Electric Double Layer Capacitor Energy Research Articles

Study of the Impact of Graphite Orientation and Ion Transport on EDLC Performance.

A model study of electric double layer capacitor (EDLC)-style capacitors in which the electrodes were composed of low surface area-oriented flakes of graphite that compressed to form a paper-like morphology has suggested that ion transport rates significantly impact EDLC energy and power density. Twelve capacitors were constructed, each using the same model electrode material and the same aqueous NaCl electrolyte, but differing in relative electrode orientation, degree of electrode compression, and presence/absence of an ionic transport salt bridge. All were tested with a galvanostat over a range of discharge currents. Significant differences in energy and power density and estimated series resistance were found as a function of all the factors listed, indicating that capacitor performance is not simply a function of the electrode surface area. This simple postulation was advanced and tested against data: net ion (Na+, Cl−) ‘velocity’ during both charge and discharge significantly impacts capacitive performance.

Novel flexible solid-state pseudo-parallel pseudocapacitor with manganese oxide active material synthesized using electrodeposition

Flexible and light-weight energy storage device is required for soft electronics. Novel flexible solid-state pseudo-parallel pseudocapacitor (SPP) with three electrodes is firstly proposed to achieve light-weight and excellent energy storage ability. SPP is assembled using only three electrodes without outer circuit. Active material of δ-MnO2 is fabricated on carbon cloth (CC) using electrodeposition with different currents. Highest specific capacitance of 9.41 F/cm2 is obtained for MnO2/CC electrode prepared using 30 mA, due to high surface area, large pore volume and suitable pore structure of nanosheet array. Normal-type pseudocapacitor (NP), two normal-type pseudocapacitor connected in parallel (NP in parallel), and two types of SPP are assembled using optimized MnO2/CC positive electrode and activated carbon negative electrode. The SPP composed of two positive electrodes and one negative electrode (PNP) shows best energy storage ability with energy density of 97.09 Wh/kg at power density of 0.65 W/kg, owing to more MnO2 pseudocapacitor electrode and better device configuration. However, worse charge/discharge stability is observed for PNP owing to lacking sufficient carbon material for providing stable electric double layer capacitor energy storage mechanism. This work greatly opens new blueprint for designing device configurations to achieve light-weight and efficient energy storage ability for flexible solid-state pseudocapacitors.

Reevaluation of Performance of Electric Double-layer Capacitors from Constant-current Charge/Discharge and Cyclic Voltammetry.

The electric characteristics of electric-double layer capacitors (EDLCs) are determined by their capacitance which is usually measured in the time domain from constant-current charging/discharging and cyclic voltammetry tests, and from the frequency domain using nonlinear least-squares fitting of spectral impedance. The time-voltage and current-voltage profiles from the first two techniques are commonly treated by assuming ideal SsC behavior in spite of the nonlinear response of the device, which in turn provides inaccurate values for its characteristic metrics. In this paper we revisit the calculation of capacitance, power and energy of EDLCs from the time domain constant-current step response and linear voltage waveform, under the assumption that the device behaves as an equivalent fractional-order circuit consisting of a resistance Rs in series with a constant phase element (CPE(Q, α), with Q being a pseudocapacitance and α a dispersion coefficient). In particular, we show with the derived (Rs, Q, α)-based expressions, that the corresponding nonlinear effects in voltage-time and current-voltage can be encompassed through nonlinear terms function of the coefficient α, which is not possible with the classical RsC model. We validate our formulae with the experimental measurements of different EDLCs.

Stationary Charging Station Design for Sustainable Urban Rail Systems: A Case Study at Zhuzhou Electric Locomotive Co., China

In 2014, more than 43 cities in China were racing to construct their urban rail systems (including metro and light rail systems), recognizing that an urban rail system will be a good solution to the tough problems that they are faced with, including traffic congestion and PM2.5 air pollution. On 22 August 2012, the first electric double-layer capacitor (EDLC) energy storage-type rail vehicle in the world was unveiled at Zhuzhou Electric Locomotive Co., China. The EDLC rail system has been considered a promising sustainable urban rail system, which is expected to further improve the energy efficiency and to reduce environmental pollution. The first commercial EDLC tram produced by Zhuzhou Electric Locomotive Co. has been applied at Guangzhou Metro Corp. recently. From the view point of scientific research, the system design and energy management of EDLC rail systems have been extensively studied in the literature, while the stationary charging station design for the EDLC energy storage-type urban rail vehicles has been rarely reported. Thus, the aim of this paper is to report a stationary charging station that has been successfully applied in the EDLC rail system produced by Zhuzhou Electric Locomotive Co., China.

