• The Transactions of the Korean Institute of Power Electronics
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• v.4 no.1
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• pp.57-65
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• 1999

This paper deals with stand-alone photovoltaic system(SPVS) with charge and discharge controller. Main power source of SPVS are generally solar cell and battery. Therefore SPVS can be classified into variable types in accordance with connection type between battery and solar cell. Mainly used one of them is direct connection type which has advantages such as simple structure and simple controller. However most big drawback of this system is energy loss by voltage disharmony between solar cell and battery. Therefore SPVS with charge and discharge controller which can operate solar cell at maximum power point is suggested and designed with instantaneous controller. And system operating characteristics are verifieded by experiment with a laboratory prototype in this paper.

• Transactions of the Korean Society of Automotive Engineers
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• v.13 no.6
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• pp.38-47
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• 2005

In this paper, a regenerative braking algorithm is proposed to make the maximum use of the regenerative braking energy for an independent front and rear motor drive parallel HEV. In the regenerative braking algorithm, the regenerative torque is determined by considering the motor capacity, motor efficiency, battery SOC, gear ratio, clutch state, engine speed and vehicle velocity. To implement the regenerative braking algorithm, HEV powertrain models including the internal combustion engine, electric motor, battery, manual transmission and the regenerative braking system are developed using MATLAB, and the regenerative braking performance is investigated by the simulator. Simulation results show that the proposed regenerative braking algorithm contributes to increasing the battery SOC, which recuperates 60 percent of the total braking energy while satisfying the design specification of the control logic. In addition, a control algorithm which limits the regenerative braking is suggested by considering the battery power capacity and dynamic response characteristics of the hydraulic control module.

• Bulletin of the Korean Chemical Society
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• v.29 no.10
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• pp.1965-1968
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• 2008

The effects of carbon-coated silicon/graphite (Si/Gr.) composite anode on the electrochemical properties were investigated. The nanosized silicon particle shows a good cycling performance with a reasonable value of the first reversible capacity as compared with microsized silicon particle. The carbon-coated silicon/graphite composite powders have been prepared by pyrolysis method under argon/10 wt% propylene gas flow at $700{^{\circ}C}$ for 7 h. Transmission electron microscopy (TEM) analysis indicates that the carbon layer thickness of 5 nm was coated uniformly onto the surface silicon powder. It is confirmed that the insertion of lithium ions change the crystalline silicon phase into the amorphous phase by X-ray diffraction (XRD) analysis. The carbon-coated composite silicon/graphite anode shows excellent cycling performance with a reversible value of 700 mAh/g. The superior electrochemical characteristics are attributed to the enhanced electronic conductivity and low volume change of silicon powder during cycling by carbon coating.

• Nuclear Engineering and Technology
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• v.48 no.3
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• pp.773-777
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• 2016

A betavoltaic battery was prepared using radioactive $^{63}Ni$ attached to a three-dimensional single trenched P-N absorber. The optimum thickness of a $^{63}Ni$ layer was determined to be approximately $2{\mu}m$, considering the minimum self-shielding effect of beta particles. Electroplating of radioactive $^{63}Ni$ on a nickel (Ni) foil was carried out at a current density of $20mA/cm^2$. The difference of the short-circuit currents ($I_{sc}$) between the pre- and post-deposition of $^{63}Ni$ (16.65 MBq) on the P-N junction was 5.03 nA, as obtained from the I-V characteristics. An improved design with a sandwich structure was provided for enhancing performance.

• Transactions of the Korean hydrogen and new energy society
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• v.27 no.4
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• pp.365-371
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• 2016

Cell performance of the Zn-Br redox flow battery (ZBRFB) using two different type's membrane (Nafion117 and SF-600) was evaluated at $20mA/cm^2$ of current density in 1M (mol/L) $ZnBr_2$ + 2M KCl + 0.3M EMPBr(1-ethyl-1-methyl pyrrolidinium bromide) electrolyte. The average energy efficiencies of ZBRFB were 74.9% and 74.7% for Nafion117 and SF-600, respectively. The electrolyte added the 1-ethyl-3-methylimidazolium dicyanamide (EMICA) as an additive was tested for the electrolyte in ZBRFB using SF-600 at $30mA/cm^2$ of current density. An average energy efficiency of the ZBRFB was 74.5% and 77.4% for the electrolyte non-added EMICA and added 1wt% of EMICA, respectively. ZBRFB using the electrolyte added EMICA was showed the higher performance than that using the electrolyte non-added EMICA.

