Shorter Charging Time Research Articles

Modeling the Effect of Fast Charge Protocol on the Temperature Rise of a Lithium-Ion Battery during Charge

The lithium-ion battery (LIB) is a preferred power source for battery electric vehicles (BEVs),because LIBs have higher energy density, longer life and higher power density than most other practical batteries. Although there is still a plenty of room to be improved for the cost, life, and safety of the LIB in BEV applications,another important issue to be overcome for the BEV battery is searching for an appropriate fast charge protocol to enable a rapid growth of BEV market. A short charge time, however, results in a rapid temperature rise of an LIB cell during charge. Therefore, it is essential to find an optimized fast charge protocol that can keep the peak temperature of LIB cell below the maximum allowable limit recommended by the LIB manufacturer.In this work, the effect of fast charge protocol on the temperature rise of an LIB cell during charge is analyzed based on the two-dimensional thermal modeling of the LIB cell under various fast charge protocols. The thermal modeling during fast charge is validated by the comparison of the modelling results with the experimental measurements using IR thermal images and thermocouples. The fast charge protocols are evaluated based on the peak temperatures of the LIB cell after charge.

Radio Frequency Energy Harvesting with Phase Shift Keying Modulation Technique

Radio Frequency (RF) energy harvesting is a promising alternative energy source to provide power for low power electronic devices through the air. RF energy harvesting technologies are used in many application fields such as building automation, industrial monitoring, data center, security and defense. In this study, effects of frequency shift keying modulation technique on charging times of RF energy harvesting were measured and investigated in detail. An advanced measurement system was established and this measurement system was performed using an RF energy harvesting circuit, a signal generator, patch antennas and other equipment. The modulated signal at 14 dBm output power was generated by signal generator. Then, the energy produced by the signal generator was obtained from 20 cm to 60 cm at the interval of 5 cm distance by the RF energy harvesting circuit with 6 dBi patch antenna. According to measurement results, the shortest charging time was calculated as 1 s at a distance of 20 cm. In addition to that, the longest charging time was calculated as 7 s at a distance of 60 cm. It was determined that the charging time of the RF energy harvesting decreased as the distance between signal generator and RF energy harvesting circuit reduced.

Effects of Different Modulation Techniques on Charging Time in RF Energy-Harvesting System

Radio-frequency (RF) energy harvesting is a promising technology that obtains energy from electromagnetic waves. As an alternative energy source, this modern technology can provide power wirelessly enabling the practical use of battery-free devices and it is also expected to be widely used in future applications. Many studies have examined the effects of different modulation techniques on power or efficiency in RF energy-harvesting systems. In this article, the effects of different modulation techniques, such as amplitude shift keying (ASK), quadrature amplitude modulation (QAM), phase-shift keying (PSK), and frequency shift keying (FSK) on charging time, were measured and theoretically analyzed in detail. The measurement system was designed using a signal generator, an RF energy-harvesting circuit, and other auxiliary devices. The signal generator produced four different modulated signals as transmit power signals from 1 to 10 dBm at the interval of 1 dBm, and then, the RF energy-harvesting circuit was fed with these power signals. According to the measurement results, four different modulation techniques charged the RF energy-harvesting circuit at different times. It was observed that the 4-ASK modulation technique had the shortest charging time in the range of 1-10 dBm when comparing to QAM, PSK, and FSK modulation techniques, and thus, it was evaluated to be the most suitable modulation technique for the RF energy-harvesting system among these modulation techniques in terms of charging time.

Identifying rate limitation and a guide to design of fast‐charging Li‐ion battery

AbstractFast‐charging is highly demanded for applications requiring short charging time. However, fast‐charging triggers serious problems, leading to decline in charge acceptance and energy efficiency, accelerated capacity degradation, and safety risk. In this work, a three‐electrode coin cell with a Li metal reference electrode is designed to individually record the potential of two electrodes, and measure the impedance of each electrode by using a power‐optimized graphite‐LiNi0.80Co0.15Al0.05O2 electrode couple. It is shown that regardless of the state‐of‐charge the Li‐ion cell's impedance is contributed predominantly by the cathode, and that the cathode's impedance is dominated by the charge‐transfer resistance. In consistence with the impedance results, polarization of the Li‐ion cell is dominated by the cathode. It is surprised to find that no Li plating occurs on the graphite anode even if the charging rate is increased to 10 C (1 C = 1.30 mA cm−2). The results of this work indicate that low overall impedance with a high cathode‐to‐anode impedance ratio is the key to enabling safe fast‐charging, and that fast‐charging Li‐ion batteries without Li plating on the graphite anode is possible if the cathode and graphite anode are optimistically engineered.image

