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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 1,207 records · Page 67
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

A Distributed Reinforcement Learning Yaw Control Approach for Wind Farm Energy Capture Maximization: Preprint

In this paper, we present a reinforcement-learning based distributed approach to wind farm energy capture maximization using yaw control, also known as wake steering. In order to maximize the power output of a wind farm, it is often necessary for individual turbines to decrease their own power output through yaw misalignment so as to deflect their wakes away from downstream turbines. Although using model-based methods to achieve yaw misalignment is one option, a model-free method might be better suited to incorporate factors that are difficult to model or changing conditions. We propose an algorithm that adapts concepts of temporal difference reinforcement learning distributed to a multi-agent environment that allows individual turbines to act so as to optimize overall wind farm output and react to unforeseen disturbances.

controls↗
DOE OSTI2015

Wind Turbine Wake-Redirection Control at the Fishermen's Atlantic City Windfarm: Preprint

In this paper, we will present our work towards designing a control strategy to mitigate wind turbine wake effects by redirecting the wakes, specifically applied to the Fishermen’s Atlantic City Windfarm (FACW), proposed for deployment off the shore of Atlantic City, New Jersey. As wind turbines extract energy from the air, they create low-speed wakes that extend behind them. Full wake recovery Full wake recovery to the undisturbed wind speed takes a significant distance. In a wind energy plant the wakes of upstream turbines may travel downstream to the next row of turbines, effectively subjecting them to lower wind speeds, meaning these waked turbines will produce less power.

17 WIND ENERGY↗
NASA NTRS2022

Low-Speed Performance Enhancement using Localized Active Flow Control: Simulations, Scaling and Design of Localized Active Flow Control on the Common Research Model (4/4)

This report is dedicated to the application of localized AFC on the NASA CRM-HL wind tunnel model, with focus on the aileron application discussed in the CFD study (final report document #2). The experience developed for the Reference Aircraft guided the implementation on the CRM model. CFD evaluations are performed on a representative high-lift configuration, for a set of aileron deflections, and at relevant flow conditions. Alternative flow control actuator layouts are proposed and design consideration for practical integration into the existing CRM-HL model are set forth. The CFD simulations indicate that the aerodynamic performance improvements due to AFC obtained for the CRM-HL are consistent with those achieved for the Reference Aircraft. The observed changes in L/D are smaller than for the Reference Aircraft because the CRM has a higher leading edge sweep angle and a different relative aileron size. Conceptual design studies confirmed that the integration of an AFC equipped aileron into the existing wind tunnel model is feasible.

AFC↗
DOE OSTI2017

Tailoring the response of Autonomous Reactivity Control (ARC) systems

The Autonomous Reactivity Control (ARC) system was developed to ensure inherent safety of Generation IV reactors while having a minimal impact on reactor performance and economic viability. In this study we present the transient response of fast reactor cores to postulated accident scenarios with and without ARC systems installed. Using a combination of analytical methods and numerical simulation, the principles of ARC system design that assure stability and avoids oscillatory behavior have been identified. A comprehensive transient analysis study for ARC-equipped cores, including a series of Unprotected Loss of Flow (ULOF) and Unprotected Loss of Heat Sink (ULOHS) simulations, were performed for Argonne National Laboratory (ANL) Advanced Burner Reactor (ABR) designs. With carefully designed ARC-systems installed in the fuel assemblies, the cores exhibit a smooth non-oscillatory transition to stabilization at acceptable temperatures following all postulated transients. To avoid oscillations in power and temperature, the reactivity introduced per degree of temperature change in the ARC system needs to be kept below a certain threshold the value of which is system dependent, the temperature span of actuation needs to be as large as possible.

ARC↗
DOE OSTI2016

Self-assembly of designed precursors: A route to crystallographically aligned new materials with controlled nanoarchitecture

