Power Energy Storage Devices Research Articles

Research on Battery Charging and Discharging Control Strategy Based on AGC Scheduling

In this paper, a battery charging and discharging method for AGC scheduling is described. For the practical consideration of the northern region, due to the lack of abundant hydropower resources, it is greatly affected by the temperature in winter and can only be used as a fine-tuning function, so the hydropower effect during the heating period in winter is not considered. Thermal power and battery energy storage devices are established to participate in the AGC scheduling system. The system state is mainly divided into four control states: conventional power supply control state, battery discharge state, battery charging state, and clean energy control state. The working area is judged on the premise that all new energy is connected to the network, and the limit control strategy is used. The lower limit of output of thermal power unit and the limit of capacity of battery unit are critical conditions. Thermal power is the main power and battery is the auxiliary power stability.

Study on the start‐up and fault‐restart strategies and reactive power analysis of DC distribution systems

The DC distribution network is becoming the basic supporting component of the urban distribution network. A variety of power supplies, loads, and energy storage devices can be directly integrated into a DC distribution network, which can improve the economical and energy efficiency of the power system. This study proposes two charging strategies, two-stage charging and one-by-one charging, to make the converter start up safely or quickly return to the normal operation state after the fault clearance. Owing to the existence of numerous DC capacitors in voltage source converters, the reactive power consumption in the start-up process needs to be explicitly calculated. Mathematical expressions of reactive power requirements for different charging strategies are investigated in detail, from where it can be seen that the current-limiting resistance can significantly affect the reactive power and the entire charging time. Simulation results show that the AC voltage can be seriously affected by the oscillation of the reactive power, which will lead to voltage drop and waveform distortion in mode switching.

FeCo-Nx encapsulated in 3D interconnected N-doped carbon nanotubes for ultra-high performance lithium-ion batteries and flexible solid-state symmetric supercapacitors

Lithium-ion batteries and supercapacitors represent the predominant electrochemical power sources and energy storage devices. High-capacity and long-life electrode materials are essential for the next-generation lithium-ion batteries (LIBs) and supercapacitors (SCs) with high power density and high energy density. Herein, FeCo-Nx doped hollow shelled polyhedrons excessively covered with a 3D network of carbon nanotubes (FeCo–Nx@CNTs) have been successfully developed and investigated as one of the most promising materials for lithium-ion batteries and supercapacitors. We developed a self-template strategy to synthesize a series of FeCo–Nx@CNTs via one step carbonization process of Fe doped ZIF-67 MOF. Such a FeCo-Nx doped 3D network of carbon nanotubes effectively tolerates the volume strain and prevents the metal nanoparticles aggregation. In the interim, the 3D network of porous N-doped carbon nanotubes agrees fast electron transport to accomplish remarkably excellent rate capability. Consequently, the FeCo–Nx@CNTs-1.5 shows excellent electrochemical activity for Li-ion hopping in LIBs and SCs. Additionally, this effort also unveils the synergistic effect of the iron doping on the Li-ion storage capability.

High-Energy and High-Power-Density Potassium Ion Batteries Using Dihydrophenazine-Based Polymer as Active Cathode Material.

Polymeric aromatic amines were shown to be very promising cathodes for lithium-ion batteries. Surprisingly, these materials are scarcely used for designing post-lithium batteries. In this Letter, we investigate the application of the high-voltage poly(N-phenyl-5,10-dihydrophenazine) (p-DPPZ) cathodes for K-ion batteries. The designed batteries demonstrate an impressive specific capacity of 162 mAh g-1 at the current density of 200 mA g-1, operate efficiently at high current densities of 2-10 A g-1, enabling charge and discharge within ∼1-4 min, and deliver the specific capacity of 125-145 mAh g-1 with a retention of 96 and 79% after 100 and 1000 charge-discharge cycles, respectively. Finally, these K-ion batteries with polymeric p-DPPZ cathodes showed rather outstanding specific power of >3 × 104 W kg-1, thus paving a way to the design of ultrafast and durable high-capacity metal-ion batteries matching the increasing demand for highpower and highenergydensity electrochemical energystorage devices.

