insulation contractors, mechanical contractors, general contractors who have previously done remodeling and homeowners as a guide to the work that needs to be done.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗
DOE OSTI2014

Measure Guideline: Guide to Attic Air Sealing

The purpose of this measure guideline is to provide information and recommendations for the preparation work necessary prior to adding attic insulation. Even though the purpose of this guide is to save energy, health, safety, and durability should not be compromised by energy efficiency. Accordingly, combustion safety and ventilation for indoor air quality are addressed first. Durability and attic ventilation then follow. Finally, to maximize energy savings, air sealing is completed prior to insulating. The guide is intended for home remodelers, builders, insulation contractors, mechanical contractors, general contractors who have previously done remodeling and homeowners as a guide to the work that needs to be done.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗
NASA NTRS1979

Efficient laser anemometer for intra-rotor flow mapping in turbomachinery

A fringe type laser anemometer is described. Features of the anemometer include; a rapid and efficient data acquisition process; a detailed real time graphic display of the data being accumulated; and input laser beam positioning that maximizes the size of the intrarotor region being mapped. Results are presented that demonstrate the anemometer's capability in flow mapping within a transonic axial flow compressor rotor. A velocity profile, derived from 30,000 measurements along 1000 sequential circumferential positions covering 20 blade passages, was obtained in 30 seconds. The use of fluorescent seed particles allowed flow measurements near the rotor hub and the casing window.

Powell, J. A.↗
NASA NTRS1987

Experimental study of laminar boundary layer receptivity to a traveling pressure field

Study is made of the production of Tollmien-Schlichting (T-S) waves within a Blasius boundary layer by an externally-imposed, two-dimensional, pressure field of a particular type. The field is that due to flow past a relatively small cylinder aligned parallel to the test plate and normal to the flow. The cylinder was carried on a circular path about an axis located well above the plate and such that the closest approach of the cylinder to the layer was several times the layer thickness or cylinder diameter. The turbulent wake did not, therefore, directly perturb the layer. Through adjustment of the circumferential velocity, the pressure field was swept along a certain region of the plate with controllable speed. Both the pressure field and the layer response are described in detail. It is shown that the production of T-S waves was sharply maximal for the case of circumferential speed near that of freely-propagating T-S waves, and that the coupling efficiency was extremely high for this case of resonance. The relevance of this energy transfer process to T-S wave production by the unsteady pressure fields resulting from wind tunnel wall turbulent boundary layers for both subsonic and supersonic flow is mentioned.

Kendall, James M.↗
NASA NTRS2000

Algorithmic Perspectives on Problem Formulations in MDO

This work is concerned with an approach to formulating the multidisciplinary optimization (MDO) problem that reflects an algorithmic perspective on MDO problem solution. The algorithmic perspective focuses on formulating the problem in light of the abilities and inabilities of optimization algorithms, so that the resulting nonlinear programming problem can be solved reliably and efficiently by conventional optimization techniques. We propose a modular approach to formulating MDO problems that takes advantage of the problem structure, maximizes the autonomy of implementation, and allows for multiple easily interchangeable problem statements to be used depending on the available resources and the characteristics of the application problem.

Alexandrov, Natalia M.↗
NASA NTRS2017

Knowledge Base for Distributed Spacecraft Mission Design Using the Trade-Space Analysis Tool for Constellations (TAT-C)

Opportunities for multi-point measurements, greater revisit frequency, failure robustness, and improved cost effectiveness motivate consideration of Distributed Spacecraft Missions (DSMs) for future Earth science missions. However, careful analysis is required to assess the distributed sensing capabilities of a constellation compared to more mature monolithic spacecraft while also considering other important dimensions such as cost and risk. The large combinatorial DSM design space limits existing mission analysis tools and exploration methods which emphasize monolithic design variables. The Trade-space Analysis Tool for Constellations (TAT-C) under development at Goddard seeks to enumerate and evaluate alternative mission architectures to minimize cost and maximize scientific return for pre-defined goals during pre-phase A analysis.Similar to other model-centric engineering efforts, efficient data management is a significant challenge for DSM mission analysis. In TAT-C, a Knowledge Base (KB) is envisioned as a cumulative central repository of information and meta-information about DSMs. Initial KB concepts store related data for reuse within or across mission analyses; however, over time, the KB is envisioned to be an important layer to coordinate actions of both human analysts and automated design agents to search a large design space for desirable mission alternatives. Preliminary KB research builds on a modern web technology stack to provide the following functionality: 1) storage of trade-space search requests which set requirements and constraints for DSM concepts, 2) storage of analysis results which quantify performance metrics for evaluated DSM concepts, 3) a RESTful application programming interface (API) for scripted access to data from TAT-C modules, 4) web-based graphical user interface (GUI) for manual access to underlying data, and 5) access control and management restrictions relevant to data protection and security. These efforts have culminated in a prototype KB used by the research team during TAT-C development to assess opportunities for future work.

