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Wood, David

Publications and source records attributed to Wood, David.

At least 19 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2024

User Impressions and Gait Analysis of Exoskeleton Device Usage in Generalized Tank Farm Activities

Tank farm workers involved in nuclear cleanup activities perform physically demanding tasks, typically while wearing heavy personal protective equipment (PPE). Exoskeleton devices have the potential to bring considerable benefit to this industry but have not been thoroughly studied in the context of nuclear cleanup. In this paper, we examine the performance of exoskeletons during a series of tasks emulating jobs performed on tank farms while participants wore PPE commonly deployed by tank farm workers. The goal of this study was to evaluate the effects of commercially available lower-body exoskeletons on a user’s gait kinematics and user perceptions. Three participants each tested three lower-body exoskeletons in a 70-min protocol consisting of level treadmill walking, incline treadmill walking, weighted treadmill walking, a weight lifting session, and a hand tool dexterity task. Results were compared to a no exoskeleton baseline condition and evaluated as individual case studies. The three participants showed a wide spectrum of user preferences and adaptations toward the devices. Individual case studies revealed that some users quickly adapted to select devices for certain tasks while others remained hesitant to use the devices. Temporal effects on gait change and perception were also observed for select participants in device usage over the course of the device session. Here, device benefit varied between tasks, but no conclusive aggregate trends were observed across devices for all tasks. Evidence suggests that device benefits observed for specific tasks may have been overshadowed by the wide array of tasks used in the protocol.

Tank farm↗
DOE OSTI2023

Modeling the Yaw Behavior of Tail Fins for Small Wind Turbines: November 22, 2021 - May 21, 2024

This report describes the aerodynamic modelling of the yaw behavior of tail fins for small wind turbines (SWTs). The analysis is based on unsteady slender body theory (USBT) and is formulated to be used with the proposed tail fin module to be added to OpenFAST. Linearized USBT, which has been applied in the past to SWT tail fins, is developed in three main ways. First, USBT is extended to high yaw angles and aspect ratios by modelling the associated nonlinear vortex dynamics and the chordwise load distribution respectively. Second, we consider the effect of time-varying wind speed. The extended theory is compared to recent unpublished measurements at the University of Perugia, Italy, for the yaw behavior of delta, elliptical, and rectangular tail fins without a rotor and nacelle. The fins were released from initial yaw angles of -40 degrees and -80 degrees ; the latter is of sufficient magnitude to show the importance of the nonlinear yaw dynamics. Further, the friction in the model tail fin bearings was measured and modelled. The constants in the aerodynamic models were taken from the literature but significant improvement in accuracy is achieved by using system identification techniques to optimize the values. This leads to the third main finding: extended USBT is accurate for all generic tail fin shapes that we considered and is, therefore, very suitable for inclusion in aeroelastic codes for SWTs. The final development is of a general nonlinear equation for yaw response that is simpler than the extended USBT and is also suitable for inclusion in OpenFAST. The two nonlinear models are used to highlight the geometric requirements for good tail fin design.

distributed wind↗
DOE OSTI2023

Improvements to the Simplified Loads Methodology in IEC 61400-2: November 22, 2021 - November 21, 2022

The "Simplified Loads Model" (SLM) of IEC 61400-2 provides a simple methodology to assess the structural integrity of a small wind turbine (SWT). The SLM is unique to the small wind turbine standard. It was included to allow SWT manufacturers with limited resources to undertake integrity checks at a reasonable cost in time and resources and avoid the expense of detailed aeroelastic simulations. Unfortunately, the SLM has gained the reputation of being overly conservative and this has reduced its value to the SWT community and its use in SWT design and certification. Conservatism in design standards is needed but excessive conservatism is not. The aim of this report is to address the principal areas of excess conservatism and recommend changes to the SLM that preserve its simplicity but reduce the excess. The changes for the ultimate loads are consistent with their treatment in aeroelastic modelling for certification and with related codes for wind loading on structures. The recommendations for a new fatigue design load case are also based on aeroelastic simulations, in this case of five SWTs of varying configurations with rated power from 2.4 to 50 kW. It is also pointed out the design load case for yawed operation omits an important term. The recommended inclusion of this term would make the SLM slightly more conservative for this case.

