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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 325 records · Page 18
All sourcesNASA NTRSDOE OSTI
DOE OSTI2024

Seasonal modulation of crustal seismicity in northeastern Japan driven by snow load

Numerous studies have reported that surface hydrological loading can seasonally modulate seismicity rates at crustal depths. For example, substantial winter snow accumulation occurs across the Japanese Islands, and these snowy regions appear to have seasonally modulated the occurrence of previous large inland earthquakes. Therefore, it is important to investigate the impact of seasonal stress changes on crustal seismicity to deepen our understanding of earthquake generation. Here we constrain seasonal changes in the surface load across northeastern Japan using Global Navigation Satellite System surface displacements and evaluate the potential relationship between temporal trends in inland seismicity and estimated seasonal stress changes. The spatial distribution of the seasonal surface load is consistent with snow depth along the Sea of Japan. The inland seismicity beneath northeastern Japan is modestly modulated by the seasonal stress changes that are induced by the annual snow load. However, this seasonal response is weaker than that in other regions. This weak modulation may be due to the small surface-load-induced stress perturbation relative to the long-term-averaged stressing rate and/or the limited presence of crustal fluids to trigger seismicity in Japan.

58 GEOSCIENCES↗
DOE OSTI2020

Research and Development Priorities for Silicon Photovoltaic Module Recycling to Support a Circular Economy

Large-scale deployment of photovoltaic (PV) modules has considerably increased in recent decades. Given an estimated lifetime of 30 years, the challenge of how to handle large volumes of end-of-life PV modules is starting to emerge. In this Perspective, we assess the global status of practice and knowledge for end-of-life management for crystalline silicon PV modules. We focus in particular on module recycling, a key aspect in the circular economy of photovoltaic panels. We recommend research and development to reduce recycling costs and environmental impacts compared to disposal while maximizing material recovery. We suggest that the recovery of high-value silicon is more advantageous than the recovery of intact silicon wafers. This approach requires the identification of contaminants and the design of purification processes for recovered silicon. The environmental and economic impacts of recycling practices should be explored with techno–economic analyses and life-cycle assessments to optimize solutions and minimize trade-offs. As photovoltaic technology advances rapidly, it is important for the recycling industry to plan adaptable recycling infrastructure.

c-Si↗
DOE OSTI2022

Modulation of intensity emerging from zero effort (MIEZE) with extended Fourier time at large scattering angle

Modulation of Intensity Emerging from Zero Effort (MIEZE) is a neutron resonant spin echo technique that allows one to measure time correlation scattering functions in materials by implementing radio-frequency (RF) intensity modulation at the sample and the detector. The technique avoids neutron spin manipulation between the sample and the detector and, thus, could find applications in cases where the sample depolarizes the neutron beam. However, the finite sample size creates a variance in the path length between the locations where scattering and detection happen, which limits the contrast in intensity modulation that one can detect, in particular, toward long correlation times or large scattering angles. We propose a modification to the MIEZE setup that will enable one to extend those detection limits to longer times and larger angles. Furthermore, we use Monte Carlo simulations of a neutron scattering beamline to show that by tilting the RF flippers in the primary spectrometer with respect to the beam direction, one can shape the wave front of the intensity modulation at the sample to compensate for the path variance from the sample and the detector. The simulation results indicate that this change enables one to operate a MIEZE instrument at much increased RF frequencies, thus improving the effective energy resolution of the technique. For the MIEZE instrument simulated, it shows that for an incident beam with the maximum divergence of 0.33°, the maximum Fourier time can be increased by a factor of 3.