Pattern Recognition↗
DOE OSTI2016

Thermal Flux Maximization from a DD Neutron Generator

The University of Sharjah recently acquired a model DD-109.4M neutron generator from Adelphi Technology. The generator is moderated and has three neutron ports which are capable of providing fast and thermal neutrons. The neutron ports are plugged with polyethylene layers of different thickness in order to control the neutron flux at different regions in the port. Neutron Activation Analysis (NAA) is an important analysis technique to determine the amounts of isotopes in a sample at different concentrations. For many isotopes the ability to precisely determine their concentrations is enhanced by utilizing thermal neutrons in the activation process; where the capture cross section is greatest. It is thus important to subject the sample to the maximum thermal flux in order to minimize the time required to activate the sample and consequently extend the lifetime of the neutron generator. A detailed MCNP model of the neutron generator has been developed for the purpose of determining the moderator thickness required to maximize the thermal neutron flux in the neutron port. The maximization of the neutron flux must therefore take into account both the forward and backscattered neutrons reaching the sample. Also provided in this work is a mapping of the thermal flux at different moderator thicknesses in order to study the variation of the flux over the area of the sample. The developed model will be used as the basis for optimizing experiments and predicting their results. A study was performed to determine the moderator thickness needed to maximize the thermal neutron flux that can be obtained from a DD neutron generator. This has a significant role in the efficient utilization of the neutron generator. The maximum thermal neutron flux was found at approximately a 3.2 cm moderator thickness. The thermal neutron flux is resulting from both the directly moderated neutrons and the backscattered neutrons from the surrounding polyethylene. The results obtained in this work will be verified experimentally by irradiating samples at different moderator thickness and performing a neutron activation analysis for these samples. (authors)

07 ISOTOPE AND RADIATION SOURCES↗
DOE OSTI2022

Real-time dispatch optimization for concentrating solar power with thermal energy storage

Concentrating solar power (CSP) plants present a promising path towards utility-scale renewable energy. The power tower, or central receiver, configuration can achieve higher operating temperatures than other forms of CSP, and, like all forms of CSP, naturally pairs with comparatively inexpensive thermal energy storage, which allows CSP plants to dispatch electricity according to market price incentives and outside the hours of solar resource availability. Currently, CSP plants commonly include a steam Rankine power cycle and several heat exchange components to generate high-pressure steam using stored thermal energy. The efficiency of the steam Rankine cycle depends on the temperature of the plant's operating fluid, and so is a main concern of plant operators. However, the variable nature of the solar resource and the conservatism with which the receiver is operated prevent perfect control over the receiver outlet temperature. Therefore, during periods of solar variability, collection occurs at lower-than-design temperature. To support operator decisions in a real-time setting, we develop a revenue-maximizing non-convex mixed-integer, quadradically-constrained program which determines a dispatch schedule with sub-hourly time fidelity and considers temperature-dependent power cycle efficiency. The exact nonlinear formulation proves intractable for real-time decision support. Here we present exact and inexact techniques to improve problem tractability that include a hybrid nonlinear and linear formulation. Our approach admits solutions within approximately 3% of optimality, on average, within a five-minute time limit, demonstrating its usability for decision support in a real-time setting.

