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At least 1,531 records · Page 85
All sourcesNASA NTRSDOE OSTI
DOE OSTI2021

Interfacial Characterization of Positive Bias Voltage Degradation in PV Modules

Degradation from high system voltage is a prevailing failure mode in fielded photovoltaic modules, and the degradation mechanism is inherently dependent on the bias polarity. Here we report the effects of positive bias. Modules under positive bias demonstrated a significant photocurrent loss caused by two routes. First, delamination and discoloration of the silicon nitride layer, leading to optical loss determined by reflectance measurements. Second, chemical discoloration of the cell gridlines and encapsulant (EVA), which is linked to an electrochemical reaction at the silver electrodes. Chemical compositional analysis using X-ray photoemission spectroscopy demonstrated that the discoloration is attributed to Ag 2 S and/or Ag 2 O. Evidence of Ag ion migration from the cell grid into the encapsulant is observed after shallow depth profiling on the EVA surface. However, Ag was not detected at the EVA/glass interface, inferring limited Ag ion transport through the EVA. The source of sulfur is believed to be ambient air, which diffused into the module through the breathable backsheet.

characterization↗
DOE OSTI2023

Luminescence and Thermal Imaging Applied to Half-Cut-Cell and Emitter-Wrap-Through-Cell Modules

Imaging techniques provide spatial details and visualization of module defects and degradation mechanisms that affect energy conversion efficiency and performance. We apply photoluminescence, electroluminescence, and dark lock-in thermography imaging techniques to evaluate new modules in their initial state and after applying stresses of damp heat, light-induced-degradation regeneration parameters, thermal cycling, and humidity-freeze cycles. One module uses emitter-wrap-through cells with back contacts connected to a metal-foil backplane, and the other is composed of half-cut cells. Imaging shows examples on non-uniform degradation and damage such as cells that degrade and recover under the applied conditions, cells with cracks and handling damage, and cells with increasing series resistance.

degradation↗
DOE OSTI2025

On the Development of Compact HTS Coil Modules for Large Bore High Field Superconducting Magnets

Lower cost, high current density superconducting coil modules producing higher magnetic fields and cooled affordably are crucial for obtaining cost-effective, compact commercial fusion reactors. Accessibility to low cost, higher field magnets (>30 T) is also critical for the discovery of new quantum phenomena in materials, cosmic frontier and other topics in basic science research. The Princeton Plasma Physics Laboratory (PPPL) is working with Princeton University to develop unique large bore, compact superconducting magnets to support science experiments including the development of new instrumentation for condensed matter physics and Axion dark matter search in the cosmic frontier. Core elements of these experiments are unique for access to lower cost, simple fabrication of compact superconducting magnets that can be cooled affordably, while integrated with dedicated science instruments. Conductor qualification and coil design concepts are discussed in support of needs for these experiments. PPPL has the unique expertise and experimental facilities to design, construct and test subscale coil modules for these projects. Compact high field coil modules were fabricated and tested to validate coil design concepts and coil performance. Finally, the design and model coil integration challenges are discussed to identify performance risks and demonstrate feasibility for deploying full scale large bore compact superconducting magnets for cost effective operations of multiple laboratory experiments.

axion dark matter↗
DOE OSTI2019

Self-Powering High Frequency Modulated SiC Power MOSFET Isolated Gate Driver

A novel implementation of an isolated gate driver for power switches is proposed in this study. The driver is bespoke designed for SiC power mosfet s. The proposal achieves the main driver characteristics—isolation capability, gate switching command, and power transfer to the secondary side by using a unique magnetic transformer. The resulting simple circuitry enables the integration of the driver into the power cell, achieving theoretical higher power density values of the final system. The principle of operation of the driver is described in detail. The original pulsewidth modulation signal is modulated with a pure ac square waveform under a two-level modulation scheme, that guarantees no saturation of the magnetic core. Here, the signal is then magnetically coupled to the secondary side, where it is rectified and reconstructed to effectively drive the target device. In addition, the steps needed to provide a suitable design taking into account the parameters of the target power switch are also detailed. The resulting driver is characterized and a prototype of the driver is built and tested. The main results of the driver performance on a SiC mosfet -based prototype are presented. Based on the analysis of these results, this study experimentally demonstrates the feasibility of the proposal.

