Supercapacitor Charging Research Articles

Highly Scalable Fabrication of Planar-Type Thermally Chargeable Supercapacitor Based on Graphene Oxide

The development of efficient and sustainable energy sources has become important to power the rapidly growing portable electronic devices. Newly developed thermally chargeable supercapacitors that can be charged by heat energy including human body heat have great potential to become standalone power sources for wearable electronics. However, the complex fabrication process of electrodes and devices limits the cost-effectiveness and scalability for widespread application. Here we demonstrate highly scalable fabrication of planar-type thermally chargeable supercapacitor (pTCSC) by using one-step laser printing method on graphene oxide films with a general DVD burner. We utilized the Soret effect in graphene oxide (GO) films, producing a very high thermally induced voltage (9 mV/K) under a temperature gradient. With a temperature gradient of 10 K, pTCSC device achieved a thermally charged voltage of 58 mV and stored charge of 154 µC/cm2. Also, higher voltage is thermally charged by simply connecting the multiple devices in series. We believe that our scalable fabrication of pTCSC devices suggests a future direction of sustainable energy devices utilizing thermal energy.

Intercalated graphene oxide for flexible and practically large thermoelectric voltage generation and simultaneous energy storage

We report a new planar-type “thermally” chargeable supercapacitor (pTCSC) that can be charged by converting thermal energy into electricity without an external electrical power supply. The pTCSC was fabricated using a facile and scalable laser irradiation on graphene oxide films intercalated by sulfate ions (SGO) to control the mobility and concentration of dissociated protons without any liquid-phase electrolytes typically used in conventional supercapacitors. We utilized the Soret effect as a dominant transport mechanism for producing a very high thermally induced voltage up to 9 mV/K, compared with typically much lower thermoelectric voltages mainly from the Seebeck effect in traditional inorganic and organic thermoelectric materials. The key parameters to obtain the strikingly high thermopower with decent electrical conductivity were identified to be the improved mobility and concentration of proton. At the same time, the harvested electrical energy was stored on the reduced SGO electrodes. With a temperature gradient of 10.5 K, our “single” pTCSC device generated a large thermally charged voltage of 58 mV without electrical power supply. We also demonstrated that an array of pTCSC can be batch-fabricated and connected together to linearly raise the output voltage as large as 2.1 V, suggesting excellent suitability for roll-to-roll mass manufacturing of practical pTCSC. We demonstrated that it is feasible to operate an electrochromic device that darkens with power supply like a smart window using the batch-fabricated pTCSC when a temperature gradient is applied. Our results suggest that the pTCSC could eliminate needs for battery replacement and wired connections to power lines for various distributed electronic systems whenever and wherever a temperature gradient is present.

Радиационно-индуцированное разделение и накопление электрического заряда в суперконденсаторах

Радиационно-индуцированное разделение и накопление электрического заряда в суперконденсаторах

Predictive energy management of fuel cell supercapacitor hybrid construction equipment

The application of fuel cell hybrid construction equipment (FCHCE) represents an attractive option for future industrial development. Construction equipment has highly repetitive modes of operation, which can be used for predictive control. However, the loads usually change markedly and frequently, leading to adverse scenarios for energy management. In this paper, we focus on alleviating this problem by presenting a predictive energy management strategy based on a model predictive control (MPC) framework for FCHCE. The supervisory-level energy management objectives are to respond to rapid variations in the load of the construction equipment while minimizing the fuel consumption, improving fuel cell durability, and maintaining the state of charge (SoC) of supercapacitors within the allowable bounds. To improve the performance and practicality of the predictive controllers, we present two power demand prediction methodologies based on Markov chains and neural networks. Simulations are carried out on the representative driving cycles of a wheel loader. Simulation results validate the feasibility and effectiveness of the proposed MPC. Neural network model made better predictions than the Markov chain model, which is preferable when modeling comprehensive driving cycles.

Simultaneous active and reactive power compensation using STATCOM with supercapacitor energy storage system

STATCOM is taking challenges skilfully in the field of power system to maintain the AC bus voltage constant and to compensate for reactive power. When the STATCOM is integrated with energy storage device through DC/DC buck-boost converter, it compensates the active power also. In this paper, the regulation of DC link voltage to its rated value has been done to compensate simultaneous active and reactive power demanded by the load. The circuit model, mathematical expressions and MATLAB/Simulation model based on the mathematical model has been analysed. The hysteresis current control (HCC) strategy is used to generate the pulses for the 6-pulse 2-level voltage source converter (VSC). The conventional PI controller is used to generate the reference current direct and quadrature axis components. The PI controller is also used to generate the modes, whether it works in buck mode or boost mode. These modes decide the charging and discharging of supercapacitor. Here total reactive power is taken by STATCOM and the grid reactive power is near to zero and hence the burden on the grid is drastically reduced.

