Flexible Charging Research Articles

Manipulating Hierarchical Orientation of Wet-Spun Hybrid Fibers via Rheological Engineering for Zn-Ion Fiber Batteries.

Wet-spinning is a promising strategy to fabricate fiber electrodes for real commercial fiber battery applications, according to its great compatibility with large-scale fiber production. However, engineering the rheological properties of the electrochemical active materials to accommodate the viscoelasticity or liquid crystalline requirements for continuous wet-spinning remains a daunting challenge. Here, with entropy-driven volume-exclusion effects, the rheological behavior of vanadium pentoxide (V2 O5 ) nanowire dispersions is regulated through introducing 2D graphene oxide (GO) flakes in an optimal ratio. By optimizing the viscoelasticity and liquid-crystalline behavior of the spinning dope, the wet-spun hybrid fibers display controlled hierarchical orientation. The wet-spun V2 O5 /rGO hybrid fiber with the optimal 10:1 mass fraction (V2 O5 /rGO10:1 ) exhibits a highly oriented nanoblock arrangement, enabling efficient Zn-ion migration and an excellent Zn-ion storage capacity of 486.03 mAh g-1 at 0.1 A g-1 . A half-meter long quasi-solid-state fiber Zn-ion battery is assembled with a polyacrylamide gel electrolyte and biocompatible Ecoflex encapsulation. The thus-derived fiber Zn-ion battery is integrated into a wearable self-powered system, incorporating a highly efficient GaAs solar cell, which delivers a record-high overall efficiency (9.80%) for flexible solar charging systems.

Research on circuit analysis and optimization of wireless power transmission system with embedded coil

PurposeThe wireless power transmission (WPT) system with an embedded coil will achieve a more flexible charging operation and higher system efficiency. However, the comprehensive analysis considering cross-coupling for WPT with embedded coil is rarely investigated. This study aims to improve the system efficiency of WPT with the embedded coil based on circuit analysis and optimization of embedded coil loops.Design/methodology/approachThe circuit model of WPT system with the non-resonant compensated embedded coil is developed by taking the cross-coupling of all coils and the circuit compensation degree of the embedded coil into consideration. On the basis of system characteristics analysis, optimization of embedded coil position and non-resonant compensation are proposed to improve the efficiency of WPT system with embedded coil. Experimental studies demonstrate the correctness of theoretical research.FindingsThe WPT system with embedded coil designed by optimizing the position and non-resonant compensation achieves higher efficiency than those of the system with two-coil mode and the three-coil system with a resonant compensated embedded coil.Practical implicationsA WPT system with embedded coil could be more efficient by using a non-resonant compensated coil embedded into the buffer material of the storage box for sophisticated electrical equipment.Originality/valueThe cross-coupling between all coils is considered in circuit analysis for WPT system with embedded coil. Optimization of the position and non-resonant compensation of embedded coil achieves higher efficiency.

Joint power distribution and charging network design for electrified mobility with user equilibrium decisions

AbstractRapid adoption of electric vehicles (EVs) requires the development of a highly flexible charging network. The design and management of the charging infrastructure for EV‐dominated transportation systems are intertwined with power grid operations both economically and technically. High penetration of EVs in the future can increase the charging loads and cause a wide range of operational issues in power distribution networks (PDNs). This paper aims to design an EV charging network with an embedded PDN layout to account for energy dispatch and underlying traffic flows in urban transportation networks supporting electric mobility in the near future. A mixed‐integer bilevel model is proposed with the EV charging facility location and PDN energy decisions in the upper level and user equilibrium traffic assignment in the lower level considering an uncertain charging demand. The objective is to minimize the cost of PDN operations, charging facility deployments, and transportation. The proposed problem is solved using a column and constraint generation (C&CG ) algorithm, while a macroscopic fundamental diagram concept is implemented to estimate the arc travel times. The methodology is applied to a hypothetical and two real‐world case study networks, and the solutions are compared to a Benders decomposition benchmark. The east‐coast analysis results indicate a 77.3% reduction in the computational time. Additionally, the benchmark technique obtains an optimality gap of 1.15%, while the C&CG algorithm yields a 0.61% gap. The numerical experiments show the robustness of the proposed methodology. Besides, a series of sensitivity analyses has been conducted to study the impact of input parameters on the proposed methodology and draw managerial insights.

