Electrical Cycling Research Articles

Simultaneous direct measurement of the electrocaloric and dielectric dynamics of ferroelectrics with microsecond temporal resolution

A contactless technique for direct time-resolved measurements of the full dynamics of the adiabatic temperature change in electrocaloric materials is introduced. The infrared radiation emitted by the electrocaloric sample is sensitively detected with μs time resolution and mK temperature resolution. We present time-resolved measurements of the electrocaloric effect up to kHz frequencies of the driving electric field and down to small field strengths. The simultaneous recording of transients for applied electric field and induced polarization gives a comprehensive view of the correlation of electrocaloric and ferroelectric properties. The technique can further be applied to the continuous measurement of fatigue for >106 electric field cycles.

Structural distortion in ferroelectric HfO2 – The factor that determines electric field-induced phase transformation

The origin of the wake-up effect and the factor that determines the amount of the wake-up effect in ferroelectric (FE) HfO2 were systematically investigated. By observing both the waking-up and the phase transformation induced by electric field cycling on the same scale, we clarified that the wake-up effect in our FE-HfO2 system is dominated by the phase transformation induced by electric field cycling. Nevertheless, other mechanisms might be prominent in other FE-HfO2 systems. In our study, we found an anomalous structural distortion induced in both FE and none-FE HfO2 films. We hypothesized that structural distortion is the factor that governs the phase transformation to be induced by electric field cycling. We verified our hypothesis by conducting a series of experiments to clarify the factor that determines the amount of anomalous structural distortion, and that the amount of structural distortion would be the universal factor that determines the amount of the phase transformation. We found that the structural distortion is originating from the shrinkage in the volume of HfO2 films during crystallization due to the difference in the densities among the crystallized phases. Finally, we verified that the amount of structural distortion can be regarded as the universal factor that determines the amount of phase transformation to be induced by electric field cycling.

Influence of Different Data Interpolation Methods for Sparse Data on the Construction Accuracy of Electric Bus Driving Cycle

Battery electric vehicles (BEVs) are one of the most promising new energy models for industrialization and marketization at this stage, which is an important way to solve the current urban haze air pollution, high fuel cost and sustainable development of the automobile industry. This paper takes pure electric buses as the research object and relies on the operation information management platform of new energy buses in Nantong city to propose an electric bus cycle construction method based on the mixed interpolation method to process sparse data. Three different interpolation methods, linear interpolation, step interpolation and mixed interpolation, were used to preprocess the collected data. The principal component analysis method and K-means clustering algorithm were used to reduce and classify the eigen parameter matrix. According to the clustering results, different categories of moving section and idle section libraries were established. According to the length of time and the correlation among various types, several moving sections and idle sections were selected to form a representative driving cycle of Nantong city buses. The results show that the mixed interpolation method, based on linear interpolation and cubic spline interpolation, has a good processing effect. The average relative error between the synthesized working conditions and the measured data are 15.71%, and the relative error of the seven characteristic parameters is less than 10%, which meets the development requirements. In addition, the comparison and analysis with the characteristic parameters of the world typical cycle conditions (NEDC, WLTC) show that the constructed cycle conditions of Nantong city are reasonable and reliable to represent the driving conditions of pure electric buses in Nantong city, which can provide a reference for the optimization of the bus energy control strategy.

Evolution of the Ferroelectric Properties of AlScN Film by Electrical Cycling with an Inhomogeneous Field Distribution

AbstractThis work investigates the evolution of the ferroelectric (FE) performance of the sputtered aluminum scandium nitride (AlScN) thin film, which has a high remanent polarization (Pr, > 100 µC cm−2) and coercive field (Ec, > 6 MV cm−1), with the electric field cycling. The work aims at elucidating the underlying origin of the severe fatigue behavior, even with a relatively small number of endurance cycles (<105). When cycled with a low electric field, an internal field is created by charges trapped between the FE layer and the interfacial dielectric layer (non‐FE). On the other hand, fatigue is observed when cycled with a high electric field cycling. This work proposes a new method to simulate a switching current utilizing an inhomogeneous field mechanism and the appropriate circuit model to assess the thickness change of the non‐FE layer. It is concluded that the thickened non‐FE layer after the field cycling results in fatigue.

