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At least 73 records · Page 4

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DOE OSTI2024

Solar Photovoltaic (PV) Damage Assessment After Typhoon Mawar: Findings and Recommendations for Resilient PV on Guam

A team from the National Renewable Energy Laboratory (NREL) visited Guam in August 2023 to assess failure modes of solar photovoltaic (PV) systems after Typhoon Mawar and to provide recommendations to increase the resilience of PV systems on Guam. The team visited 30 systems: commercial and utility scale, and rooftop and ground-mounted. The team observed systems with no apparent damage, as well as systems that were completely lost. Systems fared very well overall. The average failure rate of rooftop systems was 18%, with a median failure rate of 2%, meaning the few systems that suffered total loss pulled up the average. Only eight 8 of the 25 rooftop systems suffered more than 5% damage. All ground-mounted systems suffered less than 0.5% damage, aside from a carport that lost 16% of its modules. PV systems at Andersen Air Force Base suffered 5% damage on average, with a median system failure of 0.6%. In almost all cases, failures were the result of: (1) Inadequate clamping of the module frame to the mount, (2) Module mounting clamps rotating out of underlying support rail (i.e., T-bolt that rotates free at less than 60 degrees of rotation), (3) An object hitting the panel resulting in a fracture, and in some cases leading to a cascading failure of several more panels, and (4) Excessive tilt angle (in Guam, greater than 5 degrees can be a risk due to wind speed, and power production trade-offs are insignificant).

14 SOLAR ENERGY↗

DOE OSTI2025

Mechanical Design of the PIP-II ORBUMP Pulsed Dipole Magnet

The Proton Improvement Plan-II (PIP-II) is a vital upgrade to Fermilab's accelerator complex. The upgrade is designed to power the world s most intense high-energy neutrino beam in future experiments. The magnet pulse repetition rate of the PIP-II injection system is being upgraded from 15 Hz to 20 Hz and requires a roughly 30% increase in the magnetic field of the new Orbital Bump (ORBUMP) magnets in the Booster. The magnet is secured in a vacuum box and the core is made up of 0.127 mm thick, low carbon steel laminations with a C-5 inorganic coating. The core is clamped using external tie bars welded to the core end plates. ANSYS Finite Element Analysis (FEA) was used to evaluate the clamping design to minimize the deflection of the core post welding of the tie bars. The water-cooled single turn coil is electrically isolated from the core using virgin PEEK insulating material in the gap. An investigation into the high voltage performance of the virgin PEEK insulator was conducted. The design of the coil which shapes the magnetic field by acting as the pole tips is critical for the integrated field homogeneity. The coil manufacturing tolerances and fabrication techniques were evaluated to ensure the magnetic properties of the magnet could be obtained. The ORBUMP magnet mechanical design is presented in this paper.

Karas, Dino [Fermilab] (ORCID:0000000304340670)↗

DOE OSTI2025

Investigation of Anomalous Thread Wear in EDS Vessels

Potential causes of anomalous thread wear observed on EDS system fasteners were investigated using the V25 two-piece clamped vessel as a test bed. Thread wear and metal particulate were analyzed across operational conditions. Despite intensive testing, galling wear was not triggered, reducing uncertainty about design tolerances, material selection, and environmental factors. Minimum service life benchmarks were established for two-piece clamp fasteners under normal EDS conditions.

42 ENGINEERING↗

DOE OSTI2021

Interleaved multi-channel, multi-level, multi-quadrant DC-DC converters

Direct-current-to-direct-current (DC-DC) power converters that include two or more multi-quadrant, multi-level, DC-DC, switching converter subcircuits, connected in parallel at respective input and output sides, so as to provide a multi-channel, multi-quadrant, multi-level configuration, are disclosed. The DC-DC power converters further include a control circuit configured to control the switching converter subcircuits so that corresponding switching semiconductors in each of the switching converter subcircuits are switched in an interleaved manner. In some embodiments, each of the switching converter subcircuits is a three-level, neutral-point-clamped, four-quadrant DC-DC converter circuit. In other embodiments, each of the switching converter subcircuits is a three-level, neutral-point-clamped, two-quadrant DC-DC converter circuit. In any of these embodiments, a filter capacitor may be connected between across a pair of output terminals at the output sides of the switching converter subcircuits.

