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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 667 records · Page 37
All sourcesNASA NTRSDOE OSTI
DOE OSTI2019

Modelling an electro-optical modulator based on a vertical p – n junction in a silicon-on-insulator structure

We report the results of numerical simulation of a Mach – Zehnder electro-optical modulator using beam splitters based on multimode interference in a silicon-on-insulator structure. The control is provided due to the depletion effect in the vertical p – n junction, which can be fabricated using the self-alignment technology. An optimal modulator design is proposed, which impedance is matched with an external 50-Ω load, for which, with a reverse bias of – 5 V and an active length of 1.7 mm, the optical frequency bandwidth of ∼ 50 GHz can be achieved. A special doping profile of the p – n junction of the modulator is presented, which provides an optical frequency bandwidth of 30 GHz with a reverse bias of –3 V and a modulator length of 2.5 mm. Such modulators can be used in integrated optics, optical communications and radio photonics devices. (paper)

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2021

Beam modulation and bump-on-tail effects on Alfvén eigenmode stability in DIII-D

Beam modulation effects on Alfvén eigenmode stability have been investigated in a recent DIII-D experiment and show that variations in neutral beam modulation period can have an impact on the beam driven Alfvén eigenmode spectrum and resultant fast ion transport despite similar time-averaged input power. The experiment was carried out during the current ramp phase of L-mode discharges heated with sub-Alfvénic 50–80 kV deuterium neutral beams that drive a variety of Alfvén eigenmodes unstable. The modulation period of two interleaved beams with different tangency radii was varied from shot to shot in order to modify the relative time dependent mix of the beam pitch angle distribution as well as the persistence of a bump-on-tail feature near the injection energy (a feature confirmed by imaging neutral particle analyzer measurements). As the beam modulation period is varied from 7 ms to 30 ms on/off (typical full energy slowing down time of τ slow ≈ 50 ms at mid-radius), toroidicity-induced Alfvén eigenmodes (TAEs) located in the outer periphery of the plasma become intermittent and coincident with the more tangential beam. Core mode activity changes from reversed shear Alfvén eigenmodes (RSAEs) to a mix of RSAE and beta-induced Alfvén eigenmodes. Discharges with 30 ms on/off period do not have a persistent bump-on-tail feature, have the lowest average mode amplitude and least fast ion transport. Furthermore, detailed analysis of an individual TAE using TRANSP kick modeling (Monte Carlo evolution of the distribution function with probabilistic 'kicks' by the AEs) and the resistive MHD code with kinetic fast ions, MEGA, find no strong role of energy gradient drive due to bump-on-tail features. Instead, the observed TAE modulation with interleaved beams is likely a pitch angle dependent result combined with slowing down of the tangential beam between pulses. For the conditions investigated, bump-on-tail contributions to TAE drive were found to be 5% or less of the total drive at any given time.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2018

Test beam demonstration of silicon microstrip modules with transverse momentum discrimination for the future CMS tracking detector

A new CMS Tracker is under development for operation at the High Luminosity LHC from 2026 onwards. It includes an outer tracker based on dedicated modules that will reconstruct short track segments, called stubs, using spatially coincident clusters in two closely spaced silicon sensor layers. These modules allow the rejection of low transverse momentum track hits and reduce the data volume before transmission to the first level trigger. The inclusion of tracking information in the trigger decision is essential to limit the first level trigger accept rate. A customized front-end readout chip, the CMS Binary Chip (CBC), containing stub finding logic has been designed for this purpose. A prototype module, equipped with the CBC chip, has been constructed and operated for the first time in a 4 GeemVem/emc positron beam at DESY. The behaviour of the stub finding was studied for different angles of beam incidence on a module, which allows an estimate of the sensitivity to transverse momentum within the future CMS detector. A sharp transverse momentum threshold around 2 emVem/emc was demonstrated, which meets the requirement to reject a large fraction of low momentum tracks present in the LHC environment on-detector. This is the first realistic demonstration of a silicon tracking module that is able to select data, based on the particle's transverse momentum, for use in a first level trigger at the LHC . The results from this test are described here.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2023

