Search NASA⌕ Search

SEARCH · Search NASA

Results for “capacitance”

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.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,747 records · Page 97
All sourcesNASA NTRSDOE OSTI
DOE OSTI2018

Advanced Models for Nondestructive Evaluation of Aging Nuclear Power Plant Cables

Background: Nuclear power plant (NPP) cables must function correctly for proper power supply and control of the nuclear reactor. This is especially important for public and environmental safety at critical times such as during reactor shut-down following loss of coolant. Over extended periods of service, the cable insulation and jacket polymer materials suffer from degradation due to exposure to environmental stressors such as heat and ionizing radiation. The focus of this project has been the development of detailed descriptions of the way in which insulation polymers degrade, from a materials science perspective, and the development of new electrical techniques to monitor cable polymer condition nondestructively. Objectives: The objectives of this project have been to i) perform detailed characterization experiments upon cable insulation polymers that have experienced thermal and radiation exposure mimicking that received during NPP operation, including the exploration of novel cable nondestructive evaluation methods; capacitive, THz and infrared methods; ii) identify the most sensitive indicators of aging in these materials, and iii) develop advanced, validated models describing microstructural and chemical changes that are observed in cable insulation polymers due to thermal and radiation exposure. Methods: Accelerated aging was performed on the two most common United States NPP cable insulation polymers (cross-linked polyethylene (XLPE) and ethylene propylene rubber (EPR)) under various conditions of elevated temperature and gamma radiation dose. Aging mechanisms were elucidated through extensive thermal, mechanical and microscopic characterization of the aged samples, and materials modeling. Dielectric and IR spectra were measured on pristine and aged samples. Data was analyzed statistically, via multiple linear regression, partial least squares and probabilistic neural network approaches. Impact: Extant cable monitoring techniques do not deal successfully with all polymer types. This research has laid a foundation upon which new electrical nondestructive test methods for cable polymer condition monitoring may be developed, hence launching the development of new test methods for cable insulation monitoring based on measuring electrical rather than mechanical parameters. Collaboration: This project has benefitted from collaboration between experts in materials science and engineering, materials modeling, electrical engineering, and nondestructive evaluation. The majority of the characterization measurements were carried out at Iowa State University. Materials modeling was carried out primarily at Washington State University. Irradiation of samples took place at Pacific Northwest National Laboratory (PNNL), where a student intern from Iowa State was hosted for one summer, setting up the aging experiments. A research student from the University of Bologna, Italy, joined the project for their thesis research at Iowa State University with samples provided by PNNL. The project benefitted from regular involvement of senior engineers in US-based industry partners. Project investigators presented findings at various national and international conferences and workshops.

21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS↗
DOE OSTI2018

γ-Valerolactone-Extracted Lignin to Porous Carbon Materials

Synthesis of multiphase materials from lignin, a biorefinery coproduct, offers limited success due to the inherent difficulty in controlling dispersion of these renewable hyperbranched macromolecules in the product or its intermediates. Effective use of the chemically reactive functionalities in lignin, however, enables tuning morphologies of the materials. Here, we bind a lignin oligomer with a rubbery macromolecule followed by thermal crosslinking to form a carbon precursor with phase contrasted morphology at submicron scale. The solvent-free mixing is conducted in a high-shear melt-mixer. With this, the carbon precursor is further modified with potassium hydroxide for a single-step carbonization to yield activated carbon with tunable pore structure. A typical precursor with 90% lignin yields porous carbon with 2120 m 2 /g surface area and a supercapacitor with 215 F/g capacitance. The results show a simple route towards manufacturing carbon-based energy-storage materials, eliminating the need for conventional template-synthesis.