Du, Yu↗

DOE OSTI2022

TREAT Slide Decks for Alabama A&M

Slides to introduce TREAT and two senior design projects to a professor and senior engineering students at Alabama A&M. Slide Deck 1 is an overview of the TREAT Reactor and its mission. Use for Space Nuclear Thermal Propulsion Testing is mentioned, but no details of space reactor fuel are included. Review for unlimited release is requested. Slide deck 2 presents technical background for neutron radiography, with contrast to x-radiography, and then presents the application of TREAT for Flash Radiography. Slide Deck 3 describes the background behind the second senior design project, which is to design powered actuators for TREAT core clamps. Slide Deck 3 includes photos of different sides of the TREAT reactor and sketches of internal components associated with the core clamping system. These were presented via Teams on October 5, but we want to provide the slidedeck files to the university for student reference.

21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS↗

DOE OSTI2025

A Digital Three Level Space Vector Modulator for High Frequency Vector Sequence Generation

This letter proposes a digital high-speed three-level space vector pulse width modulator (3L-SVPWM). A conventional 3L-SVPWM is typically computation-based, involving a sequential execution of sub-tasks on a digital signal processor (DSP) based controller. The resulting high computation time of 5.4 μs limits the implementation of additional control blocks for switching frequencies greater than 100 kHz. This is overcome by transforming sub-tasks into digital blocks with 1-0 decisions and simpler arithmetic operations. The sub-task blocks are executed concurrently on a programmable logic device (PLD). Hence, a fast 3L-SVPWM execution in 140 ns is achieved. The proposed digital 3L-SVPWM enables high switching frequency operation of wide bandgap (WBG) device-based 3 L inverters to generate high fundamental frequency waveforms. A finite state machine is an integral part of the proposed implementation with the ability to generate any vector sequence, maximizing the usage of redundant vector states in 3L-SVPWM. Here, the proposed digital 3L-SVPWM operation is demonstrated with a GaN-based 3 L active neutral point clamped (3L-ANPC) inverter. Experimental results are presented at 250 kHz switching frequency to generate vector sequences for center-aligned SVPWM (CA-SVPWM) and common mode voltage reduced SVPWM (CMVR-SVPWM). The results also showcase a high fundamental frequency generation capability of 10 kHz.

active neutral point clamped inverter↗

DOE OSTI2021

A Generic Two-Vector Model Predictive Control for Hybrid Multilevel Converters

In this article, a generic two-vector model predictive control (TV-MPC) strategy is proposed for the hybrid multilevel converters (HMCs). The proposed method selects two optimal voltage vectors among all the vector candidates using a geometric positioning approach to reduce the computational burden, which is a common issue in the existing MPC methods for HMC. Then duty cycles of the two selected vectors are optimized to minimize the current tracking error, such that the current tracking performance can be enhanced compared with the conventional MPC. In addition, the voltages of the floating dc capacitors can be balanced by evaluating all switching sequences that belong to the optimal voltage vectors with optimal duty cycles. Here, the concept of the proposed TV-MPC is generic and applicable for any HMCs. A typical HMC based on active neutral-point-clamped topology is adopted as a case study in this work. Comprehensive simulation and experimental studies are performed on an all silicon-carbide HMC prototype to validate the effectiveness of the proposed control scheme.

42 ENGINEERING↗

DOE OSTI2020

A New Configuration of Paralleled Modular ANPC Multilevel Converter Controlled by an Improved Modulation Method for 1 MHz, 1 MW EV Charger

In this work, a new configuration of the modular multilevel converter (MLC) based on the parallel connection of three-level active-neutral-point-clamped (3L-ANPC) cells as well as its improved modulation method is proposed for 1 MHz, 1 MW electric vehicle (EV) megacharger. In the proposed paralleled modular ANPC-MLC, only six high-frequency silicon carbide (SiC) power switches operating at 333 kHz are required to generate 1 MHz switching frequency spectrum. Moreover, the operating voltage of all power devices is halved, the magnitude of the first switching frequency harmonic cluster is decreased by the factor of five, and the load current is equally distributed between the 3L-ANPC legs by employing the proposed improved modulation method. Hence, the modularity, efficiency, and power density of the proposed converter are notably increased, whereas the value of passive components and the overall switching loss are remarkably decreased. In addition, an optimized design of the one 3L-ANPC cell of the proposed paralleled modular ANPC-MLC for 1 MHz, 1MW EV megacharger using Ansys SIwave, Icepak, and Q3D finite element method platforms is presented and analyzed in detail. The provided experimental results of the down-scaled setup verify the feasibility and viability of the proposed configuration as well as its improved switching pattern.