47 OTHER INSTRUMENTATION↗
DOE OSTI2024

Electron energy gain due to a laser frequency modulation experienced by electron during betatron motion

Direct laser acceleration of electrons is an important energy deposition mechanism for laser-irradiated plasmas that is particularly effective at relativistic laser intensities in the presence of quasi-static laser-driven plasma electric and magnetic fields. These radial electric and azimuthal magnetic fields provide transverse electron confinement by inducing betatron oscillations of forward-moving electrons undergoing laser acceleration. Electrons are said to experience a betatron resonance when the frequency of betatron oscillations matches the average frequency of the laser field oscillations at the electron position. In this paper, we show that the modulation of the laser frequency as seen by an electron performing betatron oscillations can be another important mechanism for net energy gain that is qualitatively different from the betatron resonance. Specifically, we show that the frequency modulation experienced by the electron can lead to net energy gain in the regime where the laser field performs three oscillations per betatron oscillation. There is no net energy gain in this regime without the modulation because the energy gain is fully compensated by the energy loss. The modulation slows down the laser oscillation near transverse stopping points, increasing the time interval during which the electron gains energy and making it possible to achieve net energy gain.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2025

The influence of laser power modulation on melt pool dynamics in laser powder bed fusion

While the majority of laser powder bed fusion (LPBF) metal additive manufacturing uses a continuous wave (CW) laser heat source, some commercial applications of LPBF additive manufacturing instead involve the modulation of the laser power on tens-of-microsecond timescales as an adjustable process variable. This article reports the use of in situ, high speed x-ray and optical imaging to probe melt pool fluid flow, defect formation, and nearby powder motion during LPBF with both modulated and CW laser heat sources. We observe melt pool dynamics unique to modulated laser melting even at very high duty cycles that are related to fluctuations in vapor depression depth, complex pore formation mechanisms, and changes to denudation physics when compared to CW melting. These behaviors are present in Ti–6Al–4V, 316L stainless steel, and AL1100 alloys but vary slightly as a function of material, indicating a substantial dependence on the viscosity and surface tension of the liquid metal. While high duty cycles produce weld tracks of comparable quality to CW melting, lower duty cycles introduce substantial defect concentrations. At intermediate duty cycles, careful control of modulation parameters can repeatably and precisely yield one pore per laser pulse, suggesting a method for intentionally inserting engineered porosity at specific sites during an LPBF build.

3D printing↗
DOE OSTI2020

Methods and algorithms for computer synthesis of holographic elements to obtain a complex impulse response of optical information processing systems based on modern spatial light modulators

The possibilities of designing optical devices for data processing and imaging based on the manipulation of coherent light beams by means of spatial light modulators (SLMs) are investigated. A review of commercially available SLMs is presented and the limitations of their complex modulation characteristics are analysed. The main problem of using present-day SLMs is the lack of the ability to modulate directly all states within a unit circle in the complex plane. In this regard, the characteristics of current methods for the synthesis of holographic elements are described that implement a given complex impulse response of the optical system and are optimal for using SLMs with purely amplitude, purely phase, and hybrid amplitude – phase modulation. (paper)

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2024

Effect of hollow fiber membrane packing on the performance of modules formed with fiber tows

Membrane processes are the preferred option for many gas separations. Hollow fiber membranes are commonly used in these processes. Commercial hollow fiber membrane modules are often fabricated from small groups of fibers (i.e., a tow) that are arranged into a larger cylindrical bundle. The existence of fiber tows can lead to packing non-uniformity. This nonuniformity can result in nonideal fluid distribution in the shell and be detrimental to module performance. In this work, full three-dimensional models of flow and mass transfer within fiber bundles formed from tows have been developed. These models account for the detailed fiber arrangement within modules and are solved to evaluate module separation performance in terms of stage cut and required membrane area as a function product gas purity for carbon capture applications. Results are presented illustrating the effects of varying fiber packing arrangements within a tow and varying tow packing arrangements. Further, the results suggest smaller tows are preferred over larger tows, at fixed overall fiber packing and lower intra- and inter-tow packings are preferred. To reduce the computational cost of simulating large fiber bundles, the use of an equivalent planar bundle is proposed (EPB). A simple procedure for determining the geometry of the EPB is described and validated through comparisons of calculated performance metrics with results obtained from full three-dimensional simulations.