D-Egg: a dual PMT optical module for IceCube

The D-Egg, an acronym for "Dual optical sensors in an Ellipsoid Glass for Gen2," is one of the optical modules designed for future extensions of the IceCube experiment at the South Pole. The D-Egg has an elongated-sphere shape to maximize the photon-sensitive effective area while maintaining a narrow diameter to reduce the cost and the time needed for drilling of the deployment holes in the glacial ice for the optical modules at depths up to 2700 m. The D-Egg design is utilized for the IceCube Upgrade, the next stage of the IceCube project also known as IceCube-Gen2 Phase 1, where nearly half of the optical sensors to be deployed are D-Eggs. With two 8-inch high-quantum efficiency photomultiplier tubes (PMTs) per module, D-Eggs offer an increased effective area while retaining the successful design of the IceCube digital optical module (DOM). The convolution of the wavelength-dependent effective area and the Cherenkov emission spectrum provides an effective photodetection sensitivity that is 2.8 times larger than that of IceCube DOMs. The signal of each of the two PMTs is digitized using ultra-low-power 14-bit analog-to-digital converters with a sampling frequency of 240 MSPS, enabling a flexible event triggering, as well as seamless and lossless event recording of single-photon signals to multi-photons exceeding 200 photoelectrons within 10 ns. Mass production of D-Eggs has been completed, with 277 out of the 310 D-Eggs produced to be used in the IceCube Upgrade. In this paper, we report the design of the D-Eggs, as well as the sensitivity and the single to multi-photon detection performance of mass-produced D-Eggs measured in a laboratory using the built-in data acquisition system in each D-Egg optical sensor module.

47 OTHER INSTRUMENTATION↗
DOE OSTI2022

Constraining the charge-, time-, and rigidity-dependence of cosmic-ray solar modulation with AMS-02 observations during Solar Cycle 24

Our basic theoretical understanding of the sources of cosmic rays and their propagation through the interstellar medium is hindered by the Sun, that through the solar wind affects the observed cosmic-ray spectra. This effect is known as solar modulation. Recently released cosmic-ray observations from the Alpha Magnetic Spectrometer (AMS-02) and publicly available measurements of the solar wind properties from the Advanced Composition Explorer and the Wilcox observatory allow us to test the analytical modeling of the time-, charge- and rigidity-dependence of solar modulation. We rely on associating measurements on the local heliospheric magnetic field and the heliospheric current sheet’s tilt angle, to model the time-dependence and amplitude of cosmic-ray solar modulation. We find evidence for the solar modulation’s charge- and rigidity-dependence during the era of solar cycle 24. Our analytic prescription to model solar modulation can explain well the large-scale time evolution of positively charged cosmic-ray fluxes in the range of rigidities from 1 GV to 10 GV. Here, we also find that cosmic-ray electron fluxes measured during the first years of cycle 24 are less trivial to explain, due to the complex and rapidly evolving structure of the heliosphere’s magnetic field that they experienced as they propagated inwards.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2025

Daily modulation of low-energy nuclear recoils from sub-GeV dark matter

At sufficiently low nuclear recoil energy, the scattering of dark matter (DM) in crystals gives rise to single phonon and multiphonon excitations. In anisotropic crystals, the scattering rate into phonons modulates over each sidereal day as the crystal rotates with respect to the DM wind. This gives a potential avenue for directional detection of DM. The daily modulation for single phonons has previously been calculated. Here we calculate the daily modulation for multiphonon excitations from DM in the mass range 1 MeV–1 GeV. We generalize previous multiphonon calculations, which made an isotropic approximation, and implement results in the DarkELF package. We find daily modulation rates up to 1%–10% for an Al 2 O 3 target and DM mass below 30 MeV, depending on the recoil energies probed. We obtain similar results for SiC, while modulation in Si, GaAs, and SiO 2 is negligible. Published by the American Physical Society 2025

Stratman, Connor↗
DOE OSTI2019

Smectic and nematic phase modulations and transitions under electron beam in Tb 2 Cu 0.83 Pd 0.17 O 4

Understanding the structural origin of the functionality in cuprates has attracted tremendous attention over several decades. In particular, probing distortions in the Cu- O bonding is of great importance for exploring the coupling between the charge and the lattice, a key mechanism for superconductivity and other functionality in correlated materials. Here we study a superlattice modulation in the Tb 2 Cu 0.83 Pd 0.17 O 4 “214” material, which possesses no superconductivity itself but has the parent structure of the R 2 CuO 4 (R = a rare earth element) superconducting cuprate group. Using transmission electron microscopy (TEM), we find that this superlattice modulation is formed by Cu ion displacements in a direction perpendicular to the Cu-O planes. The superlattice modulation undergoes a reversible electronic smectic-nematic phase transition under electron-beam illumination. With the help of in situ TEM results, our findings imply that the superlattice modulation in this material arises from spatially modulated charge ordering at the Cu sites.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2018

