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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 901 records · Page 50
All sourcesNASA NTRSDOE OSTI
DOE OSTI2022

Investigating the impact of atmospheric conditions on wake-steering performance at a commercial wind plant

Wake steering is a wind farm control strategy in which upstream wind turbines are misaligned with the wind to deflect their wakes away from downstream turbines, thereby increasing net energy production. But research suggests that the effectiveness of wake steering strongly depends on atmospheric conditions such as stability. In this paper, we investigate results from a two-turbine wake-steering experiment at a commercial wind plant to assess the impact of stability and five other atmospheric variables on wake-steering performance. Specifically, for different atmospheric condition bins we compare the ability of the controller to achieve the intended yaw offsets, the power gain from wake steering, and the reduction in wake losses. Further, we analyze wake-steering performance as a function of wind speed to eliminate the confounding impact of different wind speed distributions in different atmospheric conditions. Overall, we find that wind direction standard deviation is the best predictor of wake-steering performance, followed by turbulence intensity and turbulent kinetic energy. The results suggest the importance of adapting wake-steering control strategies to different atmospheric conditions.

17 WIND ENERGY↗
DOE OSTI2020

1.2 Mfps standalone X-ray detector for Time-Resolved Experiments

We present a standalone and autonomous X-ray detector capable of operation with the speed of up to1.2Mfps. The detector utilizes UFXC32k hybrid pixel detectors for sensing X-rays, Spartan-6 LX45 FPGA placed in commercially available sbRIO 9628 controller for data acquisition and processing including a compression with zero-suppression algorithm. A Linux-RT system working on the 400 MHz Dual-Core CPU is used for FPGA control and data streaming to the higher-level system over 1 Gbps Ethernet connection. 1.2 M frames per second is achieved in so-called burst mode of operation while in zerodead-time mode 70 kfps is possible. Due to efficient data compression in FPGA there’s no need of using high-speed transceivers and Frame-Grabber cards on the data server side and the detector can stream the data infinitely over standard 1 Gbps network connection. Operation modes were tested at Advanced Photon Source Synchrotron at Argonne National Laboratory.

47 OTHER INSTRUMENTATION↗
DOE OSTI2022

Melt-Pool Dynamics and Microstructure of Mg Alloy WE43 under Laser Powder Bed Fusion Additive Manufacturing Conditions

Magnesium-based alloy WE43 is a state-of-the-art bioresorbable metallic implant material. There is a need for implants with both complex geometries to match the mechanical properties of bone and refined microstructure for controlled resorption. Additive manufacturing (AM) using laser powder bed fusion (LPBF) presents a viable fabrication method for implant applications, as it offers near-net-shape geometrical control, allows for geometry customization based on an individual patient, and fast cooling rates to achieve a refined microstructure. In this study, the laser–alloy interaction is investigated over a range of LPBF-relevant processing conditions to reveal melt-pool dynamics, pore formation, and the microstructure of laser-melted WE43. In situ X-ray imaging reveals distinct laser-induced vapor depression morphology regimes, with minimal pore formation at laser-scan speeds greater than 500 mm/s. Optical and electron microscopy of cross-sectioned laser tracks reveal three distinct microstructural regimes that can be controlled by adjusting laser-scan parameters: columnar, dendritic, and banded microstructures. These regimes are consistent with those predicted by the analytic solidification theory for conduction-mode welding, but not for keyhole-mode tracks. The results provide insight into the fundamental laser–material interactions of the WE43 alloy under AM-processing conditions and are critical for the successful implementation of LPBF-produced WE43 parts in biomedical applications.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Intelligent driving passive pedal control

A method for assignment of vehicle control includes receiving route data indicating a route between a starting location of a vehicle and a destination location, and determining an optimal vehicle configuration for the route based on a target vehicle speed and a hybrid torque split. The method further includes receiving a driver requested torque value and determining a passive pedal torque value based on the route data and vehicle powertrain data. The method further includes selectively assigning control of the vehicle to a vehicle system or to a driver of the vehicle based on the driver requested torque value and the passive pedal torque value.

