Discharge Energy Efficiency Research Articles

Digital Control of a High-Voltage (2.5 kV) Bidirectional DC--DC Flyback Converter for Driving a Capacitive Incremental Actuator

This paper presents a digital control technique to achieve valley switching in a bidirectional flyback converter used to drive a dielectric electroactive polymer-based capacitive incremental actuator. This paper also provides the design of a low input voltage (24 V) and variable high output voltage (0–2.5 kV) bidirectional dc–dc flyback converter for driving a capacitive incremental actuator. The incremental actuator consists of three electrically isolated mechanically connected capacitive actuators. It requires three high-voltage (HV) (2–2.5 kV) bidirectional dc–dc converters to accomplish the incremental motion by charging and discharging the capacitive actuators. The bidirectional flyback converter employs a digital controller to improve the efficiency and charge/discharge speed using the valley switching technique during both charge and discharge processes, without the need to sense signals on the output HV side. Experimental results verifying the bidirectional operation of a HV flyback converter are presented using a 3-kV polypropylene-film capacitor as the load. The energy-loss distributions of the converter are presented when 4- and 4.5-kV HV mosfet s are used on HV side. The flyback prototype with a 4 kV mosfet demonstrated 89% charge energy efficiency to charge the capacitive load from 0 V to 2.5 kV, and 84% discharge energy efficiency to discharge it from 2.5 kV to 0 V.

Investigation the Influence of Different Salts on the Degradation of Organic Dyes Using Non-Thermal Plasma

In dye decolorization tests a non-thermal plasma (NTP) corona discharge generated by a high voltage pin-to-ground plate displayed 82% color removal within 11 min. Total color removal was accomplished after 28 min. Different salts such as KCl, NaCl, CaCl2 and AlCl3 were utilized to check the influence of conductivity changes on the dye decolorization process. Higher dye solution conductivity improved the color removal efficiency. The discharge energy and degradation efficiency were computed for diverse concentrations for NaCl, KCl, CaCl2 and AlCl3, whereby it was noticed that the salts generally have a small impact on the level of dye decolorization using corona discharge. In addition, the essential reactive species involved in the oxidation of organic dye compounds such as ozone (O3) generated in treated water and hydrogen peroxide (H2O2) were investigated and the energetic species that produced the non-thermal plasma at the optimum operation time were determined. Energy yields for decolorization and Electrical Energy per Order (EE/O) were calculated for different concentrations of NaCl, KCl, CaCl2 and AlCl3. This work may help in designing plasma systems appropriate for treatment of industrial wastewaters polluted by dyes.

Graphite felt electrode modified by square wave potential pulse for vanadium redox flow battery

In this paper, graphite felts treated by square wave potential pulse were modified as electrode for vanadium redox flow battery (VRFB). X-ray photoelectron spectroscopy measurements indicated that the treatment for graphite felt can introduce oxygen-containing groups on the surface. Moreover, graphite felt can also be etched to form nano-scale pores, without damage of mechanical property by treatment. The formed nano-scale pores and introduced oxygen-containing groups can enhance the wettability of electrolyte on graphite felt and electrochemical kinetics of V(II)/V(III) and V(IV)/V(V) redox reactions. The treated graphite felt was employed as electrode to assemble the static cell, and its electrochemical performance was evaluated. The cell using modified graphite felt exhibits larger discharge capacity and energy efficiency compared with the pristine graphite felt. The average energy efficiency for graphite felt treated for 1600 s can reach 87.0% at 30 mA cm−2, 4.2% larger than that for the pristine graphite felt. This study demonstrates that the square wave potential pulse treatment is an efficient way to enhance the electrochemical properties of graphite felt for VRFB system. Copyright © 2016 John Wiley & Sons, Ltd.