Simultaneous active and reactive power compensation using STATCOM with supercapacitor energy storage system

STATCOM is taking challenges skilfully in the field of power system to maintain the AC bus voltage constant and to compensate for reactive power. When the STATCOM is integrated with energy storage device through DC/DC buck-boost converter, it compensates the active power also. In this paper, the regulation of DC link voltage to its rated value has been done to compensate simultaneous active and reactive power demanded by the load. The circuit model, mathematical expressions and MATLAB/Simulation model based on the mathematical model has been analysed. The hysteresis current control (HCC) strategy is used to generate the pulses for the 6-pulse 2-level voltage source converter (VSC). The conventional PI controller is used to generate the reference current direct and quadrature axis components. The PI controller is also used to generate the modes, whether it works in buck mode or boost mode. These modes decide the charging and discharging of supercapacitor. Here total reactive power is taken by STATCOM and the grid reactive power is near to zero and hence the burden on the grid is drastically reduced.

Implementation of an Energy Management in DSPACE for a Fuel Cell -Ultracapacitor Vehicle

This article presents an energy management of an electric hybrid vehicle using a fuel cell (FC) as the primary energy source and an ultracapacitor (UC) as the auxiliary source. Both energy sources are characterized by a low voltage which is generally not sufficient to be exploited on electrical vehicle. Consequently, using a power converter is required to interface the energy source to the DC bus. For the energy management strategy, it is used to determine the converter current of each source so as to share accurately the power between the two electrical sources, according to the requested power (Traction or braking) and the state of charge of supercapacitor. The proposed method has the capability to minimize the hydrogen consumption and increase the fuel cell time. The suggested algorithm is applied to for the New European Driving Cycle (NEDC) and. implemented in dspace controller. Simulation and experimental results prove the significant reduction of the hydrogen.

Heuristic Versus Optimal Charging of Supercapacitors, Lithium-Ion, and Lead-Acid Batteries: An Efficiency Point of View

Electrical energy storage systems are extensively utilized in applications, including electrified vehicles, renewable power generation, and electronic devices. While discharging events are a function of the power demand, the charging procedure is often controllable. This paper evaluates different charging strategies for stand-alone supercapacitors (SCs), lithium-ion (Li-ion), and lead-acid batteries. Constant power and optimal charging strategies are formulated and the corresponding charging currents are obtained. Efficiency analysis for different charging strategies and charging times (slow and fast) is performed. The identical objective function for all modules is to minimize the resistive losses during a given charging time by utilizing Pontryagin’s minimum principle. An analytical solution exists for the SC case, which is constant current charging. The variation of the total internal resistance with state of charge in lead-acid chemistry is considerable, and the optimal charging problem results in a two-point boundary value problem. In case of the Li-ion battery, the model includes the electronic as well as polarization resistance. Furthermore, in order to investigate the influence of temperature on the optimal charging of the Li-ion battery, a constrained optimal control problem for a three state electrothermal model is formulated and solved using dynamic programming.

Research and Application of Supercapacitor Charging System

Based on the special power supply requirements of the project, the AD8210YRZ (current monitoring operational amplifier) monitors the charging current in real time, and its output is fed back to the detection pin of the TPS5430DDA to adjust the charging voltage of the capacitor. Combined with the charge-discharge characteristics of the super capacitor, the circuit realizes high current constant current charging at low voltage and constant voltage charging when the capacitor terminal voltage increases. This method can effectively and reasonably improve the charging efficiency of the super capacitor and meet the design requirements. The product has been put into use and achieved good results.

Thermally chargeable supercapacitor based on nickel-coated nanoporous carbon

ABSTRACTNanoporous carbon is coated by pure nickel via an electroless plating method. The nanoporous carbon provides a high-surface-area substrate, leading to a large capacitance; the nickel surface layer is of a high work function, resulting in a thermally sensitive electrode potential. Such a system is ideal for thermally chargeable supercapacitor (TCS) system, which converts low-grade heat (LGH) to electrical energy. The specific energy per thermal cycle per gram of electrode mass is ~1.8 mJ, with a temperature difference of 50°C.

Estimation of Supercapacitor Charge Capacity Bounds Considering Charge Redistribution.