36 MATERIALS SCIENCE↗
DOE OSTI2018

MilliKelvin HEMT Amplifiers for Low Noise High Bandwidth Measurement of Quantum Devices

We demonstrate ultra-low power cryogenic high electron mobility transistor (HEMT) amplifiers for measurement of quantum devices. The low power consumption (few uWs) allows the amplifier to be located near the device, at the coldest cryostat stage (typically less than 100 mK). Such placement minimizes parasitic capacitance and reduces the impact of environmental noise (e.g. triboelectric noise in cabling), allowing for improvements in measurement gain, bandwidth and noise. We use custom high electron mobility transistors (HEMTs) in GaAs/A1GaAs heterostructures. These HEMTs are known to have excellent performance specifically at mK temperatures, with electron mobilities that can exceed 10 6 cm 2 /Vs, allowing for large gain with low power consumption. Low temperature measurements of custom HEMT amplifiers at T = 4 K show a current sensitivity of 50 pA at 1 MHz bandwidth for 5 mW power dissipation, which is an improvement upon performance of amplifiers using off-the-shelf HEMTs.

47 OTHER INSTRUMENTATION↗
DOE OSTI2018

Advanced Control Architecture and Sensor Information Development for Process Automation, Optimization, and Imaging of Chemical Looping Systems

The Syngas Chemical Looping (SCL) process developed at The Ohio State University (OSU) uses an iron-based oxygen carrier to convert syngas into high-purity hydrogen while simultaneously capturing carbon dioxide that is readily sequestrable. A 25 kWth sub-pilot unit was successfully demonstrated multiple times on the OSU Clean Coal Research Facility, and a 250 kWth – 3 MWth pilot demonstration unit has been designed and constructed at the National Carbon Capture Center (NCCC) in Wilsonville, Alabama. The focus of this project is to develop multiple technologies to automate the startup and shutdown of chemical looping system. Success of this project will propel the advanced carbon capture method toward commercialization, hence be disruptive to the fossil fuel and power industries. Advanced process automation control architecture and imaging and optimization sensor software were developed for OSU chemical looping process. A high-level controller (HLC) consisting of decision-making and controller-selection logic integrated with sliding mode controllers (SMCs) were developed to perform chemical looping process startup and shutdown. Babcock & Wilcox Power Generation Group’s FocalPoint Optimization System was implemented to optimize the process operating conditions. The process automation controller and optimization information were realized and tested on OSU’s existing sub-pilot chemical looping test unit under atmospheric condition. The implemented control architecture was able to perform the complete process procedure from startup, steady-state reaction operation to shutdown with minimal operator intervention. The controller was also implemented on the pressurized syngas chemical looping (SCL) pilot test unit constructed at the National Carbon Capture Center (NCCC), demonstrating its pressure control capability with a designed transient state trajectory. An electrical capacitance volume tomography (ECVT) sensor device and its software were developed to image the packed moving bed and slugging fluidized bed of oxygen carriers in chemical looping systems at elevated temperatures. The ECVT device constructed was capable of tracking the subtle voidage variance along the moving bed axis as a feature for directly measuring the oxygen carrier particles’ linear velocity. Also, the high temperature ECVT device was used to study the fluidization characteristics of Geldart Group D particles.

08 HYDROGEN↗
DOE OSTI2018

Hole Spin Qubits in Germanium

Holes in germanium-rich heterostructures provide a compelling alternative for achieving spin based qubits compared to traditional approaches such as electrons in silicon. In this project, we addressed the question of whether holes in Ge/SiGe quantum wells can be confined into laterally defined quantum dots and made into qubits. Through this effort, we successfully fabricated and operated single-metal-layer quantum dot devices in Ge/SiGe in multiple devices. For single quantum dots, we measured the capacitances of the quantum dot to the surface electrodes and find that they reasonably compare to expected values based on the electrode dimensions, suggested that we have formed a lithographic quantum dot. We also compare the results to detailed self-consistent calculations of the expected potential. Finally, we demonstrate, for the first time, a double quantum dot in the Ge/SiGe material system.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Improving Land-Surface Modeling of Evapotranspiration Processes in Tropical Forests (Final Report)