Aggoune, Karim↗
DOE OSTI2014

SU-E-T-61: Capabilities and Considerations for the Clinical Use of Flattening Filter Free (FFF) Beams for Volumetric Modulated Arc Therapy (VMAT)

Purpose: Machines with FFF beams are becoming more prevalent. As technology evolves, guidelines for its use need to be developed. FFF beams have the potential for much greater dose rates and lower out-of-field dose. The use of VMAT with FFF adds additional complexity. This work attempts to define the capabilities and limitations of FFF when applied to VMAT fields and characterize the situations which this technology is best suited. Methods: The total monitor units of a VMAT delivery is modified to determine the minimum deliverable dose rate for FFF and non-FFF beams on an Elekta VersaHD linear accelerator. The minimum dose rate limits the minimum dose per segments, thus reducing the available modulation. Time is assessed by recording the beam-on time for FFF and non-FFF beams. For 10 plans with standard fraction sizes (180–212 cGy/Fx) maximum dose rate per control point and number of control points exceeding 400 MU/min are recorded. Results: VMAT minimum dose rate is related to the pulse rate. The minimum deliverable dose rate is ∼36 MU/min (0.12 MU/deg) for 6x-FFF (max 1400 MU/min) and ∼75 MU/min (0.27 MU/deg) for 10x-FFF (max 2400 MU/min) beams. Delivery time is independent of dose rate for dose rates below 1500 MU/min as it is limited by gantry speed. The maximum dose rate across in all plans according to Pinnacle is 1170 MU/min for FFF plans and 800 MU/min for non-FFF plans. The percentage of control points exceeding 400 MU/min is 13.3% for FFF and 9% for non-FFF beams. Conclusion: FFF does not improve delivery time of VMAT fields for conventional fraction sizes, since the dominant factor is gantry speed instead of dose rate. However, there may be potential for speed improvement for very large fraction sizes. Due to pulse rate dependency, FFF beams require a higher minimum dose rate.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2020

Performance Evaluation of Three RTU Energy Efficiency Technologies

This project was part of an effort by CLEAResult and ComEd to evaluate the energy saving potential of emerging technologies in the Chicago area. This project focused on evaluating emerging technologies related to rooftop units (RTUs). An RTU with a single-stage compressor and a constant-speed fan with an induction motor was selected as the baseline for technology comparison. Three retrofit strategies were investigated. The first two involved replacing the single-stage compressor of an RTU by either a two-stage or variable-speed compressor and adding a variable frequency drive (VFD) to the constant speed fan. The use of a multi-/variable-stage compressor improves the part-load efficiency of the compressor which will ultimately result in annual energy savings as well as peak demand shaving in some cases where the design capacity of the RTU is larger than the maximum cooling load of the building space that it is serving. The third technology was the use of a high rotor pole switched reluctance motor (SRM) as a replacement for the constant-speed supply fan. The SRM was applied in single-speed, two-stage and variable-speed compressor RTUs. SRM motors run via reluctance torque. Their stator poles are driven by direct current (DC) power and require an inverter as well as active control when using alternating current (AC) power. This inherent property results in high efficiency over a range of operating conditions. It also exhibits higher efficiency compared to variable frequency drives (VFDs) since its switching frequency is much slower (SCE, 2018).The three technologies investigated are summarized below: 1) Replacing the single-speed compressor with a two-stage compressor and adding a VFD to the supply fan. 2)Replacing the single-speed compressor with a variable-speed compressor and adding a VFD to the supply fan. 3) Replacing the constant-speed induction motor of the supply fan with a high rotor pole SRM. DOE’s building simulation platform EnergyPlus and its graphical user interface OpenStudio were used to evaluate the energy-saving potential of upgrading RTUs, by leveraging experimental data from previous research.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗
DOE OSTI2019

Characterizations of Binary FeCr (AISI 430) Thin Films Deposited from a Single Magnetron Sputtering Under Easy Controllable Deposition Parameters