14 SOLAR ENERGY↗
DOE OSTI2016

Chapter 32: A Global Survey of Stakeholder Views and Experiences for Systems Needed to Effectively and Efficiently Govern Sustainability of Bioenergy

The increased international trade led to growing concerns over sustainability of biofuels and a variety of governance systems has emerged to regulate the bioenergy sector for maximization of the benefits and minimization of the possible negative impacts. The general concept of governance is used in different ways. But in this chapter it is used in the broad sense of governance processes undertaken by governments, market actors, voluntary organizations or networks. This concept of governance recognizes the interdependence of the public, market-based and voluntary governing processes, and the relationships that may exist between them. A survey was designed with the objective of analyzing stakeholders' views, experiences, and ideas in relation to the governance challenges. The survey revealed a broad support for existing and new co-regulation among stakeholders, but also that low share of certified land is seen as a challenge for both forestry and agriculture.

29 ENERGY PLANNING, POLICY, AND ECONOMY↗
DOE OSTI2025

Maximizing long-term biohydrogen production with Clostridium thermocellum for high solids conversion of lignocellulosic biomass

Biological hydrogen production from lignocellulosic biomass sustainably couples organic waste reduction with renewable energy generation. Efficient conversion is challenged by the structural complexity of lignocellulose and resulting recalcitrance to enzymatic degradation. Clostridium thermocellum natively breaks down biomass with highly effective hemi-/cellulases systems (i.e., cellulosomes) and generates hydrogen in anaerobic cultivation, creating a compelling platform for lignocellulosic biohydrogen production. Achieving commercially viable production rates requires balancing high biomass loading and throughput against uniform mixing conditions required for enzyme dispersion, pH and temperature control, and efficient hydrogen and metabolite removal in continuous operation. To address these barriers to process intensification, we implemented novel reactor and process designs for high-solids lignocellulosic biomass fermentations using the C. thermocellum KJC19-9 strain, genetically engineered for co-utilization of cellulose and hemicellulose sugars (i.e., xylose). Via computational fluid dynamics (CFD) modeling and experimental validation, we achieved a >50% improvement in biohydrogen production with an improved anchor-type impeller morphology, coupled to a threefold reduction in agitation rate. To further reduce rheological constraints and accumulation of toxic metabolites, we then transitioned the process to sequencing fed-batch operation. The resulting process generated 24.87 L H 2 L −1 from 160 g L −1 of deacetylated and mechanically refined (DMR)-pretreated corn stover biomass over 16 days while solubilizing >95% of influent cellulose and hemicellulose, setting a new performance benchmark for continuous production of biohydrogen from lignocellulose.

08 HYDROGEN↗
DOE OSTI2019

A finalized determinant for complete lignocellulose enzymatic saccharification potential to maximize bioethanol production in bioenergy Miscanthus

Miscanthus is a leading bioenergy crop with enormous lignocellulose production potential for biofuels and chemicals. However, lignocellulose recalcitrance leads to biomass process difficulty for an efficient bioethanol production. Hence, it becomes essential to identify the integrative impact of lignocellulose recalcitrant factors on cellulose accessibility for biomass enzymatic hydrolysis. In this study, we analyzed four typical pairs of Miscanthus accessions that showed distinct cell wall compositions and sorted out three major factors that affected biomass saccharification for maximum bioethanol production. Among the three optimal (i.e., liquid hot water, H 2 SO 4 and NaOH) pretreatments performed, mild alkali pretreatment (4% NaOH at 50 °C) led to almost complete biomass saccharification when 1% Tween-80 was co-supplied into enzymatic hydrolysis in the desirable Miscanthus accessions. Consequently, the highest bioethanol yields were obtained at 19% (% dry matter) from yeast fermentation, with much higher sugar–ethanol conversion rates by 94–98%, compared to the other Miscanthus species subjected to stronger pretreatments as reported in previous studies. By comparison, three optimized pretreatments distinctively extracted wall polymers and specifically altered polymer features and inter-linkage styles, but the alkali pretreatment caused much increased biomass porosity than that of the other pretreatments. Based on integrative analyses, excellent equations were generated to precisely estimate hexoses and ethanol yields under various pretreatments and a hypothetical model was proposed to outline an integrative impact on biomass saccharification and bioethanol production subjective to a predominate factor (CR stain) of biomass porosity and four additional minor factors (DY stain, cellulose DP, hemicellulose X/A, lignin G-monomer). Using four pairs of Miscanthus samples with distinct cell wall composition and varied biomass saccharification, this study has determined three main factors of lignocellulose recalcitrance that could be significantly reduced for much-increased biomass porosity upon optimal pretreatments. It has also established a novel standard that should be applicable to judge any types of biomass process technology for high biofuel production in distinct lignocellulose substrates. Hence, this study provides a potential strategy for precise genetic modification of lignocellulose in all bioenergy crops.