Flexible Fault Current Adaptation Features of a Novel DC Circuit Breaker Assisted by Superconducting Fault Current Limiters

The high d <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">i</i> /d <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">t</i> before zero-crossings easily leads to delayed or failed operations for the active current injection mechanical DC circuit breaker, especially for small direct current interruptions. The pre-charging process also makes this type of circuit breaker hard to realize repeat operations economically in the high voltage DC system. This paper proposes a novel DC circuit breaker and its design method that deeply coordinating a superconducting fault current limiter with the active current injection DC circuit breaker. This method significantly reduces d <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">i</i> /d <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">t</i> before current zero-crossings and enables repeat operations economically. Besides limiting fault currents, the superconducting fault current limiter also charges the resonance capacitor flexibly in the circuit breaker, realizing the injected reverse current keep a constant proportion to the arbitrary fault current. Validations of the flexible capacitor charge and repeat operations are made by simulation and low voltage experiments. The charging times are within 2.5 ms and the reverse current keeps 1.2 to 1.7 times over the fault current under arbitrary conditions. D <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">i</i> /d <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">t</i> at current zero is reduced by 80% under 30% of rated interruption capacity. Flexible capacitor charge experiments are consistent with the simulation design. The superconducting tapes can recover within 300 ms to support repeat operations.

Joint routing and charging optimization for eVTOL aircraft recovery

We study the eVTOL aircraft recovery problem (eVTOL-ARP) raised in the use cases of airport shuttles and intercity flights in Urban Air Mobility (UAM). One distinctive feature of the eVTOL-ARP is that charging tasks are allowed to be deferred and canceled. An optional charging scheme is proposed to improve recovery flexibility. Jointly handling routing and charging in an integrated manner makes the problem different from classical aircraft recovery literature and much more challenging. We formulate an integer linear program model and propose a branch-and-price algorithm to solve the eVTOL-ARP exactly. A tailored label setting algorithm that exploits the structure of the problem is proposed for the parallel pricing subproblems. Extensive experiments are conducted on the instances based on the Beijing-Tianjin-Hebei airport cluster and the Zhejiang Province airport cluster. Experimental results show that the proposed algorithms can provide efficient and timely recovery solutions in real-world operations. The recovery cost gap is over 9% between non-flexible charging and the proposed flexible charging. We conduct sensitivity analysis on a key factor, i.e. charging time that may affect the recovery cost and highlight the decreasing marginal value of the charging time.

Collaborative Robust Optimization Strategy of Electric Vehicles and Other Distributed Energy Considering Load Flexibility

Aggregated electric vehicles (EVs) integrated to the grid and intermittent wind and solar energy increased the complexity of the economic dispatch of the power grid. Aggregated EVs have a great potential to reduce system operating costs because of their dual attributes of load and energy storage. In this paper, plugged-in EV is refined into three categories: rated power charging, adjustable charging, and flexible charging–discharging, and then control models are established separately; the concept of temporal flexibility for EV clusters is proposed for the adjustable charging and flexible charging–discharging of EV sets; then, the schedule boundary of EV clusters is determined under the flexibility constraints. The interval is used to describe the intermittent nature of renewable energy, and the minimum operating cost of the system is taken as the goal to construct a distributed energy robust optimization model. By decoupling the model, a two-stage efficient solution is achieved. An example analysis verifies the effectiveness and superiority of the proposed strategy. The proposed strategy can minimize the total cost while meeting the demand difference of EV users.

Inhaled mRNA Nanoformulation with Biogenic Ribosomal Protein Reverses Established Pulmonary Fibrosis in a Bleomycin‐Induced Murine Model (Adv. Mater. 14/2022)

Nanomedicine In article number 2107506, Xinyi Jiang and co-workers introduce an inhaled nanoformulation that is developed with biogenic ribosomal protein for mRNA delivery. The variety of isoelectric points of ribosomal proteins endows them with flexible positive charge properties, by which negatively charged mRNA is efficiently condensed to form a nanocomplex in a biomimetic fashion.

Self-healing Growth of LaNiO3 on a Mixed-Terminated Perovskite Surface.