This paper investigates the impact of charge redistribution on supercapacitor charge capacity by experimentally estimating the charge capacity bounds. An analysis of a physics-based RC ladder circuit model for supercapacitors reveals the theoretical bounds and provides guidelines for designing experiments to estimate the bounds. The upper bound corresponds to a long time constant voltage charging process and the lower bound is established using a charging process with the largest possible current. Bounds of two types of supercapacitor charge capacity are estimated: the total charge stored in the supercapacitor that can be released during multiple discharging processes and the utilized charge delivered during one discharging action. The relationship between the utilized charge capacity and the discharge current is examined and different patterns are observed depending on the supercapacitor state of charge (SOC). For a fully charged supercapacitor, the utilized capacity increases when the discharge current decreases. For a supercapaictor partially charged by a relatively large current, the utilized capacity is dependent on both the discharge current and the supercapacitor operation voltage range. The difference between the bounds is significant for both types of charge capacity. These observations provide guidelines for optimizing the supercapacitor charging and discharging policies for different applications.

Synchronized Cell-Balancing Charging of Supercapacitors

As a classical cell balancing solution in low-power supercapacitor applications, the switched resistor circuit is vulnerable to resistance deviation effects with existing cell balancing methods. In this paper, we propose a synchronized cell balancing method for switched resistor circuits based on the consensus theory and a cyber-physical approach, with the aim of synchronizing cell voltages before they are fully charged. It is shown that the proposed cell-balancing algorithm is robust to resistance deviation effects. Extensive simulations are provided to show the effectiveness of the proposed method.

Investigation of Energy Scavenging Interface Circuit for Embedded Systems in WSN

Objectives: To investigate and design energy scavenging interface circuit for embedded systems focus on wireless sensor network (WSN) using photovoltaic cell. Experimenting with storage elements like super capacitors. Methods/ Statistical Analysis: Embedded systems in wireless sensor networks are the sensor node which plays an important role in monitoring applications. These sensor nodes are battery powered and have limited lifetime. To increase the lifetime of the sensor node energy scavenging is a better solution along with storage element like super capacitor and rechargeable batteries. In the presented work sensor node power requirements are calculated and based on calculations a solar energy scavenging interface circuit was designed and experimented. Findings: Performance analysis of photovoltaic cell and proposed circuit was done successfully with super capacitor as storage element. Charge and discharge characteristics of the super capacitors shows that the sensor node lifetime can be increased significantly and keep it alive for almost full day. Presented work outlines our real-time experiences with the energy scavenging interface circuit in terms of simulation and experimental work. Novelty/Improvement: The proposed system will work as a base for further experimentation to improve the scavenger design in wireless sensor network. Larger value of super capacitor can improve the system performance. More experiments can be done by having both options of super capacitor and rechargeable batteries.

State-Of-Charge Evaluation Of Supercapacitors

In the last years, energy storage systems are increasingly involved in applications in which they are required to deliver or adsorb significant charging or discharging currents in short intervals of time, typically a few seconds. Thanks to their high specific power, supercapacitors may represent one of the most promising technologies for this kind of applications. However, one of the main concerns regarding their operation is the accurate estimation of their state of charge; the most common technique, based on ampere-hour counting, typically requires some correction mechanisms, since it implies a significant loss of accuracy over time, due to the accumulation of measuring errors.In the present paper, a novel algorithm to assess the state of charge of supercapacitors is described and implemented. The algorithm is based on the evaluation of the parameters of an equivalent electric circuit of the supercapacitor, and on the consequent use of a Luenberger-style technique for the runtime evaluation of its state of charge, based on the measure of current and voltage at supercapacitor's terminals. The algorithm estimates the cell open circuit voltage while the current is highly variable, as typical in power-oriented applications, hence the corresponding state of charge.

Ionic Thermoelectric Figure of Merit for Charging of Supercapacitors

Thermoelectric materials enable conversion of heat to electrical energy. The performance of electronic thermoelectric materials is typically evaluated using a figure of merit ZT = σα2T/λ, where σ is the conductivity, α is the so‐called Seebeck coefficient, and λ is the thermal conductivity. However, it has been unclear how to best evaluate the performance of ionic thermoelectric materials, like ionic solids and electrolytes. These systems cannot be directly used in a traditional thermoelectric generator, because they are based on ions that cannot pass the interface between the thermoelectric material and external metal electrodes. Instead, energy can be harvested from the ionic thermoelectric effect by charging a supercapacitor. In this study, the authors investigate the ionic thermoelectric properties at varied relative humidity for the polyelectrolyte polystyrene sulfonate sodium and correlate these properties with the charging efficiency when used in an ionic thermoelectric supercapacitor (ITESC). In analogy with electronic thermoelectric generators, the results show that the charging efficiency of the ITESC can be quantitatively related to the figure of merit ZTi = σiαi2T/λ. This means that the performance of ionic thermoelectric materials can also be compared and predicted based on the ZT, which will be highly valuable in the design of high‐performance ITESCs.

