• Korean Journal of Metals and Materials
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• v.49 no.5
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• pp.419-424
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• 2011

Carbon nanotubes (CNTs) were directly synthesized on a copper (Cu) plate as a current collector by the catalytic thermal vapor deposition method for an electric double-layer capacitor (EDLC) electrode. The diameters of vertically aligned CNTs grown on the Cu plate were 20~30 nm. From cyclic voltammetry (CV) results, the CNTs/Cu electrode showed high specific capacitance with typical profiles of EDLCs. Rectangularshaped CV curves suggested that the CNTs/Cu electrode could be an excellent candidate for an EDLC electrode. The specific capacitances were in a range of 25~75 F/g with a scan rate of 10~100 mV/s and KOH electrolyte concentration 1~6 M, and were maintained up to 1000 charge/discharge cycles due to strong adhesion between the Cu substrate and the CNTs.

• KEPCO Journal on Electric Power and Energy
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• v.7 no.2
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• pp.329-333
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• 2021

V2G (Vehicle to Grid) technology for an EV (Electric Vehicle) has been assumed as so promising in a near future for its useful energy resource concept but still yet to be developed around the world for specific service purposes through various R&BD projects. Basically, V2G returns power stored in vehicle at a cheaper or unused time to the grid at more expensive or highly peaked time, and is accordingly supposed to provide such roles like peak shaving or load levelling according to customer load curve, frequency regulation or ancillary reserves, and balancing power fluctuation to grid from the weather-sensitive renewable sources like wind or solar generations. However, it has recently been debated over its prominent usage as diffusing EVs and the required charging/discharging infrastructure, partially for its addition of EV ownership costs with more frequent charging/discharging events and user inconvenience with a relative long-time participation in the previously engaged V2G program. This study suggests that a Korean DR (Demand Response) service integrated V2G system especially based upon a dynamic charge/pause/discharge scheme newly proposed to ISO/IEC 15118 rev. 2 can deal with these concerns with more profitable business model, while fully making up for the additional component (ex. battery) and service costs. It also indicates that the optimum economic, environmental, and grid impacts can be simulated for this V2G-DR service particularly designed for EV aggregators (V2G service providers) by proposing a specific V2G engagement program for the mediated DR service providers and the distributed EV owners.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.39 no.6
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• pp.639-644
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• 2015

A cylindrical secondary Li-ion cell is a device in which stored chemical energy is converted to electrical energy via an electrochemical reaction. These cells are widely used for applications that require high capacity and rate power, such as notebooks, power tools, and electric vehicles. The role of a center pin is to retain the channel for gas release, preventing blockage of the hollow of the jelly roll during a charge-discharge cycle, and to prevent an internal short circuit for tearing of separator under mechanical free fall. In this paper, two experiments are conducted with and without the center pin to experimentally verify the importance of the role of the center pin. The first experiment is a 50-cycle charge-discharge cycle test, and the second is a free fall test conducted according to the Underwriters Laboratories (UL) standards. Based on these experiments, we demonstrate that the center pin in a cylindrical cell is a very important component in terms of safety.

• Journal of the Korean Electrochemical Society
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• v.21 no.4
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• pp.61-67
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• 2018

As emerging the new electric devices, the commercial lithium ion batteries have faced with various challenges. In this regard, many efforts to solve challenges have been tried. In order to solve the above problems in terms of development of a new secondary battery, we successfully demonstrated the two electrocatalysts, such as MCWB and PPY hydrogel, PPY hydrogel and MCWB showed typical H3-type BET isotherm, indicating that micro- and mesopores existed. Especially, in terms of voltage efficiency at the first cycle, PPY hydrogel was higher than that of MCWB, but lower than that of PtC. More interestingly, the PPY hygrogel based seawater battery exhibited charge-discharge reversibility during 20 cycles, and the voltage efficiencies ranged from 70.32 % to 77.35 % in cyclic performance test.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.24 no.2
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• pp.127-132
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• 2024

Recently, secondary batteries, commonly known as rechargeable batteries, find widespread applications across various industries. Particularly valued for their compact and lightweight characteristics, they play a crucial role in diverse portable electronic devices such as smartphones, laptops, and tablets, offering high energy density and efficient charge-discharge capabilities. Moreover, they serve as vital components in electric vehicles and contribute significantly to the field of renewable energy as part of Energy Storage Systems(ESS). However, despite advancements in this technology, issues such as reduced lifespan, cracking, damage, and even the risk of fire can arise due to excessive charging and discharging of secondary batteries. To address these challenges, Battery Management System(BMS) are employed to protect against overcharging and improve overall performance. Nevertheless, understanding the protective range settings of BMS using lithium-ion batteries, the most commonly used secondary batteries, and lead-acid batteries can be challenging. Therefore, this paper aims to utilize a battery charge-discharge tester and simulator to investigate the charging and discharging characteristics of lithium-ion batteries and lead-acid batteries, addressing the associated challenges of reduced lifespan, cracking, damage, and fire hazards in secondary batteries.