A Novel Control-Independent Online Fault Diagnosis of Interturn Short Circuits in SRMs Using Signal Injection Technique

Most of the existing diagnosis techniques for interturn short circuits (ITSCs) in switched reluctance motors (SRMs) suffer from three major issues. 1) The problem of lower sensitivity where the system cannot detect an ITSC if a lower number of turns are short-circuited; 2) Interference of load variation on the detection reliability in which the fault index might initiate false alarm without any fault; 3) The dependency of the diagnosis system on the control strategy on which the motor is operating. This article proposes a novel method to diagnose ITSCs in SRMs independent of control schemes with better sensitivity and reliability using the signal injection technique. In SRMs, not all the phases take part in the torque production at any instant. The idle or inactive phase is injected with a high-frequency (HF) voltage signal for a preselected injection ratio within an electrical cycle. Any change in the winding parameters owing to an ITSC fault is deciphered by monitoring the HF currents generated in the phase windings. The results are validated experimentally for a four-phase 8/6 SRM employing two control strategies: 1) chopped current control and 2) angle position control.

ACTIVE STRIDES-CP: protocol for a randomised trial of intensive rehabilitation (combined intensive gait and cycling training) for children with moderate-to-severe bilateral cerebral palsy

IntroductionFor children with cerebral palsy (CP), who are marginally ambulant, gross motor capacity peaks between 6 and 7 years of age with a subsequent clinical decline, impacting their ability to...

E-micromobility, Cycling, and ‘Good’ Active Travel

This article explores how e-micromobility (EMM) can produce 'good' active travel together with cycling. Foregrounding the unique affordances of the electric unicycle (EUC) and e-bike, we highlight their potential to produce good active travel with cycling through protected bike lanes and traffic-calmed neighbourhood greenways. We argue that electric unicycling and e-biking can create good active travel together with cycling by advancing multiple and competing visions of the common good or political philosophies of mutual flourishing. We imagine 'good' active travel as practices and infrastructures that equip a plurality of commons goods, based on industrial, market, civic, domestic and ecological worths, as well as challenge the hegemonies of automobility and market worth. Using mobile ethnographic data from Vancouver, our analysis shows that electric unicycling and e-biking can, through infrastructures shared with cycling, advance these common goods, including decolonizing extensions of domestic worth, while challenging the car and neoliberal capitalism. Ultimately, we conclude that 'good' futures for electric unicycling, e-biking and cycling demand mobility justice through a consolidation of their decolonizing, civi and ecological worths at the expense of their industrial and market worths. 

Development, exergoeconomic assessment and optimization of a novel municipal solid waste-incineration and solar thermal energy based integrated power plant: An effort to improve the performance of the power plant

Due to the growing population rate and increasing social activities, the content of municipal solid waste (MSW) production is increasing. Energy production from MSW is one of the promising ways to dispose of waste and reduce the limitations of fossil energies. However, this technology has a relatively low efficiency due to the high volume of moisture and inert materials in MSW and the lower heating value of waste. The integration of solar thermal collectors is one of the suggested solutions to increase the temperature of inlet steam to the power generation cycle in order to improve the power plant performance. In this regards, the present study develops a comprehensive thermodynamic-conceptual and exergoeconomic investigation of the performance of a MSW-incineration (MSWI) plant integrated with a parabolic trough collector (PTC)-based solar field. Accordingly, the temperature of the steam elevates by the solar field before entering the electric power generation cycle. Additionally, the solar unit is integrated with a phase change material (PCM)-based storage system. The use of storage tank at the delivery line of PTC can improve the power plant’s reliability. A comprehensive comparison of the developed power plant with the conventional MSWI power plant is presented. In addition, the technical and economic behaviors of the considered power plant have been optimized under two different single and multi-objective optimization scenarios. The outcomes indicated that the developed power plant can provide 15.75% and 15.68% higher energetic and exergetic efficiencies compared to MSWI power plant. In addition, the rate of electric power obtained from S-MSWI power plant is almost 16.1% more compared to MSWI power plant. However, the total cost rate of MSWI plant is almost 24.13% lower compared to the developed power plant. But, the value of LCOE in the developed power plant is approximately 8.93% lower than MSWI power plant. It was also found that, the multi-objective optimization can provide better and optimal results to energy engineers and decision makers compared the single-optimization. The conceptual design of the implementation of the solar field is also developed in a specific geographical condition. Additionally, this research comes from the key technology of the National Key Laboratory of Environmental Protection.

