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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 1,153 records · Page 64
All sourcesNASA NTRSDOE OSTI
DOE OSTI2023

Quantifying optical loss of high-voltage degradation modes in photovoltaic modules using spectral analysis

The direct current bias for photovoltaic (PV) modules interconnected in series-strings may include both high voltage negative (“HV-”) and positive (“HV+”) polarity with respect to the electrical ground. Multiple degradation modes, resulting in quantifiable optical loss, were found to occur during HV-/HV+ sequential stress, including corrosion of the external glass surface, encapsulant delamination (at its interfaces with the glass and the PV cell), internal haze formation (resulting from a chemical interaction between the glass and the encapsulant), corrosion and migration of the gridlines, and corrosion of the silicon nitride (Si x N y ) antireflective coating on the cell. The effects of these separate modes were examined using monolithic (e.g., glass or PV cell) and laminated-coupon (glass/encapsulant/glass or glass/encapsulant/cell/encapsulant/backsheet) specimens. Characterizations during and after unbiased accelerated testing at 85°C/85% relative humidity included spectrophotometry, optical microscopy, electron microscopy, and ellipsometry. For some module components (i.e., the glass and the Si x N y coating), the optical performance was determined through iterative analysis of empirical measurements. Concentrating on just their spectral effect, a novel model was then developed to estimate the transfer of light to the PV cell and the return of light from the PV module with simultaneous degradation mechanisms, which was compared with a mini-module previously subjected to HV-/HV+ stress. Here the model suggests that one third of the current loss observed for the mini-module can be attributed to the optical degradation of the packaging materials. The dominant degradation modes include encapsulant delamination and corrosion of the Si x N y coating. Recommendations are given so that the optical model may be improved relative to accelerated testing and validated relative to field aging.

14 SOLAR ENERGY↗
DOE OSTI2023

Whole-Voltage-Range Solid-Solution Reaction in Layered Oxide Cathode of Sodium-Ion Batteries

Layered manganese-based oxides (LMOs) are promising cathode materials for sodium-ion batteries (SIBs) due to their versatile structures. However, the Jahn–Teller effect of Mn 3+ induces severe distortion of MnO 6 octahedra, and the resultant low symmetry is responsible for the gliding of MnO 2 layers and then inferior multiple-phase transitions upon Na + extraction/insertion. Here, hexagonal P2-Na 0.643 Li 0.078 Mn 0.827 Ti 0.095 O 2 is synthesized through the incorporation of Li and Ti into the distorted orthorhombic P'2-Na 0.67 MnO 2 to function as a phase-transition-free oxide cathode. Further, it is revealed that Li in both the transition-metal and Na layers enhances the covalency of Mn–O bonds and allows degeneracy of Mn 3d e g orbitals to favor the formation of hexagonal phase, and the high strength of Ti–O bonds reduces the electrostatic interaction between Na and O for suppressed Na + /vacancy rearrangements. These collectively lead to a whole-voltage-range solid-solution reaction between 1.8 and 4.3 V with a small volume variation of 1.49%. This rewards its excellent cycling stability (capacity retention of 90% after 500 cycles) and rate capability (89 mAh g -1 at 2000 mA g -1 ).

25 ENERGY STORAGE↗
DOE OSTI2021

Perovskite Photovoltaic Devices with Carbon-Based Electrodes Withstanding Reverse-Bias Voltages up to –9 V and Surpassing IEC 61215:2016 International Standard

One of the key challenges of perovskite photovoltaics (PV) is the long-term stability. Although efforts are made to improve the lifetime of perovskite PV devices, their degradation under reverse-bias conditions is barely addressed. Herein, perovskite solar cells with carbon-based electrodes are presented which demonstrate superior resilience against reverse-bias-induced degradation. Although their breakdown voltage is identified to be at approximately -3.6 V, cells do not degrade until the applied reverse-bias exceeds -9 V. Two main degradation mechanisms are identified: 1) iodine loss due to hole tunneling into perovskite, which takes place even at low reverse-bias but decomposes the perovskite only after long time durations; and 2) rapid heating at large reverse-bias leading to formation of PbI2, which starts at shunts and then follows the path of the least resistance for the cell current, which is primarily influenced by the electrode sheet resistances. Finally, perovskite solar modules with carbon-based electrodes are demonstrated, which are subjected to a "hotspot" test described in the IEC 61215:2016 international standard at an accredited module testing laboratory. Passing this accelerated test for the first time confirms the superior stability of perovskite PV devices with carbon-based electrodes and highlights their large industrialization potential.