Stabilization of wind energy conversion system with hydrogen generator by using EDLC energy storage system

AbstractThe spread of wind power generation has progressed hugely in recent years from the viewpoint of environmental problems including global warming. Though wind power is considered as a very prospective energy source, wind power fluctuation due to the random fluctuation of wind speed has still created some problems. Therefore, research has been performed on how to smooth the wind power fluctuation. This paper proposes Energy Capacitor System (ECS) for the smoothing of wind power which consists of Electric Double‐Layer Capacitor (EDLC) and power electronics devices and works as an electric power storage system. Moreover, hydrogen has received much attention in recent years from the viewpoint of the problem of exhaustion of fossil fuel. Therefore, it is also proposed that a hydrogen generator be installed at the wind farm to generate hydrogen. In this paper, the effectiveness of the proposed system is verified by simulation analyses using PSCAD/EMTDC. © 2009 Wiley Periodicals, Inc. Electr Eng Jpn, 168(3): 10–18, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.20864

Stabilization of Wind Energy Conversion System with Hydrogen Generator by Using EDLC Energy Storage System

The spread of wind power generation is progressed hugely in recent years from a viewpoint of environmental problems including global warming. Though wind power is considered as a very prospective energy source, wind power fluctuation due to the random fluctuation of wind speed has still created some problems. Therefore, research has been performed how to smooth the wind power fluctuation. This paper proposes Energy Capacitor System (ECS) for the smoothing of wind power which consists of Electric Double-Layer Capacitor (EDLC) and power electronics devices and works as an electric power storage system. Moreover, hydrogen has received much attention in recent years from a viewpoint of exhaustion problem of fossil fuel. Therefore it is also proposed that a hydrogen generator is installed at the wind farm to generate hydrogen. In this paper, the effectiveness of the proposed system is verified by the simulation analyses using PSCAD/EMTDC.

Output leveling of wind power generation system by EDLC energy storage system

AbstractUtilization of renewable energy is becoming increasingly important from the viewpoints of environmental protection and conservation of fossil fuel. However, the generating power of renewable energy is always fluctuating due to the environmental status. Energy storage systems are indispensable in compensating these fluctuating components. An energy capacitor system (ECS) composed of an electric double‐layer capacitor (EDLC) with power‐electronics devices is useful for compensation of fluctuating power, since it is capable of controlling both active and reactive power simultaneously. This paper proposes a current‐source ECS (CS‐ECS), which consists of an EDLC, a bidirectional buck‐boost DC‐DC converter, and a bidirectional inverter. We present the control systems for active/reactive power control of CS‐ECS, and show the effectiveness of CS‐ECS through computer simulations for the case of a wind power generation system. © 2006 Wiley Periodicals, Inc. Electr Eng Jpn, 154(4): 34–41, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.20181

Output Power Leveling of Wind Turbine Generator by EDLC Energy Storage System

The increased renewable energy utilization, especially photovoltaic panels using solar energy or wind turbine generators (WTGs) using wind energy, has been expected in recent years from view point of CO2 gas emission reduction and environmental conservation. However, the generated power is always fluctuating because the WTGs are driven by fluctuating wind. Therefore, an energy storage system should be installed to compensate these fluctuating elements. The energy capacitor system (ECS) which combined the electric double-layer capacitor (EDLC) and the electronic circuits are now under development. In this paper, control system configuration for active and reactive output power simultaneous control and the bi-directional inverter using current source EDLC are proposed. Moreover, we discusse control methods required in generating-power leveling for WTGs, and show the effectiveness of the proposed system through simulations.