Development of a low-inductance SiC trench MOSFET power module for high-frequency application

This paper deals with the development of a low-inductance multiple-chip power module with state-of-art 1200 V SiC Trench MOSFETs for high-frequency application. Specifically, a phase-leg power module package with integrated decoupling capacitance is fabricated based on P-cell/N-cell concept, and the packaging design is discussed in detail. Dedicated double pulse test is built, and a gate driver with cross-talk suppression function is designed to support the fast switching speed operation of SiC Trench MOSFETs. The parasitic inductance and current density distribution of the power module are simulated and extracted for the purpose of voltage spike limiting. The temperature dependent static and switching characteristics of the developed module are evaluated as well, and the key differences from traditional SiC double-diffused MOS (DMOS) are identified and discussed. Based on the turn-off switching characterization results, a lumped equivalent power-loop parasitic inductance of ~6 nH is achieved for the designed power module.

Wang, Zhiqiang↗
DOE OSTI2020

Characterization and Analysis of Insulated Metal Substrate-Based SiC Power Module for Traction Application

This paper presents the electrical characterization and drive cycle--based thermal analysis of an insulated metal substrate (IMS)--based silicon carbide power module for high-power traction inverters. The substrate was constructed using a thin layer of polymer--ceramic blend dielectric material with a thick copper core to improve transient thermal performance. The cooling performance of this module has already been validated with promising results. In this paper, an experimental test bed was set up to evaluate the dynamic and static electrical performance of the designed module under a wide range of operating conditions. The characterization results were then used to develop a drive cycle--based thermal model to validate the performance compared to the traditional direct bonded copper--based power module. The results indicate that the IMS-based power module is a suitable solution for high-power traction applications.

Chowdhury, Shajjad↗
DOE OSTI2018

Reducing Operating Temperature in Photovoltaic Modules

Reducing the operating temperature of photovoltaic modules increases their efficiency and lifetime. This can be achieved by reducing the production of waste heat or by improving the rejection of waste heat. We tested, using a combination of simulation and experiment, several thermal modifications in each category. To predict operating temperature and energy yield changes in response to changes to the module, we implemented a physics-based transient simulation framework based almost entirely on measured properties. The most effective thermal modifications reduced the production of waste heat by reflecting unusable light from the cell or the module. Consistent with previous results and verified in this work through year-long simulations, the ideal reflector resulted in an annual irradiance-weighted temperature reduction of 3.8 K for crystalline silicon (c-Si). Our results illustrate that more realistic reflector concepts must balance detrimental optical effects with the intended thermal effects to realize the optimal energy production advantage. Methods improving thermal conductivity or back-side emissivity showed only modest improvements of less than 1 K. We also studied a GaAs module, which uses high-efficiency and high-subbandgap reflectivity to operate at an annual irradiance-weighted temperature 12 K cooler than that of a c-Si module under the same conditions.

14 SOLAR ENERGY↗
DOE OSTI2019

The Polyhedral Specular Reflector: A Spectrum-Splitting Multijunction Design to Achieve Ultrahigh ( >50%) Solar Module Efficiencies

The most feasible pathway to record 50% efficiency photovoltaic devices is by utilizing many (>4) junctions to minimize thermalization and nonabsorption losses. Here we propose a spectrum-splitting design, the polyhedral specular reflector (PSR), that employs an optical architecture to divide and concentrate incident sunlight, allowing the incorporation of more junctions compared with traditional monolithic architectures. This paper describes the PSR design and indicates the requirements to achieve a 50% efficiency module by coupling robust cell, optical, and electrical simulations. We predict that a module comprised of the seven subcells with an average external radiative efficiency of at least 3%, an optical architecture capable of a splitting efficiency of at least 88% and 300× concentration, small (≤1 μm) metallic fingers for subcell contact, and a state-of-the-art power conditioning system (>98% efficiency) can achieve a module efficiency of 50%, a record for both multijunction cells and modules. We also discuss the flexibility of the design and explore how adjusting the size and type of concentrators can still yield record module efficiencies (>40%).