Land surface models are used to represent terrestrial processes that shape global climate; examples of these processes include evaporation, plant water use, and photosynthesis. While much progress has been made to improve and refine these models, some hydrological processes are not well captured, which hinders our ability to understand land-atmosphere interactions and ultimately to predict impacts of climate change on water resources. The inadequate representation of evapotranspiration may partly explain why global climate models do not match observed precipitation patterns. Multiple factors contribute to this problem. In moist tropical regions, high humidity, leaf wetness, and cloud cover combine to suppress forest water use and possibly reduce forest growth in ways that are poorly understood. Mountainous areas pose additional difficulties, as standard modeling and measurement techniques are not readily applied in rough terrain. In this project, we aimed to improve our understanding and modeling of fluxes of water vapor and carbon dioxide to and from tropical forests. To do this, we collected a suite of data from the mountainous rainforest surrounding the Texas A&M Soltis Center in San Ramon, Costa Rica. From 2014 to 2018, a suite of variables were measured, including: in-canopy profiles of water vapor, carbon dioxide, temperature, light, and leaf wetness; transpiration, evapotranspiration, carbon flux, and soil respiration; and local weather conditions. Leaf-scale measurements were used to find photosynthesis rates and derive their parameters. Using this data set, we were able to better quantify the relationships between assimilation and transpiration and their main drivers in tropical forests. These variables were namely available light, vapor pressure deficit, and leaf wetness, but not soil moisture, which exerted no detectable control. We also showed the vertical variability in canopy microclimates and how neglecting forest layers in models may misrepresent overall fluxes. The data were then used to test and refine evapotranspiration and energy budget formulations in the Community Land Model. Fluxes and energy budget components were compared to simulated values from CLM4.5 and CLM.5. The biggest discrepancies arose from hillslope shading effects, particularly mismatches in afternoon carbon fluxes, with notable differences in transpiration rates and sap flux due to capacitance in large trees. Secondary, but still significant issues included unrealistic leaf wetness and leaf drying rates, as well as air and vegetation temperatures, both of which were likely linked to CLM’s formulations controlling wet leaf and sunlit/shaded leaf fractions. Modeling multiple layers in the canopy via the newly released CLM-ml and making adjustments to existing parameters both show promise in resolving these issues. In total, the project has produced 5 peer-reviewed articles, 24 presentations, 2 theses, 4 public outreach items, and 4 publically available datasets, to date. Additional products are expected pending the completion of an additional thesis. Data has also been shared with several collaborative networks, including PHENOCAM and SAPFLUXNET.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2018

BPM Button Testing

Initial testing was performed by P. Cameron. Ten assemblies were tested for the electrical resistance, stray capacitance, trapped mode frequency, dimensional tests, voltage standing wave ratio (VSWR), pin insertion/withdrawal force, and vacuum leak check. After satisfactory results the production run started. The acceptance tests are described below.

42 ENGINEERING↗
DOE OSTI2019

Self-powered Wireless Dual-mode Langasite Sensor for Pressure/Temperature Monitoring of Nuclear Reactors