CeO2 embedded electrospun carbon nanofibers as the advanced electrode with high effective surface area for vanadium flow battery

Although electrospun carbon nanofibers (ECNFs) possess excellent conductivity, high surface area and good electrochemical activity toward vanadium redox couples, much surface area of ECNFs was still unutilized because of its poor hydrophilicity. CeO2 nanoparticles as an excellent hydrophilic agent are embedded in polyacrylonitrile (PAN) based carbon nanofibers by a simple electrospinning and subsequent carbonization process. The physicochemical characterizations show that the introduction of CeO2 nanoparticles slightly changes the structure and compositions of ECNFs, while the corresponding wettability is greatly improved. It is worth noting that the electrochemical surface area (ECSA) of CeO2/ECNFs is more than four times of that for ECNFs. According to the cyclic voltammograms (CV) and electrochemical impedance spectra (EIS) results, the addition of CeO2 improves the electrocatalytic activity toward the negative reaction of vanadium flow battery (VFB) to some extent while has less effect on that toward the positive reaction, the significant improvement in the electrochemical performance of CeO2/ECNFs might be mostly ascribed to the remarkable enhancement in ECSA. In addition, the charge/discharge tests further verify that CeO2/ECNFs with high ECSA could significantly reduces the electrochemical polarization during the discharging process and results in an enhanced discharge capacity and energy efficiency. The accomplishment of this work provides a new concept that it might be more convenient and effective to improve the electrochemical performance of the electrode materials for VFB by increasing their ECSA.

Experiments on electrohydraulic forming and electromagnetic forming of aluminum tube

Electromagnetic forming (EMF) and electrohydraulic forming (EHF) are typical high speed forming technologies characterized with improved formability of sheet metal, single-sided die, and high precision deformation of parts. In this work, the bulging experiments of aluminum alloy tubes by EMF and EHF were performed to investigate the attaching-die capability, wall thickness, working hardness, and residual plasticity of deformed tubes. The results showed that the bulged tube by EMF is of low attaching-die capability, remarkable rebound, serious thinning of wall thickness, and prone to rupture in the outer corner. However, the parts by EHF process are of high attaching-die capability, almost no rebound, relatively uniform thickness, and remarkable fillet filling in the inner corner. The load mechanism contributes to the different deformation results of both processes. With the almost equivalent deformation, the tensile deformation ability of EHF part is better than that of EMF one, and the discharge energy efficiency of the former is higher than that of the latter.

Exploring the relationship of dielectric relaxation behavior and discharge efficiency of P(VDF-HFP)/PMMA blends by dielectric spectroscopy

The dielectric relaxations in P(VDF-HFP)/PMMA blends were investigated by dielectric relaxation spectroscopy. Various dielectric relaxation and their molecular mechanisms of P(VDF-HFP), PMMA, and P(VDF-HFP)/PMMA composite films were analyzed. According to the fitted data of the Havriliak–Negami (HN) function, all relaxation processes belong to non-debye relaxation, the activation energy (Ea), relaxation time (τHN) and dielectric relaxation strength (Δϵ) of P(VDF-HFP)/PMMA blends significantly decreased around and below room temperature with increasing PMMA content. But, the results of αc relaxation are opposite. In addition, the conductivities (σ) of P(VDF-HFP)/PMMA composite films also sharply decreased with the addition of PMMA. Thus, the high discharge energy density and efficiency of dielectric materials closely related with the lower Ea, τHN, Δϵ and σ.

Development of Practical Sodium-Ion Batteries Using Amide Ionic Liquids: High Energy Efficiency, Excellent Cycleability and Wide Temperature Range Operation

Over five years, we have been conducting R&D of sodium secondary batteries using amide ionic liquids as electrolytes. The new batteries intrinsically have high safety due to the nonflammability and nonvolatility of ionic liquids. Moreover, they can be operated in a wide temperature range of 273-363 K. We found that several types of FSA-based (FSA: bis(fluorosulfonyl)amide) ionic liquids exhibit superior properties for the application to sodium secondary batteries. In the present paper, we first investigated the fundamental electrolyte properties for the binary Na[FSA]-[C3C1pyrr][FSA] (C3C1pyrr: N-methyl-N-propylpyrrolidinium) ionic liquid system. Then, NaCrO2 and hard carbon (HC) were selected as positive electrode and negative electrode active materials, respectively, and their fundamental charge–discharge characteristics were examined with coin-type half-cells. A 1.5 mAh coin-type full cell composed of HC/NaCrO2 exhibited excellent cycle properties, maintaining 90% of its initial capacity after 1000 cycles at 333 and 363 K. On the basis of these results, the 1.5 mAh full cell was fabricated and its performance was tested. It showed a high charge–discharge energy efficiency of 97.5% at 363 K and C/5 rate. Finally, we constructed a large-sized prismatic HC/NaCrO2full cell with a capacity of 27 Ah by a mass production process. We confirmed that its performance is comparable with that of the 1.5 mAh coin-type cell. Acknowledgements This study was partly supported by Advanced Low Carbon Technology Research and Development Program (ALCA) of Japan Science and Technology Agency (JST) and the Japanese Ministry of Education Culture, Sports, Science and Technology (MEXT) program “Elements Strategy Initiative to Form Core Research Center” (since 2012).