Environmental impacts of upgrading gas to electric heating and cooling, considering decarbonisation of the electricity grid

Rising temperatures and higher energy costs have created the imperative for Australian households to reduce energy consumption via more efficient heating and cooling systems. These energy efficient systems could lower the overall environmental impacts as heating and cooling accounts for around 20%–50% of total energy usage of residential buildings. Nonetheless, the embodied energy of efficiency upgrades and whether it is offset by operational savings as well as decarbonisation of the electricity grid, is often overlooked. This research aims to determine the environmental impacts of 59 gas heater to electric reverse cycle air conditioner upgrades via a life cycle assessment. A reference gas heater and air conditioner were deconstructed and assessed on their material compositions. The operational energy savings of one year prior and after were collected for all upgrades.The results show that operational energy savings offset the embodied energy for the following impact categories: climate change (short-term), fossil and nuclear energy use, mineral resources use and ozone layer depletion. However, climate change (long-term), photochemical oxidant formation, human toxicity (cancer) freshwater and terrestrial acidification, marine eutrophication, particulate matter formation, ionizing radiation, water scarcity, land occupation and transformation (biodiversity) can only be offset with the decarbonisation of the electricity grid. Notwithstanding, human toxicity (non-cancer), freshwater ecotoxicity and eutrophication cannot be offset even with a complete decarbonisation of the electricity grid, as the impacts from the production stage are too high. Notwithstanding the limited effectiveness of full decarbonisation, it is worthwhile considering the materials used in the appliance to further lower the environmental impact.

Construction of three‐dimensional crumpled Ni‐Co TMOs for electrochemical energy storage

AbstractDue to excellent electrochemical performances, mixed transition metal oxides (TMOs) as electrode materials have attracted scholarly attention. However, the issues of volume expansion, unstable structure, and low electrical conductivity have limited their development for lithium battery (LIB). Drawing on the strategy of MOFs derivation synthesis combined with low temperature hydrothermal method, this study successfully synthesized the three‐dimensional (3D) NiCo2O4@Fe2O3 with a flower‐like crossing channel and a surface crumpled structure. As anode for LIBs, NiCo2O4@Fe2O3 exhibits more reliable performance than Ni−Co oxides. Our experiments verified that the Ni−Co composite electrical conductivity and cycling stability were both improved by the Fe2O3 coating. Under the high current density of 1000 mA g−1, the capacity decay rate of NiCo2O4@Fe2O3 tends to be stable after 60 cycles, and the capacity remains at 945 mAh g−1 after 400 cycles. Besides, the specific crossing porous‐channel structure mode improved the composite's carrier transport efficiency, and coulombic efficiency reached 100 % after 400 cycles. Noteworthy is the fact that the crumpled surface structure formed by the 2D Ni−Co nanosheets promotes the construction of heterostructures, further enhances the interface capacitance effect, and strengthens the rating capacity.

Reliability Improvement from La2O3 Interfaces in Hf0.5Zr0.5O2‐Based Ferroelectric Capacitors

AbstractFurther optimization of a typically reported ferroelectric capacitor comprised of a Hf0.5Zr0.5O2 ferroelectric thin film with TiN electrodes is explored by introducing an additional non‐ferroelectric La2O3 interfacial layer evaluated at different positions in the capacitor stack. The role of the interface to the ferroelectric layer is investigated and discussed, with the main focus directed toward the reliability of the device for non‐volatile memory applications. With this investigation, different degradation mechanisms determining electric field cycling and polarization retention are observed, and it is concluded that modifying the bottom interface between the electrode and the ferroelectric layer has the best potential to provide a benefit in device performance.

Flux-Weakening Controller Design of Dual Three-Phase PMSM Drive System With Copper Loss Minimization

The performance of flux-weakening controllers in the multiphase permanent magnets (PM) machines depends on the accurate fundamental voltage limit derivation, and the minimal copper loss design in the flux-weakening operation region has not been well discussed. In this article, the accurate fundamental voltage limit with considering harmonic current suppression is derived at first. Then, two control concepts are addressed, and the corresponding flux-weakening control strategies are designed with the gradient descent method. In the first control strategy, both the fundamental and harmonic voltage vectors are feasible, resulting in the larger amplitude of the phase currents. The second control strategy obtains higher bus voltage utilization by an additional transition stage. At the same time, the harmonic currents cannot be further suppressed in the flux-weakening operation region. Third, the copper loss per electrical cycle is calculated, and a switching scheme is designed to obtain lower copper loss in the flux-weakening operation region. Finally, both strategies are successfully implemented in a dual three-phase PMSM. Moreover, the proposed switching scheme obtains minimal copper loss in the whole flux-weakening operation region.