Safety issues in nuclear power plants are of extreme importance. Numerous sensors are used within nuclear power plants for sensing and monitoring of its critical operation parameters. As currently implemented, during massive losses of power across the plant in accidents, the backup batteries for the monitoring sensors will ultimately be drained and can cease to operate. The overall objective of this NEUP project is to develop a novel self-powered wireless hybrid sensor which can accurately monitor both pressure and temperature using a single device, even in the extreme harsh environments of severe nuclear accidents, without the requirement of external electricity. At Virginia Tech side, a heat pipe assisted thermoelectric generator (TEG) energy harvester and associated power management and data transmission circuits were developed. The energy harvester can produce electrical power continuously, even in loss of plant and external power situations, providing power for important data transmission for accident diagnosis. The self-powered sensing system could be integrated directly onto key nuclear components including pipes, pump housings, heat exchangers, reactor vessels, and shielding structures inside and outside of the reactor core. Two TEG based energy harvesters which can work in relatively low (50-250 ºC) and high temperature ranges (250-350 ºC) were established and tested. In the prototypes, heat pipes were introduced to reduce the heat resistances of the device at the hot and cold ends. The power output of the heat pipe assisted TEG module is 2.22 W, which is 6 times more than one using an aluminum rod. In-lab tests showed that these devices canmeet the requirement to power the sensors and circuit during normal and off-normal conditions.Amodel was then built to analyze the thermal network in the energy harvester, and was used to optimize its performance and reduce its geometry size. The design and testing of the vibrational energy harvester were completed. The harvester, has shown to effectively increase the vibrational potential of the main coolant pump, though it has been shown that thermal energy has a much higher potential for the powering of sensors. In this project, a self-start charger circuit for the energy harvester was designed to regulate and manage the power. An energy storage element was incorporated into the energy harvesting module for sensors and wireless transceivers in an off-normal situation. The signal conditioning and wireless communication electronic circuits were developed and tested in the lab. An important consideration for an energy harvester within a nuclear power plant is the level of radiation it will encounter during operation. The two main sources of radiation in a nuclear power plant are gamma and neutron radiation. Aradiation experiment was conducted in the Westinghouse Electric Company during which the prototypes were placed in a 106 rad radiation environment to test their ability to operate in the extreme environment. The results showed that this level of radiation had little effect on the performance of the TEGmaterial and heat pipe heat exchanging system. Its influence on the circuit was still under research, however the need for more development on radiation hardened electronics is needed. Pressure measurement based on piezoelectric crystal resonators has advantages over the commercially available methods like capacitive, electromagnetic, optical, potentiometric, and piezo resistive strain gauges. Since the output of piezoelectric based sensors are digital in format, it has a very high resolution, high accuracy, and long-term stability. Quartz is one of the commonly used piezoelectric material in digital pressure sensors design. This material is elastic in nature, providing high stability, high repeatability, high elasticity, repeatable mechanical behavior for many cycles of operation, and is free of hysteresis. The quartz resonator has a high Q, which means that very high vibration can be driven with the very low electric power. Langasite (LGS) is a new promising piezoelectric material that combines the advantageous properties of quartz with a better performance at high temperatures. LGS will not undergo any phase transitions up to its melting temperature of 1473 C, and hence, the application of Langasite in measuring pressure at high temperatures is promising. In this project, the design and fabrication of the piezo oscillator crystal for temperature and pressure measurement has been completed. The entire sensor has been fabricated and tested to see its sensitivity to temperature and pressure changes. The design and optimization of the radiation shielding systems that can effective protect the duel-mode Langasite sensor inside reactor core were demonstrated. To maximize the radiation shielding effectiveness, different types of materials are investigated based upon recent developments of radiation shielding systems including aluminum + Boron carbide and bismuth borosilicate glass B2O3 in addition to tungsten/B4C. New materials based upon metatheses is included as potential shielding to mitigate neutron fluencies. The radiation shielding effectiveness of selected composites are evaluated within a broader neutron spectrum from thermal, epithermal, fast (1 MeV) and 15 MeV neutrons. Performance analysis was also conducted to evaluate the effects of selected composite systems.Aconceptual design was also proposed for the packaging and integration of the radiation shielding system with the sensor, and its applicability within the reactor core was discussed. At end of the project, all components necessary for a complete sensing and monitoring system, including a langasite sensor, electrodes, the TEG harvester, an energy storage device, and power management and transmission electronics were integrated to demonstrate feasibility in powering the sensor. Finally, integration of each component into a full package, and a full demonstration were done.

