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Ultracapacitors have been attracting interest to apply as energy storage devices with advantages of fast charging capability, high power density, and long lifecycle. As a storage device, accurate monitoring is required to ensure and operate safely during the charge/discharge process. Therefore, high accuracy estimation of the state of charge (SOC) is needed to keep the Ultracapacitor working properly. This paper proposed SOC estimation using the Adaptive Neuro-Fuzzy Inference System (ANFIS). The ANFIS is tested by comparing it to true SOC based on an equivalent circuit model. To find the best method, the ANFIS is modified and tested with various membership functions of triangular, trapezoidal, and gaussian. The results show that triangular membership is the best method due to its high accuracy. An experimental test is also conducted to verify simulation results. As an overall result, the triangular membership shows the best estimation. Simulation results show SOC estimation mean absolute percentage error (MAPE) is 0.70 % for charging and 0.83 % for discharging. Furthermore, experimental results show that MAPE of SOC estimation is 0.76 % for random current. The results of simulations and experimental tests show that ANFIS with a triangular membership function has the most reliable ability with a minimum error value in estimating the state of charge on the Ultracapacitor even under conditions of indeterminate random current.

The growing penetration of converter-interfaced distributed renewable energy sources (CI-DRES) has posed several challenges into the electric power systems, e.g., the instability caused by the intermittent nature of the primary sources, power quality issues, etc. Several algorithms have been proposed to mitigate the CI-DRES power fluctuations and reduce high active power ramp-rates (RRs) at the point of common coupling (PCC) with the grid using energy storage systems (ESS). However, these algorithms present some drawbacks. In this article, a new ramp-rate limitation (RRL) control method is proposed to address existing gaps in the technical literature. This algorithm is performed considering the connection of a supercapacitor (SC) at the dc-link of a DRES converter. The relationship between the SC voltage and the degree to which the RRL is achieved is established, aiming to reduce the SC voltage fluctuations and increase the SC life time. The RRL control is validated in a real experimental testbed and compared to state-of-the-art approaches. This control is also modeled in Matlab/Simulink in order to perform techno-economic investigations on the influence that several parameters (SC size, SC charging/discharging cycles, cost, etc.) have on the achieved RRL at the DRES PCC. [ABSTRACT FROM AUTHOR]

Summary: Carbon and metal oxide nanocomposites have been extensively studied as electrode materials to develop energy and power‐dense supercapacitors in recent years. Nevertheless, nano carbons with improved porosity and functional moieties are the most eco‐friendly and cost‐effective supercapacitor materials. In this work, carbon nano‐onions (CNOs) synthesized by a single‐step flame soot collection method, subsequently calcined at 600°C in an inert environment (CNO‐600), are used as electrode material for the supercapacitors. CNO‐600 s have a layer‐by‐layer nano onion structure with a ~25 nm particle size and a Brunauer–Emmett–Teller surface area of 147 m2 g−1. CNO‐600 delivers 266 and 186 F g−1 of capacitance at 0.5 A g−1 for half cells and symmetric ultracapacitors, respectively. Ultracapacitors show capacitance retention of 91% with 20 000 GCD cycles in 1 M H2SO4 electrolyte. The stable capacitance of CNO‐600 is due to easy intercalation/de‐intercalation of electrolyte ions and electrons in the layer‐by‐layer structure of CNOs, contributing to pseudocapacitive charge storage with electric double layer capacitor behavior. The lead‐carbon hybrid ultracapacitor fabricated using CNO‐600 as anode material and PbO2 as cathode delivers a specific capacitance of 515 F g−1 at 1 A g−1 in 4.5 M H2SO4 electrolyte in the voltage range of 2.3 and 0.6 V. The substantial improvement of charge storage in CNO‐based symmetric and lead‐carbon hybrid system, demonstrate an excellent opportunity for the development of high‐performance supercapacitors. [ABSTRACT FROM AUTHOR]

The power output obtained from the hydrokinetic renewable system fluctuates with changes in weather conditions, which could cause adverse effects on the voltage, frequency and stability of the electrical grid. In this article, an evaluation of power smoothing is performed for a renewable hydrokinetic on grid system using a supercapacitor. The power fluctuations are mitigated and smoothed by the proposed energy control and supplied to the utility grid and household load. Moreover, this paper studies the impact of the temporal resolution of data sampling with respect to the self-consumption of prosumers under technical, economic and environmental parameters using Matlab/Simulink software. The simulation results show that the fluctuations of the hydrokinetic turbine output power can be significantly mitigated, using the supercapacitor based storage system for different temporal resolutions reducing up to 90% of power peaks and power fluctuations produced by the hydrokinetic turbine and the load. Besides, the use of supercapacitors allows increasing the self-consumption of prosumers up to 17.27% for time resolutions of 1 min. Finally, the proposed control reduces up to 0.54 kgCO 2 /day at cost of energy 0.15 USD/kWh. [Display omitted] [ABSTRACT FROM AUTHOR]