17 WIND ENERGY↗
DOE OSTI2022

Current status and grand challenges for small wind turbine technology

While modern wind turbines have become by far the largest rotating machines on Earth with further upscaling planned for the future, a renewed interest in small wind turbines (SWTs) is fostering energy transition and smart grid development. Small machines have traditionally not received the same level of aerodynamic refinement as their larger counterparts, resulting in lower efficiency, lower capacity factors, and therefore a higher cost of energy. In an effort to reduce this gap, research programs are developing worldwide. With this background, the scope of the present study is 2-fold. In the first part of this paper, an overview of the current status of the technology is presented in terms of technical maturity, diffusion, and cost. The second part of the study proposes five grand challenges that are thought to be key to fostering the development of small wind turbine technology in the near future, i.e. (1) improving energy conversion of modern SWTs through better design and control, especially in the case of turbulent wind; (2) better predicting long-term turbine performance with limited resource measurements and proving reliability; (3) improving the economic viability of small wind energy; (4) facilitating the contribution of SWTs to the energy demand and electrical system integration; (5) fostering engagement, social acceptance, and deployment for global distributed wind markets. To tackle these challenges, a series of unknowns and gaps are first identified and discussed. Based on them, improvement areas are suggested, for which 10 key enabling actions are finally proposed.

17 WIND ENERGY↗
DOE OSTI2020

A simple method for modelling fatigue spectra of small wind turbine blades

Small-scale wind turbines have market opportunities in distributed energy generation applications but face future challenges in remaining cost competitive compared with solar photovoltaic systems. High unit costs can be attributed to design conservatism when calculating fatigue loads of key structural components such as the blades. In this study, we use the aeroelastic software FAST to highlight limitations of the International Electrotechnical Commission 61400-2:2013 small wind turbine design standard for calculating fatigue life using the simplified load model. We present a modified method for calculating the fatigue spectra of small wind turbine blades. An advantage of this method is that it does not require complex aeroelastic simulations or field measurements. This modified method is intended to be implemented early in the blade design stage, such as during rotor optimization simulations, allowing for multiple rotor configurations to be rapidly compared.

17 WIND ENERGY↗
DOE OSTI2020

Co-Extrusion (CoEx) for Cost Reduction of Advanced High-Energy-and-Power Battery Electrode Manufacturing

Co-Extrusion (CoEx) is a deposition technology developed at PARC that uses engineered fluidic channels to cause multiple streams of dissimilar fluids to impart shape to one another. Here, we describe the use of CoEx to produce structured cathode electrode films to improve electrochemical performance of thick electrode films. CoEx enables us to create structured electrode films that have periodic regions of enhanced ionic conductivity, enabling higher utilization of thicker cathode films at high discharge rates. While increasing electrode thickness is a known method for increasing energy density of battery electrodes, this increase in energy density typically also results in reduced power density. This project, a collaboration between the Palo Alto Research Center, Oak Ridge National Laboratories, and Ford Motor Company, seeks to first validate the benefits of CoEx at the coin cell level, before performing the necessary R&D effort to scale production up to large (10+ Ah) pouch cells that will show increased energy density without a reduction in power density. We used conventional battery materials (commercially available NMC, PVDF, carbon black, and graphite) to produce structured electrodes via CoEx and compared them to thick and thin conventionally produced (unstructured) battery electrodes. CoEx electrodes show improved high rate performance compared to unstructured electrodes, resulting in higher energy density pouch cells compared to the baseline electrode of 7 and 11% in volumetric and gravimetric energy density, respectively. These electrodes also showed substantially improved electrochemical performance at high discharge rates compared to thick conventional electrodes.