22 GENERAL STUDIES OF NUCLEAR REACTORS↗
DOE OSTI2019

Low-Loss, High-Flux Saturation Magnetic Cores for Power Converters

As new and alternative energy sources are added to the energy grid, efficient and low-loss power converters are essential to the storage of energy from these intermittent power sources. Higher operating frequency can reduce the size and weight of transformers. However, current magnetic cores limit the operating frequency because core losses increase with frequency. Therefore, new magnetic core materials are needed with higher resistivity (lower eddy-current losses), lower coercivity (lower hysteresis losses), and higher permeability and flux density (higher power density). These new materials must be integrated into isolated power converters designed to optimize efficiency based on the transformer performance. To address this need, Mainstream pursued a two-pronged approach in Phase I to develop novel magnetic materials and model a planar transformer design. We irradiated silicon steel with a high-energy electron beam in an attempt to induce nanocrystalline grain formation. The nanocrystalline grains were expected to increase resistivity to reduce eddy-current losses and decrease coercivity to reduce hysteresis losses. We also modeled the transformer performance through Simulation Program with Integrated Circuit Emphasis (SPICE) and analytical models to establish the effect of magnetic properties of the core on the performance of the transformer. There still are hurdles to be overcome in Phase II. The electron beam processing was successful in increasing the resistivity and the flux saturation density. However, the resistivity is still too low for high-frequency magnetic cores, because the eddy-current losses would be prohibitively high. Additionally, the coercivity increased for the processed samples leading to higher hysteresis losses. In comparing our SPICE and analytical models to the planar transformer measured values and impedance plots, good agreement was seen for primary and secondary short-circuit impedance measurements and for primary-to-secondary capacitance measurements. The SPICE model deviated from measured values, though, when measuring the transformer open-circuit impedance, indicating that we might need to add more model complexity to the transformer model. Phase II research will continue to build on the transformer model and integrating novel magnetic materials into high-frequency transformers.

15 GEOTHERMAL ENERGY↗
DOE OSTI2019

Characterization of 14YWT & ODS Base Metals

Nanostructured ferritic alloys (NFA) with oxide dispersion strengthening are being developed for next generation reactor applications. Applications such as transmutation of long lived isotopes in used fuels require cladding materials that can withstand high irradiation doses, potentially in the hundreds of displacements per atom (dpa). Currently, however, there are no joining processes that retain the strength and fine distribution of oxide precipitates characteristic of ODS alloys. As part of a larger effort to adapt a solid state capacitive discharge welding technique for use with ODS cladding, presented will be characterization of the initial materials including 14YWT and MA956 ODS alloys.

36 MATERIALS SCIENCE↗
DOE OSTI2019

SBIR Phase I Final Technical Report

The main purpose of this program, a Phase I SBIR effort, was to demonstrate the feasibility of constructing a fast void detector that can detect and localize voids with a quantifiable detection limit superior to a capacitive void sensor. The project used modeling and simulation of the radio- frequency (RF) sensor and environment, designed RF elements for the harsh environment, and fabricated the devices for temperature and pressure requirements. The project concluded with a demonstration of the system and feasibility of approach. First, the project performed theoretical work to simulate the system capabilities. Second, the project refined the RF sensor designs. Third, the effort fabricated devices. Fourth, the project demonstrated feasibility with a demonstration of the technology, individual components, and integrated elements. We assess that the project ended at Technology Readiness Level 3 (TRL-3) and demonstrated the feasibility of our concept.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2019

High lifetime and mobility CdTe alloys by co-sublimation

The focus of this project was to understand controlled doping of CdTe and CdSe x Te 1-x films using group V element dopants such as nitrogen and arsenic. Using methods such as metal organic precursor injection as well as deposition of absorber with source charge incorporated with desired group V dopant. Using characterization methods such as Secondary Ion Mass Spectroscopy and capacitance vs voltage measurement dopant incorporation and activation was verified. Since our deposition system had CuCl deposition source, this source was permanently removed from the system and vacuum chamber was thoroughly cleaned out. CdSe x Te 1-x grading into CdTe has led to higher device efficiency owing to an improvement in short-circuit current (J SC ) due to its lower band-gap. More device fabrication and characterization was performed in an effort to optimize the lower band-gap CdSe x Te 1-x . This optimization was performed using different co-sublimation method where CdTe and Se were co-sublimated in varying proportion to sweep the band-gap of CdSe x Te 1-x that deposited on the substrate.

14 SOLAR ENERGY↗
DOE OSTI2019

Transition Metal Oxides Nanomaterials for Aqueous Electrochemical Energy Storage

A key technical challenge for capacitive energy storage devices to rival the performance of lithium-ion batteries is to improve their energy density (E), which is proportional to the capacity (C) and square of potential window (V) as following equation shows: E = ½ C V 2 . Therefore, the primary objective of this project is to develop the electrode materials with high capacity and/or wide potential window. Through this research support, the PI has been working on two major groups of metal oxides materials to tackle this challenge.