14 SOLAR ENERGY↗
DOE OSTI2022

Oxygen Vacancy Introduction to Increase the Capacity and Voltage Retention in Li‐Excess Cathode Materials

Li‐rich rocksalt oxides are promising cathode materials for lithium‐ion batteries due to their large capacity and energy density, and their ability to use earth‐abundant elements. The excess Li in the rocksalt, needed to achieve good Li transport, reduces the theoretical transition metal redox capacity and introduces a labile oxygen state, both of which lead to increased oxygen oxidation and concomitant capacity loss with cycling. Herein, it is demonstrated that substituting the labile oxygen in Li‐rich cation‐disordered rocksalt materials with a vacancy is an effective strategy to inhibit oxygen oxidation. It is found that the oxygen vacancy in cation‐disordered lithium manganese oxide favors high Li coordination thereby reducing the concentration of unhybridized oxygen states, while increasing the theoretical Mn capacity. It is shown that in the vacancy‐containing compound, synthesized by ball milling, the Mn valence is lowered to less than +3, providing access to more than 300 mAh g −1 capacity from the Mn 2+ /Mn 4+ redox reservoir. The increased transition metal redox and decreased O oxidation are found to improve the capacity and voltage retention, indicating that oxygen vacancy creation to remove the most vulnerable oxygen ions and reduce transition metal valence provides a new opportunity for the design of high‐performance Li‐rich rocksalt cathodes.

25 ENERGY STORAGE↗
DOE OSTI2023

Assessment of potential impact of magnetic fields from a subsea high-voltage DC power cable on migrating green sturgeon, Acipenser medirostris

Abstract Empirical evidence suggests that marine animals perceive and orient to local distortions in the earth’s natural magnetic field. Magnetic fields (MFs) generated by electrified underwater cables may produce similar local distortions in the earth’s main field. Concern exists that these distortions may impact migration movements of MF-sensitive animals. The Trans Bay Cable (TBC) is a ± 200-kV, 400-megawatt, 85-km high-voltage direct current transmission line buried through San Francisco Bay (37° 56′ 8.81″ N, 122° 27′ 0.19″ W). Detections of adult green sturgeon implanted with acoustic transmitters were used from six cross-bay receiver arrays from 2006 to 2015 to investigate how inbound and outbound migration movements through lower portions of their route to/from upstream breeding grounds are related to the TBC’s energization status (off/on) and other local environmental variables. Here, we assess how these variables impacted transit success, misdirection from the migration route, transit times, and migration path locations within stretches between the Bay’s mouth and the start of the Sacramento River. Overall, there was varied evidence for any effect on migration behavior associated with cable status (off/on). A higher percentage of inbound fish successfully transited after the cable was energized, but this effect was nonsignificant in models including temperature. Outbound fish took longer to transit after cable energization. Inbound and outbound migration path locations were not significantly influenced by cable energization, but results suggest a potential subtle relationship between energization and both inbound and outbound paths. Overall, additional migration-based studies are needed to investigate the impact of anthropogenic cables on marine species.

Wyman, Megan T. (ORCID:0000000256844603)↗
DOE OSTI2020

Engineering lithium-ion battery cathodes for high-voltage applications using electromagnetic excitation

Microwave radiation (MWR), a type of electromagnetic excitation source, reduces the synthesis temperature and processing time for chemical reactions compared to traditional synthesis methods. Recently, we demonstrated that MWR can engineer ceramics with different crystal phases compared to traditional methods [ Journal of Materials Chemistry A 5 , 35 (2017)]. Here, we further apply the MWR-assisted technique to improve the electrochemical performance of LiCoO 2 cathodes by engineering TiO 2 and ZrO 2 ceramic coatings. Electrochemical tests suggest that the TiO 2 coating improves the rate capability of the LiCoO 2 electrode. Both TiO 2 and ZrO 2 coatings improve the high-voltage (4.5 V) cycling stability of LiCoO 2 . The capacity remaining is improved from 52.8 to 84.4% and 81.9% by the TiO 2 coating and the ZrO 2 coating, respectively, after 40 cycles. We compare these results with existing studies that apply traditional methods to engineer TiO 2 /ZrO 2 on LiCoO 2 , and find that the MWR-assisted method shows better performance improvement. X-ray photoelectron spectroscopy measurements suggest that the improved cycling stability arises from the formation of metal fluorides that protect the electrode from side reactions with electrolytes. This mechanism is further supported by the reduced Co dissolution from TiO 2 /ZrO 2 -coated LiCoO 2 electrode after cycling. This study provides a new toolbox facilitating the integration of many delicate, low melting point materials like polymers into battery electrodes.