Enhanced energy storage properties of (1−x)Bi0.5Na0.5TiO3-xBa0.85Ca0.15Ti0.9Zr0.1O3 ceramics

Energy storage properties of (1−x)Bi0.5Na0.5TiO3-xBa0.85Ca0.15Ti0.9Zr0.1O3 ceramics prepared by solid state reaction were first investigated. The results of XRD for all samples show a pure perovskite phase and a pseudo-cubic symmetry. The P-E loops illustrate that the addition of Ba0.85Ca0.15Ti0.9Zr0.1O3 can enhance the breakdown strength, discharge and charge energy density and energy efficiency. The sample with x=0.525 exhibits the highest breakdown strength of 9.35kV/mm, discharge energy density of 0.87J/cm3 and charge energy density of 1.06J/cm3. The sample with x=0.55 exhibits the highest energy efficiency of 82.37%. Four evident current peaks are found in the I-E curves of x=0.475. Two current peaks are the evidence of ferroelectric domain switching for x≥0.50.

Performance validation of sodium-ion batteries using an ionic liquid electrolyte

Charge–discharge properties of sodium-ion batteries using the Na[FSA]–[C3C1pyrr][FSA] (FSA: bis(fluorosulfonyl)amide, C3C1pyrr: N–methyl–N–propylpyrrolidinium) ionic liquid were investigated over a temperature range of 273–363 K. NaCrO2 and hard carbon (HC) were used as positive electrode and negative electrode active materials, respectively, and their fundamental charge–discharge characteristics were examined with coin-type half-cells. A 1.5 mAh coin-type full cell composed of HC/NaCrO2 showed excellent cycle properties, maintaining 90 % of its initial capacity after 1000 cycles at 333 and 363 K. The 1.5 mAh full cell also exhibited a high charge–discharge energy efficiency of 97.5 % at 363 K and C/5 rate. A large-sized prismatic HC/NaCrO2 full cell with a capacity of 27 Ah was fabricated by a mass production process, and its performance was confirmed to be comparable with that of the 1.5 mAh coin-type cell.

경부고속철도 회생 에너지 저장시스템 성능 분석

Recently, various researches are conducted in the application of regenerative energy produced during the operation of an electric locomotive. Regenerative energy is produced by a generator in the brake procedure. The generator is operated by kinetic energy of an electric railroad using an electric motor. The process of producing regenerative energy varies with the current type of a railroad and its running condition. The quality of electric power can be improved and electric energy can be utilized effectively, especially in the use of an energy storage system (ESS). Thus, it is necessary to apply ESS into AC section and high speed railway. This study analyses the composition of the regenerative ESS equipment installed in Yong-Jeong sectioning post, operational principle, charge and discharge algorithm and energy efficiency. The analysis shows that CO2 emissions can be reduced about 0.5 ton per a day. In addition, ESS helps saving the energy and the compensation of the voltage drop caused by the operation of high speed train when it is installed at the end of the feeder section. The number of high speed train will be increased continuously related to the electrification rate. Therefore, applying the ESS to high speed railway is expected to solve the instability of the feeder voltage and the equipment capacity problem caused by the high speed trains.