25 ENERGY STORAGE↗
DOE OSTI2019

Linear Induction Accelerator Cell Voltage Calibration Using Compact Electron Permanent Magnet Spectrometer

The Dual-Axis Radiographic Hydrodynamic Test (DARHT) facility provides flash radiography capabilities using electron Linear Induction Accelerators (LIA’s). The strict requirements for flash radiography require a detailed understanding of the LIA’s performance, including precision measurements of the electron beam energy. Axis-1 of DARHT produces a 20 MeV, 2 kA, 80-ns-FWHM electron beam. Electronic measurement with cell-voltage monitors which consists of a 75 ohm load resistor and a current viewing resistor (CVR) that are coupled together and injector capacitive monitors (EVACSUM) are summed to give the total beam energy at the output of the accelerator. Calibration of these monitors was last done in 1999 and is needed. Using the Compact electron Permanent Magnet Spectrometer (CePMSpec), we have developed a technique for measuring and adjusting the calibration of the accelerator cell load resistor/CVR by using the total energy of the beam. Each pair of cells is driven by pulsed power Blumleins, and each Blumlein is charged by a Blumlein Charge Unit (BCU). There are 64 cells and 32 Blumleins and BCUs. This technique is applied to all 32 BCUs.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2019

3D printed segmented electrodes for water desalination

In this project, we attempted to use additive manufacturing techniques to produce capacitive deionization (CDI) devices with improved performance. Direct ink writing, two-photon polymerization, and microstereolithography were used to produce segmented electrodes for CDI with a lower thickness than can be produced currently with bulk fabrication methods. The electrode thickness is a principle driver of device resistance, and, therefore, the energy consumption of the device. While we identified several pitfalls for producing interdigitated electrodes with low thickness and potential paths to overcome them, we were unable to print a useful structure within the scope of this project.

36 MATERIALS SCIENCE↗
DOE OSTI2019

In Situ Monitoring of Direct Ink Write Process Using Electromagnetic Resonant Coupling

Additive manufacturing (AM) of multi-material objects enables the design of complex 3D architectures such as printed electronics and devices. The ability to detect the composition of multi-material printed inks in real time is an emerging need for a wide range of manufacturing applications. This study demonstrates the feasibility of using an in situ sensor to locally measure the composition of inks as they are being printed to facilitate greater control over the resulting properties and functionality of printed materials. Dielectric properties of microscale embedded metal particles in a dielectric matrix are measured and characterized as a function of particle size, shape, volume percentage and frequency. Results show that particle shape has a much greater influence on impedance measurements than the particle size. Measurements are found to agree with calculations based on an anisotropic Maxwell-Garnett dielectric function model. The resulting data can be used to generate a calibration curve correlating metal loading with impedance or capacitance and thus applied as an in situ sensor for compositional measurements during extrusion-based AM.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Developing Novel Electrode Materials for Aqueous Battery

Aqueous rechargeable batteries (ARBs) are particularly interesting for large-scale energy storage due to their inherent safety, superior rate capability and environmental friendliness. However, ARBs are not widely explored as yet, so we proposed designing, preparing, and testing new intercalation materials for ARBs. Development of these electrodes will enrich the electrode chemistry of existing ARBs, open up new avenues for high-performance electrode and system design, offer opportunities to improve energy efficiency of water purification, and inform future development of controls strategies and management systems for stationary aqueous energy storage. Researchers from Bosch and LBNL collaborated on relevant materials to pursue and the general design of experiments to implement. Bosch researchers prepared and fabricated the electrodes and used various characterization facilities at LBNL to evaluate electrode performance in-device. The research collaboration resulted in identifying electrode materials capable of Na + and Ca 2+ intercalation in aqueous systems, and their application for desalination was explored using testing platform available at LBNL. Besides the specific materials and their performance, the data collected during the study was also used to inform a broader techno-economic analysis to compare intercalation-desalination technique to commercially available capacitive desalination approach. Outcomes of this research effort will be published in peer-reviewed journals.

25 ENERGY STORAGE↗