Developing atomic-scale synthesis control is a prerequisite for understanding and engineering the exotic physics inherent to transition-metal oxide heterostructures. Thus, far, however, the number of materials systems explored has been extremely limited, particularly with regard to the crystalline substrate, which is routinely SrTiO3. Here, we investigate the growth of a rare-earth nickelate─LaNiO3─on (LaAlO3)(Sr2AlTaO6) (LSAT) (001) by oxide molecular beam epitaxy (MBE). Whereas the LSAT substrates are smooth, they do not exhibit the single surface termination usually assumed necessary for control over the interface structure. Performing both nonresonant and resonant anomalous in situ synchrotron surface X-ray scattering during MBE growth, we show that reproducible heterostructures can be achieved regardless of both the mixed surface termination and the layer-by-layer deposition sequence. The rearrangement of the layers occurs dynamically during growth, resulting in the fabrication of high-quality LaNiO3/LSAT heterostructures with a sharp and consistent interfacial structure. This is due to the thermodynamics of the deposition window as well as the nature of the chemical species at interfaces─here, the flexible charge state of nickel at the oxide surface. This has important implications regarding the use of a wider variety of substrates for fundamental studies on complex oxide synthesis.

Bamboo-inspired cell-scale assembly for energy device applications

Rapid advances in flexible and wearable smart textiles demand low-cost, high-energy/power-density fiber-shaped supercapacitors (FSCs). The performance of FSCs is determined by the fabrication and assembly of fiber-shaped electrodes (FSEs), where an active charge-storage material is always clad around flexible charge transmission current collectors. Inspired by the tissue structure of natural bamboo, wherein parenchyma cells (PCs) that store nutrients are clad around bamboo fibers (BFs), we propose a strategy for converting bamboo cells into FSEs using conductive BFs and activated PCs as current collectors and active materials, respectively. The assembled electrode has a high specific capacitance of 1454 mF cm−2 at 0.64 mA cm−2. A solid-state FSC with a pair of bamboo-structured electrodes exhibited a substantially high energy density. Its mechanical flexibility enabled the knitting of wearable wristbands to drive ultra-small voltmeter indicators. This lightweight, low cost, and high-energy-density bamboo-structured FSC could enable numerous smart textile applications.

CWoT-Share: Context-Based Web of Things Resource Sharing in Blockchain Environment

Web of Things (WoT) resources are not only numerous, but also have a wide range of applications and deployments. The centralized WoT resource sharing mechanism lacks flexibility and scalability, and hence cannot satisfy requirement of distributed resource sharing in large-scale environment. In response to this problem, a trusted and secure mechanism for WoT resources sharing based on context and blockchain (CWoT-Share) was proposed. Firstly, the mechanism can respond quickly to the changes of the application environment by dynamically determining resource access control rules according to the context. Then, the flexible resource charging strategies, which reduced the fees paid by the users who shared more resources and increased the fees paid by users who frequently used resources maliciously, were used to fulfill efficient sharing of WoT resources. Meanwhile, the charging strategies also achieve load balancing by dynamic selection of WoT resources. Finally, the open source blockchain platform Ethereum was used for the simulation and the simulation results show that CWoT-Share can flexibly adapt to the application environment and dynamically adjust strategies of resource access control and resource charging.

A novel domino protocol for three-component synthesis of new dibenzo[e,g]indoles: flexible intramolecular charge transfers

New and electronically interesting 2-aryl-3-nitrodibenzo[e,g]indoles were synthesized effectively via a hitherto unreported three-component domino reaction under catalysis of a superparamagnetic nano-composite.

STUDYING MULTILAYERED GRAPHENES &#x0D; BY ELECTROPHYSICAL METHODS

The paper studies multilayer graphenes in the form of free-standing films. The authors provide data about the morphology and electrical properties of films treated with plasma of various chemical composition. It is shown that it is possible to control the electrical properties of the surface and electron work function without significantly affecting its morphology. The obtained samples, combining mechanical flexibility with unreactiveness and high electrical conductivity, are promising for application in flexible charge storage devices.