42 ENGINEERING↗
DOE OSTI2025

Thermal modulation of nonlinear ultrasonic waves for nondestructive evaluation of elastic materials

Temperature variation is often considered an undesirable factor in ultrasonic testing, as wave velocity is highly sensitive to thermal fluctuations. However, completely eliminating the temperature effect is difficult, particularly in tests requiring precise velocity measurements. Recently, a method called Thermal Modulation of Nonlinear Ultrasonics (TMNL) has been developed. Instead of eliminating the thermal effect, the TMNL method leverages the temperature variation as a driving force to stimulate the nonlinear response of the medium and modulate the ultrasonic waves propagating in it. These modulated waves can then be used to evaluate the nonlinear behaviours of the test medium. This paper presents a focused review of the TMNL technique, including its theoretical foundations, particularly the conceptual challenges in integrating thermal effects into classical acoustoelastic theory, and recent applications in non-destructive evaluation (NDE). Three case studies are presented to demonstrate TMNL’s application in detecting microcracking in concrete, assessing ageing in polymer materials, and enabling temperature compensation in acoustoelastic tests. In conclusion, the review also summarises related studies, including photothermal crack modulation, and discusses current limitations and future directions of TMNL in elastic media.

NDE↗
DOE OSTI2021

Reliability Analysis of Large-Area, Low Pressure-Assisted Silver Sintering for Medium-Voltage Power Modules

Multi-layer insulating ceramic substrates can enable medium-voltage (MV) power modules with reduced peak electric field. This benefit is particularly important for MV silicon carbide (SiC) MOSFETs due to their higher operating voltages. Large-area, low-pressure assisted silver sintering is a potential solution for bonding substrates to create a multi-layer structure. The voiding content and defect density of the bond used to create the multi-layer substrate stack-up is critical to the reliability of the power module and the thermal performance, as this bond is in the primary path for heat dissipation in the power module structure. Here, samples of two-layer direct bonded aluminum (DBA) stacks have been fabricated and subjected to thermal cycling to analyze their reliability. Passive thermal cycling from -40 degrees C to 200 degrees C was performed. Cross-sections were cut at pre-determined intervals and imaged with Scanning Electron Microscopy (SEM). After 1000 thermal cycles, adhesive failures are observed between the sintered silver and the DBA surface. Cross-sections were cut and imaged via optical microscope and SEM. Thermal analyzer measurements are recorded on a 10-kV SiC power module utilizing the sintered DBA substrate stacks.

30 DIRECT ENERGY CONVERSION↗
DOE OSTI2026

Surface Stress Characterization and Trends in Thermally Strengthened Photovoltaic Module Glass

Simultaneous changes in photovoltaic (PV) module architecture-such as increased area, replacing the polymeric backsheet with a glass backsheet, and reducing glass thickness from 3.2 to 2.0 mm-have resulted in a novel failure called spontaneous glass breakage. Spontaneous glass breakage results in front and/or rear glass failure without any obvious cause. The resulting low-energy fracture patterns have raised concerns about the thermal strengthening in 2.0-mm glass. We present validation of a nondestructive method for measuring the glass surface stress in PV modules. We use a scattered light polariscope to examine the glass properties of 11 modules from 6 solar fields, with and without spontaneous glass breakage. Based on a Mann-Whitney test p-value of 1.4 x 10-6, we conclude that there is a correlation between lower surface stress and susceptibility to spontaneous breakage. A Kendall's Tau test p-value of 2.0 x 10-4 indicates a correlation between increased module area and lower surface stress. We find that 2.0-mm glass can be, and often is, fully tempered (surface stress ≥69 MPa), but inspecting the fracture pattern is not a reliable way to assess the amount of thermal strengthening. A combination of factors, not just surface stress, influences glass breakage.

