1,304 research outputs found
Feasibility of an electrostatic energy harvesting device for CFCs aircraft
A novel energy harvesting concept is proposed for treating local electrostatic energy produced on flying composite
aircrafts. This work focuses on the feasibility research on collecting static charges with capacitive collectors. The
existing energy harvesting system and the electrification of the typical carbon fibre composites (CFCs) aircraft has
been reviewed. The detailed model experiments were then designed to characterize different configurations for
electrostatic energy harvesting on aeroplane. In the lab, the static charge was produced by a corona discharging
device, and a capacitor or a metal sheet was put in the electric field to collect the charges under four different
configurations. After that, the rest results for these configurations were analysed, which is followed by the
discussion about the results application on the aircraft. This work has proved that it is feasible to collect the local
static electricity on flying aircraft, and it could provide a new direction of energy harvesting system in aviation field
Developing vanadium redox flow technology on a 9-kW 26-kWh industrial scale test facility: Design review and early experiments
Redox Flow Batteries (RFBs) have a strong potential for future stationary storage, in view of the rapid expansion of renewable energy sources and smart grids. Their development and future success largely depend on the research on new materials, namely electrolytic solutions, membranes and electrodes, which is typically conduced on small single cells. A vast literature on these topics already exists. However, also the technological development plays a fundamental role in view of the successful application of RFBs in large plants. Despite that, very little research is reported in literature on the technology of large RFB systems. This paper presents the design, construction and early operation of a vanadium redox flow battery test facility of industrial size, dubbed IS-VRFB, where such technologies are developed and tested. In early experiments a peak power of 8.9 kW has been achieved with a stack specific power of 77Wkg−1. The maximum tested current density of 635 mA cm−2 has been reached with a cell voltage of 0.5 V, indicating that higher values can be obtained. The test facility is ready to be complemented with advanced diagnostic devices, including multichannel electrochemical impedance spectroscopy for studying aging and discrepancies in the cell behaviors
Cavallo's Multiplier for in situ Generation of High Voltage
A classic electrostatic induction machine, Cavallo's multiplier, is suggested
for in situ production of very high voltage in cryogenic environments. The
device is suitable for generating a large electrostatic field under conditions
of very small load current. Operation of the Cavallo multiplier is analyzed,
with quantitative description in terms of mutual capacitances between
electrodes in the system. A demonstration apparatus was constructed, and
measured voltages are compared to predictions based on measured capacitances in
the system. The simplicity of the Cavallo multiplier makes it amenable to
electrostatic analysis using finite element software, and electrode shapes can
be optimized to take advantage of a high dielectric strength medium such as
liquid helium. A design study is presented for a Cavallo multiplier in a
large-scale, cryogenic experiment to measure the neutron electric dipole
moment.Comment: 9 pages, 10 figure
Nanoscale Voltage Enhancement at Cathode Interfaces in Li-ion Batteries
Interfaces are ubiquitous in Li-ion battery electrodes, occurring across
compositional gradients, regions of multiphase intergrowths, and between
electrodes and solid electrolyte interphases or protective coatings. However,
the impact of these interfaces on Li energetics remains largely unknown. In
this work, we calculated Li intercalation-site energetics across cathode
interfaces and demonstrated the physics governing these energetics on both
sides of the interface. We studied the olivine/olivine-structured
LixFePO4/LixMPO4 (x=0 and 1, M=Co, Ti, Mn) and layered/layered-structured
LiNiO2/TiO2 interfaces to explore different material structures and transition
metal elements. We found that across an interface from a high- to low-voltage
material the Li voltage remains constant in the high-voltage material and
decays approximately linearly in the low-voltage region, approaching the Li
voltage of the low-voltage material. This effect ranges from 0.5-9nm depending
on the interfacial dipole screening. This effect provides a mechanism for a
high-voltage material at an interface to significantly enhance the Li
intercalation voltage in a low-voltage material over nanometer scale. We showed
that this voltage enhancement is governed by a combination of electron transfer
(from low- to high-voltage regions), strain and interfacial dipole screening.