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Choice of hybrid electric vehicles (HEVs) in transportation systems is becoming more prominent for optimized energy consumption. HEVs are attaining tremendous appreciation due to their eco-friendly performance and assistance in smart grid notion. The variation of energy storage systems in HEV (such as batteries, supercapacitors or ultracapacitors, fuel cells, and so on) with numerous control strategies create variation in HEV types. Therefore, choosing an appropriate control strategy for HEV applications becomes complicated. This paper reflects a comprehensive review of the imperative information of energy storage systems related to HEVs and procurable optimization topologies based on various control strategies and vehicle technologies. The research work classifies different control strategies considering four configurations: fuel cell-battery, battery-ultracapacitor, fuel cell-ultracapacitor, and battery-fuel cell- ultracapacitor. Relative analysis among different control techniques is carried out based on the control aspects and operating conditions to illustrate these techniques’ pros and cons. A parametric comparison and a cross-comparison are provided for different hybrid configurations to present a comparative study based on dynamic performance, battery lifetime, energy efficiency, fuel consumption, emission, robustness, and so on. The study also analyzes the experimental platform, the amelioration of driving cycles, mathematical models of each control technique to demonstrate the reliability in practical applications. The presented recapitulation is believed to be a reliable base for the researchers, policymakers, and influencers who continuously develop HEVs with energy-efficient control strategies.

This paper presents the design and implementation of a microcontroller system for the measurement of various environmental parameters such as temperature, humidity, luminosity, air quality, pressure, etc. We target application scenarios that need the deployment of such systems in the open without the availability of an electrical power grid. For this purpose, we put a strong emphasis on the energy efficiency and the development of an autonomous environment-friendly power supply consisting of solar panels and an ultracapacitor. The sensor data transmission is done over the license-free radio frequencies around 433 MHz or 868 MHz. On the software side, a lot of attention is paid to the reliability and the security of the data transmissions by the development of a custom data transmission protocol. Overall, we aim at keeping the production and deployment costs of our system economically feasible for small and medium-sized businesses. The experimental results prove that our approach has much potential and that our systems can be successfully used to build autonomous sensor data gathering networks. [ABSTRACT FROM AUTHOR]

The piezoelectricity allows the generation of electric power taking advantage of the movement of vehicles and pedestrians. Many prototypes have been made with piezoelectric generators, but at present, their commercialization and use have not been popularized due to their low power generation and energy losses. A design of an experimental prototype of an energy harvester with piezoelectric materials that reduces these losses and generates more energy thanks to the resonance with the beams is proposed in this article. An equilateral triangular tile is designed such it will not deform when a force acts on it. The tile has four-cantilever beams, and it is designed to resonate with the natural frequency of the piezoelectric material. This is coupled to the piezoelectric device. The vibration generated on the beam, by a mechanical load, is used to generate more energy when it resonates. The piezoelectric is a ceramic material and generates a nominal power of 75 mW before placing it on the beam, and 375 mW after being placed on the beam. However, the energy collection circuit has losses due to its own consumption, the transmission of energy to the storage system, and in the mechanical system.

Utilization of an ultracapacitor (UC)-based energy storage device can provide one of the most efficient solutions for short-term operational challenges in grid-connected photovoltaic (PV) systems. This paper proposes an algorithm for coordinated control of PV and ultracapacitor-based energy storage system to minimize the effects of sudden changes in solar irradiance and the presence of low voltages at the point of common coupling. In addition, this work proposes an improved multi-mode operational scheme for control of an ultracapacitor-based energy storage system that takes into consideration various associated limits during charging and discharging modes. The effectiveness of the proposed algorithm in mitigating the impacts of low voltages and short term changes in irradiance is demonstrated using simulation analysis carried out on the modified Consortium for Electric Reliability Technology Solutions (CERTS) microgrid testbed.

Ultracapacitors has now become an integral part of the contemporary energy storage systems. Their uniqueness in optimal power delivery, charge storage capabilities and long cyclic stability (˃105) are what make them attractive to the energy storage industries. Basically, Ultracapacitor consists of two separated electrodes impregnated with an electrolyte. Its performance is largely a function of the chosen electrode-electrolyte materials. The choice of the materials depends on the prevailing conditions at hand and is always at a tradeoff between certain merits and demerits. In this communication, we reviewed two contemporary materials namely; Transition Metal Oxides and Conducting Polymers with emphasis on the challenges associated with each. This will create an avenue in determining the direction and future perspective of Ultracpacitors materials. [ABSTRACT FROM AUTHOR]

To overcome the failure of power electronic transformer in resisting input voltage interruption in power grid, a combination between energy storage link and PET(power electronic transformer) is utilized. The energy storage link consists of an ultracapacitors and a bidirectional DC/DC converter. When input voltage interruption occurs, PET with energy storage link can maintain PET′s low DC voltage to be stable. The main parameters of energy storage link are analyzed, the control strategy of the link is designed, and the simulation experiment is built in the MATLAB/Simulink. The simulation experiment results verify the ability of a diagram of PET with energy storage link can resist input voltage interruption in power grid, making the safe and stable operation of equipment in power grid.

As energy storage device of hybrid electric vehicles (HEVs), ultracapacitors feature the advantages of higher power density and longer life cycle compared with batteries. However, when ultracapacitors of the same power level are used instead of batteries, fuel consumption becomes more sensitive to changes in control parameters as ultracapacitors store much less energy, and the state of charge (SOC) is power-sensitive. In this paper, optimization of control parameters for a power-split HEV with ultracapacitors is addressed to achieve better fuel economy. First, a power-split HEV model and a corresponding control strategy are established under the MATLAB script environment for convenient analysis and application of an optimization algorithm. Second, focusing on the power-sensitive characteristic of the SOC, three key control parameters are determined, and their effects on fuel consumption are analyzed. Third, an improved particle swarm optimization (IPSO) algorithm is proposed to overcome the disadvantage of the PSO trapping into “local optimum” and improve optimization efficiency. To fully exploit the fuel-saving capability of the HEV, driving cycle segmentation is also considered. The IPSO is used to optimize three key control parameters under the segmented adapted world transient vehicle cycle. Finally, the optimal results are applied to hardware-in-the-loop test to verify the effectiveness of the proposed optimization method. Compared with the fuel consumption before optimization, the fuel saving rate reaches 9.20% in the urban section, 6.40% in the roadway section, and 5.40% in freeway section.