25 ENERGY STORAGE↗
DOE OSTI2018

Thick Co-Extruded Cathode Electrodes for High Energy Lithium-Ion Batteries

Co-Extrusion (CoEx) is a high speed, scalable deposition process for creating finely patterned, interdigitated thick films. Our CoEx printhead is designed to be a drop-in replacement for slot-die heads on web coaters, enabling novel geometric structuring of electrodes with minor changes to existing battery electrode processing lines. Here, we present the use of CoEx to prepare thick (~ 120 µm) NMC cathode electrodes consisting of alternating regions of high lithium-ion transport and high lithium-ion storage capacity. By structuring the cathode electrode, we enable full lithium utilization at C/2, despite near doubling of the electrode thickness compared to conventional baseline electrodes. CoEx cathode electrodes are paired with thick, graded graphite anode electrodes and assembled into 1 Ah pouch cells for electrochemical testing. CoEx pouch cells demonstrate 10 – 20% improved energy density with respect to conventional electrodes and > 30% improved power density with respect to thick conventional (unstructured) electrodes at high discharge rates,

25 ENERGY STORAGE↗
DOE OSTI2018

Roll-to-Roll Advanced Materials Manufacturing Lab Consortium

Oak Ridge National Laboratory (ORNL), Argonne National Laboratory (ANL), Lawrence Berkeley National Laboratory (LBNL), and the National Renewable Energy Laboratory (NREL) in collaboration with Eastman Kodak Business Park (Kodak) and Citrine Informatics (Citrine) formed a consortium to broadly disseminate materials, process science, and advanced technologies to industry in the area of R2R manufacturing.

36 MATERIALS SCIENCE↗
DOE OSTI2017

Measurements of Long-range Electronic Correlations During Femtosecond Diffraction Experiments Performed on Nanocrystals of Buckminsterfullerene

The precise details of the interaction of intense X-ray pulses with matter are a topic of intense interest to researchers attempting to interpret the results of femtosecond X-ray free electron laser (XFEL) experiments. An increasing number of experimental observations have shown that although nuclear motion can be negligible, given a short enough incident pulse duration, electronic motion cannot be ignored. The current and widely accepted models assume that although electrons undergo dynamics driven by interaction with the pulse, their motion could largely be considered 'random'. This would then allow the supposedly incoherent contribution from the electronic motion to be treated as a continuous background signal and thus ignored. The original aim of our experiment was to precisely measure the change in intensity of individual Bragg peaks, due to X-ray induced electronic damage in a model system, crystalline C 60 . Contrary to this expectation, we observed that at the highest X-ray intensities, the electron dynamics in C 60 were in fact highly correlated, and over sufficiently long distances that the positions of the Bragg reflections are significantly altered. Our paper describes in detail the methods and protocols used for these experiments, which were conducted both at the Linac Coherent Light Source (LCLS) and the Australian Synchrotron (AS) as well as the crystallographic approaches used to analyse the data.

43 PARTICLE ACCELERATORS↗
DOE OSTI2017

Material-Process-Performance Relationships for Roll-to-Roll Coated PEM Electrodes

Roll-to-roll (R2R) coating is the most economical and highest throughput method for producing fuel cell electrodes. R2R coating encompasses many different methodologies to create uniform films on a moving web substrate. Here we explore two coating methods, gravure and slot die, to understand the impacts of each on film uniformity and performance.

30 DIRECT ENERGY CONVERSION↗
DOE OSTI2016

Processing-Structure-Property Relationships for Lignin-Based Carbonaceous Materials Used in Energy-Storage Applications

Lignin, an abundant organic polymer and a byproduct of pulp and biofuel production, has potential applications owing to its high carbon content and aromatic structure. Processing structure relationships are difficult to predict because of the heterogeneity of lignin. Here, this work discusses the roles of unit operations in the carbonization process of softwood lignin, and their resulting impacts on the material structure and electrochemical properties in application as the anode in lithium-ion cells. The processing variables include the lignin source, temperature, and duration of thermal stabilization, pyrolysis, and reduction. Materials are characterized at the atomic and microscales. High-temperature carbonization, at 2000 °C, produces larger graphitic domains than at 1050 °C, but results in a reduced capacity. Coulombic efficiencies over 98 % are achieved for extended galvanostatic cycling. Consequently, a properly designed carbonization process for lignin is well suited for the generation of low-cost, high-efficiency electrodes.

25 ENERGY STORAGE↗