25 ENERGY STORAGE↗
DOE OSTI2021

A 10-Gb/s Driver/Receiver ASIC and Optical Modules for Particle Physics Experiments

We present the design and test results of a Drivers and Limiting AmplifierS ASIC operating at 10 Gbps (DLAS10) and three Miniature Optical Transmitter/Receiver/Transceiver modules (MTx+, MRx+, and MTRx+) based on DLAS10. DLAS10 can drive two Transmitter Optical Sub-Assemblies (TOSAs) of Vertical Cavity Surface Emitting Lasers (VCSELs), receive the signals from two Receiver Optical Sub-Assemblies (ROSAs) that have no embedded limiting amplifiers, or drive a VCSEL TOSA and receive the signal from a ROSA, respectively. Each channel of DLAS10 consists of an input Continuous Time Linear Equalizer (CTLE), a four-stage limiting amplifier (LA), and an output driver. The LA amplifies the signals of variable levels to a stable swing. The output driver drives VCSELs or impedance-controlled traces. DLAS10 is fabricated in a 65 nm CMOS technology. The die is 1 mm x 1 mm. DLAS10 is packaged in a 4 mm x 4 mm 24-pin quad-flat no-leads (QFN) package. DLAS10 has been tested in MTx+, MRx+, and MTRx+ modules. Both measured optical and electrical eye diagrams pass the 10 Gbps eye mask test. Furthermore, the input electrical sensitivity is 40 mVp-p, while the input optical sensitivity is -12 dBm. The total jitter of MRx+ is 29 ps (P-P) with a random jitter of 1.6 ps (RMS) and a deterministic jitter of 9.9 ps. Each MTx+/MTRx+ module consumes 82 mW/ch and 174 mW/ch, respectively.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2013

Automatic Layout Design for Power Module

The layout of power modules is one of the key points in power module design, especially for high power densities, where couplings are increased. In this paper, along with the design example, an automatic design processes by using a genetic algorithm are presented. Some practical considerations and implementations are introduced in the optimization of module layout design.

42 ENGINEERING↗
DOE OSTI2019

Bond Wire Damage Detection and SOH Estimation of a Dual Pack IGBT Power Module using Active Power Cycling and Reflectometry

High thermal and electrical stress, over a period of time tends to cause deterioration of the health of power electronic switches. A huge fraction of research efforts involves the study of power electronic device reliability and development of novel techniques with higher accuracy in health estimation of such devices. Until today, no other existing techniques can determine the number of lifted bond wires and their locations in a live IGBT module. Through this paper, a new method for online condition monitoring of IGBTs and IGBT modules using SSTDR has been proposed. Unlike traditional methods, this research work concentrates at the gate terminals of the device instead of looking at the collector side. In addition, the RL-equivalent circuit to represent a bond wire has been developed for the DUT and simulated in CST Studio Suite to measure the reflection amplitudes. Both the experimental and simulation results have been compared. These results prove that a single measurement is sufficient to predict the failure of the device instead of looking at the traditional precursor parameter. With only two sets of measurements, it is possible to locate the aged device inside a module and detect the number of bond wire lift offs associated to that device.

30 DIRECT ENERGY CONVERSION↗
DOE OSTI2018

New Educational Modules Using a Cyber-Distribution System Testbed

At Washington State University (WSU), a modern cyber-physical system testbed has been implemented based on an industry grade distribution management system (DMS) that is integrated with remote terminal units (RTUs), smart meters, and a solar photovoltaic (PV). In addition, the real model from the Avista Utilities distribution system in Pullman, WA, is modeled in DMS. The proposed testbed environment allows students and instructors to utilize these facilities for innovations in learning and teaching. For power engineering education, this testbed helps students understand the interaction between a cyber system and a physical distribution system through industrial level visualization. The testbed provides a distribution system monitoring and control environment for students. Compared with a simulation based approach, the testbed brings the students' learning environment a step closer to the real world. The educational modules allow students to learn the concepts of a cyber-physical system and an electricity market through an integrated testbed. Furthermore, the testbed provides a platform in the study mode for students to practice working on a real distribution system model. Here, this paper describes the new educational modules based on the testbed environment. Three modules are described together with the underlying educational principles and associated projects.

24 POWER TRANSMISSION AND DISTRIBUTION↗
DOE OSTI2017

Relating Product Prices to Long‐Run Marginal Cost: Evidence from Solar Photovoltaic Modules

Abstract A basic tenet of microeconomics is that for a competitive industry in equilibrium the market price of a product will be equal to its marginal cost. This paper develops a model framework and a corresponding empirical inference procedure for estimating long‐run marginal cost in industries where production costs decline over time. In the context of the solar photovoltaic (PV) module industry, we rely primarily on firm‐level financial accounting data to estimate the long‐run marginal cost of PV modules for the years 2008–2013. During those years, the industry experienced both unprecedented price declines and significant expansions of manufacturing capacity. We compare the trajectory of average sales prices with the estimated long‐run marginal costs in order to quantify the extent to which actual price declines were attributable to reductions in production costs. The trajectory of estimated product costs is then extrapolated to forecast an equilibrium trend line for future PV module prices.