In this investigation, the rice-like ZnO material was successfully synthesized using the CTAB assisted chemical co-precipitation method followed by a probable annealing process. The internal structure, thermal properties, phase studies, and morphological features were analyzed using Fourier transform infrared spectroscopy (FTIR), Thermogravimetric analysis (TGA), X-ray diffraction analysis (XRD), and scanning electron microscopy (SEM) techniques, respectively. The CTAB serves as a template that influences the fabrication process and exclusively alters ZnO materials' morphological features. The high concentration of the CTAB (2 mM) template provides a rice-like ZnO structure. The synthesized ZnO material's electrochemical properties were inspected using cyclic voltammetry (CV) and galvanostatic charge/discharge studies (GCD). The CV curves provide a specific capacitance of 457 F g−1 at a scan rate of 5 mVs−1, whereas the GCD curves affirm a specific capacitance of 449 F g−1 at a current density of 1 Ag−1. Furthermore, it also exhibits high cyclic stability with 94% of the initial capacitance retained even after continuous 2000 CV cycles at a scan rate of 100 mV s−1. These results signify that the rice-like ZnO material could be a significant postulant for ultra-capacitor electrode applications. [ABSTRACT FROM AUTHOR]

The piezoelectricity allows the generation of electric power taking advantage of the movement of vehicles and pedestrians. Many prototypes have been made with piezoelectric generators, but at present, their commercialization and use have not been popularized due to their low power generation and energy losses. A design of an experimental prototype of an energy harvester with piezoelectric materials that reduces these losses and generates more energy thanks to the resonance with the beams is proposed in this article. An equilateral triangular tile is designed such it will not deform when a force acts on it. The tile has four-cantilever beams, and it is designed to resonate with the natural frequency of the piezoelectric material. This is coupled to the piezoelectric device. The vibration generated on the beam, by a mechanical load, is used to generate more energy when it resonates. The piezoelectric is a ceramic material and generates a nominal power of 75 mW before placing it on the beam, and 375 mW after being placed on the beam. However, the energy collection circuit has losses due to its own consumption, the transmission of energy to the storage system, and in the mechanical system. [ABSTRACT FROM AUTHOR]

The rough and porous structure of the electrode and electrolyte interface in ultracapacitors results in hysteresis between the excitation current and corresponding terminal voltage. The hysteretic behavior causes an increment in terminal voltage even after the removal of input excitation current, referred to as remnant voltage. The design and operation of any ultracapacitor-based energy system should necessarily take into account the hysteretic behavior and the associated remnant voltage for optimal utilization of ultracapacitor as a storage device. Proper modeling of hysteresis allows for determining the optimal excitation profile for charging the ultracapacitor, such that proper balance between the load demand and energy storage is achieved. Motivated by the effectiveness of fractional calculus in representing the long-term memory effect and charge diffusion phenomena in ultracapacitors, this article proposes a fractional calculus-based approach for modeling the hysteresis and estimating the related remnant voltage and associated energy availability after the completion of periodic charging excitations. Analytical expressions for ultracapacitor voltage and energy storage have been formulated for different hysteresis levels using fractional calculus. The formulation helps in quantifying the hysteresis as a function of the excitation magnitude/duration and ultracapacitor model parameters, thus providing a platform for improving the energy efficiency of the ultracapacitor-based energy management applications by optimal charging. The derived expressions have been experimentally validated for varying dynamics of current excitation. [ABSTRACT FROM AUTHOR]

Summary: Fossil fuel depletion and its adverse impact on global warming is a major driving force for a recent upsurge in the development of hybrid electric vehicles technologies. This paper is a conglomeration of the recent literature in the usages of an energy storage system and power conversion topologies in electric vehicles (EVs). An EV requires sources that have high power and energy density to decrease the charging time. Commonly used energy storage devices in EVs are fuel cells, batteries, ultracapacitors, flywheel, and photovoltaic arrays. The power output from energy storage sources is conditioned to match load characteristics with the source for maximum power delivery. A DC‐DC converter topology performs this task by way of transforming voltage under the condition of power invariance. In addition, power electronics is also required to power DC/AC motors efficiently with precise control as these motors provide tractive efforts and acts as prime movers. This paper therefore brings out a critical review of the literature on EV's power conversion topologies and energy storage systems with challenges, opportunities and future directions by systematic classification of EVs and energy storage. [ABSTRACT FROM AUTHOR]

Spent honeycomb biomass as sustainable source is used to generate value added product, such as activated carbon. The generated activated carbon is characterized by X‐ray diffraction, Fourier transformed infra‐red spectroscopy, Raman spectroscopy, Scanning electron microscope, High‐resolution transmission electron microscope, and Brunauer‐Emmett‐Teller analyses. The activated carbon is explored as intercalation anode material for lithium‐ion battery in half‐cell and full cell as electrodes for ultracapacitor in aqueous and non‐aqueous electrolytes. The coin‐type CR‐2032 full cell lithium‐ion battery consists of the honeycomb‐derived carbon as anode and commercial LiCoO2 as cathode delivers discharge capacity of 140 mAh/g at C/5 rate with excellent cycling stability. On the other hand, the symmetric ultracapacitor consists of the carbon electrode exhibits energy density of 72 Wh/kg at a power density of 4800 W/kg with excellent coulombic efficiency as well as stability. The laboratory proto‐type battery and ultracapacitor devices are demonstrated to power a consumer electronics, namely green light emitting diode bulb for more than 3 hours and 20 minutes, respectively. [ABSTRACT FROM AUTHOR]