Mn3O4 anchored on carbon nanotubes as an electrode reaction catalyst of V(IV)/V(V) couple for vanadium redox flow batteries

Mn3O4/MWCNTs (multi-walled carbon nanotubes) composite fabricated by a simple solvothermal method was developed as electrochemical catalyst of V(IV)/V(V) redox couple for vanadium redox flow batteries. The electrochemical activity of V(IV)/V(V) redox couple can be enhanced by the electrochemical catalysts (Mn3O4, MWCNTs, Mn3O4/MWCNTs), and the electrocatalytic kinetics of the redox reactions were in the order of Mn3O4/MWCNTs>MWCNTs>Mn3O4. The cell using Mn3O4/MWCNTs composite as electrochemical catalyst was assembled and the charge-discharge performance was evaluated. Compared with the pristine cell, the cell using positive graphite felt modified by Mn3O4/MWCNTs had lower electrochemical polarization, larger discharge capacity and energy efficiency. The average energy efficiency of the cell using modified positive electrode for 50 cycles was 84.65%, 3.73% higher than that of the pristine cell. The superior electrocatalytic performance of Mn3O4/MWCNTs composite was mainly due to the effective mixed conducting network, facilitating the electron transport and ion diffusion in the electrode/electrolyte interface.

An Electrochemical Analogy to the Fuel Injector: The Electrochemical Direct Injection Reactor

ElectroChemical Direct Injection (ECDI) is a newly proposed battery architecture. ECDI involves the direct injection of small quantities of cathode and anode materials into a reactor, where they are rapidly discharged, then flushed out. The process repeats, and much like a standard combustion engine, the quantity of fuel injected, in addition to the rate of discharge, can be tailored to meet the power demand in an efficient way. We investigate some of the most interesting electrochemical and mechanical features of the system, and present some key results illustrating the promise of such an approach. Results from the discharge rate performance and energy efficiency of the system are presented, to highlight the benefits of this architecture. From an electrochemical perspective, using a high-surface area, nano-structured zinc [1], we demonstrate that high discharge utilization efficiencies (% of theoretical capacity) are possible in this free standing system. At 3C rates of discharge, efficiencies of up to 80% are achievable with this zinc morphology. Even at rates up to 30C, efficiencies are up to 50% are still achievable. The system can be improved through optimization of the electrolyte, and with various additives. The benefits of electrolyte optimization and additives will be discussed, including a mechanistic study of the additives.

Structure change and energy storage property of poly(vinylidene fluoride-hexafluoropropylene)/poly (methyl methacrylate) blends

In this work, in order to reduce the energy loss induced by the ferroelectric P(VDF-HFP) and improve energy storage property, a series of P(VDF-HFP)/PMMA blend films were prepared via biaxiallyoriented technology. The results showed that the ratio of alpha crystal continuously decreased with the addition of PMMA, the ratio of beta crystal firstly increased, followed by a reduction with further rising the PMMA percentage. Though gamma ratio was small, it enhances steadily. With the addition of PMMA, it could be found out the disorder in crystal structure, the reduction in crystal size, and the drop in crystallinity of P(VDF-HFP). The structure change improved the discharge efficiency and temperature stability. With the addition of PMMA, tanδ is enhanced more than 10°C, and the discharge energy efficiency improved from 45% of pure PVDF to 75% under 400 MV/m after modifying with PMMA. This improvement in the discharge energy efficiency is thought due to the formation of new crystal γ-2b.

Enhancing low-grade thermal energy recovery in a thermally regenerative ammonia battery using elevated temperatures.

A thermally regenerative ammonia battery (TRAB) is a new approach for converting low-grade thermal energy into electricity by using an ammonia electrolyte and copper electrodes. TRAB operation at 72 °C produced a power density of 236 ± 8 Wm(-2), with a linear decrease in power to 95 ± 5 Wm(-2) at 23 °C. The improved power at higher temperatures was due to reduced electrode overpotentials and more favorable thermodynamics for the anode reaction (copper oxidation). The energy density varied with temperature and discharge rates, with a maximum of 650 Wh m(-3) at a discharge energy efficiency of 54% and a temperature of 37 °C. The energy efficiency calculated with chemical process simulation software indicated a Carnot-based efficiency of up to 13% and an overall thermal energy recovery of 0.5%. It should be possible to substantially improve these energy recoveries through optimization of electrolyte concentrations and by using improved ion-selective membranes and energy recovery systems such as heat exchangers.

