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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 271 records · Page 15
All sourcesNASA NTRSDOE OSTI
DOE OSTI2016

Few-layer SnSe{sub 2} transistors with high on/off ratios

We report few-layer SnSe{sub 2} field effect transistors (FETs) with high current on/off ratios. By trying different gate configurations, 300 nm SiO{sub 2} and 70 nm HfO{sub 2} as back gate only and 70 nm HfO{sub 2} as back gate combined with a top capping layer of polymer electrolyte, few-layer SnSe{sub 2} FET with a current on/off ratio of 10{sup 4} can be obtained. This provides a reliable solution for electrically modulating quasi-two-dimensional materials with high electron density (over 10{sup 13} cm{sup −2}) for field-effect transistor applications.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2016

Time-resolved single-photon detection module based on silicon photomultiplier: A novel building block for time-correlated measurement systems

We present the design and preliminary characterization of the first detection module based on Silicon Photomultiplier (SiPM) tailored for single-photon timing applications. The aim of this work is to demonstrate, thanks to the design of a suitable module, the possibility to easily exploit SiPM in many applications as an interesting detector featuring large active area, similarly to photomultipliers tubes, but keeping the advantages of solid state detectors (high quantum efficiency, low cost, compactness, robustness, low bias voltage, and insensitiveness to magnetic field). The module integrates a cooled SiPM with a total photosensitive area of 1 mm{sup 2} together with the suitable avalanche signal read-out circuit, the signal conditioning, the biasing electronics, and a Peltier cooler driver for thermal stabilization. It is able to extract the single-photon timing information with resolution better than 100 ps full-width at half maximum. We verified the effective stabilization in response to external thermal perturbations, thus proving the complete insensitivity of the module to environment temperature variations, which represents a fundamental parameter to profitably use the instrument for real-field applications. We also characterized the single-photon timing resolution, the background noise due to both primary dark count generation and afterpulsing, the single-photon detection efficiency, and the instrument response function shape. The proposed module can become a reliable and cost-effective building block for time-correlated single-photon counting instruments in applications requiring high collection capability of isotropic light and detection efficiency (e.g., fluorescence decay measurements or time-domain diffuse optics systems).

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2023

Radiation tolerance studies of the HV-mux GaNFETs for the HL-LHC ATLAS ITk Strip detector

For the High-Luminosity upgrade of the LHC, the current ATLAS inner detector will be replaced with a new silicon charged-particle tracker, the ITk, which consists of the ITk Pixel and the ITk Strip subdetector. The high voltage multiplexing (HV-Mux) GaNFETs are radiation-tolerant transistors that permit switching off high voltage to malfunctioning sensors on the ITk Strip modules. To ensure the reliability of the GaNFETs in the high radiation environment expected at the HL-LHC, a sample of the production batch was exposed to gamma radiation. Finally, the GaNFETs were characterized pre-irradiation and post-irradiation, and monitored during irradiation.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2016

Damage in Monolithic Thin-Film Photovoltaic Modules Due to Partial Shade

The typical configuration of monolithic thin-film photovoltaic modules makes it possible for partial shade to place one or more cells in such a module in reverse bias. Reverse bias operation leads to high voltage, current density, and power density conditions, which can act as driving forces for failure. We showed that a brief outdoor shadow event can cause a 7% permanent loss in power. We applied an indoor partial shade durability test that moves beyond the standard hot spot endurance test by using more realistic mask and bias conditions and by carefully quantifying the permanent change in performance due to the stress. With the addition of a pass criterion based on change in maximum power, this procedure will soon be proposed as a part of the module-type qualification test. All six commercial copper indium gallium diselenide and cadmium telluride modules we tested experienced permanent damage due to the indoor partial shade test, ranging from 4% to 14% loss in maximum power. We conclude by summarizing ways to mitigate partial shade stress at the cell, module, and system levels.

14 SOLAR ENERGY↗
DOE OSTI2021

Solder Bond Fatigue is Insensitive to Module Size

In this article, we explore the influence of module size on the rate of interconnecting solder bond thermomechanical fatigue (TMF) damage. Structural mechanics models of crystalline silicon PV models are created to solve with the finite-element method. Results conclusively demonstrate that the rate of solder bond TMF damage is independent of module size, interconnect location across the cell and cell location across the module.

14 SOLAR ENERGY↗
DOE OSTI2015

Evaluation of Dynamic Mechanical Loading as an Accelerated Test Method for Ribbon Fatigue

Dynamic Mechanical Loading (DML) of photovoltaic modules is explored as a route to quickly fatigue copper interconnect ribbons. Results indicate that most of the interconnect ribbons may be strained through module mechanical loading to a level that will result in failure in a few hundred to thousands of cycles. Considering the speed at which DML may be applied, this translates into a few hours o testing. To evaluate the equivalence of DML to thermal cycling, parallel tests were conducted with thermal cycling. Preliminary analysis suggests that one +/-1 kPa DML cycle is roughly equivalent to one standard accelerated thermal cycle and approximately 175 of these cycles are equivalent to a 25-year exposure in Golden Colorado for the mechanism of module ribbon fatigue.