Energy Optimization Dispatching of Microgrid in The Stand-alone Mode

A microgrid system in the stand-alone mode with photovoltaic, wind turbine, microturbine, fuel cell and energy storage unit is studied. Mathematical models of different distributed power supply and energy storage devices are established. The load demand of the system, the price of purchasing and selling electricity when interacting with the power grid and other constraints are considered. An economic model for optimizing stand-alone operation cost is established. According to the characteristics of the model, an improved genetic algorithm is selected to optimize the nonlinear system. The algorithm has better stability in solving the optimization problem of large state space dimension. The case study show that the proposed economic model is reasonable and the algorithm is effective.

Robust Mixed H 2 / H ∞ Controller Design for Energy Routers in Energy Internet

In this paper, a class of mixed H 2 / H ∞ controller is designed for an energy router (ER) within the scenario of an energy Internet (EI). The considered ER is assumed to have access with photovoltaic panels, wind turbine generators, micro-turbines, fuel cells, diesel engine generators, battery energy storage devices, flywheel energy storage devices, loads, and other ERs. Two types of control targets are considered. First, due to the access of large-scale renewable energy sources, the DC bus voltage deviation within the ER system shall be regulated. Second, an optimal energy management strategy shall be achieved, such that the autonomous power supply-demand balance within each ER is achieved with priority and the rational utilization of controllable power generation devices and energy storage devices are realized. When these objectives are considered simultaneously, the control issues with respect to ER is formulated as a mixed robust H 2 / H ∞ control problem with analytical solutions provided. Several numerical examples are given, and the feasibility and effectiveness of the proposed method are demonstrated.

Multi-Objective Day-Ahead Scheduling of Power Market Integrated With Wind Power Producers Considering Heat and Electricity Trading and Demand Response Programs

The large-scale penetration of renewable energy, such as wind power, brings a lot of economic and environmental benefits to the grid, and it also causes hidden dangers in the reliability and security of the power system due to its uncertainty. As an effective demand-side management method, demand response has unique advantages in smoothing wind power fluctuations and mitigating grid pressure. This paper proposes a new model for the demand response aggregator (DRA) that includes both combined heat and power systems (CHPS) and energy storage devices. DRA can interact with the Independent system operator (ISO) through combined heat and power (CHP) units, energy storage devices, and the heat buffer tank to benefit from the electricity market and the thermal market simultaneously. At the same time, wind power producers (WPP) are modeled to turn wind power that was initially passively consumed into active market participants. The problem is modeled using an improved weighted method, which aims to take the diverse objectives of multiple market participants into account. The proposed model is tested on the modified IEEE RTS-24 test system to analyze the optimal scheduling strategies of each participant in the power market.

Optimal configuration method based on optimal expected power characteristics for micro power supply and energy storage device

In this study, an optimal configuration method based on optimal expected power characteristics for micro power supply and energy storage device is proposed, which takes the minimum average fluctuation rate of the total output power characteristics of renewable micro power supply and microgrid as the optimisation objective, respectively. The proposed method can improve the smoothness of the total output power characteristics of the renewable micro power supplies, and effectively reduce the maximum adjustable power and available capacity of the energy storage devices. At last, the feasibility and effectiveness of the proposed method are verified by the case study results.

DC Railway Simulation Including Controllable Power Electronic and Energy Storage Devices

This paper presents a comprehensive set of steady-state models to be included in power flow simulation studies of dc railway networks. This simulation framework covers all important aspects and features of each element of modern dc railways. The proposed models are simplified to achieve the maximum simulation speed while keeping the required accuracy. Not only nonreversible, controlled, and uncontrolled reversible substations are considered, but also onboard and offboard accumulation systems. The train model can consider the low network receptivity (overvoltage protection for trains equipped with regenerative braking) and overcurrent protection. It is also possible to include in the simulation dc/dc links between nodes of the railway network at the same or different voltage. To date, there is no other work able to conjugate all the mentioned models in a complex multitrain scenario.

Flexible Carbon Cloth Based PPy-Ag Nanoparticles Composite Film for Supercapacitors

Polypyrrole-Ag nanoparticles composite film was prepared based on flexible carbon cloth as substrate using silver nitrate as oxidizing agent through simple one-pot chemical synthesis method. The composite sample was characterized by scanning electron microscopy, X-ray diffraction, cyclic voltammetry and galvanostatic charge-discharge techniques. The electrochemical measurements showed such an electrode had a specific capacitance of 257 F g−1 and good cycle stability at a discharge current density of 1 A g−1. The composite electrode also had a wide working potential window, which can be applied in the field of power energy storage devices.