Hybrid electric power systems based on fuel cell stack and energy storage sources like batteries and ultracapacitors are a plausible solution to vehicle electrification due to their balance between acceleration performance and range. Having a high degree of hybridization can be advantageous, considering the different characteristics of the power sources. Some parameters to be considered are: specific power and energy, energy and power density, lifetime, cost among others. Ultracapacitors (UC) are of particular interest in electric vehicle applications due to its high-power capability, which is commonly required during acceleration. UCs are commonly used without a power electronics interface due to the high-power processing requirement. Although connecting UCs directly to the DC bus, without using a power converter, presents considerable advantages, the main disadvantage is related to the UC energy-usage capability, which is limited by constant DC bus control. This paper proposes a novel energy-management strategy based on a fuzzy inference system, for fuel-cell/battery/ultracapacitor hybrid electric vehicles. The proposed strategy is able to control the charge and discharge of the UC bank in order to take advantage of its energy storage capability. Experimental results show that the proposed strategy reduces the waste of energy due to dynamic brake in 14%. This represents a reduction in energy consumption from 218 Wh/km to 192 Wh/km for the same driving conditions. By using the proposed energy management strategy, the estimated fuel efficiency in miles per gallon equivalent was also increase from 96 mpge to 109 mpge. • An energy management strategy for a fuel cell based hybrid electric vehicle is proposed. • The proposed system considers the ultra-capacitors are directly connected to the DC bus. • The proposed system is able to control the charge and discharge of the stored energy. [ABSTRACT FROM AUTHOR]

This article explores hybrid energy storage devices in which an individual electrode is composed of a mixture of the active materials used in lithium-ion batteries and ultracapacitors, allowing them to exhibit characteristics of both device types. In order to explore the breadth of options between a pure battery electrode and a pure ultracapacitor electrode, seven different electrode compositions containing mixtures of lithium iron phosphate (LiFePO4) and activated carbon have been investigated. The hybrid electrodes have been implemented in an aqueous lithium sulfate electrolyte with single-electrode measurements using a reference electrode. The hybrid pulse power characterization (HPPC) test profile has been employed to characterize the energy and power capability of each electrode composition. An approach for converting single-electrode cycling results to full cell predictions suitable for the HPPC analysis procedure is presented. By executing this procedure, battery scale factors representing estimates of the quantity of active material required to achieve a set of energy storage target requirements have been calculated. Models of full 18650-format hybrid cells are developed to extend results to optimize a tailored energy storage system on the basis of total cell mass and volume. These results show that the required amount of active materials, total mass, or total volume of an energy storage system can be minimized for a given application by using a hybrid electrode and adjusting the constituent fraction of battery and ultracapacitor materials. [ABSTRACT FROM AUTHOR]

The use of electric vehicles and their various configurations is seen as a major alternative in efforts towards reducing pollutant emissions from motor vehicles that continue to use fossil fuels. Electric transport technology presents more efficient means of energy conversion in vehicles: electric (EV), hybrid (VH), and hybrid electric (HEV) vehicles. For example, the energy storage system in the latter can be made up of ultracapacitors (UCs), batteries (Bs), and fuel cells. This work focuses on HEVs powered by batteries and ultracapacitors. In particular, the multiple converter configuration (C-CM) for the HEV powertrain system is analyzed using electric models of the vehicle powertrain components. To analyze the multiple converter configuration, parameters of a vehicle taken from the literature and the electrical model of the configuration were developed. With the above, the proposed configuration was evaluated before driving cycles (CITY II and ECE) and the configuration performance was compared with respect to other configurations. In the C-CM model, limitations in the choice of the number of Bs and UCs were observed in the powertrain depending on the maximum power of both energy sources and vehicle load demand. The results show that more energy is extracted from the batteries in the ECE cycle than in the CITY taking into account that the batteries are used as the main power source. C-CM results compared to other configurations show that energy extracted from batteries in the CITY is the same across all configurations. While energy consumption is lower in the ECE, C-CM results were not very significant compared to other configurations. However, the C-MC has the advantage of having better power flow control due to having two converters, thus improving HEV safety. [ABSTRACT FROM AUTHOR]

In this paper, a lifetime prediction model, including an equivalent circuit model, a thermal model and an aging model is developed for the prediction of the state of charge (SOC), temperature and state of health (SOH) of the ultracapacitor. The aging model is developed based on the evolution of impedance parameters in the accelerated aging tests conducted at various voltages and temperatures. Based on the fitting results of various aging models for capacitance fade and conductance loss, a power function of the equivalent aging time is chosen for better prediction of the nonlinear aging process including the burning phase and slow aging phase. The consistency and accuracy of the power function aging model allow straightforward implementation in the lifetime prediction model as the equivalent aging time and thus the capacitance, resistance and SOH can be updated with the voltage and temperature of the ultracapacitor at each time step. The experimental results show that the lifetime prediction model is capable of predicting SOC, temperature and SOH of test cells of various aging conditions under three types of charge/discharge current profiles. In the future, the lifetime prediction model can be utilized for the development of predictive estimators and energy management of ultracapacitors. • Lifetime prediction model includes equivalent circuit, thermal and aging models. • Different aging models for ultracapacitors and Lithium-ion batteries are compared. • Power function model predicts better the fast burning and slow aging phases. • The aging model achieves accurate prediction and high computation efficiency. • Model validated against data from cells of various aging conditions. [ABSTRACT FROM AUTHOR]