A series of 50-nm binary FeCr martensitic thin films were sputtered from a single source made of commercial AISI 430 ferritic stainless steel under the deposition rates gradually increased from 0.03 to 0.11 nm/s with 0.02 nm/s steps at stationary condition. And, under 0.09 nm/s deposition rate, a second series of the films were also deposited under the rotation speed of their substrates which was chosen at 0, 25, and 45 rpm. As far as we are concerned, this study is the first investigation of properties of the thin films produced from AISI 430. The atomic Fe content in the films increased from 79.3 to 98.6% while atomic Cr content decreased from 20.5 to 1.2% with the increase of deposition rate from 0.03 to 0.11 nm/s. According to compositional analysis, the Fe content increased while Cr content decreased with increasing deposition rate. The reason for this may be attributed to the relatively different bond energy/melting point of metals which have different contents sputtered from source material since this physical parameter is very significant for the sputtering process. And, the Fe content in the films decreased from 84.9 to 79.2 at. % while the Cr content increased from 14.9 to 20.6 at. % when the increase of rotation speed of substrate. The crystal structure of all films was observed to have a body-centered tetragonal phase and the intensity of (110) peak varied with the atomic Fe content. The surface observations of films performed by a scanning electron microscope exposed that the number of surface grains increased with the increase of deposition rate and decreased with the increase of rotation speed. According to surface roughness analysis done by an atomic force microscope, the roughness of the film surfaces increased as the deposition rate increased. And, the roughness of the film surfaces decreased as the rotation speed increased. This has been consistent with the grain size and roughness parameters. Thus, increasing deposition rate and decreasing rotation speed of the substrate caused an increase in grain size and roughness parameters. The magnetic measurements of the films achieved, by a vibrating sample magnetometer at room temperature, displayed that the saturation magnetization, M{sub s}, values increased from 820.1 to 1700.4 emu/cm{sup 3}, the remanence magnetization, M{sub r}, values increased from 293 to 817 emu/cm{sup 3}, and the coercivity, H{sub c}, value also increased from 38 to 107 Oe with the increasing of deposition rate. It is also seen that the magnetic easy axis are in the film plane due to the shape anisotropy. With the increase rotation speed, the values of M{sub s} and M{sub r} increased and the H{sub c} decreased. It was seen that variation of Fe content in the films influences the M{sub s} values and the H{sub c} values are consistent with the surface properties. It was concluded that the deposition rate and the rotation speed of the substrate play a considerable role on the structural and related magnetic properties of the sputtered FeCr thin films, and the properties of the films can be easily controlled by changing production parameters.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Control of formation of viscoelastic droplets and distribution of nano-inclusions in functional deposition for lithium–sulfur batteries

The electrospray process produces micro/nanodroplets for various applications such as thin and uniform coatings, drug carriers and mass spectrometry. In this paper, we study the spray processes of viscoelastic jets using simulations and experiments. In discretized modeling, the jet is perturbed with axisymmetric instability and the growth of this instability causes the jet to break into droplets. For the experiments, a solution of polyvinyl alcohol in water is sprayed and is visualized using a high-speed camera. The droplet size distribution is studied from simulations with experiments for three spray cases: electrospray, air spray, and air-controlled electrospray. Our simulations and experiments reveal that the electric field is effective in reducing the droplet size, while air flow offers more jet break-ups and thus a larger number of droplets. As a result, air-controlled electrospray where these two driving forces are synergistically combined leads to a larger number of smaller droplets than electrospray or air spray. As a result, we applied three spray processes to obtain a deposition of sulfur/mesoporous carbon/graphene/polymer binder composites as a lithium sulfur battery cathode and demonstrated that air-controlled electrospray leads to a higher capacity and rate capability than other processes, exhibiting 800 mA h g –1 at 0.5C and 600 mA h g –1 at 2C.

25 ENERGY STORAGE↗
DOE OSTI2020

Air compressor load forecasting using artificial neural network

Air compressor systems are responsible for approximately 10% of the electricity consumed in United States and European Union industry. As many researches have proven the effectiveness of using Artificial Neural Network inair compressor performance prediction, there is still a need to forecast the air compressor electrical load profile. The objective of this study is to predict compressed air systems’ electrical load profile, which is valuable to industry practitioners as well as software providers in developing better practice and tools for load managementand look-ahead scheduling programs. Two artificial neural networks, Two-Layer Feed-Forward Neural Networkand Long Short-Term Memory were used to predict an air compressors electrical load. Compressors with three different control mechanisms are evaluated with a total number of 11,874 observations. Here, the forecasts were validated using out-of-sample datasets with 5-fold cross-validation. Models produced average coefficient ofdetermination values from 0.24 to 0.94, average root-mean-square errors from 0.05 kW - 5.83 kW, and meanabsolute scaled errors from 0.20 to 1.33. The results indicate that both artificial neural networks yield goodresults for compressors using variable speed drive (average R 2 = 0.8 and no naïve forecasting), only the longshort-term memory model gives acceptable results for compressors using on/off control (average R 2 = 0.82 and no naïve forecasting), and no satisfactory results are obtained for load/unload type air compressors (models constituting active forecasting).