Radio Frequency Energy Harvesting with Different Antennas and Output Powers

In this study, the effects of antenna types and output powers on charging times of RF energy harvesting circuit were measured and analyzed in detail. A measurement system which consisting of a signal generator, an RF energy harvesting circuit, antennas and other devices was installed for receiving the measurement samples. According to the measurement results, the shortest charging time was obtained as 0.58 s at a distance of 20 cm, when 6.1 dBi antenna was connected to the RF energy harvesting circuit and the output power of the signal generator was set to 17 dBm. In addition to that, the longest charging time was evaluated as 25.01 s at a distance of 60 cm, when 1 dBi antenna was connected to the RF energy harvesting circuit and the output power of the signal generator was adjust to 14 dBm. As a result, it was determined that increasing of antenna gains and output powers and shortening of distances between signal generator and RF energy harvesting circuit decreased the charging times of the RF energy harvesting circuit in this study.

Radio Frequency Energy Harvesting with Frequency Shift Keying Modulation Technique

Radio Frequency (RF) energy harvesting is a promising alternative energy source to provide power for low power electronic devices through the air. RF energy harvesting technologies are used in many application fields such as building automation, industrial monitoring, data center, security and defense. In this study, effects of frequency shift keying modulation technique on charging times of RF energy harvesting were measured and investigated in detail. An advanced measurement system was established and this measurement system was performed using an RF energy harvesting circuit, a signal generator, patch antennas and other equipment. The modulated signal at 14 dBm output power was generated by signal generator. Then, the energy produced by the signal generator was obtained from 20 cm to 60 cm at the interval of 5 cm distance by the RF energy harvesting circuit with 6 dBi patch antenna. According to measurement results, the shortest charging time was calculated as 1 s at a distance of 20 cm. In addition to that, the longest charging time was calculated as 7 s at a distance of 60 cm. It was determined that the charging time of the RF energy harvesting decreased as the distance between signal generator and RF energy harvesting circuit reduced.

Optimal Design of Wireless Charging Electric Bus System Based on Reinforcement Learning

The design of conventional electric vehicles (EVs) is affected by numerous limitations, such as a short travel distance and long charging time. As one of the first wireless charging systems, the Online Electric Vehicle (OLEV) was developed to overcome the limitations of the current generation of EVs. Using wireless charging, an electric vehicle can be charged by power cables embedded in the road. In this paper, a model and algorithm for the optimal design of a wireless charging electric bus system is proposed. The model is built using a Markov decision process and is used to verify the optimal number of power cables, as well as optimal pickup capacity and battery capacity. Using reinforcement learning, the optimization problem of a wireless charging electric bus system in a diverse traffic environment is then solved. The numerical results show that the proposed algorithm maximizes average reward and minimizes total cost. We show the effectiveness of the proposed algorithm compared with obtaining the exact solution via mixed integer programming (MIP).

Computer Test of a New Silicene Anode for Lithium‐Ion Batteries

AbstractThe main requirements for lithium‐ion batteries (LIB) of the new generation are low cost, safety, short charge time, high energy and power. This article is devoted to the testing of a new anode design, which is based on the use of silicene on an Al(111) substrate. The processes of intercalation and deintercalation of lithium in a channel formed by silicene sheets in the presence of an electric field are investigated. Sheets of perfect silicene and silicene with vacancy defects are used. The largest number of Li ions is intercalated into the channel with bivacancies. The lithium density profiles in the channels, the diffusion coefficients of lithium atoms, their energy, the angular distributions of the nearest neighbors, and the distributions of the most significant stresses in the silicene sheets are determined. On average, a silicene channel with vacancy‐type defects on the Al(111) substrate is characterized by a lower charge capacity and lower stresses in silicene than a corresponding channel on an Ag(111) substrate. We expect that this article will contribute to the further selection of the substrate material for the LIB silicene anode.