25 ENERGY STORAGE↗
DOE OSTI2021

A generic method for interfacing IEDs using low voltage interfaces to real-time simulators with hardware in the loop

This study presents an interface method (IM) to interconnect real-time simulators (RTSs) without amplifiers for different intelligent electronic devices (IEDs), such as protective relays, smart meters, and other devices. It is a significant topic for the power systems protection community because there are many protection devices with different requirements. These protection devices have pinouts that measure bus voltages/currents and breaker pole states and generate trip/close pulse signals. Most of the emulation test beds with RTSs and HIL need amplifiers to connect IEDs from different product manufacturers because the low-voltage interface levels are not available in some instruction manuals. Additionally, commercial amplifiers have cutoff frequency limitations and have an excessive cost when several IEDs are wired onto test beds. Then, the validation of protection and control systems with RTSs and IEDs in the loop from different vendors without amplifiers results in an unfeasible alternative. In this paper, the IM was based on using an interface box, power source, and RTS to identify IED inputs/outputs. Here, the sequence to recognize IED pinouts and calculate the current/voltage scaling factors is described. The IM was validated satisfactorily with RTS and a protection device (with unknown pinouts) in the loop.

42 ENGINEERING↗
DOE OSTI2020

Cost-optimal evaluation of centralized and distributed microgrid topologies considering voltage constraints

Optimal design of hybrid renewable mini-grids requires both economic and power quality considerations. Existing modeling approaches address these considerations via separate or loosely coupled models. Here, we extend REopt—a techno-economic optimization model developed at the National Renewable Energy Laboratory—to consider both within a single model. REopt formulates the design problem as a mixed-integer linear program that solves for a site's optimal technology mix, sizing, and operation to minimize life cycle cost. REopt has traditionally assumed a single node system. In the work presented here, we expand the REopt platform to consider multiple connected nodes with associated voltage constraints. In order to do this, we model power flow using a fixed-point linear approximation method. Additionally, we then use the model to explore design considerations of mini-grids in Sub-Saharan Africa. Specifically, we evaluate under what combinations of transmission line distance and capacity it is technically viable and economically preferable to build multiple isolated mini-grids versus an interconnected, centralized system.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗
DOE OSTI2022

Development of high-affinity nanobodies specific for Na V 1.4 and Na V 1.5 voltage-gated sodium channel isoforms

Voltage-gated sodium channels, Na V s, are responsible for the rapid rise of action potentials in excitable tissues. Na V channel mutations have been implicated in several human genetic diseases, such as hypokalemic periodic paralysis, myotonia, and long-QT and Brugada syndromes. Here, we generated high-affinity anti-NaV nanobodies (Nbs), Nb17 and Nb82, that recognize the Na V 1.4 (skeletal muscle) and Na V 1.5 (cardiac muscle) channel isoforms. These Nbs were raised in llama (Lama glama) and selected from a phage display library for high affinity to the C-terminal (CT) region of Na V 1.4. The Nbs were expressed in Escherichia coli, purified, and biophysically characterized. Development of high-affinity Nbs specifically targeting a given human Na V isoform has been challenging because they usually show undesired crossreactivity for different Na V isoforms. Our results show, however, that Nb17 and Nb82 recognize the CTNa V 1.4 or CTNa V 1.5 over other CTNav isoforms. Kinetic experiments by biolayer interferometry determined that Nb17 and Nb82 bind to the CTNa V 1.4 and CTNa V 1.5 with high affinity (K D ~ 40–60 nM). In addition, as proof of concept, we show that Nb82 could detect Na V 1.4 and Na V 1.5 channels in mammalian cells and tissues by Western blot. Furthermore, human embryonic kidney cells expressing holo Na V 1.5 channels demonstrated a robust FRET-binding efficiency for Nb17 and Nb82. Our work lays the foundation for developing Nbs as anti-Na V reagents to capture Na V s from cell lysates and as molecular visualization agents for Na V s.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2025

How non-ohmic contact-layer diodes in perovskite pinholes affect abrupt low-voltage reverse-bias breakdown and destruction of solar cells

Perovskite solar cells (PSCs) rapidly degrade under reverse bias, a condition that may occur during partial shading. Here, in this study, we use electrical measurements, electron microscopy, and optical and thermal imaging to investigate abrupt breakdown and hotspotting under low reverse potentials (<|-2| V). We show that microscopic pinholes in the perovskite layer cause rapid, destructive breakdown under reverse bias despite minimally reducing power conversion efficiencies. Measurements on miniature (200-micrometer diameter) PSCs and perovskite-free transport-layer diodes indicate that abrupt, low-voltage breakdown occurs in nanoscale to micrometer-scale defects and that metal migration and filamentation are unlikely causes. Reverse-bias stability substantially improves when pinholes in the perovskite and transport layers are eliminated. Atomic layer deposition of tin oxide prevents abrupt breakdown by ensuring physical separation between electrodes-not by blocking metal ion migration. Perovskite researchers should adopt cleaner, more uniform deposition techniques to enable robust PSCs for further research and commercial applications.