14 SOLAR ENERGY↗
DOE OSTI2020

A New Approach to Indoor Characterization of PV Module Energy Yield Parameters

Temperature and solar irradiance are among the most relevant parameters that affect the energy yield of photovoltaic cells and modules. A rise in the module temperature leads to a significant decrease in the open circuit voltage and a small increase in the short circuit current. Here we use a new tool to determine temperature coefficients as well as to assess power rating of multi c-Si, mono c-Si, CdTe, and CIGS-based PV modules in controlled indoor conditions per IEC 60891 and IEC 61853-1. We use the tool to explore how nonuniformities in module temperature affect the accuracy of the temperature coefficients.

14 SOLAR ENERGY↗
DOE OSTI2020

Effectiveness of Rain Cleaning on Artificially Soiled PV Modules With and Without Anti-Soiling Coatings

A simple, inexpensive methodology for testing the effectiveness of rain cleaning on artificially soiled single-cell and multi-cell photovoltaic (PV) modules having anti-soiling coatings has been developed. Using an indoor soil deposition chamber and methodology as described in our previously published work, multiple layers of soil were deposited on to the glass surface of single-cell PV modules subjected to controlled temperature and humidity cycles. Three single-cell monocrystalline PV modules are reported in this study, two of which had different anti-soiling (AS) coatings applied to the surface and the third did not have any AS coating. The set-up and operation of a rain-simulator is described as well as the rain cleaning parameters the PV test modules were exposed to. The purpose of this work is to determine the effectiveness of anti-soiling coatings and cleaning techniques, so vendor claims can be quantitatively validated using an appropriately controlled soil deposition chamber and a rain simulating spray nozzle.

14 SOLAR ENERGY↗
DOE OSTI2020

Decay of Electrostatic Force of Dust Particles on Photovoltaic Modules

Photovoltaic (PV) energy yield loss due to solar module soiling has become increasingly important as solar module deployment is now at the hundreds of gigawatts scale and continues to grow rapidly. We have reported on direct measurements-using atomic force microscopy (AFM)-of strong electric-field-induced attraction and adhesion force (Fes) of dust particles onto solar panel that are 1 to 2 orders of magnitude stronger than the van der Waals and water capillary forces, corroborated by observing the increase in system voltage-induced soiling rate. Here, we report another characteristic of Fes on soiling-long lasting or slow decay after turning off the high voltage applied to solar panels. The Fes decay time varies in a wide time range of 1 to 10 hours, depending on two factors: 1) either/both the cell or/and particle were charged with high voltage before the voltages were turned off; and 2) how the cell was connected to the ground after the voltage was turned off-either connected through the power supply electronics, directly connected to the ground, or electrically floated. The Fes decay is understood in terms of 1) net electrical charge dissipations in both particle and cell, 2) thermal disordering of dipole polarization in the module glass dielectrics, and 3) charge redistribution by the electrostatic interaction of particle and module glass. This long-lasting Fes for hours can significantly affect the solar panel soiling after sunset, especially combined with water condensation.

14 SOLAR ENERGY↗
DOE OSTI2020

Highly Reliable Multi-Port Smart Inverter Modules for PV-Based Energy Systems

Generally, large electrolytic capacitors (E-caps) are required to decouple the double-line frequency power fluctuation inherent in all single-phase dc-ac or ac-dc converters. These E-caps pose the weak link in the photovoltaic (PV) inverter because they have poor reliability as a result of short life expectancy and higher equivalent series resistance (ESR) which leads to lower system efficiency. In this paper, multiport smart dual-inverter modules are proposed for residential PV inverter systems with balanced outputs to eliminate the requirement of large decoupling capacitors, thus leading to more reliable and highly efficient inverter modules. The balanced dual outputs are controlled in phase quadrature such that the double frequency current is completely eliminated. One phase supports the standalone residential loads, and the other phase interfaces with the grid, which is synchronized to the utility grid. Also, the proposed modular configuration is scalable to accommodate higher power rating by stacking and paralleling multiple modules. Simulation results for the dual-inverter modules rated for 1 kW each are presented to validate the proposed concept. Experimental results from a controller hardware-in-the-loop (CHIL) platform also verify its feasibility.