In order to enhance the electrochemical efficiency of supercapacitors, novel active electrode materials are being developed. This study provides a unique method to synthesize an integrated structure consisting of a nickel-cobalt metal-organic framework (NiCo-MOF) on functionalized carbon nanofiber (f-CNF) utilizing a single-step solvothermal method. Physicochemical characterization confirmed the successful synthesis of the integrated system of NiCo-MOF@f-CNF. This novel structure has the potential to significantly improve the electrochemical properties of the initially prepared material for use in supercapacitors. The synthesized electrode has a higher specific capacitance/capacity value of 788 F g−1 (315.2 C g−1) at 1 A g−1 and high cycling stability. The developed hybrid device exhibited a promising specific energy of 8.6 Wh kg−1 and a high specific power of 1147 W kg−1, demonstrating potential for practical applications. The current study suggests that the proposed material can be a viable electrode for high-efficiency supercapacitors. • An integrated structure of NiCo-MOF@f-CNF nanocomposite was prepared and used as an efficient electrode in supercapacitors. • Electrical conductivity, mechanical properties, and surface accessibility were enhanced when f-CNF joined NiCo-MOF. • NiCo-MOF@f-CNF hierarchical structure exhibits a specific capacitance of 788 F g−1 at a current density of 1 A g−1. • NiCo-MOF@f-CNF//AC hybrid supercapacitor shows a specific energy of 8.6 Wh kg−1 at a specific power of 1.147 kW kg−1. [ABSTRACT FROM AUTHOR]

A novel dynamic average-value model (AVM) of energy storage systems (ESS) integration in power grid for long-term control is developed and validated. It is expected to greatly improve the computational speed of power system dynamics in a long-term simulation. To end this, the development of the dynamic AVM of ESS integration including ultracapacitor, DC–DC converter, and voltage source converter is elaborated upon. A new control strategy which uses digital logic circuit is proposed to keep the ultracapacitors from overcharging without significantly increasing the charging time. To validate the proposed dynamic AVM and control strategy, case studies are carried out to perform the dynamics as affected by sudden changing of charging/discharging of ESS. The accuracy of the proposed model and controller is verified by the simulation results with that obtained from the detailed model implemented in MATLAB/Simulink. Moreover, the time-step size is enlarged greatly without sacrificing the accuracy, therefore the computational speed is improved significantly.

The science and technology of ultracapacitors are reviewed for a number of electrode materials, including carbon, mixed metal oxides, and conducting polymers. More work has been done using microporous carbons than with the other materials and most of the commercially available devices use carbon electrodes and an organic electrolytes. The energy density of these devices is 3¯5 Wh/kg with a power density of 300¯500 W/kg for high efficiency (90¯95%) charge/discharges. Projections of future developments using carbon indicate that energy densities of 10 Wh/kg or higher are likely with power densities of 1¯2 kW/kg. A key problem in the fabrication of these advanced devices is the bonding of the thin electrodes to a current collector such the contact resistance is less than 0.1 cm2.Special attention is given in the paper to comparing the power density characteristics of ultracapacitors and batteries. The comparisons should be made at the same charge/discharge efficiency.

Porous graphitic activated carbon made from biodegradable starch-based packing peanuts contain metallic impurities, such as sodium and potassium impurities. The metallic impurities are not only eliminated in the activation process and revelation. These carbon sheets appear to form an ultrathin graphitic layer on the surface of the disordered carbon framework of the packed peanut-derived activated carbon. The shell-like graphitic structure can be explained by potassium penetration into the carbon structure during chemical activation and subsequent catalytic graphitization by the metallic impurities. These graphitic structures produce high-power density properties. As sodium impurities are present in the depth of the PP-C, it is possible to synergize the effects of potassium. The combination of these structural properties enables the carbon sheets to provide a harmonious electrochemical environment for the full realization of fast ion transport and high capacitance. Image 1 • The shell-like graphitic structure was derived from biodegradable starch-based packing peanuts. • These carbon sheets seem to form an ultrathin graphitic layer on the surface of the disordered carbon framework. • The shell-like graphitic structure is capable of creating a structure that combines the high surface area of micro/mesopores. • The shell-like graphitic structure exhibited excellent electrochemical performance. • These results should encourage the establishment of a new economic platform for advanced porous graphitic carbon. [ABSTRACT FROM AUTHOR]

Ultracapacitor (UC) based dc–dc power supplies are widely used for addressing surge power demands and to provide energy backup to critical loads. The conventional control techniques, such as unified control strategy, though ensure seamless mode transition, do not offer complete flexibility in charging and discharging controls which is crucial in UC-based backup systems. On the other hand, controls, such as independent switch control, though allow great flexibility in control, do not ensure seamless mode transition without appropriate mode-switch logic. This paper proposes a time-varying virtual resistance based mode transition control for independent switch control which not only ensures smooth, seamless transition between charging and discharging control modes but also ensures complete control over the mode transition durations. The proposed control is found to be robust to error mode identification as compared to introducing dead band between control modes. The proposed control is verified on a proof of concept experimental setup at a power level of $P_o=65$ W, voltage level of $V_g=26$ V with the dc–dc converter switching at $f_{\text{sw}}=100$ kHz. The performance comparison with PWM blocking method is also evaluated where the proposed control is found to work well. [ABSTRACT FROM AUTHOR]