solar (photovoltaic), solid state lighting, phonon↗
DOE OSTI2019

Strong Attraction and Adhesion Forces of Dust Particles by System Voltages of Photovoltaic Modules

We report for the first time on direct measurements using atomic force microscopy (AFM) of electric field induced attraction and adhesion forces associated with soiling on photovoltaic (PV) modules. Real dust particles and silica spheres as surrogate to simulating dust particles were glued to AFM probe cantilevers. The electric field induced force (Fes) was measured via AFM force-distance (f-z) curves, where the electric field was generated by applying a voltage (Vs) to a simulated PV module. Fes and van der Waals (Fvw) force contributions could be separated with the f-z curves. The results show that Fes ~2.5 u N on dust particles is ~5 times larger than Fvw ~0.5 u N at even Vs = -100 V (i.e., similar to large-module operating voltages). Fes increases by an order of magnitude as the applied potential increases from Vs = -100 V to Vs = -500 V. These adhesion forces are by far the strongest that we have measured using the AFM technique for 'initial' contact of particles. Furthermore, unlike the more typical short-range forces of Fvw and liquid bridge, Fes extends sub-millimeters to a millimeter beyond the PV module surface, creating large attraction forces to even uncharged dust particles (i.e., via induced dipoles) in the air. These results indicate that the high voltages typically used with PV arrays today will attract more dust particles from the air, hold the dust particles to the surface very strongly, and potentially induce other PV module surface effects, all of which could increase the power production losses because of soiling.

14 SOLAR ENERGY↗
DOE OSTI2020

Transient Weighted Moving-Average Model of Photovoltaic Module Back-Surface Temperature

Accurate modeling of photovoltaic (PV) performance requires the precise calculation of module temperature. Currently, most temperature models rely on steady-state assumptions that do not account for the transient climatic conditions and thermal mass of the module. On the other hand, complex physics-based transient models are computationally expensive and difficult to parameterize. In order to address this, a new approach to transient thermal modeling was developed, in which the steady-state predictions from previous timesteps are weighted and averaged to accurately predict the module temperature at finer time scales. This model is informed by 3-D finite-element analyses, which are used to calculate the effect of wind speed and module unit mass on module temperature. The model, in application, serves as an added filter over existing steady-state models that smooths out erroneous values that are a result of intermittency in solar resource. Validation of this moving-average model has shown that it can improve the overall PV energy performance model accuracy by as much as 0.58% over steady-state models based on mean absolute error improvements and can significantly reduce the variability between the model predictions and measured temperature times series data.

14 SOLAR ENERGY↗
DOE OSTI2021

Nanomechanical and Fluorescence Characterizations of Weathered PV Module Encapsulation

Nanoindentation and fluorescence spectroscopy provide spatially resolved mechanical and chemical characterization for degradation of poly (ethylene-co-vinyl acetate) (EVA) encapsulants aged under accelerated weathering and in field deployed photovoltaic (PV) modules. For the accelerated weathering tests, two different EVA formulations in the glass/EVA/glass-laminated coupons were exposed to ultraviolet (UV) light for 180 days at three different temperatures (40, 60, and 80 °C) and UV intensities (0.4, 2.2, and 2.9 W/m2/nm at 340 nm). The fluorescence spectra and moduli were uniform through the cross section of both EVA formulations at the lowest temperature and UV intensity; however, under the highest temperature and UV intensity, the UV irradiated sides showed lower moduli and higher fluorescence compared to the opposite sides. For EVA obtained from PV modules deployed 27 years in Sacramento, CA, USA, changes in fluorescence intensity across the thickness were relatively greater than changes in modulus. On the other hand, for EVA obtained from the same type of module stored in the shed for 27 years, no fluorescence was observed, and a uniform modulus was seen through the EVA layer, but with substantially higher values than those obtained from the field-deployed modules. The different extent of changes between laboratory and field exposures suggests the importance of considering effects of temperature and UV intensity for designing a reliable accelerated testing. This study uniquely demonstrates the capability of microscale characterization using nanoindentation and fluorescence microscopy to monitor mechanical and chemical degradation of EVA encapsulants in PV modules.