14 SOLAR ENERGY↗
DOE OSTI2016

Degradation of Silicone Encapsulants in CPV Optics

High efficiency multijunction solar cells in terrestrial concentrator photovoltaic (CPV) modules are becoming an increasingly cost effective and viable option in utility scale power generation. As with other utility scale photovoltaics, CPV modules need to guarantee operational lifetimes of at least 25 years. The reliability of optical elements in CPV modules poses a unique materials challenge due to the increased UV irradiance and enhanced temperature cycling associated with concentrated solar flux. The polymeric and thin film materials used in the optical elements are especially susceptible to UV damage, diurnal temperature cycling and active chemical species from the environment. We used fracture mechanics approaches to study the degradation modes including: the adhesion between the encapsulant and the cell or secondary optical element; and the cohesion of the encapsulant itself. Understanding the underlying mechanisms of materials degradation under elevated stress conditions is critical for commercialization of CPV technology and can offer unique insights into degradation modes in similar encapsulants used in other photovoltaic modules.

14 SOLAR ENERGY↗
DOE OSTI2021

Representative Modules for Accelerated Thermal Cycling and Static Load Testing

In this work, we explore the influence of module size on the rate of interconnect solder bond thermomechanical fatigue (TMF) damage and the probability of cell fracture. For the solder bond TMF damage evaluation, structural mechanics models of crystalline silicon PV models are created to solve with the Finite Element Method. For the probability of cell fracture evaluation, Weibull analysis and weakest link theory are employed to resolve the probability of crystalline silicon PV cell fracture when measured as bare cells and when stressed in reduced- and full-sized modules. Results conclusively demonstrate that the rate of solder bond TMF damage is independent of module size, interconnect location across the cell and cell location across the module and that smaller, representative, modules must be loaded to a much higher level than their parent full-sized modules to achieve an equivalent driving force for cell fracture.

accelerated testing↗
DOE OSTI2021

Fatigue-Like Behavior of Silver Metallization Gridlines and Proposed Damage Mechanics Model

In this work, we present a novel method to evaluate the fracture and fatigue-like behavior of crystalline silicon PV cell metallization. Initial results demonstrate that silver metal gridlines are capable of bridging a ~10–20 µm gap prior to becoming electrically open and do demonstrate fatigue-like behavior under cyclic straining conditions. This later phenomenon was well fit with a traditional power law equation for high cycle fatigue and enabled the development of a damage mechanics model for gridline failure.

41 EE - Solar Energy Technologies Office (EE-4S)↗
DOE OSTI2013

In-Vessel Coil Material Failure Rate Estimates for ITER Design Use

The ITER international project design teams are working to produce an engineering design for construction of this large tokamak fusion experiment. One of the design issues is ensuring proper control of the fusion plasma. In-vessel magnet coils may be needed for plasma control, especially the control of edge localized modes (ELMs) and plasma vertical stabilization (VS). These coils will be lifetime components that reside inside the ITER vacuum vessel behind the blanket modules. As such, their reliability is an important design issue since access will be time consuming if any type of repair were necessary. The following chapters give the research results and estimates of failure rates for the coil conductor and jacket materials to be used for the in-vessel coils. Copper and CuCrZr conductors, and stainless steel and Inconel jackets are examined.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2019

Nishati Prototype 72-Cell Endurance Modules (Test Report)

US Manufacturer Nishati provided three prototype, 72-cell photovoltaic modules to Sandia for characterization under the US Department of Energy Small Business Voucher program. Nishati is developing the Endurance © product to address the stringent requirements associated with PV system installations sited near airports and military bases. These prototype modules are uniquely constructed of a polymeric matrix and an internal honeycomb structural element. Target features of the module design are reduced reflectivity from the front surface and reduced weight. Sandia applied a variety of in-house characterization methods to these modules with the goal of validating performance and identifying any areas for improvement. Reflectance testing revealed extremely low specular reflection, dramatically surpassing the performance of industry standard PV panels. Electrical performance testing validated performance in line with expectations for similar size and power class modules. Complimentary to reflection testing, outdoor angle of incidence testing indicated performance far exceeding expectations for industry standard PV panels. It is possible that the extremely low reflectance properties of these modules will convey an advantage in annual energy production in comparison to industry standard modules. Detailed performance modeling and experimental field validation would be required to verify this possible advantage. During the course of this testing, no obvious deficiencies in this module design were discovered. It is recommended that Nishati and Sandia proceed to the final Task associated with the SBV award. This final task will involve fielding modules at Sandia for reliability and energy production validation.

14 SOLAR ENERGY↗
NASA NTRS1971

A guide to onboard checkout. Volume 7: RF communications

The radio frequency communications subsystem for a space station is considered, with respect to onboard checkout requirements. The subsystem comprises all equipment necessary for transmitting and receiving, tracking and ranging, command, multiple voice and television information, and broadband experiment data. The communications subsystem provides a radio frequency interface between the space station and ground stations, either directly or indirectly, through a data relay satellite system, independent free-flying experiment modules, and logistics vehicles. Reliability, maintenance, and failure analyses are discussed, and computer programming techniques are presented.

Source record↗
NASA NTRS1973

Control strategies for planetary rover motion and manipulator control

An unusual insect-like vehicle designed for planetary surface exploration is made the occasion for a discussion of control concepts in path selection, hazard detection, obstacle negotiation, and soil sampling. A control scheme which actively articulates the pitching motion between a single-loop front module and a dual loop rear module leads to near optimal behavior in soft soil; at the same time the vehicle's front module acts as a reliable tactile forward probe with a detection range much longer than the stopping distance. Some optimal control strategies are discussed, and the photos of a working scale model are displayed.

Trautwein, W.↗