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗
DOE OSTI2025

The Role of Wind Speed in Prolonging Large Fire Durations in the Western US

Abstract The duration of large wildfires in the western US has increased significantly from 1992 to 2020 in the two fire seasons, by 0.76 days yr −1 in summer and 0.55 days yr −1 in fall. The factors driving the trend and variability were analyzed using multiple linear regression models. Our analysis identified the maximum daily wind speed during large fires, which has also increased during the study period, as the primary predictor for the large fire duration. Despite the observed rise in maximum wind speed specifically during large fires, there are no corresponding trends in the average daily mean wind speed throughout the fire seasons. The mechanisms underlying the increase in maximum wind speed during large fires remain unclear and warrant further investigation, as they may pose growing challenges for fire control.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2013

A digitizer based compact digital spectrometer for ion beam analysis using field programmable gate arrays and various energy algorithms

We report on the implementation of a compact multi-detector fully digital spectrometer and data acquisition system at a nuclear microprobe for ion beam analysis and imaging. The spectrometer design allows for system scalability with no restriction on the number of detectors. It consists of four-channel high-speed digitizer modules for detector signal acquisition and one low-speed digital-to-analog converter (DAC) module with two DAC channels and additional general purpose inputs/outputs to control ion beam scanning and data acquisition. Each digitizer module of the spectrometer provides its own Field Programmable Gate Array (FPGA) as digital signal processing unit to analyze detector signals as well as to synchronize the ion beam position in hard real-time. With the customized FPGA designs for all modules, all calculation intensive tasks are executed inside the modules, which reduces significantly the data stream to and CPU load on the control computer. To achieve an optimal energy resolution for all detector/preamplifier pulse shape characteristics, a user-definable infinite impulse response filter with high throughput for energy determination was implemented. The new spectrometer has an online data analysis feature, a compact size, and is able to process any type of detector signals such as particle induced x-ray emission, Rutherford backscattering spectrometry, or scanning transmission ion microscopy.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2014

Photomultiplier tube failure under hydrostatic pressure in future neutrino detectors

Failure of photomultiplier tubes (PMTs) under hydrostatic pressure is a concern in neutrino detection, specifically, in the proposed Long-Baseline Neutrino Experiment project. Controlled hydrostatic implosion tests were performed on prototypic PMT bulbs of 10-inch diameter and recorded using high speed filming techniques to capture failures in detail. These high-speed videos were analyzed frame-by-frame in order to identify the origin of a crack, measure the progression of individual crack along the surface of the bulb as it propagates through the glass, and estimate crack velocity. Crack velocity was calculated for each individual crack, and an average velocity was determined for all measurable cracks on each bulb. Overall, 32 cracks were measured in 9 different bulbs tested. Finite element modeling (FEM) of crack formation and growth in prototypic PMT shows stress concentration near the middle section of the PMT bulbs that correlates well with our crack velocity measurements in that section. The FEM model predicts a crack velocity value that is close to the terminal crack velocity reported. Our measurements also reveal significantly reduced crack velocities compared to terminal crack velocities measured in glasses using fracture mechanics testing and reported in literature.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2021

Strong influence of convective heat transfer efficiency on the cooling benefits of green roof irrigation

Abstract By enhancing evapotranspiration (ET), green roofs provide cooling benefits for the urban environment and are recognized as a promising heat mitigation strategy. The evaporative cooling effects of green roofs strongly depend on the soil moisture conditions and thus irrigation may be needed to sustain the cooling benefits. It has been shown that the magnitude of cooling benefits offered by green roof irrigation varies spatially, but its controlling factors remain elusive. In this study, we combine a surface energy balance (SEB) model with global simulations generated by an improved Earth System Model to illustrate the key factors controlling the cooling benefits of green roof irrigation. We employ a simple irrigation scheme, which is only active when there is no ice in soil layers and when the soil moisture is below field capacity. As a result, most of the irrigation water leaves the green roof system via ET. We find that the magnitude and also the spatial variability of the cooling benefits of green roof irrigation are controlled by the irrigation amount, and a surface energy redistribution factor that encodes the efficiencies of different SEB components in transferring heat. Further analysis indicates that the enhancement of latent heat flux due to irrigation is largely balanced by the reduction of sensible heat flux on green roofs. Therefore, the amount of irrigation needed per unit decrease of green roof surface temperature is mainly controlled by the convective heat transfer efficiency. A lower convective heat transfer efficiency (e.g. under a lower wind speed) helps reduce the amount of irrigation needed per unit decrease of green roof surface temperature. This study highlights the importance of SEB in constraining the cooling benefits of green roof irrigation and provides valuable guidance for urban planners and policy makers in terms of heat mitigation and sustainable water management.

Wang, Linying (ORCID:0000000308769220)↗
DOE OSTI2013

Hybrid Electro-Mechanical Simulation Tool for Wind Turbine Generators: Preprint

This paper describes the use of MATLAB/Simulink to simulate the electrical and grid-related aspects of a WTG and the FAST aero-elastic wind turbine code to simulate the aerodynamic and mechanical aspects of the WTG. The combination of the two enables studies involving both electrical and mechanical aspects of the WTG.