Optimal configuration of electric vehicles for charging stations under the fast power supplement mode

With the development of high-power charging technology for electric vehicles (EVs), fast power supplement mode (FPSM) is favoured by users and operators. An optimal configuration method of fast charging stations (FCSs) under FPSM is proposed in this paper. Firstly, the charging characteristics of the EV battery are analysed, the charging time and electricity supplementation of user's expected are introduced as quantitative indicators for judging whether to charge. According to the different fast supplement needs of different EV types, the matrix-type flexible charging stack is used to classify different levels of charging power. Various EV types in 10–20 min can be achieved fast supplement, which will have good application prospects and feasibility in the future. Secondly, the spatial-temporal distribution of EVs charging demand under the FPSM is predicted based on global positioning system (GPS) and K-means method. Thereby, an optimal FCSs configuration model is established with considering user satisfaction indicators. Voronoi diagram and the improved particle swarm algorithm (PSO) are used to determine the optimal FCSs location and capacity. Moreover, the influence of FCSs on the operation safety of distribution network is added into the model. Finally, the practicality and feasibility of the theory are verified through simulation analysis of examples.

Simultaneous Long-Term Planning of Flexible Electric Vehicle Photovoltaic Charging Stations in Terms of Load Response and Technical and Economic Indicators

Photovoltaic charging stations (PVCSs) are one of the most important pieces of charging equipment for electric vehicles (EVs). Recently, the process of designing solar charging stations as flexible sources has been growing and developing. This paper presents a relatively complete design of a solar charging station as a flexible economic resource in a 10-year planning horizon based on a genetic algorithm in two scenarios. PVCSs are not considered in the first scenario. This scenario is only to confirm the results, and the proposed method is proposed. However, in the second scenario, the effects of PVCSs and the demand response strategy (DR) on this development are considered. Copula probability distribution functions are used to create appropriate scenarios for vehicles during different planning years. The proposed energy management system shows a stable performance in terms of the annual load growth index and electricity price of each level of demand over the time horizon along with minimizing power losses and costs required, which makes PVCS efficiency higher and gives them a suitable structure and stability. The modeling results in terms of uncertainties in the system indicate that the use of load management along with PVCS design and flexible electric vehicle charge control strategies improves power quality parameters and optimizes system cost over a period of 10 years. Compared to the obtained results with the traditional case, it is observed that long-term planning in terms of DR and PVCSs and the technical specifications of the network have been improved. As a result of this proposed long-term planning, PVCSs are more flexible.

A bi-level optimization model for electric vehicle charging strategy based on regional grid load following

Because a greater proportion of large-scale electric vehicles (EVs) are connected to the grid, their stochastic charging load has a significant impact on the power quality and economic operation of the distribution network. However, a random charging load can be transformed into flexible demand response resources through intelligent control of the EV charging process. Therefore, a bi-level optimization model for EV charging is proposed in this study based on the real-time charging price according to the regional grid load, providing more flexible charging strategies for EVs. First, the framework for a bi-level optimization control strategy for EV charging based on the load is developed. Based on the regional grid load, the charging price of each period is optimized in accordance with the load elasticity coefficient of the real-time charging price. Second, an upper-level EV charging price optimization model and a lower-level EV charging load optimization model are established. Third, an optimal control strategy for the scheduling of EV charging is developed, which considers the charging cost of EV users as the objective function and the standard deviation and peak-valley difference of the regional grid load as validation functions. Finally, using a regional power grid in China as the simulation object, the daily operation data of the grid are used to analyze and verify the proposed model. The simulation results demonstrate that the optimized real-time charging price can better respond to the regional grid load, smooth the regional grid load curve, reduce the peak-valley difference, promote clean energy consumption, and further lower the charging cost for EV users.

Assessment of Energy Arbitrage Using Energy Storage Systems: A Wind Park’s Perspective

With the growing application of green energy, the importance of effectively handling the volatile nature of these energy sources is also growing in order to ensure economic and operational viability. Accordingly, the main contribution of this work is to evaluate the revenue potential for wind parks with integrated storage systems in the day-ahead electricity markets using genetic algorithm. It is achieved by the concept of flexible charging–discharging of the Energy Storage System (ESS), taking advantage of the widespread electricity prices that are predicted using a feedforward-neural-network-based forecasting algorithm. In addition, the reactive power restrictions posed by grid code that are to be followed by the wind park are also considered as one of the constraints. Moreover, the profit obtained with a Battery Energy Storage System (BESS) is compared with that of a Thermal Energy Storage System (TESS). The proposed method gave more profitable results when utilizing BESS for energy arbitrage in day-ahead electricity markets than with TESS. Moreover, the availability of ESS at wind park has reduced the wind power curtailment.