Reversible Heating in Electric Double Layer Capacitors.

A detailed comparison is made between different viewpoints on reversible heating in electric double layer capacitors. We show in the limit of slow charging that a combined Poisson-Nernst-Planck and heat equation, first studied by d'Entremont and Pilon [J. Power Sources 246, 887 (2014)JPSODZ0378-775310.1016/j.jpowsour.2013.08.024], recovers the temperature changes as predicted by the thermodynamic identity of Janssen etal. [Phys. Rev. Lett. 113, 268501 (2014)PRLTAO0031-900710.1103/PhysRevLett.113.268501], and disagrees with the approximative model of Schiffer etal. [J. Power Sources 160, 765 (2006)JPSODZ0378-775310.1016/j.jpowsour.2005.12.070] that predominates the literature. The thermal response to the adiabatic charging of supercapacitors contains information on electric double layer formation that has remained largely unexplored.

Supercapacitor charge redistribution analysis for power management of wireless sensor networks

To support many power management applications in wireless sensor networks, a previously developed model is modified to predict the terminal behaviour of a supercapacitor under a dynamic charging/discharging power profile. In addition, a robust model parameter identification method based on the genetic algorithm is developed to determine the model parameters using a dynamic test and a self-discharge experiment. On the basis of the supercapacitor power input model, charge redistribution related figures of merit are derived and used to evaluate the significance of charge redistribution for supercapacitors with various rated capacitance. The results show that supercapacitors with different sizes share similar charge redistribution phenomenon. Furthermore, the charge redistribution significance is studied from several perspectives to provide guidelines for designing power management techniques that can achieve full potential of the energy stored in the supercapacitors.

Designing and Testing Composite Energy Storage Systems for Regulating the Outputs of Linear Wave Energy Converters

Linear wave energy converters generate intrinsically intermittent power with variable frequency and amplitude. A composite energy storage system consisting of batteries and super capacitors has been developed and controlled by buck-boost converters. The purpose of the composite energy storage system is to handle the fluctuations and intermittent characteristics of the renewable source, and hence provide a steady output power. Linear wave energy converters working in conjunction with a system composed of various energy storage devices, is considered as a microsystem, which can function in a stand-alone or a grid connected mode. Simulation results have shown that by applying a boost H-bridge and a composite energy storage system more power could be extracted from linear wave energy converters. Simulation results have shown that the super capacitors charge and discharge often to handle the frequent power fluctuations, and the batteries charge and discharge slowly for handling the intermittent power of wave energy converters. Hardware systems have been constructed to control the linear wave energy converter and the composite energy storage system. The performance of the composite energy storage system has been verified in experiments by using electronics-based wave energy emulators.

Comparative Analysis of Resonant Converters for Energy Storage Systems

The following paperwork presents a comparative analysis of multiphase resonant converters for applications in energy storage systems. Models of the examined converters are developed in the software environments of MATLAB and LTspice. Results from the simulation examination of the converters during charging of supercapacitors and rechargeable batteries are presented. These results are compared to results obtained from experimental examination of the converters via a laboratory stand. For the purposes of the experimental examination, a control system is developed on the base of a virtual instrument in LabVIEW. The advantages and disadvantages of the different converters are discussed.

Promoting power density by cleaving LiCoO2 into nano-flake structure for high performance supercapacitor.

LiCoO2 (LCO) usually can deliver high energy density but low power density in Li-ion batteries (LIBs). Whether LCO could be used as electrode material for high-performance supercapacitors is dependent on promoting its power density. Owing to Faradaic redox reactions taking place on its surfaces or inside crystals through ion intercalation/deintercalation from the surfaces, increasing the specific area of LCO is a key factor to promote its rate capability. Herein, we report a facile strategy to prepare LCO nano-flakes with high specific area exceeding that of currently used micro-scale particles in LIBs. LCO as a nano-flake structure is expected to have a high fraction of Li atom exposure, which benefits fast redox reactions taking place on the surfaces. An LCO-based electrode exhibits an excellent specific capacitance of 581.3 F g-1 at 0.5 A g-1, high power density of 2262 W kg-1 at an energy density of 41.0 Wh kg-1, and good cycling stability (83.9% capacitance retention at 6 A g-1 after 2000 cycles) in LiCl aqueous electrolyte. Faradaic redox behaviors have been analyzed, indicating an ideal diffusion-controlled process. Moreover, a full solid-state symmetric supercapacitor is assembled using LCO nano-flake-based electrodes, which presents good performance with light weight and flexibility. Impressively, three charged supercapacitors in series can light 100 green light emitting diodes for 14 min. LCO in nano-flake structure form with high power density could be an excellent material for superior supercapacitors.