Highlights • Some Grid Codes impose restrictions on the ramp rate of PV plants. • Hybrid energy storage systems can be more cost efficient for ramp-rate control. • Hybridizing batteries with ultracapacitors expands their lifetime. • The proposed methodology can be used to size the components of the storage. • The total Net Present Cost of controlling ramp rate in a PV plant is optimized. Abstract This paper proposes a methodology for optimal sizing of a Hybrid (battery and ultracapacitors) Energy Storage system for ramp-rate control in PV plants. Frequency stability events can appear in power systems high non-dispatchable renewable energy generation due to sharp power output fluctuations. This has caused TSOs in several countries to require PV and wind plants to implement some method for limiting the pace at which the power injection to the grid is allowed to vary (ramp-rate control). Due to its quick response, properly controlled energy storage consisting of batteries and ultracapacitors can perform this task by dampening quick increases/decreases in the power injection to the grid by absorbing/injecting power at the point of common coupling. In this work, a techno-economic model is presented that can be used to calculate the Net Present Cost over the project life of different energy storage devices used for ramp-rate control by simulating their operation. A real case is studied for a PV power plant is presented. Results are reported comparing different configurations of the energy storage system. [ABSTRACT FROM AUTHOR]

In this paper, a new aging detection method of a supercapacitor is proposed through the study of the charge process. Good indicators to describe this aging are equivalent series resistance (ESR) and capacitance evolution, which are online unmeasurable parameters of the component model. The proposed model belongs to the class of state and parameter affine nonlinear system. A new adaptive nonlinear observer is designed to estimate, under different aging phases, both states and parameters using measurements only available at each sampling instant. This unusual observer contains an adaptive gain, an unknown parameter into the measured output equation, and the control signal into state matrix. This discrete-continuous observer is proved to be globally exponentially convergent under some sufficient conditions. Theoretical results are implemented for two cases of study, the first one through some simulations and the second one applied on real data for different sampling times and different values of observer gain. Results highlight good performances of the observer in online parameter estimation; thus, the component aging is clearly shown. [ABSTRACT FROM AUTHOR]

A novel dynamic average-value model (AVM) of energy storage systems (ESS) integration in power grid for long-term control is developed and validated. It is expected to greatly improve the computational speed of power system dynamics in a long-term simulation. To end this, the development of the dynamic AVM of ESS integration including ultracapacitor, DC–DC converter, and voltage source converter is elaborated upon. A new control strategy which uses digital logic circuit is proposed to keep the ultracapacitors from overcharging without significantly increasing the charging time. To validate the proposed dynamic AVM and control strategy, case studies are carried out to perform the dynamics as affected by sudden changing of charging/discharging of ESS. The accuracy of the proposed model and controller is verified by the simulation results with that obtained from the detailed model implemented in MATLAB/Simulink. Moreover, the time-step size is enlarged greatly without sacrificing the accuracy, therefore the computational speed is improved significantly. [ABSTRACT FROM AUTHOR]

The growing penetration of converter-interfaced renewable energy sources (CI-RES) has revealed several challenges related to the stability of the electrical grids. To mitigate these issues, there is an ongoing research regarding the concept of virtual synchronous generators, where new control schemes are employed to enable CI-RES with integrated fast-acting energy storage system (ESS) to provide ancillary services to the grid, e.g., inertial response (IR). Although several solutions have been proposed in the literature, the proper integration and energy management of the ESS towards IR provision remains an open research topic. In this paper, an holistic control approach is presented regarding IR provision by a system comprising of a CI-RES and an ultracapacitor (UC). The proposed approach is supplemented by an efficient energy management system allowing the UC to release/absorb energy during IR provision while always ensuring the operation of the UC voltage within its technical limits. The robustness and the performance of the proposed method are experimentally evaluated in a lab setup, where all the components of the proposed system, i.e., CI-RES and UC have been analytically implemented. • A comprehensive control scheme for inertial provision from CI-RES is described. • An Ultracapacitor (UC) is used to control the voltage at the dc bus. • An energy management system is applied to control the voltage of the UC. • Experiments are conducted to evaluate the performance of the presented method. [ABSTRACT FROM AUTHOR]

With the purpose of designing the electric powertrain of a high performance electric vehicle capable of running a quarter mile in 10 seconds, firstly it is necessary to calculate the required energy, torque, and power in order to size and select the suitable storage components and electric motors. Secondly, an assessment of the powertrain arrangement is needed to choose the best internal configuration of the vehicle and guarantee the highest efficiency possible. Finally, a design of the power conversion stages, specifically the DC-DC converter that interfaces the storage unit with the electric motors, is required as well. This paper shows the energy calculation procedure based on a longitudinal dynamic model of the vehicle and the selection method of the storage components and motors needed for this application, as well as the design of two 100kW interleaved boost converters with coupled inductors. In addition, a novel operation of the interleaved boost converter is proposed in order to increase the efficiency of the converter. As a result, the designed converter achieved a power density of 24,2kW/kg with an efficiency of 98 %, which was validated by experimental tests of a low power prototype.