N/S co-doped three-dimensional graphene hydrogel for high performance supercapacitor

Doping and high specific area are essential to the performance of supercapacitor electrode materials. However, the conventional single doping in two dimensional electrode materials is still unable to get high supercapacitive performance. Here we report a facile hydrothermal process using ammonia as a source of nitrogen (N) and thiourea as a sulfur (S) source to prepare N/S co-doped three dimensional (3D) graphene hydrogel (N/S-3DGH) for supercapacitor electrode application. The as-prepared N/S-3DGH is uniform and stable. The N/S co-doped 3DGH electrode material exhibits a high specific capacity of 1063 Cg-1 at a current density of 1 Ag-1. Even at a density of 20 Ag-1, it can still hold an excellent charge and discharge cycling stability, and with 76% of initial capacity retained after 6000 charge and discharge cycles at a density of 10 Ag-1. Moreover, the all-symmetric solid-state supercapacitor fabricated by N/S-3DGH without any binders owned an energy density of 6.25 Wh kg−1 at a power density of 500 W kg−1 showing very promising applications for portable power and flexible energy storage devices.

Tailoring the Kinetics of Sn Anodes for High Power Energy Storage Devices

Alkali ion batteries, such as Li-ion batteries (LIBs) and Na-ion batteries (NIBs), have recently drawn much attention due to their high energy densities, high Coulombic efficiencies and low self-discharge rates, making them useful in electronics, electric vehicles and grid-scale energy storage. One of the major obstacles to widespread applications of these rechargeable batteries, however, is their poor electrochemical performance under high power densities. The obstacle is attributed to the sluggish electrochemical kinetics, including slow diffusion rate of alkali ions in solid electrodes, low electrical conductivity and undesired phase transformation. Sn-based anodes having both high gravimetric and volumetric capacities are considered a promising candidate for next-generation LIBs and NIBs, but they also face the same challenge. Herein, we demonstrate that the electrochemical kinetics of Sn-based anodes, such as SnO2 and SnS2, can be largely enhanced by amorphization, doping of heteroatoms and facilitating the pseudocapacitive charge storage. The mechanistic insight of the enhanced kinetics is revealed by combining the electrochemical measurements with in situ TEM characterization and the first-principles calculations. Thanks to the new findings, we successfully fabricate Sb-doped SnO2/graphene-CNT aerogel anodes which deliver a high areal capacity of 2.6 mAh cm-2 at a high current density of 8 mA cm-2 in LIBs. The Na hybrid capacitor consisting of an activated carbon cathode and a SnS2/graphene-CNT aerogel anode is further developed for applications requiring high power densities and low costs. The as-assembled hybrid capacitor delivers an exceptional energy density of 26.9 Wh kg−1 at an ultrahigh power density of 6053 W kg−1. The implications of these discoveries for both fundamental understanding and practical applications are discussed.

Hollow Structural Transition Metal Oxide for Advanced Supercapacitors

AbstractElectrochemical capacitors (supercapacitors, SCs), have been deemed to be one of the most promising powerful electrochemical energy storage devices, owing to that SCs have long cycle lives, high power densities, and fast recharge capabilities. Transition metal oxide is one of the most promising electrode materials in the application of SCs, but the poor active surface areas limit their electrochemical performances. Particularly, hollow structures can enhance their active surface areas and porosity for better transportation. In this review, the development regarding hollow structures of the metal oxide, metal oxide complex, and carbon–metal oxide complex is discussed. Furthermore, performances of these materials applied in SCs are tested in various systems, and their electrochemical performances are introduced and compared. The disadvantages of SCs based on hollow metal oxide materials are also discussed, and the various solutions are provided.

