Search NASA⌕ Search

SEARCH · Search NASA

Results for “Capacitor Sizing”

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 163 records · Page 9
All sourcesNASA NTRSDOE OSTI
NASA NTRS2003

Advanced sensor systems for biotelemetry

The present invention relates to telemetry-based sensing systems that continuously measures physical, chemical and biological parameters. More specifically, these sensing systems comprise a small, modular, low-power implantable biotelemetry system capable of continuously sensing physiological characteristics using implantable transmitters, a receiver, and a data acquisition system to analyze and record the transmitted signal over several months. The preferred embodiment is a preterm labor and fetal monitoring system. Key features of the invention include Pulse Interval Modulation (PIM) that is used to send temperature and pressure information out of the biological environment. The RF carrier frequency is 174-216 MHz and a pair of RF bursts (pulses) is transmitted at a frequency of about 1-2 Hz. The transmission range is 3 to 10 feet, depending on the position of the transmitter in the body and its biological environment. The entire transmitter is encapsulated in biocompatible silicone rubber. Power is supplied by on-board silver-oxide batteries. The average power consumption of the current design is less than 30 .mu.W., which yields a lifetime of approximately 6-9 months. Chip-on-Board technology (COB) drastically reduces the size of the printed circuit board from 38.times.28 mm to 22.times.8 mm. Unpackaged dies are flip-chip bonded directly onto the printed circuit board, along with surface mount resistors and capacitors. The invention can monitor additional physiological parameters including, but not limited to, ECG, blood gases, glucose, and ions such as calcium, potassium, and sodium.

Hines, John W.↗
DOE OSTI2016

A Generic Model for Electric Double Layers in Porous Electrodes

The performance of electric-double-layer capacitors (EDLCs) hinges on microscopic charge distributions near the electrode/electrolyte interfaces. Whereas practical EDLCs consist of electrodes made of amorphous porous materials, theoretical understanding of EDLCs is mostly based on EDL structure near a planar surface or on simplistic models that have little relevance to realistic systems. In this work, we propose a spherical shell model to account for both pore size and curvature effects of amorphous porous materials. The EDL structure in spherical shells has been investigated over a broad range of pore sizes and curvatures by use of classic density functional theory. Theoretical results reveal that the curvature effects on convex and concave EDLs are drastically different and that materials with extensive convex surfaces will lead to maximized capacitance. Like a slit pore, the spherical shell model also predicts oscillatory variation of capacitance with pore size, but the oscillatory behavior is magnified as the curvature increases. The joint effects of pore size and curvature identified in this work give new insight into materials design for porous electrodes with optimal EDLC performance.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS2006

Nearly Direct Measurement of Relative Permittivity

A recently conceived technique for determining the relative permittivity of a material sample at a given frequency is more nearly direct than are prior techniques that involve measurement of such related non-electrical quantities as the size, shape, and/or weight of the specimen. The present technique involves only measurement of two voltages at the frequency in question, followed by calculation of the ratio between the voltages. The technique requires two circuits a test circuit and a reference circuit that are identical except as described below. Each circuit includes a capacitor C1 connected in series with a much larger capacitor C2 to form a voltage divider (see figure). C1 is a parallel-plate capacitor. The top electrode of C1 is connected to an AC signal source of voltage Va at the frequency of interest. The top electrode of C1 is surrounded by a guard electrode that, in turn, is surrounded by a grounded electrode. The bottom electrode of C1 is connected to the top electrode of C2. The bottom electrode of C2 is grounded. The volume enclosed by the top, bottom, and guard electrodes of C1 constitutes a sample cell. A material sample, having relative permittivity k at the frequency of interest, is placed in the sample cell. The exact shape and size of the sample volume is not critical and can be chosen to fit the material sample. What is critical is that (a) C2 in both circuits be identical and (b) the sample cell in the test circuit have the same size and shape as that in the reference circuit, so that the capacitances of the two sample cells are proportional to the permittivities of their contents.