Modulated elemental reactants is a method by which new and complex intergrowth compounds can be synthesized by the self-assembly of designed precursors prepared by physical vapor deposition. Careful calibration of the composition and thickness of the precursors ensures the formation of the desired product by precise control of local composition and diffusion lengths. Superstructures of increasing complexity can be realized using binary and ternary systems as starting points. The synthesis of systems based on three different binary compounds, either alloyed together or separated into distinct layers, expands the number of possible superstructures that can be formed using this technique, but provides analytical challenges. The synthesis of [(SnSe){sub 1.15}]{sub 1}([Ta{sub x}V{sub 1−x}]Se{sub 2}){sub 1}[(SnSe){sub 1.15}]{sub 1}([V{sub y}Ta{sub 1−y}]Se{sub 2}){sub 1} compound is used to illustrate the preparation of precursors and the challenges in both measuring and limiting the interdiffusion of layers during self-assembly. Systematic changes in the electrical properties of (SnSe){sub 1+δ}(Ta{sub x}V{sub 1−x})Se{sub 2} alloys are observed as x is varied. The electrical resistivity of [(SnSe){sub 1.15}]{sub 1}([Ta{sub x}V{sub 1−x}]Se{sub 2}){sub 1}[(SnSe){sub 1.15}]{sub 1}([V{sub y}Ta{sub 1−y}]Se{sub 2}){sub 1} can be modeled as the two constituent layers in parallel.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2018

Constructing Highly Porous Thermoelectric Monoliths with High-Performance and Improved Portability from Solution-Synthesized Shape-Controlled Nanocrystals

Thermoelectricity offers a viable and reliable solution to convert waste heat into electricity. To enhance the performance and portability of thermoelectric materials, the crystal grain and pore structure should be simultaneously manipulated to achieve high electrical conductivity (σ), low thermal conductivity (κ), high figure of merit (zT), and low relative density. However, they cannot be synchronously realized using nanocrystals with uncontrolled domain size and shape as building blocks. Here, we employ solution-synthesized PbS nanocrystals with large grain size, controllable shape and tunable spatial packing to realize the aforementioned structural tuning. In this work, the as-sintered highly porous and well crystalline monolith exhibits high σ, low κ, high zT (1.06 at 838 K) and low relative density (82%). The phonon transport is studied by density functional theory highlighting the crucial role of phonon–pore scattering in reducing κ to enhance zT. Our strategy may benefit thermoelectrics and shed light on other technical fields such as catalysis, gas sensing, photovoltaics, and so forth.

nanocrystal↗
DOE OSTI2015

Communication: State-to-state dynamics of the Cl + H{sub 2}O → HCl + OH reaction: Energy flow into reaction coordinate and transition-state control of product energy disposal

Quantum state-to-state dynamics of a prototypical four-atom reaction, namely, Cl + H{sub 2}O → HCl + OH, is investigated for the first time in full dimensionality using a transition-state wave packet method. The state-to-state reactivity and its dependence on the reactant internal excitations are analyzed and found to share many similarities both energetically and dynamically with the H + H{sub 2}O → H{sub 2} + OH reaction. The strong enhancement of reactivity by the H{sub 2}O stretching vibrational excitations in both reactions is attributed to the favorable energy flow into the reaction coordinate near the transition state. On the other hand, the insensitivity of the product state distributions with regard to reactant internal excitation stems apparently from the transition-state control of product energy disposal.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2016

Quasielastic neutron scattering with in situ humidity control: Water dynamics in uranyl fluoride

The structural phase diagram of uranyl fluoride (UO{sub 2}F{sub 2}), while incomplete, contains at least one anhydrous crystal structure and a second, zeolite-like structure with the formula [(UO{sub 2}F{sub 2})(H{sub 2}O)]{sub 7} ⋅ (H{sub 2}O){sub 4} that can be produced by adding water to the anhydrous structure. While traditional diffraction measurements can easily differentiate these crystals, additional aqueous structures (in general of the form UO{sub 2}F{sub 2} + xH{sub 2}O) have been proposed as well. We present results using a novel sample environment setup to intercalate water during a quasielastic neutron scattering measurement over the course of 86 h. Our sample environment allows low-pressure (<2 atm) humid air flow across the sample coupled with a system to control the relative humidity of this air flow between 10% and 70%. The water dynamics in UO{sub 2}F{sub 2} and [(UO{sub 2}F{sub 2})(H{sub 2}O)]{sub 7} ⋅ (H{sub 2}O){sub 4} are sufficiently different to distinguish them, with water in the latter executing a restricted diffusion (D = 2.7 × 10{sup −6} cm{sup 2}/s) within the structure's accessible pores (r = 3.17 Å) such that the dynamics can be used as a fingerprinting tool. We confirm that water vapor pressure is the driving thermodynamic force for the conversion of the anhydrous structure to [(UO{sub 2}F{sub 2})(H{sub 2}O)]{sub 7} ⋅ (H{sub 2}O){sub 4}, and we demonstrate the feasibility of extending this approach to aqueous forms of UO{sub 2}F{sub 2} + xH{sub 2}O. This method has general applicability to systems in which water content itself is a driving variable for structural or dynamical phase transitions.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