Pseudocapacitive layered iron vanadate nanosheets cathode for ultrahigh-rate lithium ion storage

Pseudocapacitive charge storage has been regarded as a promising mechanism to achieve both high specific energy and power energy storage devices. Some pseudocapacitive anode materials show great high-rate performance, however, it remains a significant challenge to develop the cathode ones. Herein, for the first time, we report a layered iron vanadate (Fe5V15O39(OH)9⋅9H2O, named as kazakhstanite) nanosheets (FeVO NSs) with featuring ultrathin layer thickness (< 10 nm). The FeVO NSs are synthesized by a facile wet-chemical approach with a high yield. Compared to the FeVO nanoparticles, the crystalline layered FeVO NSs have additional interlayered Li+ storage sites, leading to the enhanced capacity. Ex-situ X-ray diffraction results demonstrate a non-phase change process and there is only ~ 1.1% layer expansion/shrinkage during lithiation and delithiation process. Based on detail kinetics analysis and ex-situ X-ray photoelectron spectroscopy results, it is found that over 70% of total capacity is pseudocapacitive contribution, which contributes to the ultrahigh-rate capability (a high capacity of 350, 273 and 90 mAh g−1 is achieved at 0.1, 1 and 20 A g−1, respectively) and excellent cycling stability over thousands of cycles. This work presents the high performance vanadate material that delivers highly pseudocapacitive behavior, and provides a promising direction to realize both high energy and high power lithium storage.

Hamiltonian methods of modeling and control of AC microgrids with spinning machines and inverters

This paper presents a novel approach to the modeling and control of AC microgrids that contain spinning machines, power electronic inverters and energy storage devices. The inverters in the system can adjust their frequencies and power angles very quickly, so the modeling focuses on establishing a common reference frequency and angle in the microgrid based on the spinning machines. From this dynamic model, nonlinear Hamiltonian surface shaping and power flow control method is applied and shown to stabilize. From this approach the energy flow in the system is used to show the energy storage device requirements and limitations for the system. This paper first describes the model for a single bus AC microgrid with a Hamiltonian control, then extends this model and control to a more general class of multiple bus AC microgrids. Simulation results demonstrate the efficacy of the approach in stabilizing and optimization of the microgrid.

Rational Design of Nickel Hydroxide‐Based Nanocrystals on Graphene for Ultrafast Energy Storage

AbstractCompact, light, and powerful energy storage devices are urgently needed for many emerging applications; however, the development of advanced power sources relies heavily on advances in materials innovation. Here, the findings in rational design, one‐pot synthesis, and characterization of a series of Ni hydroxide‐based electrode materials in alkaline media for fast energy storage are reported. Under the guidance of density functional theory calculations and experimental investigations, a composite electrode composed of Co‐/Mn‐substituted Ni hydroxides grown on reduced graphene oxide (rGO) is designed and prepared, demonstrating capacities of 665 and 427 C g−1 at current densities of 2 and 20 A g−1, respectively. The superior performance is attributed mainly to the low deprotonation energy and the facile electron transport, as elaborated by theoretical calculations. When coupled with an electrode based on organic molecular‐modified rGO, the resulting hybrid device demonstrates an energy density of 74.7 W h kg−1 at a power density of 1.68 kW kg−1 while maintaining capacity retention of 91% after 10,000 cycles (20 A g−1). The findings not only provide a promising electrode material for high‐performance hybrid capacitors but also open a new avenue toward knowledge‐based design of efficient electrode materials for other energy storage applications.

Optimal operation of a micro-grid containing energy resources and demand response program

In profit-based unit commitment, the objective of programming is to maximize profit and optimize generation. Practically, the gross profit depends not only on the revenue but also on the total expenditures. In this article, an efficient algorithm is suggested to assess the effect of uncertainties in determining 24-hour optimal strategy of a microgrid (MG) containing wind farms, photovoltaic, fuel cell, combined heat and power units, boiler, and energy storage devices (ESDs). The optimization problem is presented to determine the optimal points for the energy resources generation and to maximize the expected profit considering demand response (DR) programs and uncertainties. The uncertainties include wind speed, photovoltaic power generation (PVPG), market price, power, and thermal load demand. For modeling uncertainties, an effort has been made to predict uncertainties through the hybrid method of wavelet transform (WT)-artificial neural network (ANN)-imperialist competitive algorithm (ICA). In this study, three cases are assessed to confirm the performance of the proposed method. In the first case study, programing MG is isolated from the grid. In the second case study, which is grid-connected mode the WT-ANN-ICA and WT-ANN uncertainties predictions methods are compered. In the third case, which is grid-connected mode the effect of DR programs on the expected profit of energy resources is assessed.