Calle, Carlos I.↗
NASA NTRS2003

Advanced Sensor Systems for Biotelemetry

The present invention relates to telemetry-based sensing systems that continuously measures physical, chemical and biological parameters. More specifically, these sensing systems comprise a small, modular, low-power implantable biotelemetry system capable of continuously sensing physiological characteristics using implantable transmitters, a receiver, and a data acquisition system to analyze and record the transmitted signal over several months. The preferred embodiment is a preterm labor and fetal monitoring system. Key features of the invention include Pulse Interval Modulation (PIM) that is used to send temperature and pressure information out of the biological environment. The RF carrier frequency is 174-216 MHz and a pair of RF bursts (pulses) is transmitted at a frequency of about 1-2 Hz. The transmission range is 3 to 10 feet, depending on the position of the transmitter in the body and its biological environment. The entire transmitter is encapsulated in biocompatible silicone rubber. Power is supplied by on-board silver-oxide batteries. The average power consumption of the current design is less than 30 microW, which yields a lifetime of approximately 6 - 9 months. Chip-on-Board technology (COB) drastically reduces the size of the printed circuit board from 38 x 28 mm to 22 x 8 mm. Unpackaged dies are flip-chip bonded directly onto the printed circuit board, along with surface mount resistors and capacitors. The invention can monitor additional physiological parameters including, but not limited to, ECG, blood gases, glucose, and ions such as calcium, potassium, and sodium.

Hines, John W.↗
DOE OSTI2018

Review of the Stability/Capacity Trade-off in Silver Hollandite Lithium Battery Cathodes

ABSTRACT Highly detailed structural characterization is required to understand the discharge mechanism in order to effectively investigate α-MnO 2 structured lithium battery cathode materials. This paper discusses recent findings which elucidate the lithiation mechanism of silver-hollandite, Ag x Mn 8 O 16 . For Ag 1.2 Mn 8 O 16 , the structure is not significantly perturbed during the first 2 equivalents of lithiation and the electrochemistry is highly reversible. Upon 4 equivalents of lithiation, the structure becomes highly distorted, in correlation with capacity fade observed over 40 cycles. Notably, regarding capacity fade, modifications to Ag/Mn ratio are less impactful than modifications to the α-MnO 2 crystallite size. This is shown in comparisons of two materials with the same stoichiometry (Ag 1.4 Mn 8 O 16 ) and differing crystallite size (10 and 15 nm).

energy storage (including batteries and capacitors↗
NASA NTRS1994

Hypervelocity Impact Test Facility: A gun for hire

An affordable technique has been developed to duplicate the types of impacts observed on spacecraft, including the Shuttle, by use of a certified Hypervelocity Impact Facility (HIF) which propels particulates using capacitor driven electric gun techniques. The fully operational facility provides a flux of particles in the 10-100 micron diameter range with a velocity distribution covering the space debris and interplanetary dust particle environment. HIF measurements of particle size, composition, impact angle and velocity distribution indicate that such parameters can be controlled in a specified, tailored test designed for or by the user. Unique diagnostics enable researchers to fully describe the impact for evaluating the 'targets' under full power or load. Users regularly evaluate space hardware, including solar cells, coatings, and materials, exposing selected portions of space-qualified items to a wide range of impact events and environmental conditions. Benefits include corroboration of data obtained from impact events, flight simulation of designs, accelerated aging of systems, and development of manufacturing techniques.

Johnson, Calvin R.↗
DOE OSTI2017

Chapter 11.2: Inverters, Power Optimizers, and Microinverters

Inverters span a wide range of sizes, topologies, and connection voltages: from utility-scale megawatt inverters to string inverters. Switch-mode power conversion relies on high frequency chopping of DC signal to periodically charge and discharge energy storage elements, such as inductors and capacitors. Additional circuit components are required to address practical issues in inverters such as voltage ripple and harmonic distortion. Inverters are beginning to incorporate components with a bandgap above should be 3 eV, such as SiC and GaN. Photovoltaic (PV) modules respond dynamically to changing temperature and irradiation conditions. Thus, maximum DC power extraction requires periodic adjustment of the PV voltage and current operating point. An inverter's total efficiency is measured by the product of its conversion efficiency and the maximum-power-point tracking (MPPT) efficiency. This chapter lists the primary functions of inverters that include auxiliary capabilities, such as monitoring of DC and AC performance, and other error reporting.