Taguchi-based PSO for searching an optimal four-stage charge pattern of Li-ion batteries

Abstract This study utilizes a Taguchi-based particle swarm optimization algorithm to search an optimal four-stage constant current charge pattern for delivering the maximum capacity to provide long runtimes within the shortest charging time. The goal is to maximize the cost function for the applied charge pattern based on the charging time and discharge capacity ratio that both share the same weight. The discharge capacity ratio is defined as the total capacity of a cell discharged at a constant current of 0.3 C using the four-stage constant current charging strategy until reaching the preset voltage of 3.0 V to the one employs the constant current constant voltage charging method. The charging time is the overall charging duration of the 4SCC charging process. Sanyo UR14500P batteries in the cylindrical shape with a nominal voltage of 3.7 V and a rated capacity of 840 mAh are tested. In the tests, the optimal 4SCC sequence of 1.262 C, 1.082 C, 0.662 C and 0.258 C is allowed to charge the battery up to 94.7% of the nominal capacity for 67 min, and the constant current constant voltage charging arrangement of 0.7 C to 4.2 V and the cut-off of 0.05 C are used to charge the battery up to 99.5% of the nominal capacity in 119 min.

Preparation of metal-organic framework-derived nitrogen-doped porous carbon and study of its supercapacitive performance in potassium citrate electrolyte

As a new kind of power storage, supercapacitors have attracted much attention due to their short charge and discharge time, good cycle performance, large power density, and environmental friendliness. However, the main drawback of supercapacitors is lower energy density than batteries, as well as high cost per unit energy. Herein, the metal-organic frameworks compound [Zn3(OH)(BTC)2(C4N2H11)(H2O)]n was used as carbon precursor to prepare the nitrogen-doped porous carbon (ZMFC-T) by one-step carbonization process. We investigated the influences of carbonization temperature on the specific surface area, pore size distribution and electrochemical properties. The results show that the ZMFC-800 has a specific surface area of 1557 m2 g−1, an average pore size of 3.85 nm, and nitrogen content of 5.25%. In the 1 M potassium citrate electrolyte solution, the stable voltage window is 2 V and the energy density is 65.28W h kg−1. In potassium citrate electrolyte, ZMFC-800 has a strong charge storage capacity and high energy density. This work sheds a new light on the potential for developing superior nitrogen-doped porous carbon for energy storage devices.

Examining Shanghai Consumer Preferences for Electric Vehicles and Their Attributes

In this study, we conducted a stated choice survey in Shanghai in order to examine the attitudes of Shanghai residents towards electric vehicles and their attributes. Multinomial Logit and Random Parameter Logit models were used to analyze the response data for three samples—the full sample, a subsample of potential electric vehicle purchasers, and a subsample of unlikely electric vehicle purchasers. We found that the respondents in each of the three groups preferred electric vehicles with a longer driving range, a shorter charging time, a faster maximum speed, lower pollution emissions, lower fuel cost, and a lower price. However, an overlong driving range seems not to be a must for potential electric vehicles (EV) purchasers. In addition, a comparison of the two subsamples showed that potential electric vehicle purchasers were willing to pay more than their counterparts for enhancing vehicle attributes. We also investigated the determinants of likely electric vehicle purchase and found a number of demographic characteristics that were statistically significant.

Recent Advances in Metal Chalcogenides (MX; X = S, Se) Nanostructures for Electrochemical Supercapacitor Applications: A Brief Review.

Supercapacitors (SCs) have received a great deal of attention and play an important role for future self-powered devices, mainly owing to their higher power density. Among all types of electrical energy storage devices, electrochemical supercapacitors are considered to be the most promising because of their superior performance characteristics, including short charging time, high power density, safety, easy fabrication procedures, and long operational life. An SC consists of two foremost components, namely electrode materials, and electrolyte. The selection of appropriate electrode materials with rational nanostructured designs has resulted in improved electrochemical properties for high performance and has reduced the cost of SCs. In this review, we mainly spotlight the non-metallic oxide, especially metal chalcogenides (MX; X = S, Se) based nanostructured electrode materials for electrochemical SCs. Different non-metallic oxide materials are highlighted in various categories, such as transition metal sulfides and selenides materials. Finally, the designing strategy and future improvements on metal chalcogenide materials for the application of electrochemical SCs are also discussed.