• Proceedings of the KIEE Conference
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• 1999.11d
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• pp.968-970
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• 1999

The trend of increasing of portable electric devices and demand for global environmental conservation have demands the development of high energy density rechargeable batteries. Lithium polymer battery has excellent theoretical energy density and energy conversion efficiency. Lithium polymer battery, included solid polymer electrolyte(SPE), can be viewed as a system suitable for wide applications from thin film batteries for microelectronics to electric vehicle batteries. The purpose of this paper is to research and development of flyash anode for lithium polymer battery. We investigated AC impedance response and charge/discharge characteristics of flyash/SPE/Li cells. The radius of semicircle associated with the interfacial resistance of flyash/SPE/Li cell increased very slowly during discharge process from 3.11V to 0.478V. And then the cell resistance was decreased at discharge process from 10% SOC to 0% SOC. Also, The radius of semicircle associated with the interfacial resistance of flyash/SPE/Li cell decreasing very slowly during charge process. And then the cell resistance was increased after 20th discharge precess. The discharge capacity based on flyash of 1st and 20th cycles was 276mAh/g and 143mAh/g.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.37 no.3
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• pp.397-403
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• 2013

The demand for eco-friendly and higher fuel economy vehicles has helped develop eco-friendly and fuel-efficient vehicles such as hybrid vehicles. In a hybrid vehicle, the change in the battery charge after driving should be added to the fuel consumption as the equivalent fuel usage based on its own characteristics. Thus, the fuel efficiency of a hybrid vehicle cannot be improved simply by increasing the battery capacity. In this study, I attempt to improve the total fuel economy of a hybrid vehicle, including the equivalent fuel consumption, by modeling a fuel cell hybrid vehicle using Matlab Simulink, analyzing the usage zone of the fuel cell with the existing control strategy, and optimizing the power distribution of the battery and fuel cell in the main usage zone of the fuel cell.

• Clean Technology
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• v.18 no.3
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• pp.320-324
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• 2012

In the present study, the discharge characteristics of a lithium-ion battery was evaluated to calculate the rate of heat generation under various discharge rates by mathematical modeling. The modeling and simulation of a pseudo-two dimensional ionic transport system for governing Butler-Volmer equation were carried out by using FEMLAB as a PDE (partial differential equation) solver, where the discharge rate was changed from 5 $A/m^2$ to 25 $A/m^2$. The computational results showed that the concentration of consumed solid-phase lithium at the surface of electrode was increased with increasing discharge rates. While the resulting diffusion limitation occurred shortly, it increased the rate of heat generation even more rapidly for the internal voltage to approach the cutoff voltage of the lithium-ion battery.

• 한국태양에너지학회:학술대회논문집
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• 2011.11a
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• pp.249-255
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• 2011

This paper is about the study of a stand-alone photovoltaic power conditioning system with an energy storage system with battery. The paper proposes the appropriate circuit model of stand-alone PV PCS considering the maintenance of the battery system. It also proposes the buck converter modeling by a state-space averaging method considering characteristics of solar cell. Lastly, it shows the way to choose the suitable battery and to design the model of bi-directional converter for charging and discharging battery. PSIM simulation is used to validate the proposed algothim of the system.

• Journal of the Semiconductor & Display Technology
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• v.7 no.2
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• pp.13-17
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• 2008

In this paper, in order to get the characteristics of the lithium secondary cell, such as charge and discharge characteristic, temperature characteristic, self-discharge characteristic and the capacity recovery rate etc, we build a thermal model that estimate the impedance of battery by experiment & simulation. In this one-dimensional model, Seven governing equations are made to solve seven variables c, $c_s,\;\Phi_1,\;\Phi_2,\;i_2$, j and T. The thermal model parameters used in this model have been adjusted according to the experimental data measured in the laboratory. The result(Voc, Impedance) of this research can be used in BMS(Battery Management System), so an efficient method of using battery is developed.