14 SOLAR ENERGY↗
DOE OSTI2020

Ultrahigh capacitive energy density in ion-bombarded relaxor ferroelectric films

Dielectric capacitors can store and release electric energy at ultrafast rates and are extensively studied for applications in electronics and electric power systems. Among various candidates, thin films based on relaxor ferroelectrics, a special kind of ferroelectric with nanometer-sized domains, have attracted special attention because of their high energy densities and efficiencies. We show that high-energy ion bombardment improves the energy storage performance of relaxor ferroelectric thin films. Intrinsic point defects created by ion bombardment reduce leakage, delay low-field polarization saturation, enhance high-field polarizability, and improve breakdown strength. We demonstrate energy storage densities as high as ~133 joules per cubic centimeter with efficiencies exceeding 75%. Deterministic control of defects by means of postsynthesis processing methods such as ion bombardment can be used to overcome the trade-off between high polarizability and breakdown strength.

Kim, Jieun↗
DOE OSTI2014

Design and development of a portable flash X-ray source driven by battery powered compact Marx generator

The design, construction and operational characteristics of a portable flash X-ray source driven by battery-powered compact Marx is reported. The novel configuration of compact Marx utilizes hollow capacitors in successive stages to enhance the erection reliability. The characteristic impedance of this system is ∼ 200 Ω. At discharge of ∼ 22 kV, >200 kV output pulse of 60 ns duration (FWHM) with rise time of <5 ns (10% - 90%) is produced. The pulser requires Nitrogen gas pressurization up to 3 atm for operation at maximum rating. The Marx generator assembly is fitted in to a stainless steel tube of 10 cm diameter and 1.2 m length. While using a demountable sealed X-ray tube of matched impedance, this device produces an X-ray pulse of approximately ∼ 30 ns duration and has maximum energy of ∼ 200 keV. This true tabletop device is able to produce dose up to 100 mR per shot, measured at the distance of 30 cm from output window. The focal spot size has been passively confirmed to be in the sub-millimeter (<1 mm) range. (author)

43 PARTICLE ACCELERATORS↗
NASA NTRS1981

Preliminary design development of 100 KW rotary power transfer device

Contactless power transfer devices for transferring electrical power across a rotating spacecraft interface were studied. A power level of 100 KW was of primary interest and the study was limited to alternating current devices. Rotary transformers and rotary capacitors together with the required dc to ac power conditioning electronics were examined. Microwave devices were addressed. The rotary transformer with resonant circuit power conditioning was selected as the most feasible approach. The rotary capacitor would be larger while microwave devices would be less efficient. A design analysis was made of a 100 KW, 20 kHz power transfer device consisting of a rotary transformer, power conditioning electronics, drive mechanism and heat rejection system. The size, weight and efficiency of the device were determined. The characteristics of a baseline slip ring were presented. Aspects of testing the 100 KW power transfer device were examined. The power transfer device is a feasible concept which can be implemented using presently available technologies.

Weinberger, S. M.↗
NASA NTRS1994

Steering capaciflector sensor

A capacitive type proximity sensor having substantial range and sensitivity between a machine and an intruding object in the immediate vicinity of the machine and having a steerable sensing field has an outer electrical conductor on the machine forming one electrode of a sensor capacitor, the other electrode is the object. The outer conductor is a thin sheet of conductive material with a pair (or more) of intermediate electrical conductors located between the outer conductor and the machine. The pair of intermediate electrical conductors are in close proximity to each other and together form a surface having a size substantially larger than the outer conductor to act as a shield for reducing the parasitic capacitance between the outer conductor and the machine and to steer the sensor field. The pair of intermediate conductors are thin sheets of conductive material substantially wider than the first conductor. The outer and pair of intermediate conductors are attached to a surface on the machine in electrical isolation and with no gaps between the conductors and no gap between the surface and the pair of intermediate conductors. The outer and pair of intermediate conductors are also in conformance with each other and the surface of the machine, and the surface of the machine acts as a ground plane. Variable gain voltage follower circuits are used for coupling, in phase, the instantaneous voltage at the outer electrical conductor to the pair of intermediate electrical conductors and a signal generator is coupled to the outer conductor and is responsive to the capacitance of the sensor capacitor for generating a control signal to the machine.