Numerously different porous carbons have been prepared and used in a wide range of practical applications. Porous carbons are also ideal electrode materials for efficient energy storage devices due to their large surface areas, capacious pore spaces, and superior chemical stability compared to other porous materials. Not only the electrical double-layer capacitance (EDLC)-based charge storage but also the pseudocapacitance driven by various dopants in the carbon matrix plays a significant role in enhancing the electrochemical supercapacitive performance of porous carbons. Since the electrochemical capacitive activities are primarily based on EDLC and further enhanced by pseudocapacitance, high-surface carbons are desirable for these applications. The porosity of carbons plays a crucial role in enhancing the performance as well. We have recently witnessed that metal–organic frameworks (MOFs) could be very effective self-sacrificing templates, or precursors, for new high-surface carbons for supercapacitors, or ultracapacitors. Many MOFs can be self-sacrificing precursors for carbonaceous porous materials in a simple yet effective direct carbonization to produce porous carbons. The constituent metal ions can be either completely removed during the carbonization or transformed into valuable redox-active centers for additional faradaic reactions to enhance the electrochemical performance of carbon electrodes. Some heteroatoms of the bridging ligands and solvate molecules can be easily incorporated into carbon matrices to generate heteroatom-doped carbons with pseudocapacitive behavior and good surface wettability. We categorized these MOF-derived porous carbons into three main types: (i) pure and heteroatom-doped carbons, (ii) metallic nanoparticle-containing carbons, and (iii) carbon-based composites with other carbon-based materials or redox-active metal species. Based on these cases summarized in this review, new MOF-derived porous carbons with much enhanced capacitive performance and stability will be envisioned.

This paper introduces a modular testbed to simulate AC/DC microgrids. The testbed is implemented in Matlab Simulink and is based on the energetic macroscopic representation (EMR) formalism. It is designed to be a tool to evaluate energy management strategies in AC/DC microgrids. The microgrid simulation model includes a photovoltaic generator, a fuel cell system, ultracapacitors, and batteries on the DC side. It includes voltage source converters (VSC) to couple the DC side with the AC side of the microgrid, which includes a variable AC load and a synchronous generator. Two case studies illustrate the use of the testbed. The model is implemented in Matlab Simulink and made openly available for the scientific community. Using this model, researchers can develop and evaluate energy management strategies in AC/DC microgrids.

The objective proposed by the EU to drastically reduce vehicular CO2 emission for the years up to 2030 requires an increase of propulsion systems’ efficiency, and accordingly, the improvement their technology. Hybrid electric vehicles could have a chance of achieving this, by recovering energy during braking phases, running in pure electric mode and allowing the internal combustion engine to operate under better efficiency conditions, while maintaining traditionally expected vehicle performances (mileage, weight, available on-board volume, etc.). The energy storage systems for hybrid electric vehicles (HEVs) have different requirements than those designed for Battery Electric Vehicles (BEVs); high specific power is normally the most critical issue. Using Li-ion Batteries (LiBs) in the designing of on-board Energy Storage Systems (ESS) based only on power specifications gives an ESS with an energy capacity which is sufficient for vehicle requirements. The highest specific power LiBs are therefore chosen among those technologically available. All this leads to an ESS design that is strongly stressed over time, because current output is very high and very rapidly varies, during both traction and regeneration phases. The resulting efficiency of the ESS is correspondingly lowered, and LiBs lifetime can be relevantly affected. Such a problem can be overcome by adopting hybrid storage systems, coupling LiBs and UltraCapacitors (UCs); by properly dimensioning and controlling the ESS’ components, in fact, the current output of the batteries can be reduced and smoothed, using UCs during transients. In this paper, a simulation model, calibrated and validated on an engine testbed, has been used to evaluate the performances of a hybrid storage HEV microcar under different operative conditions (driving cycles, environment temperature and ESS State of Charge). Results show that the hybridization of the powertrain may reduce fuel consumption by up to 27%, while LiBs lifetime may be more than doubled.

The use of electric vehicles and their various configurations is seen as a major alternative in efforts towards reducing pollutant emissions from motor vehicles that continue to use fossil fuels. Electric transport technology presents more efficient means of energy conversion in vehicles: electric (EV), hybrid (VH), and hybrid electric (HEV) vehicles. For example, the energy storage system in the latter can be made up of ultracapacitors (UCs), batteries (Bs), and fuel cells. This work focuses on HEVs powered by batteries and ultracapacitors. In particular, the multiple converter configuration (C-CM) for the HEV powertrain system is analyzed using electric models of the vehicle powertrain components. To analyze the multiple converter configuration, parameters of a vehicle taken from the literature and the electrical model of the configuration were developed. With the above, the proposed configuration was evaluated before driving cycles (CITY II and ECE) and the configuration performance was compared with respect to other configurations. In the C-CM model, limitations in the choice of the number of Bs and UCs were observed in the powertrain depending on the maximum power of both energy sources and vehicle load demand. The results show that more energy is extracted from the batteries in the ECE cycle than in the CITY taking into account that the batteries are used as the main power source. C-CM results compared to other configurations show that energy extracted from batteries in the CITY is the same across all configurations. While energy consumption is lower in the ECE, C-CM results were not very significant compared to other configurations. However, the C-MC has the advantage of having better power flow control due to having two converters, thus improving HEV safety.