Sea urchins like Na2Ti3O7 as long cycling and high-rate performance anodes for Li-ion batteries

Due to its special Z-shaped layered structure, Na2Ti3O7 has great potential as an anode material for lithium-ion battery application. However, the poor electrical conductivity and cycle life have seriously affected its application in practice. In this paper, we prepared a sea urchin shaped Na2Ti3O7 material by a simple hydrothermal method. This special morphology allows the material to have a large specific surface area, which can better contact with the electrolyte and increase the active site number. The half-cells assembled with sea urchin-like Na2Ti3O7 show excellent cycling performance and good rate performance. After 1000 cycles at a 1 C rate, the specific capacity of NTO maintains at 70%. Even at a 5 C rate, NTO-2 delivers a discharge capacity of 71 mAh g−1 after 1000 cycles. The method proposed can be extended to other new anode materials to boost their electrochemical performances.

Modeling of the impact of cycling operating conditions on durability of polymer electrolyte fuel cells and its sensitivity analysis

In the paper, the impact on durability of polymer electrolyte membrane fuel cells is investigated when varying operating conditions applied in accelerated stress tests. By this, the electric potential cycling protocol in given by a non-symmetric square profile. The electrochemical degradation of a catalyst layer is caused by platinum ion dissolution and oxide coverage. These mechanisms are described by the one-dimensional Holby–Morgan model with a modified Butler–Volmer equation for the reaction rates. For efficient numerical solution of the underlying nonlinear reaction-diffusion system, a variable time-step implicit-explicit method is suggested. Computer simulations predict durability for the catalyst by using a linear extrapolation up to the full platinum surface blockage. A parameter sensitivity analysis is presented on different time scales and measures how the platinum mass loss is impacted by the variation of specific parameters.

Time-Transient Optimization of Electricity and Fresh Water Cogeneration Cycle Using Gas Fuel and Solar Energy

In this study, a cogeneration cycle in a time-transient state is investigated and optimized. A quasi-equilibrium state is assumed because of the small time increments. Air temperature and solar power are calculated hourly. The cycle is considered in terms of energy, exergy, and economic and environmental analyses. Increasing the net present value (the difference between the present value of the cash inflows and outflows over a period of time) and reducing exergy destruction are selected as two optimization objective functions. The net present value is calculated for the period of 20 years of operation according to the operation parameters. The optimization variables are selected in such a way that one important variable is selected from each system. To optimize the cycle, the particle swarm optimization method is used. The number of particles used in this method is calculated using the trial-and-error method. This cycle is optimized using 13 particles and 42 iterations. After optimization, the energy efficiency increased by 0.5%, the exergy efficiency increased by 0.25%, and the exergy destruction decreased by 1% compared to the cycle with existing parameters.

The effects of functional electrical stimulation cycling on gait parameters in diplegic cerebral palsy: a single-blind randomized controlled trial

Purpose To investigate the effects of functional electrical stimulation cycling (FES-C) training in addition to conventional physical therapy on gait, muscle strength, gross motor function, and energy expenditure in ambulatory children with spastic diplegic cerebral palsy. Materials and methods Twenty children with diplegic cerebral palsy were randomly assigned to FES-C group (n = 10) or control group (n = 10). Subjects trained 3 days/week for 8 weeks. Control group received conventional physical therapy. The FES-C group additionally received FES-C training. The functional muscle test was used for muscle strength assessment. Vicon-3D system was used for gait analysis. Gross Motor Function Measure (GMFM-88) was used for motor function assessment and calorimeter was used for energy expenditure. Measurements were performed at the baseline, at the eight week and at the sixteenth week. Results Functional muscle strength, gross motor function, and energy expenditure improved more in the FES-C group after training and follow up (p < 0.05). There was no significant difference found between the changes in gait parameters of the two groups after treatment and follow up (p > 0.05). Pelvic tilt while walking decreased after training in the FES-C group (p < 0.05). Conclusions FES-C applied in addition to conventional physical therapy in children with diplegic cerebral palsy is more effective than conventional physical therapy for increasing functional muscle strength, improving gross motor function functions, and reducing energy expenditure. Highlights FES-C improves lower extremity functional muscle strength, gross motor function, and energy expenditure in ambulatory children with spastic dCP. The use of FES-C in combination with conventional physiotherapy methods may be beneficial in outpatients with spastic dCP.