Jenstrom, Del T.↗
DOE OSTI2017

Size-controllable porous NiO electrodes for high-performance lithium ion battery anodes

Highlights: • Size-controllable porous NiO electrodes were prepared by a simple thermal oxidation route. • The prepared porous NiO electrodes exhibit high capacity and excellent rate capability and cycling stability. • The smaller nanopore and crystallite size are benefical to improve the electrochemical properties of the porous NiO electrodes. - Abstract: Size-controllable porous NiO electrodes were prepared by a simple and easily scalable thermal oxidation route and were evaluated as anode materials for lithium ion batteries. The nanopore size of the prepared electrodes can be obtained in the range from 20 to 80 nm by varying the thermal oxidation condition. Lithium storage performance measurement showed that porous NiO electrodes exhibit high capacity and excellent rate capability and cycling stability. Furthermore, it was shown that the smaller nanopore and crystallite size are beneficial to improve the electrochemical properties of the porous NiO electrodes.

36 MATERIALS SCIENCE↗
NASA NTRS2012

Electrochemical Ultracapacitors Using Graphitic Nanostacks

Electrochemical ultracapacitors (ECs) have been developed using graphitic nanostacks as the electrode material. The advantages of this technology will be the reduction of device size due to superior power densities and relative powers compared to traditional activated carbon electrodes. External testing showed that these materials display reduced discharge response times compared to state-of-the-art materials. Such applications are advantageous for pulsed power applications such as burst communications (satellites, cell phones), electromechanical actuators, and battery load leveling in electric vehicles. These carbon nanostructures are highly conductive and offer an ordered mesopore network. These attributes will provide more complete electrolyte wetting, and faster release of stored charge compared to activated carbon. Electrochemical capacitor (EC) electrode materials were developed using commercially available nanomaterials and modifying them to exploit their energy storage properties. These materials would be an improvement over current ECs that employ activated carbon as the electrode material. Commercially available graphite nanofibers (GNFs) are used as precursor materials for the synthesis of graphitic nanostacks (GNSs). These materials offer much greater surface area than graphite flakes. Additionally, these materials offer a superior electrical conductivity and a greater average pore size compared to activated carbon electrodes. The state of the art in EC development uses activated carbon (AC) as the electrode material. AC has a high surface area, but its small average pore size inhibits electrolyte ingress/egress. Additionally, AC has a higher resistivity, which generates parasitic heating in high-power applications. This work focuses on fabricating EC from carbon that has a very different structure by increasing the surface area of the GNF by intercalation or exfoliation of the graphitic basal planes. Additionally, various functionalities to the GNS surface will be added that can exhibit pseudocapacitance. This pseudocapacitance exhibits faradaic (charge transfer) properties that can further increase the overall relative and volumetric capacitance of the material. A process is also proposed to use GNF as a precursor material to fabricate GNS that will be used as EC electrodes. This results in much better electrical conductivity than activated carbon. This is advantageous for high-pulsed-power applications to reduce parasitic heating. Larger average pore size allows more complete electrolyte wetting (faster charge transfer kinetics). These properties contribute to a lowered equivalent series resistance (ESR), increased specific power, shorter charging times, and decreased parasitic heating. The high density of basal plane edges provides nucleation sites for activation (addition of hydrophilic functional groups) that facilitate electrolyte wetting, and will contribute to pseudocapacitance.

Marotta, Christopher↗
NASA NTRS2003

MOS Circuitry Would Detect Low-Energy Charged Particles

Metal oxide semiconductor (MOS) circuits for measuring spatially varying intensities of beams of low-energy charged particles have been developed. These circuits are intended especially for use in measuring fluxes of ions with spatial resolution along the focal planes of mass spectrometers. Unlike prior mass spectrometer focal-plane detectors, these MOS circuits would not be based on ion-induced generation of electrons, and photons; instead, they would be based on direct detection of the electric charges of the ions. Hence, there would be no need for microchannel plates (for ion-to-electron conversion), phosphors (for electron-to-photon conversion), and photodetectors (for final detection) -- components that degrade spatial resolution and contribute to complexity and size. The developmental circuits are based on linear arrays of charge-coupled devices (CCDs) with associated readout circuitry (see figure). They resemble linear CCD photodetector arrays, except that instead of a photodetector, each pixel contains a capacitive charge sensor. The capacitor in each sensor comprises two electrodes (typically made of aluminum) separated by a layer of insulating material. The exposed electrode captures ions and accumulates their electric charges during signal-integration periods.

Sinha, Mahadeva↗