Reichelstein, Stefan↗
DOE OSTI2019

Caffeine and cannabinoid receptors modulate impulsive behavior in an animal model of attentional deficit and hyperactivity disorder

Abstract Attention deficit and hyperactivity disorder ( ADHD ) is characterized by impaired levels of hyperactivity, impulsivity, and inattention. Adenosine and endocannabinoid systems tightly interact in the modulation of dopamine signaling, involved in the neurobiology of ADHD . In this study, we evaluated the modulating effects of the cannabinoid and adenosine systems in a tolerance to delay of reward task using the most widely used animal model of ADHD . Spontaneous Hypertensive Rats ( SHR ) and Wistar–Kyoto rats were treated chronically or acutely with caffeine, a non‐selective adenosine receptor antagonist, or acutely with a cannabinoid agonist ( WIN 55212‐2, WIN ) or antagonist ( AM 251). Subsequently, animals were tested in the tolerance to delay of reward task, in which they had to choose between a small, but immediate, or a large, but delayed, reward. Treatment with WIN decreased, whereas treatment with AM 251 increased the choices of the large reward, selectively in SHR rats, indicating a CB 1 receptor‐mediated increase in impulsive behavior. An acute pre‐treatment with caffeine blocked WIN effects. Conversely, a chronic treatment with caffeine increased the impulsive phenotype and potentiated the WIN effects. The results indicate that both cannabinoid and adenosine receptors modulate impulsive behavior in SHR : the antagonism of cannabinoid receptors might be effective in reducing impulsive symptoms present in ADHD ; in addition, caffeine showed the opposite effects on impulsive behavior depending on the length of treatment. These observations are of particular importance to consider when therapeutic manipulation of CB 1 receptors is applied to ADHD patients who consume coffee.

Leffa, Douglas T.↗
DOE OSTI2022

Module-Level Thermal Interface Material Degradation in HALT

Abstract In this study, thermal interface material (TIM) degradation is driven through highly accelerated life test (HALT) using temperature cycling with a prescribed vibrational acceleration for two commercially available materials having thermal conductivities of 6.0 and 8.5 W/m K. HALT specimens were prepared by applying TIM through a 4-mil stencil over AlSiC baseplates in the shape of those used in Wolfspeed CAS325M12HM2 power electronics modules. Baseplates were mounted onto aluminum carrier blocks with embedded thermocouples to characterize the thermal resistance across the baseplate and TIM layer. Thermal dissipation into the top of the baseplates was provided by a custom heating block, which mimics the size and placement of the die junctions in CAS325 modules, applying power loads of 200, 300, and 400 W. After initial characterization, samples were transferred to the HALT chamber with one set of samples exposed to temperature cycling only (TCO) and the other temperature cycling and vibration (TCV). Both sample sets were cycled between temperature extremes of −40 °C and 180 °C with vibrations applied at a peak acceleration of 3.21 Grms. After hundreds of cycles, samples were reevaluated to assess changes in thermal resistance to provide an accelerated measure of TIM degradation. This allows for reliability prediction of useful lifetime (illustrated in a solar inverter case study herein), as well as to provide a basis for developing an accelerated testing method to related temperature cycling to faster methods of degradation. Such techniques provide a means to develop maintenance schedules for power modules for ensuring sufficient thermal performance over the operating lifetime.

Engineering↗
DOE OSTI2018

Long-Term Effects of Power Quality and Power Cycling on Thermoelectric Module Performance

Thermoelectric (TE) modules used in a heat pumping mode are increasingly being used for various applications involving heating and cooling. As their use becomes more prevalent and extends to lower cost applications using inexpensive commodity power supplies, it is important to characterize the long-term effects of power cycling and power quality on their performance. Two power supplies were evaluated with different levels of periodic and random deviations (PARD) from ideal DC power. This paper presents the results of an accelerated aging experimental study on intermittent power cycling of TE modules over the span of 5 actual months with each power supply. TE performance metrics that were monitored at specific time intervals are the AC resistance and figure of merit. The applied voltage, power consumption, TE hot and cold side temperatures and air temperatures were continuously measured. The experimental results indicate that the low-quality power supply quality had only a minor influence on properties and integrity of the TE modules, and is suitable for applications requiring intermittent use without a substantial reduction in performance.