Multihierarchical Structure of Hybridized Phosphates Anchored on Reduced Graphene Oxide for High Power Hybrid Energy Storage Devices

A multihierarchical structure with (NH4)(Ni, Co)PO4·0.67H2O microplatelets and (Ni, Co)3(PO4)2·8H2O ultrathin nanopieces anchored on reduced graphene oxide (NCNP/RGO) is synthesized via a mild hydrothermal approach. This unique interface-rich structure is suitable for a high power energy storage device by providing efficient pathways for both electronic conduction and ionic transportation, which are effective ways to improve the electrochemical performance. Specifically, a specific capacity of 993 F g–1 is obtained in the three-electrode measurement, with ultrahigh capacity retention of 81.2% (807 F g–1) from 0.5 to 32 A g–1. The hybrid device constructed with the as-prepared NCNP/RGO as anode and a hierarchical porous carbon (HPC) as cathode offers a very superior energy density of 42.1 Wh kg–1 at a power density of 73 W kg–1, which remains 32 Wh kg–1 at 14 kW kg–1. Meanwhile, the as-prepared hybrid capacitor exhibits a remarkable cycling stability (96.5% capacitance retention after 10 000 cycles). The c...

Poultry Farm Cooling System Based Hybrid DC Microgrid

Since the fossil fuel exhausting and causes environmental problems, renewable energy is developing rapidly. More and more importance has been given in power generation through Renewable Energy Resources (RERs) worldwide to reduce the global warming. Many research works on DC microgrid have been conducted to facilitate the integration of various Distributed Energy Resources (DERs) and Energy Storage System (ESS). In recent years, the research attention on DC grids has been resurging due to technological advancements in power electronics and energy storage devices, and increase in the variety of dc loads and the penetration of DERs such as wind, solar, fuel cells and bio-gas etc., Many research activities are being done to harness more generation from DERs and flexible control of the above generation. An Adaptive Neuro-Fuzzy Inference System (ANFIS) based Energy Management System (EMS) is proposed to control inverters in Grid connected hybrid DC microgrid system. The hybrid system consists of Wind Turbines (WTs) and Solar Photovoltaic (PV) as a primary energy sources. The Grid connected DC microgrid system is designed to satisfy the load requirement efficiently and in case if the demand is low it will return the excess power to the AC Grid also. The operational capability of proposed Hybrid DC microgrid design concept is verified through various test conditions and the results obtained are discussed.

High Performance, Biodegradable Electrochemical Capacitors for Transient Electronics

Various electronic devices with high performance and advanced structures have been effectively integrated into a functional electronic system owing to their miniaturization. In particular, extensive research on miniaturized devices that gradually lose their functionality by dissolution in water/biofluid has been recently conducted, which would accelerate the development of eco-friendly as well as bio-implantable devices for transient electronics. To satisfy the technological demand for continuous powering of implanted devices in the human body regardless of the time and place, the development of high performance wireless power generation and energy storage devices is required. Supercapacitors, so-called next-generation energy storage devices, can be used in the event of unexpected power-off owing to their superior power density and long cycling lifetimes compared to batteries. Therefore, the application of transient supercapacitors as devices essential to integrated electronic circuits in the human body is expected to play an important role in the advancement of independent and sustainable transient electronics. Here, we introduce the fabrication and applications of fully biodegradable microsupercapacitors (MSCs) consisting of interdigitated water-soluble metal (W, Fe, and Mo) electrodes, a hydrogel electrolyte (agarose gel), and a biodegradable poly(lactic-co-glycolic acid) (PLGA) substrate, encapsulated with thin films of PLGA and polyanhydride. In particular, this unusual energy storage device based on 300 nm thick Mo electrode exhibits electrochemical performance with a areal capacitance of 1.6 mF/cm2, energy density of 0.14 µWh/cm2, and power density of 1.0 mW/cm2. Such high performance is attributed to the pseudocapacitance originating from the metal-oxide film generated by electrochemical corrosion at the interface between the metal electrode and the water-containing agarose gel electrolyte, during repeated charge/discharge cycles. The oxidation states of those oxide layers are confirmed to be WO3, Fe2O3, and MoO3, respectively, via taking scanning electron microscope images and x-ray photoelectron spectra. The dissolution kinetics of all components of the MSCs are measured in phosphate-buffered saline at body temperature and an encapsulation strategy is suggested to control the functional lifetimes of the MSCs. Finally, we demonstrate the potential applications of the fabricated biodegradable MSCs as transient energy storage devices by illuminating a light-emitting diode and as a transient capacitor in integrated circuits for wireless power transmission.