• Proceedings of the KIEE Conference
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• 2007.10c
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• pp.247-249
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• 2007

Urban dynamometer driving schedule(FTP-75 mode) plays very significant role on automotive emission test, due to reference point. The overall system energy efficiency of a HEV(Hybrid Electric Vehicle) is highly dependent on the energy management strategy employed. An energy source is the heart of a HEV. In order to applicable to a vehicle component, it must be need to real world test result. But, the present state of things have numerous problems. In this paper, be studied performed based on HEV simulation software in virtual world and chassis dynamometer test in real world and the result make a comparative. Toyota Prius vehicle was adapted as a modeling and real testing to evaluate the hybrid components and energy balancing management. The point at issue is voltage and current analysis for HEV battery SOC(State of Charge), and verification for energy.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.24 no.6
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• pp.760-768
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• 2000

Filter efficiency of electrically charged particle in uncharged fibrous filter was measured. In previous studies, the effect of charged particle on filter efficiency was investigated but there was difficulty in measuring of image effect that is appeared at the charged small particle. We could easily measure the image effect with charging small particles by photoelectric charging. The spark discharge aerosol generator and a differential mobility analyzer (DMA) were used to generate sub-micron monodisperse particles (${\leq}200$ nm). The generated particles were charged in photoelectric charging process using ultraviolet lamp and electric field. The filter efficiency of the charged particles, classified by another DMA, was measured in filter tester using a condensation nucleus counter (CNC) as function of particle diameter, particle charge and airflow velocity. It is shown that the filter efficiency increases with increasing charge number of the particle and is affected by particle size and flow velocity. Single fiber filter efficiency mainly depends on image force parameter and peclet number. The peclet number was not considered at previous other papers. We propose a modi fied experimental correlation as function of image force parameter and peclet number.

• Proceedings of the KIPE Conference
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• 2019.11a
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• pp.70-72
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• 2019

For the safe and reliable operation of Lithium-ion batteries in Electric Vehicles (EVs) or Energy Storage Systems (ESSs), it is essential to have accurate information of the battery such as State of Charge (SOC). Many kinds of different techniques to estimate the SOC of the batteries have been developed so far such as the Kalman Filter. However, when it is applied to the multiple number of batteries it is difficult to maintain the accuracy of the estimation over all cells due to the difference in parameter value of each cell. Moreover the difference in the parameter of each cell may become larger as the operation time accumulates due to aging. In this paper a novel Deep Neural Network (DNN) based SOC estimation method for multi cell application is proposed. In the proposed method DNN is implemented to learn non-linear relationship of the voltage and current of the lithium-ion battery at different SOCs and different temperatures. In the training the voltage and current data of the Lithium battery at charge and discharge cycles obtained at different temperatures are used. After the comprehensive training with the data obtained with a cell resulting estimation algorithm is applied to the other cells. The experimental results show that the Mean Absolute Error (MAE) of the estimation is 0.56% at 25℃, and 3.16% at 60℃ with the proposed SOC estimation algorithm.

• The Transactions of the Korean Institute of Power Electronics
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• v.26 no.1
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• pp.1-8
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• 2021

For the safe and reliable operation of lithium-ion batteries in electric vehicles or energy storage systems, having accurate information of the battery, such as the state of charge (SOC), is essential. Many different techniques of battery SOC estimation have been developed, such as the Kalman filter. However, when this filter is applied to multiple batteries, it has difficulty maintaining the accuracy of the estimation over all cells owing to the difference in parameter values of each cell. The difference in the parameter of each cell may increase as the operation time accumulates due to aging. In this paper, a novel deep neural network (DNN)-based SOC estimation method for multi-cell application is proposed. In the proposed method, DNN is implemented to determine the nonlinear relationships of the voltage and current at different SOCs and temperatures. In the training, the voltage and current data obtained at different temperatures during charge/discharge cycles are used. After the comprehensive training with the data obtained from the cycle test with a cell, the resulting algorithm is applied to estimate the SOC of other cells. Experimental results show that the mean absolute error of the estimation is 1.213% at 25℃ with the proposed DNN-based SOC estimation method.

• Particle and aerosol research
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• v.19 no.3
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• pp.89-100
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• 2023

In our previous study, a wire-plate type electrostatic precipitator (ESP) was developed to collect bioaerosols of 100 nm size. In the study, various flow rates (40 ~ 100 L/min) and applied voltages (3 ~ 10 kV) were tested for experiment. In this study, numerical analysis was performed for the ESP of the previous study with the same flow rates and applied voltages, but with varying the size of bioaerosols to 0.04 ~ 2.5 ㎛. Overall, the numerical analysis results well predicted the experimental data. Bioaerosols of 0.1 ~ 0.5 ㎛ showed the minimum collection efficiency for all conditions because of low charge number. The effect of the ionic wind generated by the corona discharge was calculated. However, the ionic wind did not affect much the collection efficiency. The aerosol collection in the ESP of this study was due to the electrostatic force generated by particle charge in the electric field. This numerical study on the ESP can be used for the design and optimization of higher flow rate (> 100 L/min) ESP.