Patel, Viral↗
DOE OSTI2019

Design, Analysis and Comparison of Insulated Metal Substrates for High Power Wide-Bandgap Power Modules

In this technical paper, design, analysis and comparison of insulated metal substrates for high power wide-bandgap semiconductor-based power modules is discussed. The paper starts with technical description and discussion of state-of-the-art direct bonded copper substrates with different ceramic insulators such as AlN, Al2O3 and Si3N4. This is followed by introduction of insulated metal substrates, material properties and options on each layer, and design approach for high power applications. The properties of dielectric thickness, and impact on power handling capability of the substrate are discussed. Insulated metal substrate design approach for SiC MOSFET based power modules is presented. Finite element analysis-based characterization and comparison of different designs including steady-state and transient thermal response is presented. The results show that IMS is a promising alternative to DBC in high power modules with improved transient thermal performance. IMS provides flexible building structure with multi-layer stacking options and variable thicknesses at different layers.

Gurpinar, Emre↗
DOE OSTI2014

Modulated IR radiometry for determining thermal properties and basic characteristics of titanium thin films

Titanium thin films of different thicknesses were prepared by direct current magnetron sputtering to study modulated infrared (IR) radiometry as a tool for analyzing film thickness. Thickness was varied by regularly increasing the deposition time, keeping all the other deposition parameters constant. The influence of film thickness on morphological, structural, and electrical properties of the titanium coatings also was investigated. The experimental results revealed a systematic grain growth with increasing film thickness, along with enhanced film crystallinity, which led to increased electrical conductivity. Using the results obtained by modulated IR radiometry, the thickness of each thin film was calculated. These thickness values were then compared with the coating thickness measurements obtained by scanning electron microscopy. The values confirmed the reliability of modulated IR radiometry as an analysis tool for thin films and coatings, and for determining thicknesses in the micrometer range, in particular.

36 MATERIALS SCIENCE↗
DOE OSTI2026

Pulsed radio frequency power modulation for profile control in cryogenic reactive ion etching of silicon gratings

Cryogenic silicon etching with SF 6 /O 2 plasmas enables vertical sidewalls and smooth surfaces for high–aspect-ratio structures, yet precise control of etched profiles (sidewall angle, lateral etching, and linewidth retention) remains challenging under continuous-wave excitation due to coupling among radical fluxes, ion energy distributions, and in situ passivation dynamics. In this work, we investigated pulsed radio frequency bias delivery as a process knob for profile control during cryogenic silicon etching. Systematic experiments on 500 nm-wide, 1 μm-pitch gratings etched to 0.8–1.1 μm depth at 0.5–2 kHz pulsing frequency and 25%–75% duty cycle revealed strong dependencies of etch rate, linewidth, and sidewall angle on modulation conditions. We proposed a conceptual kinetic picture combined with feature-scale electrostatic analysis to understand the alternation of ion-driven etching and passivation recovery between on/off segments and local electric field shaping and modulation of ion trajectories within the trench. Moderate duty cycles (50%–75%) near 1 kHz achieved a balance between anisotropy and etch rate. These results demonstrate pulsed-bias modulation can be utilized to tune directionality and sidewall preservation in cryogenic SF 6 /O 2 etching, which are relevant to photonic, metrology, and quantum device fabrication.

36 MATERIALS SCIENCE↗
DOE OSTI2011

Tolerance levels of EPID-based quality control for volumetric modulated arc therapy