Modeling the Effect of Fast Charge Protocol on the Thermal Behavior of a Lithium-Ion Battery for Electric Vehicle Applications

The battery is the primary reason that hampers a mass adoption of electric vehicles (EVs). Although lithium ion battery (LIB) is a preferred power source for EV, there is still a plenty of room to be improved for the cost, life and safety of the LIB in EV applications. Another important issue to be overcome for the EV battery is searching for an appropriate fast charge protocol to alleviate “range anxiety” for the driver of passenger EV and thus to enable a rapid growth of EV market. A short charge time is, however, reported to be achieved always at the expense of cycle life regardless of the charge techniques. It is, therefore, essential to find an optimized fast charge protocol that can balance fast charge and healthy cycling for the LIBs. In this work, the thermal behaviors of LIB cell under various fast charge protocols are analyzed based on the two-dimensional modeling of the nonuniform temperature distribution in LIB cell during fast charge. The thermal modeling during fast charge is validated by the comparison of the modelling results with the experimental measurements using IR thermal images and thermocouples. The fast charge protocols are evaluated based on the peak temperature of LIB cell and the thermal imbalance within LIB cell during fast charge. The maximum, average, and minimum temperatures obtained from the experimental measurements are compared with those predicted by the model in Fig. 1. The maximum, average, and minimum temperatures obtained from the experiment and modelling are in good agreement with each other at charge rate of 5C during CC-CV charging. Fig. 2 shows the temperature distributions based on the experimental IR image and the modeling for a 14.6 Ah LIB at an environmental temperature of 25℃ at charge time of 180, 480, 1140 s during CC-CV charging with CC charge at 5C. The overall temperature distributions obtained from the experiment agree well with those from the modeling in Fig. 2. Figure 1

Power consumption analysis on large-sized electric bus

The increase of greenhouse gasses effect is one of the causes of climate change. The use of vehicles with fossil fuels is one of the contributors to pollution and global warming. Another reason why dependence on it should be reduced is the lack of Indonesia's petroleum reserves compared to other OPEC countries. Researchers are trying to anticipate this by developing electric vehicles capable of operating without pollution. Implementation of electric vehicles has begun with the electric train, tram, electric bus, and others. Vehicles with rails get electricity supplies from the grid along the tracks, but the type of freely moving vehicle without a rail requires another way to get electricity supplies. Electric vehicles with power storage (battery) have an advantage in the roaming area if supported by proper recharging techniques. In electric vehicles, the battery is recharged by the direct charging process or swapped with other one (swapping). If the vehicle has high mobility, such as public transport (bus) then the shortest charging time may be very important.

Controllable growth of NiSe nanorod arrays via one-pot hydrothermal method for high areal-capacitance supercapacitors

To satisfy the ever-increasing demand of smart and miniaturized portable devices, supercapacitors have attracted tremendous attention owing to their short charging time, long cycling lifespan, and reliable safety. Nevertheless, the energy density of pseudocapacitors is the major obstacle because of its kinetically sluggish reactions, low mass loading of active materials, and/or high internal resistance. Herein we develop a one-pot hydrothermal method to synthesize NiSe nanorod arrays on nickel foam (NiSe NRA/NF), which exhibit ultrahigh areal capacitance of 6.81Fcm−2 at current density of 5mAcm−2 as well as excellent cycling stability. The superior performance of NiSe NRA/NF can be attributed to metallic conductivity of nickel selenides, short diffusion length of ions from electrolyte to electrode materials, and fast electrons transport pathway between active materials and current collectors. For practical applications, an asymmetric supercapacitor was assembled by applying NiSe as positive electrode and reduced graphene oxide as negative electrode, delivering an energy density of 38.8Whkg−1 at a power density of 629Wkg−1 and 6.38Whkg−1 at a power density of 13.5kWkg−1. Moreover, the devices retained 90.09% after 3000 cycles at high current density of 3.6Ag−1, showing a promising application prospect.

REACH: An Efficient MAC Protocol for RF Energy Harvesting in Wireless Sensor Network

This paper proposes a MAC protocol for Radio Frequency (RF) energy harvesting in Wireless Sensor Networks (WSN). In the conventional RF energy harvesting methods, an Energy Transmitter (ET) operates in a passive manner. An ET transmits RF energy signals only when a sensor with depleted energy sends a Request-for-Energy (RFE) message. Unlike the conventional methods, an ET in the proposed scheme can actively send RF energy signals without RFE messages. An ET determines the active energy signal transmission according to the consequence of the passive energy harvesting procedures. To transmit RF energy signals without request from sensors, the ET participates in a contention-based channel access procedure. Once the ET successfully acquires the channel, it sends RF energy signals on the acquired channel during Short Charging Time (SCT). The proposed scheme determines the length of SCT to minimize the interruption of data communication. We compare the performance of the proposed protocol with RF-MAC protocol by simulation. The simulation results show that the proposed protocol can increase the energy harvesting rate by 150% with 8% loss of network throughput compared to RF-MAC. In addition, the proposed protocol can increase the lifetime of WSN because of the active energy signal transmission method.