14 SOLAR ENERGY↗
DOE OSTI2018

Partial Shade Endurance Testing for Monolithic Photovoltaic Modules

In monolithically integrated photovoltaic (PV) modules, including CdTe, CIGS, and a-Si modules, some shadows can cause permanent damage under some operating conditions. This damage reduces efficiency and causes shunts that are visible to the eye and in luminescence imaging. Although these shadows are sometimes forbidden by product documentation, we have observed this type of damage in utility-scale PV systems. Existing standards ensure that qualified modules are safe to use after they are damaged by shadows. But no standard test exists to quantify the loss of efficiency that can result from this damage. In this work we describe new, accelerated tests to quantify the power loss that occurs due to shadows from human bodies and narrow objects, such as tools, placed nearby or directly touching modules. The tests are designed to be easy to conduct uniformly across products and laboratories. The tests can be performed outdoors and last only a few minutes. In our trials on commercial products, these tests resulted in 2%-27% permanent loss in power at standard test conditions (STC). The relative loss was several times larger when measured at lower irradiance. The tests we describe can be used to differentiate products, to direct the development of technological solutions to shadow sensitivity at the cell and module levels, and to establish the need for system-level and administrative solutions to the occurrence of shadows. Similar tests will be the basis of a new International Electrotechnical Commission (IEC) technical specification (TS) 63140.

14 SOLAR ENERGY↗
DOE OSTI2020

Technoeconomic Analysis of Photovoltaics Module Manufacturing with Thin Silicon Wafers

Reducing silicon usage by adopting thinner wafers can significantly reduce capital expenditure (capex) and cost, and thus accelerate the growth of manufacturing capacity and deployment. In this work, we evaluated potential benefits of thin Si wafers for current and future PV modules. We apply a technoeconomic framework that couples bottom-up cost model, and a cash-flow growth model to analyze PV modules with thin wafers. First, we show that, comparing the current PERC with 160 um thick wafers to the high-efficiency concept with 50 um thin wafers, the capex is reduced from 0.39 to 0.2 $/(W/year) while the cost is from 0.32 to 0.2 $/W. Second, the potential of accelerated deployment is analyzed for the highefficiency thin wafer concept. We found the significant advantages of higher growth rate (~20% relative) and higher deployment plateau (~3 times) than the current PERC modules. modules with thin wafers. First, we show that, comparing the current PERC with 160 um thick wafers to the high-efficiency concept with 50 um thin wafers, the capex is reduced from 0.39 to 0.2 $/(W/year) while the cost is from 0.32 to 0.2 $/W. Second, the potential of accelerated deployment is analyzed for the highefficiency thin wafer concept. We found the significant advantages of higher growth rate (~20% relative) and higher deployment plateau (~3 times) than the current PERC modules.

14 SOLAR ENERGY↗
DOE OSTI2021

Cracked Solar Cell Performance Depends on Module Temperature

When cells in a crystalline silicon photovoltaic module crack, packaging materials hold the fragments together. Changes in module temperature cause cell fragments to move, allowing cracked metallization to lose and regain contact. We intentionally cracked cells in commercial PV modules and characterized the modules’ temperature-dependent electroluminescence (EL) response. Here we show that (1) metallization makes contact across cracks in a way that is temperature dependent and (2) this contact is not a function of temperature, but is hysteretic. We expect that any electro-optical characterization made at a single temperature will be misleading as to the effects of cracked cells at different temperatures. And we expect that a single temperature sweep cannot fully characterize the temperature dependence of electro-optical performance of modules with cracked cells.

crack↗
DOE OSTI2023

Life-Cycle Analysis of Potentially Longer Life Expectancy CdTe PV Modules

Research on PV module longevity shows that with lower degradation rates and better encapsulation, PV modules can significantly outlast their current life expectancy of 25-30 years. The focus of this study is on alternative CdTe PV module back-contact and encapsulation materials that show the potential of increasing module operation lives from 30 to 40 and 50 years. Life-cycle-analyis shows that some alternative materials may slightly increase cradle-to-gate environmental impacts per m2 of module, but increased operational life more than counterbalances such impacts. The life-cycle carbn footprint of systems operating under average US insolation conditions of 1800 kWh/m2/yr is reduced from 10 gCO2eq/kWh to 6 gCO2eq/kWh when the operation life increases from 30 to 50 yrs. Similar reductions are noted for all life-cycle impact indicators, whereas the EROI of the considered system increases from 67 to 177 as life increases from 30 to 50 yrs.

14 SOLAR ENERGY↗