Purpose: Volumetric modulated arc therapy (VMAT) includes features such as a variable dose rate and gantry speed in addition to the beam modulation achieved with multileaf collimator (MLC) motion patterns employed in intensity modulated radiotherapy. Three tests have previously been proposed for the evaluation of the performance of VMAT delivery. In order to enable a convenient and accurate routine machine quality control (QC) program, the present study proposes tolerance levels for these tests based on a department-wide implementation of an electronic portal imaging device (EPID)-based QC. Methods: Three different VMAT tests--a picket fence (PF) test, a dose rate versus gantry speed (DRGS) test, and a dose rate versus MLC leaf speed (DRMLC) test--were performed on nine accelerators using two different EPIDs (aS1000 and aS500, Varian Medical Systems). All tests were repeated six times for each accelerator. The images were analyzed using an in-house-developed software. For the PF test, the positions and widths of individual MLC leaf gaps were compared to the mean value. In the DRGS and DRMLC tests, different combinations of dose rate, gantry speed, and MLC leaf speed were used to deliver identical doses to separate parts of the EPID. The tests were evaluated by looking for deviations in the constancy of the measured dose for the preset combinations of dose rate, gantry speed, and MLC leaf speed. Results: For the PF test, a 0.3 mm tolerance level was suggested for the positioning of the MLC leaves. The tolerance level for the gap width was 0.5 mm. For the DRGS and DRMLC tests, a 3% tolerance level was proposed. Conclusions: With the adapted levels of tolerance for an EPID-based approach, the PF, the DRGS, and the DRMLC tests offer a convenient and accurate machine QC program for linear accelerators used for VMAT.

07 ISOTOPE AND RADIATION SOURCES↗
DOE OSTI2011

Assessing software upgrades, plan properties and patient geometry using intensity modulated radiation therapy (IMRT) complexity metrics

Purpose: The aim of this study is to compare the sensitivity of different metrics to detect differences in complexity of intensity modulated radiation therapy (IMRT) plans following upgrades, changes to planning parameters, and patient geometry. Correlations between complexity metrics are also assessed. Method: A program was developed to calculate a series of metrics used to describe the complexity of IMRT fields using monitor units (MUs) and multileaf collimator files: Modulation index (MI), modulation complexity score (MCS), and plan intensity map variation (PIMV). Each metric, including the MUs, was used to assess changes in beam complexity for six prostate patients, following upgrades in the inverse planning optimization software designed to incorporate direct aperture optimization (DAO). All beams were delivered to a 2D ionization chamber array and compared to those calculated using gamma analysis. Each complexity metric was then calculated for all beams, on a different set of six prostate IMRT patients, to assess differences between plans calculated using different minimum field sizes and different maximum segment numbers. Different geometries, including CShape, prostate, and head and neck phantoms, were also assessed using the metrics. Correlations between complexity metrics were calculated for 20 prostate IMRT patients. Results: MU, MCS, MI, and PIMV could all detect reduced complexity following an upgrade to the optimization leaf sequencer, although only MI and MCS could detect a reduction in complexity when one-step optimization (DAO) was employed rather than two-step optimization. All metrics detected a reduction in complexity when the minimum field size was increased from 1 to 4 cm and all apart from PIMV detected reduced complexity when the number of segments was significantly reduced. All metrics apart from MI showed differences in complexity depending on the treatment site. Significant correlations exist between all metrics apart from MI and PIMV for prostate IMRT patients. Treatment deliverability appeared to be more correlated with MI and MCS than MU or PIMV. Conclusions: The application of complexity metrics in the IMRT treatment planning process has been demonstrated. Complexity of treatment plans can vary for different inverse planning software versions and can depend on planning parameters and the treatment site. MCS is most suitable for inclusion within the cost function to limit complexity in IMRT optimization due to its sensitivity to complexity changes and correlation to treatment deliverability.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2012

Optimization of temporal dose modulation: Comparison of theory and experiment

Purpose: To compare theoretical predictions and experimental measurements of cell survival after exposure to two different temporally modulated radiation dose patterns that deliver the same dose in the same overall time. Methods: The authors derived an analytic expression for the dose protraction factor G in the Lea-Catcheside formalism for cell survival for 'triangle' and 'V' temporal modulation of dose. These temporal dose patterns were used in experimental clonogenic studies of a melanoma cell line (MM576) and a nonsmall-cell lung cancer line (NCI-H460) that have different alpha, beta, and repair parameters. The overall treatment time and total dose were kept constant. Results: The analytic expressions for G for the two temporal modulations are presented as a function of a single variable, the product of the exposure time, and the repair constant, enabling G to be evaluated for any exposure time and for any cell line. G for the triangle delivery pattern is always the larger. For the MM576 cell line, following a large dose of 6 Gy, a larger survival fraction was found for the V delivery pattern. No difference in survival was observed for lower doses or for the NCI-H460 cell line at any dose. These results are predicted by our theory, using published values of alpha, beta, and repair time within the limits of experimental uncertainty. Conclusions: The study provides evidence to confirm that cell lines having large beta values exhibit a response that is sensitive to the pattern of dose delivery when the delivery time is comparable with the repair time. It is recommended that the dose delivery pattern be considered in hypofractionated treatments.

60 APPLIED LIFE SCIENCES↗