• International Journal of Automotive Technology
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• v.8 no.1
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• pp.119-126
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• 2007

Because of the low temperature operation, proton exchange membrane (PEM) fuel cell has a water phase transition. Therefore, water management is an important operation issue in a PEM fuel cell because the liquid water in the fuel cell causes electrode flooding that can lower the cell performance under high current density conditions. In this study, in order to understand the reactant distributions in the cathode channels of the PEM fuel cell, an experimental technique that can measure the species concentrations of reactant gases by using gas chromatograph (GC) is applied for an operating PEM fuel cell. The oxygen distribution along the cathode flow channels of PEM fuel cell is mainly investigated with various operating conditions. Also, the relations between cathode flooding and oxygen concentrations and oxygen consumption pattern along the cathode channel configurations of the unit cell adopted for this study are discussed using GC measurement and visualization experiment of cathode flooding. It is found that the amount of oxygen consumption is very sensitive to various operating conditions of the fuel cell and was much affected by the flooding occurrence in cathode channels.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 2005.05a
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• pp.288-291
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• 2005

This paper is aimed at presenting a proton exchange membrane (PEM) fuel cell stack. The fuel cell electrical output voltage and current (V-I) characteristic is described for the first time by a simplified closed form suitable. The characteristics obtained from the simulation are compared with the experimental results on a Ballard commercial fuel cell stack as well as to the manufacturer given data.

• Proceedings of the KIPE Conference
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• 2005.07a
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• pp.781-784
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• 2005

This paper is aimed at presenting a proton exchange membrane ( PEM ) fuel cell stack. The fuel cell electrical output voltage and current (V-I) characteristic is described for the first time by a simplified closed form suitable. The characteristics obtained from the simulation are compared with the experimental results on a Ballard commercial fuel cell stack as well as to the manufacturer given data.

• Proceedings of the KSME Conference
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• 2003.11a
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• pp.460-465
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• 2003

The modeling of PEM (Proton Exchange Membrane) fuel cell system consisting of fuel cell stack and BOP (Balance of Plant) is presented in this paper. The effects of temperature, pressure (air, hydrogen), and humidity on the fuel cell system performance were mainly investigated using thermo-dynamical and electro-chemical equations. To understand the power distribution characteristics of fuel cell system, the effects of operating temperature and air pressure on maximum power and system power were also demonstrated. Through this study, we can get the basic insight into the fuel cell stack and BOP component sizing and it can be used effectively for the optimization of the practical fuel cell systems in purpose.

• Journal of the Korean Chemical Society
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• v.59 no.5
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• pp.413-422
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• 2015

Proton exchange membrane (PEM), which transfers proton from the anode to the cathode, is the key component of the proton exchange membrane fuel cell (PEMFC). Nafion is widely used as PEM due to its high proton conductivity as well as excellent chemical and physical stabilities. However, its high cost and the environmental hazards limit the commercial application in PEMFCs. To overcome these disadvantages, various alternative polymer electrolytes have been investigated for fuel cell applications. We used densely sulfonated polymers to maximize the ion conductivity of the corresponding membrane. To overcome high swelling, dipole-dipole interaction was used by introducing nitrile groups into the polymer backbone. As a result, physically-crosslinked membranes showed improved swelling ratio despite of high water uptake. All the membranes with different hydrophilic-hydrophobic compositions showed higher conductivity, despite their lower IEC, than that of Nafion-117.

• 한국신재생에너지학회:학술대회논문집
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• 2007.06a
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• pp.539-542
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• 2007

The transient response of PEMFC (proton exchange membrane fuel cell) is important criteria in the application of PEM fuel cell to real automotive system. In this work, using a transparent unit PEM fuel cell, the transient response and cathode flooding during load change are investigated. The cell voltage is acquired according to the current density change($0.3Acm^2$ to $0.6A/cm^2$) under various stoichiometry conditions and different flooding intensities, Also the cathode gas channel images are obtained by CCD imaging system simultaneously. The different level of undershoots appeared at the moment of load changes under different cathode stoichiometries and flooding intensities. The correlation of the dynamic behavior with stoichiometry and cathode flooding is induced from the results of these experiments.

• Journal of Electrical Engineering and Technology
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• v.7 no.6
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• pp.891-897
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• 2012

In this paper, the observer based nonlinear state feedback controller has been developed to control the pressures of the oxygen and the hydrogen in the PEM(Proton Exchange Membrane) fuel cell system. Nonlinear model of the PEM fuel cell system was introduced to study the design problems of the state observer and model based controller. A cascade observer using the filtering technique was used to estimate the pressure derivatives of the cathode and the anode in the system. In order to estimate the pressures of the cathode and the anode, the sliding mode observer was designed by using these pressure derivatives. To estimate the oxygen pressure and the hydrogen pressure in the system, the nonlinear state observer was designed by using the cathode pressure estimates and the anode it. These results will be very useful to design the state feedback controller. The validity of the proposed observers and the controller has been investigated by using the Lyapunov's stability analysis strategy.

• 한국신재생에너지학회:학술대회논문집
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• 2007.06a
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• pp.157-160
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• 2007

The catalyst layer of a proton exchange membrane (PEM) fuel cell is a mixture of polymer, carbon, and platinum. The characteristics of the catalyst layer play critical role in determining the performance of the PEM fuel cell. This research investigates the role of catalyst layer composition using a Central Composite Design (CCD) experiment with two factors which are Nafion content and carbon loading while the platinum catalyst surface area is held constant. For each catalyst layer composition， polarization curves are measured to evaluate cell performance at common operating conditions, Electrochemical Impedance Spectroscopy (EIS), and Cyclic Voltammetry (CV) are then applied to investigate the cause of the observed variations in performance. The results show that both Nafion and carbon content significantly affect MEA performance. The ohmic resistance and active catalyst area of the cell do not correlate with catalyst layer composition, and observed variations in the cell resistance and active catalyst area produced changes in performance that were not significant relative to compositions of catalyst layers.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.06a
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• pp.207-210
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• 2005

In this paper, a two-dimensional cross-channel model was applied to investigate influence of the gas diffusion layer(GDL) property and flow field geometry in the anode side for proton exchange membrane fuel cell(PEMFC). The GDL is made of a porous material such as carbon cloth, carbon paper, or metal wire mesh. To the simplicity, the GDL is represented as a block of material containing numerous pathways through which gaseous reactants and liquid water can pass. The purpose of present work was to study the effect of the GDL thickness and the porosity, and flow field geometry by computational fluid dynamics(CFD)

• 한국신재생에너지학회:학술대회논문집
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• 2006.11a
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• pp.105-108
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• 2006

The fuel cell is one of the promising environment-friendly energy sources for the next generation. The fuel cell provides good energy efficiency above 40% without pollution or noise. Different fuel cell types are usually distinguished by the kind of electrolyte. Among these, the proton exchange membrane fuel cell (PEMFC) has advantages of high power density. low operating temperature, relatively quick start-up, and rapid response to varying loads. The bipolar plate is a major component of the PEM fuel cell stack, and it takes a large portion of stack volume, weight and cost. In this study, as alternative materials for bipolar plate of PEM fuel cells, graphite composites were fabricated by compression molding and by machining. Graphite particles mixed with epoxy resin were used as the main substance to provide electric conductivity. Flow channels were fabricated by compression molding with design of experiments (DOE) to evaluate moldability. The cost for compression molding of graphite-composite bipolar plate was compared with machining cost to make the same bipolar plate.