09 BIOMASS FUELS↗
DOE OSTI2021

Delivering Effective Virtual Energy-Focused Trainings: Successful Strategies and Lessons Learned from the Virtual Cohort In-Plant Training Pilot

While there are always barriers to energy efficiency efforts, few challenges have been as severe as the global COVID-19 pandemic. Many manufacturers throughout the United States and the world have been trying to determine how to safely open and operate their plants. To minimize the number of people working within facilities and maximize the physical distance between workers, only essential facility engineers are allowed into plants to ensure proper operations. The Department of Energy’s Better Plants Program created In-Plant Trainings (INPLTs) to help partners develop in-house expertise in energy efficiency. Delivering INPLTs in the traditional in-person fashion is infeasible under these circumstances. To continue providing INPLTs during this difficult time, the Better Plants Program piloted Virtual Cohort In-Plant Trainings (VINPLTs) on wastewater treatment and ammonia industrial refrigeration systems from October 27 to November 19, 2020. This paper provides an overview of the pilot, then discusses successful strategies and lessons learned from this pilot for delivering effective virtual energy-focused trainings.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗
DOE OSTI2013

Distributed Sensor Coordination for Advanced Energy Systems

The ability to collect key system level information is critical to the safe, efficient and reliable operation of advanced energy systems. With recent advances in sensor development, it is now possible to push some level of decision making directly to computationally sophisticated sensors, rather than wait for data to arrive to a massive centralized location before a decision is made. This type of approach relies on networked sensors (called “agents” from here on) to actively collect and process data, and provide key control decisions to significantly improve both the quality/relevance of the collected data and the associating decision making. The technological bottlenecks for such sensor networks stem from a lack of mathematics and algorithms to manage the systems, rather than difficulties associated with building and deploying them. Indeed, traditional sensor coordination strategies do not provide adequate solutions for this problem. Passive data collection methods (e.g., large sensor webs) can scale to large systems, but are generally not suited to highly dynamic environments, such as advanced energy systems, where crucial decisions may need to be reached quickly and locally. Approaches based on local decisions on the other hand cannot guarantee that each agent performing its task (maximize an agent objective) will lead to good network wide solution (maximize a network objective) without invoking cumbersome coordination routines. There is currently a lack of algorithms that will enable self-organization and blend the efficiency of local decision making with the system level guarantees of global decision making, particularly when the systems operate in dynamic and stochastic environments. In this work we addressed this critical gap and provided a comprehensive solution to the problem of sensor coordination to ensure the safe, reliable, and robust operation of advanced energy systems. The differentiating aspect of the proposed work is in shifting the focus towards “what to observe” rather than “how to observe” in large sensor networks, allowing the agents to actively determine both the structure of the network and the relevance of the information they are seeking to collect. In addition to providing an implicit coordination mechanism, this approach allows the system to be reconfigured in response to changing needs (e.g., sudden external events requiring new responses) or changing sensor network characteristics (e.g., sudden changes to plant condition). Outcome Summary: All milestones associated with this project have been completed. In particular, private sensor objective functions were developed which are aligned with the global objective function, sensor effectiveness has been improved by using “sensor teams,” system efficiency has been improved by 30% using difference evaluation functions, we have demonstrated system reconfigurability for 20% changes in system conditions, we have demonstrated extreme scalability of our proposed algorithm, we have demonstrated that sensor networks can overcome disruptions of up to 20% in network conditions, and have demonstrated system reconfigurability to 20% changes in system conditions in hardware-based simulations. This final report summarizes how each of these milestones was achieved, and gives insight into future research possibilities past the work which has been completed. The following publications support these milestones [6, 8, 9, 10, 16, 18, 19].

97 MATHEMATICS AND COMPUTING↗