42 ENGINEERING↗

DOE OSTI2020

A Virtual Space Vector Model Predictive Control for a Seven-Level Hybrid Multilevel Converter

This paper proposes a virtual space vector (VSV) model predictive control (MPC) for a three-phase seven-level (7L) hybrid multilevel converter (HMC), where each phase consists of an active-neutral-point-clamped converter with a floating H-bridge. To achieve the best current tracking, which is the primary goal of the proposed algorithm, a novel geometrical positioning approach is proposed to select the optimal voltage vector among all the realspace vectors and VSVs. Then, all the possible switching sequences that belong to the optimal voltage vector are evaluated to realize the dc capacitor voltage balancing and common-mode voltage reduction. Through an external modulator, the optimal voltage vector can be synthesized by using either one-, three-, or seven-segment switching sequence. Compared with the conventional MPC, the proposed VSV-MPC can reduce not only the computational burden but also the current THD. Both simulation and experimental results obtained on silicon carbide based 7L-HMC prototype are presented to validate the feasibility and effectiveness of the proposed VSVMPC strategy.

42 ENGINEERING↗

DOE OSTI2020

Simplified Two-Stage Model Predictive Control for a Hybrid Multilevel Converter With Floating H-Bridge

This paper proposes a simplified two-stage model predictive control (ST-MPC) for a hybrid multilevel converter, which is an active-neutral-point-clamped converter with floating H-bridge (ANPC-H). The objective of the first stage is to select the voltage vector that has the optimal current tracking performance by using a novel geometrical positioning approach in the complex plane. The second stage selects the best switching state among all the available switching states that belong to the same voltage vector obtained in the first stage, to balance dc capacitor voltages and reduce the common mode voltage. The proposed ST-MPC can dramatically reduce the computational burden and ensure the best current tracking by the two-stage structure, such that the execution time is much shorter compared with the conventional MPC. In addition, the geometrical positioning approach in the first stage is generic and can be applicable for any multilevel converters with N-level output; thus, this ST-MPC can be applied for both sevenand nine-level operation of the hybrid ANPC-H converter under different dc voltage ratios. Both simulation results and experimental results obtained on a silicon carbide hybrid ANPC-H converter prototype validate the feasibility and effectiveness of the proposed ST-MPC strategy.

42 ENGINEERING↗

DOE OSTI2021

Flaming Moe

Current clamp measurements collected on various small electronic devices. Details on the data set can be found in J. M. Vann, T. P. Karnowski, R. Kerekes, C. D. Cooke and A. L. Anderson, A Dimensionally Aligned Signal Projection for Classification of Unintended Radiated Emissions, in IEEE Transactions on Electromagnetic Compatibility, vol. 60, no. 1, pp. 122-131, Feb. 2018, doi: 10.1109/TEMC.2017.2692962.

24 POWER TRANSMISSION AND DISTRIBUTION↗

DOE OSTI2021

High Efficiency OLED Light Engine

LED Specialists has accomplished the program objective in designing a high efficiency OLED light engine combining high-performance OLED panels in the 5W-8W range. We achieved our goal by using an Active-Clamp Flyback circuit topology using state-of-the-art electronics. Evaluation testing of our second-generation prototype PC board has demonstrated an efficiency rating of 93% and dimming capability between 100% and 5% of OLED brightness. A reliability analysis of the design shows it to have a predicted Mean Time Between Failures (MTBF) of approximately 1,000,000 hours.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗

DOE OSTI2022

Alabama A&M University Senior Project

21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS↗

DOE OSTI2023

Alabama A&M University Senior Project Cont'd

This entry is being conducted in order to review documents (drawings and pictures) necessary for senior students of Alabama A&M to conduct their senior project. This project will include helping design an upgraded operating system for the TREAT core clamping units. A previous has been completed for the project per STI # INL/MIS-22-69603 Rev:000, these additional items will further assist the students in there work.