14 SOLAR ENERGY↗
DOE OSTI2021

Design and production of the high voltage electrode grids and electron extraction region for the LZ dual-phase xenon time projection chamber

The dual-phase xenon time projection chamber (TPC) is a powerful tool for direct-detection experiments searching for WIMP dark matter, other dark matter models, and neutrinoless double-beta decay. Successful operation of such a TPC is critically dependent on the ability to hold high electric fields in the bulk liquid, across the liquid surface, and in the gas. Careful design and construction of the electrodes used to establish these fields is therefore required. We present the design and production of the LUX-ZEPLIN (LZ) experiment's high-voltage electrodes, a set of four woven mesh wire grids. Grid design drivers are discussed, with emphasis placed on design of the electron extraction region. Here, we follow this with a description of the grid production process and a discussion of steps taken to validate the LZ grids prior to integration into the TPC.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2023

Generation and characterization of magnetized electron beam from a DC high voltage photogun for electron beam cooling application

One of the most challenging requirements for the proposed Electron-Ion Collider is the strong cooling of the proton beam, which is key to achieving the collider’s desired luminosity of order 10 33 -10 34 cm -2 s -1 . Magnetized bunched-beam electron cooling could be a means to achieve the required high luminosity, where strong cooling is accomplished inside a cooling solenoid where the ions co-propagate with an electron beam generated from a source immersed in a magnetic field. To increase the cooling efficiency, a bunched electron beam with high bunch charge and high repetition rate is required. This work describes the production and characterization of magnetized electron beam using a compact 300 kV DC high voltage photogun and bi-alkali antimonide photocathode. Beam magnetization was studied using a diagnostic beamline that includes viewer screens for measuring the shearing angle of the electron beamlet passing through a narrow upstream slit. Simulations and corresponding measurements of beam magnetization are presented as a function of laser spot size and magnetic field strength. Correlated beam emittance with magnetic field (0–0.15 T) at the photocathode was measured for various laser spot sizes. Measurements of photocathode lifetime were carried out at different magnetized electron beam currents up to 28 mA, and bunch charge up to 0.7 nC (not simultaneously).

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2021

Degradation mechanisms and partial shading of glass-backsheet and double-glass photovoltaic modules in three climate zones determined by remote monitoring of time-series current–voltage and power datastreams

Degradation and partial shading impact the long-term reliability and power production of photovoltaic (PV) modules and power plants. Time-series power (P mp ) and current–voltage (I-V) curve datastreams from PV modules enable a remote diagnostic approach to quantify active degradation mechanisms and identify partial shading. We study three to nine years of these datastreams, including 3.6 million P mp I-V curves and 36 million values, from eight PV modules, four each of double-glass and glass-backsheet module architectures, located in three distinctly different Köppen-Geiger climate zones, to determine the module’s performance loss rates (PLR), identify active degradation mechanisms and power loss modes, along with partial shading by local objects. Considering both module architectures, PLR results indicate that the BSh climate zone is the most aggressive for module degradation, while the Alpine ET zone is the mildest climate. PLR of double-glass modules located in BWh and BSh climate zones are different due to the significantly greater uniform current loss (ΔP Isc ) for double-glass modules in BSh, at a 5% significance level. Power loss for four out of five modules located in the BWh and BSh climates are dominated by uniform current degradation. Statistical analysis of multistep I-V curves detects partial shading experienced by three studied modules with details of the shading profile, the shading Poynting vector diagram for the obstacle’s relative position, shading scenarios, and duration. Lastly, this work demonstrates how remote monitoring and diagnosis of P mp & I-V time-series of modules can provide quantitative operations and maintenance insights into system performance, degradation mechanisms, and shading.

14 SOLAR ENERGY↗
DOE OSTI2022

Cell dark current–voltage from non-calibrated module electroluminescence image analysis

Here, we present a fast, accurate, and reliable method of obtaining cell dark current–voltage (I–V) curves from module electroluminescence (EL) images without requiring calibration or correction. For a pristine module, EL-derived dark I–V are compared to directly probed data for a variety of changing imaging parameters: camera sensor, lens, filter, aperture width, exposure time (level of sensor saturation), number of images used, and various combinations of these. Pristine modules and those experiencing different modes and degrees of degradation are examined. A recent study of modules using five different cell technologies demonstrates the practicality of our “EL sweep” technique for performance and degradation studies.