We explored the implications of this voltage enhancement for a novel
heterostructured-cathode design and redox pseudocapacitors
Repetitive Operation of the University of Saskatchewan Compact Torus Injector
Development of fueling technologies for modern and future tokamak reactors is essential for their implementation in a commercial energy production setting. Compared to the presently available fueling technologies, gas or cryogenic pellet injection, compact torus injection presents an effective and efficient method for directly fueling the central core of tokamak plasmas. Fueling of the central core of a tokamak plasma is pivotal for providing efficient energy production. The central core plasma of a reactor contains the greatest density of fusion processes. For consistent and continuous fueling of tokamak fusion reactors, compact torus injectors must be operated in a repetitive mode.
The goal of this thesis was to study the feasibility of firing the University of Saskatchewan Compact Torus Injector (USCTI) in a repetitive mode. In order to enable USCTI to fire repetitively, modifications were made to its electrical system, control system and data acquisition system. These consisted primarily of the addition of new power supplies, to enable fast charging of the many capacitor banks used to form and accelerate the plasma. The maximum firing rate achieved on USCTI was 0.33 Hz, an increase from the previous maximum firing rate of 0.2 Hz achieved at UC Davis.
Firing USCTI in repetitive modes has been successful. It has been shown that the CTs produced in any given repetitive series are properly formed and repeatable. This is made evident through analysis of data collected from the CTs' magnetic fields and densities as they traveled along the injector barrel. The shots from each experiment were compared to the series' mean data and were shown to be consistent over time. Calculations of their correlations show that there are only minimal deviations from shot to shot in any given series
Charging and Discharging Mechanism of Polyimide under Electron Irradiation and High Voltage
Polyimide has been widely used as insulating and structural materials in spacecraft due to its excellent electrical, thermal and mechanical properties. However, its charging and discharging problem in harsh space environment has been a major limit to the development of high-voltage and high-power spacecraft. In this chapter, charging and discharging phenomena of dielectric materials under electron irradiation environment were presented. First, the electrical properties of polyimide consisting of dielectric properties, trap properties, conductivity and electrical breakdown properties were investigated, which have great influences on charging and discharging characteristics. Then, a surface charging model under relatively low-energy electron irradiation was proposed for polyimide, based on the synergistic effects of electron movement above surface and charge transport in surface layer. The DC surface flashover of polyimide under electron irradiation with different energies, fluxes and incident angles was investigated. Furthermore, a deep charging model under high-energy electron irradiation with the Fluence Model for Internal Charging (FLUMIC) spectrum was established. The effects of electron flux enhancement and operating voltage on charging characteristics were discussed in different grounding modes. It indicates that the processes of discharging under electron irradiation have a close link with the charge transport characteristics of polyimide
DEVELOPMENT OF FAST SWITCHING AND DATA ACQUISITION CIRCUIT FOR IN HOUSE ECT SYSTEM
Electrical Capacitance tomography, or ECT, is the technology to generate visual representation of flow’s different phases using the distribution of electrical permittivity [1].
In this project, an enhanced design of data collection and switching circuit which aims to improve the in-house ECT system, especially to implement an automatic switching circuit, and increase the data collection rates.
The proposed design uses short analogue signals routes by implementing a local ADC module for every data collection circuit. Furthermore, this design has adheres to universal communication standards and can be integrated in most of nowadays technologies. Furthermore, it implements an on-board reprogrammable microcontroller. Therefore, the design enjoys high portability and can be re-configured to meet various ECT system requirements for different applications with minimum hardware adjustments.
The main focus of this project is to improve the performance of the in-house ECT system by improving the data collection circuitry to incorporate an automatic switching module that is able to switch operation of the electrode modules between four modes namely, Excitation, Detection, floating and grounding. As well as, increasing the data collection data rate by enabling parallel detection operations
Design guidelines for assessing and controlling spacecraft charging effects
The need for uniform criteria, or guidelines, to be used in all phases of spacecraft design is discussed. Guidelines were developed for the control of absolute and differential charging of spacecraft surfaces by the lower energy space charged particle environment. Interior charging due to higher energy particles is not considered. A guide to good design practices for assessing and controlling charging effects is presented. Uniform design practices for all space vehicles are outlined
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