21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS↗

DOE OSTI2020

Beyond Substrates: Strain Engineering of Ferroelectric Membranes

Strain engineering in perovskite oxides provides for dramatic control over material structure, phase, and properties, but is restricted by the discrete strain states produced by available high-quality substrates. Here, using the ferroelectric BaTiO3, production of precisely strain-engineered, substrate-released nanoscale membranes is demonstrated via an epitaxial lift-off process that allows the high crystalline quality of films grown on substrates to be replicated. In turn, fine structural tuning is achieved using interlayer stress in symmetric trilayer oxide-metal/ferroelectric/oxide-metal structures fabricated from the released membranes. Additionally, in devices integrated on silicon, the interlayer stress provides deterministic control of ordering temperature (from 75 to 425 °C) and releasing the substrate clamping is shown to dramatically impact ferroelectric switching and domain dynamics (including reducing coercive fields to <10 kV cm-1 and improving switching times to <5 ns for a 20 µm diameter capacitor in a 100-nm-thick film). In devices integrated on flexible polymers, enhanced room-temperature dielectric permittivity with large mechanical tunability (a 90% change upon ±0.1% strain application) is demonstrated. This approach paves the way toward the fabrication of ultrafast CMOS-compatible ferroelectric memories and ultrasensitive flexible nanosensor devices, and it may also be leveraged for the stabilization of novel phases and functionalities not achievable via direct epitaxial growth.

36 MATERIALS SCIENCE↗

DOE OSTI2021

Texture Formation in Polycrystalline Thin Films of All‐Inorganic Lead Halide Perovskite

Abstract Controlling grain orientations within polycrystalline all‐inorganic halide perovskite solar cells can help increase conversion efficiencies toward their thermodynamic limits; however, the forces governing texture formation are ambiguous. Using synchrotron X‐ray diffraction, mesostructure formation within polycrystalline CsPbI 2.85 Br 0.15 powders as they cool from a high‐temperature cubic perovskite (α‐phase) is reported. Tetragonal distortions (β‐phase) trigger preferential crystallographic alignment within polycrystalline ensembles, a feature that is suggested here to be coordinated across multiple neighboring grains via interfacial forces that select for certain lattice distortions over others. External anisotropy is then imposed on polycrystalline thin films of orthorhombic (γ‐phase) CsPbI 3‐ x Br x perovskite via substrate clamping, revealing two fundamental uniaxial texture formations; i) I‐rich films possess orthorhombic‐like texture (<100> out‐of‐plane; <010> and <001> in‐plane), while ii) Br‐rich films form tetragonal‐like texture (<110> out‐of‐plane; <110> and <001> in‐plane). In contrast to relatively uninfluential factors like the choice of substrate, film thickness, and annealing temperature, Br incorporation modifies the γ‐CsPbI 3− x Br x crystal structure by reducing the orthorhombic lattice distortion (making it more tetragonal‐like) and governs the formation of the different, energetically favored textures within polycrystalline thin films.

Steele, Julian A.↗

DOE OSTI2021

Freestanding Ferroelectric Bubble Domains

Bubble-like domains, typically a precursor to the electrical skyrmions, arise in ultrathin complex oxide ferroelectric-dielectric-ferroelectric heterostructures epitaxially clamped with flat substrates. Here, it is reported that these specially ordered electric dipoles can also be retained in a freestanding state despite the presence of inhomogeneously distributed structural ripples. By probing local piezo and capacitive responses and using atomistic simulations, this study analyzes these ripples, sheds light on how the bubbles are stabilized in the modified electromechanical energy landscape, and discusses the difference in morphology between bubbles in freestanding and as-grown states. Furthermore, these results are anticipated to be the starting point of a new paradigm for the exploration of electric skyrmions with arbitrary boundaries and physically flexible topological orders in ferroelectric curvilinear space.

36 MATERIALS SCIENCE↗

DOE OSTI2025

Scale-Up of Friction Self-piercing Riveting Process for Multi-material Joints

A single-class joining process known as “friction self-piercing riveting (F-SPR)” has been developed for joining various low-ductility lightweight materials on a laboratory scale. The frictional heat generated during the F-SPR process improved local ductility, resulting in crack-free joints and robust mechanical performance. This innovative joining technology was further advanced through the scale-up of the process using a new system with several key features (e.g., automatic rivet feeding and clamping system, vacuum system) toward industry readiness. The new integrated F-SPR systems were effectively demonstrated for joining different material combinations (e.g., carbon fiber composite to 7075 Al alloy, 7075 Al alloy to 7075 Al alloy, and 7075 Al alloy to casting Al Aural 5) with a unified technique. Crack-free joint with adequate mechanical interlocking resulted in good mechanical joint strength for each material combination. Then, the process was successfully scaled up by producing multiple joints without any cracks on larger CFC-Al and Al-Al components by the new integrated system, bringing it closer to industrial application.

Lim, Yong Chae [ORNL] (ORCID:0000000321773988)↗