Thermal performance analysis of a thermocline thermal energy storage system with FLiNaK molten salt

A thermocline thermal storage unit with a heat transfer fluid (HTF) of high-temperature molten salt is considered as one of the most promising methods of thermal storage due to its lower cost and smaller size. The main objective of this work is to analyze the transient behavior of the available molten salt FLiNaK used as the HTF in heat transfer and heat storage in a thermocline thermal energy storage (TES) system. Thermal characteristics including temperature profiles influenced by different inlet velocities of HTF and different void fractions of porous heat storage medium are analyzed. The numerical investigation on the heat storage and heat transfer characteristics of FLiINaK has been carried out. A comparison between two different molten salts, FLiNaK and Hitec, has been explored in this paper with regards to their charging and discharging operations. The results indicate the system with FLiNaK has a greater energy storage capability, a shorter charging time and a higher output power. The numerical investigation reveals heat storage and heat transfer characteristics of the thermocline TES system with FLiNaK, and provide important references for molten salt selection of the TES system in the future.

Mixed bus fleet management strategy for minimizing overall and emissions external costs

Diesel buses add substantially to air pollution. To mitigate this problem, more and more clean-energy buses are introduced. Among them, electric bus has been recognized as the cleanest with lower emissions. But the deployment of electric bus is limited by its short travel distance and long charging time. In this paper, based on the approach of remaining life additional benefit-cost (RLABC), we propose an approach called new life additional benefit-cost (NLABC) to solve the mixed bus fleet management (MBFM) problem. An integer program is developed based on the NLABC analysis for maximizing the total net benefit of early replacement, where both the optimal fleet size and composition under budget constraints can be determined. Arguably, the routing problem is a major issue to be tackled due to the range limitations and operating costs of electric buses in the MBFM problem. Hence, we include the routing problem associated with bus services coordination among multiple routes in this formulation. Two routing methods are proposed to solve the recharging problem to study the tradeoff between accuracy and efficiency. Four types of buses, including electric bus, compressed natural gas bus, hybrid-diesel bus, and diesel bus, are considered, while accounting for their different operating costs, external costs of emissions, and purchase costs. To illustrate the approach, we apply the formulation to some transit lines in Hong Kong. The results show that vehicle routing with bus service coordination and mixed fleet optimization are important considerations for managing the bus fleet; both of which can produce considerable benefits.

The two timescales in the charge trapping mechanism for the hysteresis behavior in graphene field effect transistors

To understand the hysteresis phenomenon in the transfer characteristic curve of graphene field effect transistor is crucial to develop new graphene based sensors and memory devices. We investigated the hysteresis through a charging and discharging procedure and found that there exist two time constants with different timescales in the trapping mechanism. A fast trapping at the interface with a time constant of 0.68 s and a slow trapping in the bulk oxide with a time constant of 23.85 s were presented in our work. By identifying a linear relation between the interface trap densities and the gate voltage, we also found that the release of trapped charges was decided by the magnitude decrease of gate voltage instead of the voltage’s polarity switch. Based on the findings, a bi-resistive state memory prototype with a shorter charging time was realized at last.

A PSO-Based Fuzzy-Controlled Searching for the Optimal Charge Pattern of Li-Ion Batteries

This paper proposes a searching strategy based on particle swarm optimization, combined with a fuzzy-deduced fitness evaluator (FDFE), to find the optimal multistage charging pattern that delivers the most discharged capacity within the shortest charging time (CT). The objective function of the optimization problem is to maximize the cost effectiveness for the applied charging pattern based on the CT and normalized discharged capacity (NDC). Therefore, this paper proposes an FDFE to combine CT and NDC into a unified cost function to properly evaluate the multiple performance characteristics index in the charge problem. The experimental results show that the obtained pattern is capable of charging the batteries to over 88% capacity within 51 min. Compared with the conventional constant current–constant voltage method, the CT, the obtained life cycle, and the charging efficiency of the lithium-ion (Li-ion) battery for the devised approach are improved by approximately 56.8%, 21%, and 0.4%, respectively. The presented charging approach is suitable for the increasingly applications, in which the batteries are “sealed” inside the products to extend the life span.