17 WIND ENERGY↗
DOE OSTI2022

Modeling of RMS Current in CSI Filter Capacitor and Minimum Conduction Loss Operation of CSI-Fed PMSM Drives for Traction Applications

This paper presents a new minimum conduction loss (MCL) torque control algorithm for current source inverter- (CSI-) fed permanent-magnet synchronous machine drives that improves the overall machine drive efficiency by minimizing the combined conduction losses in the inverter and machine at each operating point. First, analytical models of conduction losses in CSI-fed motor drives are presented, and a closed-form expression for optimal d-axis stator current to achieve MCL operation is derived. An expression for the rms current in both wye- and delta-connected CSI output capacitors is derived. A detailed simulation model that emulates the operation of a 100 kW SiC CSI-fed integrated machine drive (IMD) has been developed based on experimental results and finite element analysis. This simulation model is used to evaluate the proposed MCL control algorithm applied to a CSI-fed IMD system for a battery-electric vehicle traction drive, and the predicted total drive system loss with MCL control is compared to predicted losses with maximum-torque-per-ampere (MTPA) and minimum dc-link current (MDCC) control. Results show that MCL control can achieve loss reductions compared to the other two control algorithms over a wide range of operating conditions, with significant loss reductions >20% in the medium-speed regime.

42 ENGINEERING↗
DOE OSTI2020

A Hybrid Framework Combining Model-Based and Data-Driven Methods for Hierarchical Decentralized Robust Dynamic State Estimation

This paper combines model-based and data-driven methods to develop a hierarchical, decentralized, robust dynamic state estimator (DSE). A two-level hierarchy is proposed, where the lower level consists of robust, model-based, decentralized DSEs. The state estimates sent from the lower level are received at the upper level, where they are filtered by a robust data-driven DSE after a principled sparse selection. This selection allows us to shrink the dimension of the problem at the upper level and hence significantly speed up the computational time. The proposed hybrid framework does not depend on the centralized infrastructure of the control centers; thus it can be completely embedded into the wide-area measurement systems. This feature will ultimately facilitate the placement of hierarchical decentralized control schemes at the phasor data concentrator locations. Also, the network model is not necessary; thus, a topology processor is not required. Finally, there is no assumption on the dynamics of the electric loads. The proposed framework is tested on the 2,000-bus synthetic Texas system, and shown to be capable of reconstructing the dynamic states of the generators with high accuracy, and of forecasting in the advent of missing data.

24 POWER TRANSMISSION AND DISTRIBUTION↗
DOE OSTI2018

KiteFAST

KiteFAST is a simulator for airborne wind energy systems based on NREL's OpenFAST whole turbine simulator. KiteFAST is a multi-physics engineering tool for modeling the coupled aero-servo-elastic dynamics of airborne wind energy systems i.e. a wind-energy kite. The engineering model is like NREL's OpenFAST tool for land-based or offshore horizontal-axis wind turbines atop towers, in that KiteFAST models the important physical phenomena and system couplings, including the wind/aerodynamic excitation and full-system dynamics response (fuselage, wings, tail, stabilizers, pylons, nacelles, rotors, tether, ground station, control surfaces, and controller) under both normal (for fatigue) and extreme (for ultimate) loading conditions. The configuration of the wind-energy kite is assumed to have one fuselage; two wings (starboard, port) attached to the fuselage; one vertical stabilizer attached the fuselage; two horizontal stabilizers (starboard, port) attached to the vertical stabilizer; one or more pylons per wing, each with two rotors (top, bottom); one ground-station-fixed tether with a bridal connection to the wings, and nominal circular motion of the energy kite in the port (left) direction. The general configuration of the control surfaces assumes one or more flaps per wing, two rudders on the vertical stabilizer, two elevators per horizontal stabilizer, and rotors with variable speed and rotor-collective blade pitch. KiteFAST was developed from (1) the existing MBDyn open-source multi-body dynamics code; (2) the existing/modified OpenFAST modules NWTC Subroutine Library, AirfoilInfo, InflowWind, MoorDyn, and TurbSim; and (3) new source code for a) generating MBDyn models of the energy kite (KiteMBDyn Preprocessor), b) computing quasi-steady energy-kite aerodynamics (KiteAeroDyn, KiteAeroDyn Driver, KiteVSM, ActuatorDisk), c) interfacing an energy-kite controller, and d) coupling the various KiteFAST modules together (KiteFASTMBD).

Jonkman, Jason↗