Cardiac Alternans: From Bedside to Bench and Back

Cardiac alternans arises from dynamical instabilities in the electrical and calcium cycling systems of the heart, and often precedes ventricular arrhythmias and sudden cardiac death. In this review, we integrate clinical observations with theory and experiment to paint a holistic portrait of cardiac alternans: the underlying mechanisms, arrhythmic manifestations and electrocardiographic signatures. We first summarize the cellular and tissue mechanisms of alternans that have been demonstrated both theoretically and experimentally, including 3 voltage-driven and 2 calcium-driven alternans mechanisms. Based on experimental and simulation results, we describe their relevance to mechanisms of arrhythmogenesis under different disease conditions, and their link to electrocardiographic characteristics of alternans observed in patients. Our major conclusion is that alternans is not only a predictor, but also a causal mechanism of potentially lethal ventricular and atrial arrhythmias across the full spectrum of arrhythmia mechanisms that culminate in functional reentry, although less important for anatomic reentry and focal arrhythmias.

Preparation and electrochemical properties of cobalt aluminum layered double hydroxide/carbon-based integrated composite electrode materials for supercapacitors

Supercapacitors have been widely developed in electrochemical energy storage field. Cobalt aluminum layered double hydroxide (CoAl-LDH) has attracted much attention because of its potential characteristics in energy storage. However, this materials also have the disadvantages of poor electrical conductivity and short cycle life. In order to solve this problem, a special structure of CoAl-LDH/carbon-based composite integrated electrode materials are constructed by one-step hydrothermal method, and the electrochemical properties of the materials are improved by changing the solvent composition. It is found that the electrochemical properties of CoAl-LDH/graphitic carbon nitrides (g-C3N4), CoAl-LDH/carbon nanotube (CNT) and CoAl-LDH/activated carbon (AC) composites are superior to those of pure CoAl-LDH, and CoAl-LDH/AC, as a new type of lamellar structure electrode material, has the best capacitance performance. Compared with CoAl-LDH/AC prepared with pure water as the solvent, adding 5 mL ethanol to the solvent can increase the specific capacitance of CoAl-LDH/AC composites from 1700 F g−1 (850 C g−1) to 1891 F g−1 (946 C g−1) at 1 A g−1 current density. At 7 A g−1 high current density, after 5000 cycles, the capacitance retention rate is increased from 40.6% to 66.3%. These electrochemical properties suggest that CoAl-LDH/AC composites can be one of the high performance electrodes for supercapacitors.Hydrothermal method; CoAl-LDH/carbon-based composite integrated electrode materials; Solvent composition; Specific capacitance; Electrochemical performance.

First direct observation of the built-in electric field and oxygen vacancy migration in ferroelectric Hf0.5Zr0.5O2 film during electrical cycling.

The wake-up and fatigue effects exhibited by ferroelectric hafnium oxide (HfO2) during electrical cycling are two of the most significant obstacles limiting its development and application. Despite a mainstream theory relating these phenomena to the migration of oxygen vacancies and the evolution of the built-in field, no supportive experimental observations from a nanoscale perspective have been reported so far. By combining differential phase contrast scanning transmission electron microscopy (DPC-STEM) and energy dispersive spectroscopy (EDS) analysis, we directly observe the migration of oxygen vacancies and the evolution of the built-in field in ferroelectric HfO2 for the first time. These solid results indicate that the wake-up effect is caused by the homogenization of oxygen vacancy distribution and weakening of the vertical built-in field whereas the fatigue effect is related to charge injection and transverse local electric field enhancement. In addition, using a low-amplitude electrical cycling scheme, we exclude field-induced phase transition from the root cause of the wake-up and fatigue in Hf0.5Zr0.5O2. With direct experimental evidence, this work clarifies the core mechanism of the wake-up and fatigue effects, which is important for the optimization of ferroelectric memory devices.

Life Cycle Assessment of Electric Vehicle Batteries: Review and Critical Appraisal

The most environmentally damaging aspect of using electric vehicles is the batteries. The Life Cycle Assessment (LCA) approach has been widely used to conduct inventory analysis of energy usage and GHG emissions throughout battery production and assembly. There are many analytical frameworks and models for conducting LCA, but each method uses different results. This study aims to investigate numerous LCA studies on electric vehicle batteries using ISO 14040 and its derivatives. We propose the limits of a cradle-to-grave system so that LCA provides optimal results for comparative studies and potential for continuous improvement. A schematic overview of the electric car battery life cycle covers material extraction, material processing, product manufacture, product use, and end-of-life recovery measures. Global warming, eutrophication, acidification, ozone depletion, abiotic depletion, particulate matter, human toxicity, ecotoxicity, and Cumulated Energy Demand (CED) are all impact categories in LCA study.