14 SOLAR ENERGY↗
DOE OSTI2021

On the Ambiguity of Using Isc for Analyzing Suns-Voc Data on Modules

In standard silicon solar modules, cells are strung in series with bypass diodes incorporated to reduce the effects of shading. When all of the strings are partially shaded the measured short circuit current is affected and the Isc of the module will be equal to that of the lowest current cell in the least shadowed string. In bifacial modules the ability to assess losses due to shading is especially important. This paper advocates an alternative approach to converting the raw suns-voc data to pseudo IV data in modules where shading may be affecting the suns-voc curve results.

41 EE - Solar Energy Technologies Office (EE-4S)↗
DOE OSTI2024

PV Modules Temperature Variation and Patterns in Medium and Utility-Scale Floating PV Systems

This paper presents the preliminary results and findings of the four operational Floating PV systems across the USA. At each site, temperature of five PV modules located at North-West, North-East, Middle, South-West, and, South-East have been monitored through the Resistant Temperature Detector (RTD) sensors. Three RTDs were attached to each PV module on the rear-side along the diagonal at top, middle and bottom cells. The preliminary results reveal wide temperature differences among the inter and intra PV modules. Besides this, wave pattern temperatures were observed in a few PV modules. The final results, findings, and, factors responsible will be investigated during the next few months.

array↗
DOE OSTI2020

Hysteresis Reduction in Tunneling Magnetoresistive Sensor With AC Modulation Magnetic Field

A simple and practical AC modulation method to reduce the hysteresis in tunneling magnetoresistive sensor is demonstrated. It is shown that with a suitable AC modulation magnetic field that is applied along the sensing direction of TMR sensor, the hysteresis in the sensor can be reduced to a negligible level. And depending on the amplitude of the modulation field, the sensitivity and the dynamic range of the TMR sensor can be tuned to meet practical requirements in specific applications. Here, the influence of the modulation on the noise of TMR sensor is also studied.

42 ENGINEERING↗
DOE OSTI2021

New Modulation and Impact of Transformer Leakage Inductance on Current-Source Solid-State Transformer

This article presents a novel modulation scheme for device voltage stress mitigation and comprehensive analysis of the impact of transformer leakage inductance in a current-source solid-state transformer (SST). Different from dual active bridge (DAB) SST, the operation of the current-source SST is similar to that of a flyback converter. The device bridge on only one side of the transformer is active to store energy into or release energy from the magnetizing inductance which acts as a current-source dc link. Such flyback operation with reverse-blocking switches can lead to additional device voltage stress and incomplete zero-voltage switching (ZVS) on the current-source soft-switching solid-state transformer (S4T) under conventional modulation. A new modulation scheme is proposed to address this issue. Moreover, different from the DAB, the leakage inductance of the medium-frequency transformer (MFT) in the S4T is a parasitic element similar to that in a matrix SST and can cause additional device voltage stress. Though the resonant capacitors, originally added to achieve ZVS, can absorb and recycle the leakage energy in the S4T, these capacitors need to be increased with larger leakage inductances to limit the voltage stress. However, large resonant capacitors can result in more lost duty cycles and reduced efficiency. The impact of such leakage inductance on device voltage stress is analyzed comprehensively, which is critical to guide future research and design of the S4T. Experimental results from S4T prototypes for DC-DC, multiport AC-DC, and AC-AC conversion with 1:1 and 4:1 MFT comprehensively verify the proposed concepts. Lastly, a case study of a three-phase AC-AC S4T over a power range from 1 kVA to 100 kVA each module reveals that the MFT leakage inductance should be less than 1% of the magnetizing inductance for safe operation.

14 SOLAR ENERGY↗