Ultracapacitors (UCs), with their features of high power density and high current charge-discharge, have become the best choice for dynamic power compensation to improve the stability of microgrids and are increasingly being applied in microgrids. This paper presents the control of an energy storage system (ESS) based on ultracapacitors in the context of grid-connected microgrids. The ESS is composed of DC/AC and DC/DC converters tied by a dc link. An improved dynamic model for the ESS is proposed. Based on the proposed model a Proportional-Integral-Resonant (PIR) DC link voltage controller is proposed to maintain the DC link voltage through the charging-discharging control of ultracapacitors, capable of working properly under all operating conditions. An extra double frequency component is injected into the UC current by a R controller to dynamically compensate for DC instantaneous power and double frequency AC instantaneous power due to unbalanced grid conditions and disturbances. This feature maintains the DC link voltage constant under unbalanced conditions and increases the degrees of freedom of the DC/AC converter and thus facilitates the application of UCs in microgrids. Simulation and experimental results verify the effectiveness of the proposed control strategy.

This study highlights an attempt of comparing the performance of several energy storage (ES) devices like battery ES, flywheel ES, capacitive ES, superconducting magnetic ES, ultra‐capacitors and redox flow battery (RFB) in automatic generation control under bilateral deregulated scenario. The considered system comprises gas and thermal generations wherein a geothermal power plant (GTPP) is also incorporated. Gas and thermal systems are provided with appropriate generation rate constraints. A new fractional order (FO) cascade controller named as FO proportional‐integral–FO proportional‐derivative (FOPI–FOPD) is proposed as secondary controller and its performance is compared with commonly used classical controllers. A novel stochastic algorithm, sine cosine algorithm, has been used to optimise controller gains and other parameters. Analyses of dynamic responses reveal the superiority of FOPI–FOPD over others in terms of settling time, peak deviation and magnitude of oscillation. The effect due to GTPP introduction has been examined and the responses disclose that the integration of GTPP leads to better dynamics. Performances of various ES devices in the presence of FOPI–FOPD controller are also compared and dynamic responses of RFB found superior to others. For a more realistic scenario, analysis is done considering time delay and some practical plants of Nevada, USA. [ABSTRACT FROM AUTHOR]

This work carries out a comparison of non-isolated topologies for power electronic converters applied to Hybrid Energy Storage Systems. At the considered application, several options for three-port circuits are evaluated when interfacing a DC link with two distinct electrical energy storage units. This work demonstrates how the proposed structure, referred to as Series-Parallel Connection, performs as a simple, compact and reliable approach, based on a modification of the H-bridge configuration. The main advantage of this solution is that an effective large voltage gain at one of the ports is attained by means of a simple topology, preventing the use of multilevel or galvanic-isolated power stages. The resulting structure is thoroughly compared against the most significant direct alternatives. The analysis carried out on the switching and conduction losses in the power switches of the target solution states the design constraints at which this solution shows a performance improvement. The experimental validations carried out on a 10 kW prototype demonstrate the feasibility of the proposed scheme, stating its benefits as well as its main limitations. As a conclusion, the Series-Parallel Connection shows a better performance in terms of efficiency, reliability and controllability in the target application of compensating grid or load variations in Non-Isolated Hybrid Storage Systems, with large mismatch in the storage device voltage ratings. [ABSTRACT FROM AUTHOR]

• A Mixed-Integer Linear Programming (MILP) framework based decision making model. • Consideration of the tram-station and internal tram transactions in a single structure. • All-in-one renewable energy assisted refueling and recharging station concept. • Hydrogen and electric energy supply based multi-energy management. Fuel cell (FC) and ultracapacitor hybrid trams offer a sustainable and efficient transportation option, with the ability to store and use renewable energy for propulsion. However, their widespread adoption is limited by the availability of reliable and cost-effective refueling and recharging infrastructure. In this study, the use of mixed-integer linear programming (MILP) optimization for the energy management of photovoltaic (PV)-assisted refueling and recharging stations for fuel cell ultracapacitor hybrid trams is investigated. The electrolyzers and recharging units can either be supplied by the grid or by PV, depending on the availability of renewable energy. The study's main contribution is the consideration of the tram-station and internal tram transactions in a single optimization-based energy management structure and the all-in-one renewable energy assisted refueling and recharging station concept, which considers both the hydrogen and electricity supply requirements. The proposed structure was tested using the data of the Istanbul Kabataş-Bağcılar tram line, and the results showed a 46.48% reduction in operating cost and a significant decrease in carbon dioxide emissions and power drawn from the grid. The study provides valuable information for rail system operators and state authorities and opens up possibilities for future studies in the integration of hydrogen fuel cell vehicles into refueling stations. [ABSTRACT FROM AUTHOR]

Ultracapacitors (UCs) are the focus of increasing attention in electric vehicle and renewable energy system applications due to their excellent performance in terms of power density, efficiency, and lifespan. Modeling and parameterization of UCs play an important role in model-based regulation and management for a reliable and safe operation. In this paper, an equivalent circuit model template composed of a bulk capacitor, a second-order capacitance-resistance network, and a series resistance, is employed to represent the dynamics of UCs. The extended Kalman Filter is then used to recursively estimate the model parameters in the Dynamic Stress Test (DST) on a specially established test rig. The DST loading profile is able to emulate the practical power sinking and sourcing of UCs in electric vehicles. In order to examine the accuracy of the identified model, a Hybrid Pulse Power Characterization test is carried out. The validation result demonstrates that the recursively calibrated model can precisely delineate the dynamic voltage behavior of UCs under the discrepant loading condition, and the online identification approach is thus capable of extracting the model parameters in a credible and robust manner.