Study of the electrochemical performance of VO2+/VO2 + redox couple in sulfamic acid for vanadium redox flow battery

The present work was performed in order to evaluate sulfamic acid as the supporting electrolyte for VO2+/VO2 + redox couple in vanadium redox flow battery. The oxidation process of VO2+ has similar electrochemical kinetics compared with the reduction process of VO2 +. The exchange current density and standard rate constant of VO2+/VO2 + redox reaction on a graphite electrode in sulfamic acid are determined as 7.6 × 10−4 A cm−2 and 7.9 × 10−5 cm s−1, respectively. The energy efficiency of the cell employing sulfamic acid as supporting electrolyte in the positive side can reach 75.87 %, which is adequate for redox flow battery applied in energy storage. The addition of NH4 + to the positive electrolyte can enhance the electrochemical performance of the cell, with larger discharge capacity and energy efficiency. The preliminary exploration shows that the vanadium sulfamate electrolyte is promising for vanadium redox flow battery and is worthy of further study.

Synergistic Effect of Carbon Nanofiber/Nanotube Composite Catalyst on Carbon Felt Electrode for High-Performance All-Vanadium Redox Flow Battery

Carbon nanofiber/nanotube (CNF/CNT) composite catalysts grown on carbon felt (CF), prepared from a simple way involving the thermal decomposition of acetylene gas over Ni catalysts, are studied as electrode materials in a vanadium redox flow battery. The electrode with the composite catalyst prepared at 700 °C (denoted as CNF/CNT-700) demonstrates the best electrocatalytic properties toward the V(2+)/V(3+) and VO(2+)/VO2(+) redox couples among the samples prepared at 500, 600, 700, and 800 °C. Moreover, this composite electrode in the full cell exhibits substantially improved discharge capacity and energy efficiency by ~64% and by ~25% at 40 mA·cm(-2) and 100 mA·cm(-2), respectively, compared to untreated CF electrode. This outstanding performance is due to the enhanced surface defect sites of exposed edge plane in CNF and a fast electron transfer rate of in-plane side wall of the CNT.

Influence of crystalline properties on the dielectric and energy storage properties of poly(vinylidene fluoride)

AbstractPoly(vinylidene fluoride) (PVDF) films with various crystal phases (α, β, and γ phases) and varied crystallinities were fabricated via different processes. The influence of the crystalline properties, such as the crystallinity and crystal phases, on the breakdown strength and dielectric and energy storage properties of the films were studied. Under low electric field, the dielectric constant was governed by the crystallinities of the films, and the dielectric loss was more related to the polarity of their crystal phases. Under high electric field, the high polarity of the crystal phases favored high‐maximum, remnant, and irreversible polarization of the films. The lower crystallinity of the films with the same crystal phases led to a higher maximum and remnant polarization but a lower irreversible polarization. Under direct‐current electric field, the discharged energy efficiency was mainly dominated by the polar nature of crystal phases. Under an electric field below 300 MV/m, the discharged energy density and energy loss of the three kinds of films were rather close, regardless of the phase transition. When the electric field was over 300 MV/m, the overall discharged energy density was dominated by the practical breakdown strength. γ‐PVDF with a proper crystallinity and crystal grain size is expected to realize an energy density over 10 J/cm3 under an electric field over 400 MV/m. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011

Implementation of a Ad-Hoc based LED-IT-Sensor Integrated Streetlight with Selective Remote Control

With the issue of a Green IT Technology, studies on a environment-friendly luminous source that can reduce Carbon discharge and increase energy efficiency are actively progressed all over the world. Especially, with the problems of high oil price and environmental pollution, LED has made a great attention as a new luminous source that can replace the existing incandescent bulbs and fluorescent lights. In this paper, the proposed streetlight system becomes more intellectual by combining the low power consuming, high efficient, and high luminous LED module with a complex sensor module with temperature, humidity, illumination and motion sensors. Then, we design and implement the Ad-Hoc based LED-IT-Sensor integrated streetlight system that can maximize the energy savings efficiently with central monitoring system and selective remote dimming control by connecting them to the wireless ubiquitous sensor network(USN) using a Zigbee module.

Frequency effects in a pancake coil

An aluminum pancake coil is designed to amplify pulsed power in the range of 100-MW to a 100-m/spl Omega/ electro-thermal load. For the tradeoff between the coil energy density limit and energy discharge efficiency, the frequency dependence of its current and magnetic field distributions is calculated in the range of DC to 1 kHz. Near DC magnetic field measurements are compared to the calculated results. Energy efficiency of about 85% has been measured for the discharge of 1.6 kA from the coil to a linear resistive load in the range of 40-400 m/spl Omega/.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>