14 SOLAR ENERGY↗
DOE OSTI2020

The performance evaluation of direct detection electron energy-loss spectroscopy at 200 kV and 80 kV accelerating voltages

Direct electron detectors (DeDs) have been widely used for imaging studies because of their higher beam sensitivity, lower noise, improved pixel resolution, etc. However, there have been limited studies related to the performance in spectroscopic applications for the direct electron detection. Hereby, taking the advantage of the DeD installed on a high-performance electron energy-loss spectrometer, we systematically studied the performance of a DeD (Gatan's K2 IS) fitted on an aberration-corrected transmission electron microscope (TEM) equipped with an electron monochromator. Using SrTiO3 as the model system, the point spread function in the zero-loss region of the spectrum and the performance for core loss spectroscopy have been investigated under both 200 kV and 80 kV operating conditions. We demonstrate that the K2 detector can achieve an overall better performance at 200 kV than a charge coupled device (CCD) detector. At 80 kV, the K2 DeD is still better than a CCD, except for the relative broad tails of the zero-loss peak. The signal-to-noise ratio is very close for DeD and CCD under 80 kV. Based on our data obtained at different operating voltages, it is clear that DeD will benefit the microscopy community and boost the development of cutting-edge materials science studies by pushing the frontiers in electron energy-loss spectroscopy.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2020

High Voltage Mg-Ion Battery Cathode via a Solid Solution Cr–Mn Spinel Oxide

We discuss how lattice Mg 2+ in a tailored solid solution spinel, MgCrMnO 4 , is electrochemically utilized at high Mn-redox potentials in a nonaqueous electrolyte. Complementary evidence from experimental and theoretical analyses supports bulk Mg 2+ (de)intercalation throughout the designed oxide frame where strong electrostatic interaction between Mg 2+ and O 2- exists. Mg/Mn antisite inversion in the spinel is lowered to similar to 10% via postannealing at 350 degrees C to further improve Mg 2+ mobility. Spinel lattice is preserved upon removal of Mg 2+ without any phase transformations, denoting structural stability at the charged state at a high potential similar to 3.0 V (vs Mg/Mel. Clear remagnesiation upon first discharge, harvesting up to similar to 180 Wh/kg at 60 degrees C is shown. In the remagnesiated state, insertion of Mg 2+ into interstitial sites in the spinel is detected, possibly resulting in partial reversibility which needs to be addressed for structural stability. The observations constitute a first clear path to the development of a practical high voltage Mg-ion cathode using a spinel oxide.

25 ENERGY STORAGE↗
DOE OSTI2025

Toward High-Voltage Cathodes for Zinc-Ion Batteries: Discovery Pipeline and Material Design Rules

Efficient energy storage systems are crucial to address the intermittency of renewable energy sources. As multivalent batteries, Zn-ion batteries (ZIBs), while inherently low voltage, offer a promising low-cost alternative to Li-ion batteries due to the viable use of zinc as the anode. However, to maximize the potential impact of ZIBs, rechargeable cathodes with improved Zn diffusion are needed. To better understand the chemical and structural factors influencing Zn-ion mobility within battery electrode materials, we employ a high-throughput computational screening approach to systematically evaluate candidate intercalation hosts for ZIB cathodes, expanding the chemical search space on empty intercalation hosts that do not contain Zn. We leverage a high-throughput screening funnel to identify promising cathodes in ZIBs, integrating screening criteria with density functional theory (DFT)-based calculations of Zn2+ intercalation and diffusion inside the host materials. Using these data, we identify the design principles that favor Zn-ion mobility in candidate cathode materials. Building on previous work on divalent-ion cathodes, this study broadens the chemical space for next-generation multivalent energy storage systems.

electrodes↗
DOE OSTI2021

“How Should I Think about Voltage? What Is Overpotential?”: Establishing an Organic Chemistry Intuition for Electrochemistry

Redox reactions are ubiquitous in organic synthesis and intrinsic to organic electrosynthesis. The language and concepts used to describe reactions in these domains are sufficiently different to create barriers that hinder broader adoption and understanding of electrochemical methods. To bridge these gaps, this Synopsis compares chemical and electrochemical redox reactions, including concepts of free energy, voltage, kinetic barriers, and overpotential. Furthermore, this discussion is intended to increase the accessibility of electrochemistry for organic chemists lacking formal training in this area.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