Electric vehicle charging stations in the workplace with high-resolution data from casual and habitual users

Problems of poor network interoperability in electric vehicle (EV) infrastructure, where data about real-time usage or consumption is not easily shared across service providers, has plagued the widespread analysis of energy used for transportation. In this article, we present a high-resolution dataset of real-time EV charging transactions resolved to the nearest second over a one-year period at a multi-site corporate campus. This includes 105 charging stations across 25 different facilities operated by a single firm in the U.S. Department of Energy Workplace Charging Challenge. The high-resolution data has 3,395 real-time transactions and 85 users with both paid and free sessions. The data has been expanded for re-use such as identifying charging behaviour and segmenting user groups by frequency of usage, stage of adoption, and employee type. Potential applications include but are not limited to simulating and parameterizing energy demand models; investigating flexible charge scheduling and optimal power flow problems; characterizing transportation emissions and electric mobility patterns at high temporal resolution; and evaluating characteristics of early adopters and lead user innovation.

‘Horror Vacui’ in the Oxygen Sublattice of Lithium Niobate Made Affordable by Cationic Flexibility

The present review is intended for a broader audience interested in the resolution of the several decades-long controversy on the possible role of oxygen-vacancy defects in LiNbO3. Confronting ideas of a selected series of papers from classical experiments to brand new large-scale calculations, a unified interpretation of the defect generation and annealing mechanisms governing processes during thermo- and mechanochemical treatments and irradiations of various types is presented. The dominant role of as-grown and freshly generated Nb antisite defects as traps for small polarons and bipolarons is demonstrated, while mobile lithium vacancies, also acting as hole traps, are shown to provide flexible charge compensation needed for stability. The close relationship between LiNbO3 and the Li battery materials LiNb3O8 and Li3NbO4 is pointed out. The oxygen sublattice of the bulk plays a much more passive role, whereas oxygen loss and Li2O segregation take place in external or internal surface layers of a few nanometers.

Active and Reactive Power Collaborative Optimization for Active Distribution Networks Considering Bi-Directional V2G Behavior

Due to their great potential for energy conservation and emission reduction, electric vehicles (EVs) have attracted the attention of governments around the world and become more popular. However, the high penetration rate of EVs has brought great challenges to the operation of the Active Distribution Network (ADN). On the other hand, EVs will be equipped with more intelligent chargers in the future, which supports the EVs’ high flexibility in both active and reactive power control. In this paper, a distributed optimization model of ADN is proposed by employing the collaborative active and reactive power control capability of EVs. Firstly, the preference of EV users is taken into account and the charging mode of EVs is divided into three categories: rated power charging, non-discharging, and flexible charging–discharging. Then, the reactive power compensation capacity of the plugged-in EV is deduced based on the circuit topology of the intelligent charger and the active–reactive power control model of the EV is established subsequently. Secondly, considering the operation constraints of ADN and the charging–discharging constraints of EVs over the operation planning horizon, the optimization objective of the model is proposed, which consists of two parts: “minimizing energy cost” and “improving voltage profile”. Finally, a distributed solution method is proposed based on the Alternating Direction Method of Multipliers (ADMM). The proposed model is implemented on a 33-bus ADN. The obtained results demonstrate that it is beneficial to achieve lower energy cost and increase the voltage profile of the ADN. In addition, the energy demand of EV batteries in their plugin intervals is met, and the demand preference of EV users is guaranteed.

Flexible Charging of Electric Vehicles: Results of a Large-Scale Smart Charging Demonstration

Flexible charging can be applied to avoid peak loads on the electricity grid by curbing demand of electric vehicle chargers as well as matching charging power with availability of sustainable energy. This paper presents results of a large-scale demonstration project “Flexpower” where time-dependent charging profiles are applied to 432 public charging stations in the city of Amsterdam between November 2019 and March 2020. The charging current on Flexpower stations is reduced during household peak consumption hours (18:00–21:00), increased during the night-time, and dynamically linked to solar intensity levels during the day. The results show that the EV contribution to the grid peak load can be reduced by 1.2 kW per charging station with very limited user impact. The increased charging current during sunny conditions does not lead to a significantly higher energy transfer during the day because of lack of demand and technical limitations in the vehicles. A simulation model is presented based on empirical power measurements over a wide range of conditions combining the flexibility provided by simulations with the power of real-world data. The model was validated by comparing aggregated results to actual measurements and was used to evaluate the impact of different smart charging profiles in the Amsterdam context.