• Proceedings of the KIEE Conference
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• 1999.07d
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• pp.1824-1826
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• 1999

In order to develop key technologies for a kW class for polymer electrolyte fuel cell (PEFC), various membranes (Nafion(112, 115, 117), Dow, Flemion, Gore, and Hanwha), and electrocatalysts (Pt/C, PtNi/C PtNiCo/C and PtRu/C) were used in the fabrication of the MEAs by using transfer printing technique. The effects of the thickness of Nafion membranes, electrocatalysts and the operating conditions (e.g. temperature, reactant gas pressure, and composition) on the performance of the MEA were investigated in the PEFC single cell($O_2/H_2$, and Air/$H_2$ cell). The performances of the MEAs for $O_2/H_2$ and Air/$H_2$ cells has been evaluated.

• Journal of Hydrogen and New Energy
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• v.23 no.1
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• pp.8-18
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• 2012

This paper presents a three-dimensional, transient cold-start polymer electrolyte fuel cell (PEFC) model to numerically evaluate the effects of membrane electrode assembly (MEA) design and cell location in a PEFC stack on PEFC cold start behaviors. The cold-start simulations show that the end cell experiences significant heat loss to the sub-freezing ambient and thus finally cold-start failure due to considerable ice filling in the cathode catalyst layer. On the other hand, the middle cells in the stack successfully start from $-30^{\circ}C$ sub-freezing temperature due to rapid cell temperature rise owing to the efficient use of waste heat generated during the cold-start. In addition, the simulation results clearly indicate that the cathode catalyst layer (CL) composition and thickness have an substantial influence on PEFC cold-start behaviors while membrane thickness has limited effect mainly due to inefficient water absorption and transport capability at subzero temperatures.

• Journal of Hydrogen and New Energy
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• v.22 no.6
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• pp.868-877
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• 2011

This paper presents a parallel computing methodology for polymer electrolyte fuel cells (PEFCs) and detailed simulation contours of a real-scale fuel cell. In this work, a three-dimensional two-phase PEFC model is applied to a large-scale 200 $cm^2$ fuel cell geometry that requires roughly 13.5 million grid points based on grid-independence study. For parallel computing, the large-scale computational domain is decomposed into 12 sub-domains and parallel simulations are carried out using 12 processors of 2.53 GHz Intel core i7 and 48GB RECC DDR3-1333. The work represents the first attempt to parallelize a two-phase PEFC code and illustrate two-phase contours in a representative industrial cell.

• 한국가시화정보학회:학술대회논문집
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• 2007.11a
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• pp.155-158
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• 2007

Water management for Polymer Electrolyte Fuel Cell (PEFC) has been receiving large attention as an important issue in practical applications. Proper water management is vital to achieve high performance and durability of PEFC. In this study, an X-ray imaging technique was employed to visualize the water distribution in a PEFC quantitatively. X-ray images of the PEFC components with and without water are distinguished clearly. From the visualized X-ray images, we could confirm the water distribution in the region between separator and gas diffusion layer (GDL). In addition, the contact angle of water in the micro-channels was also clearly visualized..

• Journal of the Korean Society of Visualization
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• v.5 no.2
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• pp.33-38
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• 2007

Water management in polymer electrolyte fuel cell (PEFC) has been receiving large attention as an important issue in practical applications. Proper water management is vital to achieve high performance and durability of PEFC. In this study, an X-ray imaging technique was employed to visualize the water distribution in a PEFC quantitatively. X-ray images of the PEFC components with and without water were distinguished clearly. From the visualized X-ray images, we could evaluate the water distribution in the region between separator and gas diffusion layer (GDL) quantitatively. In addition, the contact angle of water in the micro-channels was also clearly visualized.

• New & Renewable Energy
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• v.1 no.2 s.2
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• pp.41-52
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• 2005

The effects of internal manifold designs on the reactants feed-stream in Polymer Electrolyte Fuel Cells [PEFCs] is studied to figure out flow and thermal distribution patterns over an entire fuel cell stack. Reactants flows are modeled either laminar of turbulent depending on regions and the open channels in the bipolar plates are simulated by porous media where permeability should be pre-deter-mined for computational analysis. In this work, numerical models for reactants feed-stream In the PEFC manifolds are classified Into two major flow patterns: Z-shape and U-shape. Several types of manifold geometries are analyzed to find the optimal manifold configurations. The effect of heat generation in PEFC on the flow distribution is also Investigated applying a simplified heat transfer model in the stack level (i.e. multi-cell electrochemical power-generation unit). This modeling technique Is well suited for many large scale problems and this scheme can be used not only to account for the manifold flow pattern but also to obtain Information on the optimal design and operation of PEFC systems.

• Transactions of the Korean Society of Automotive Engineers
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• v.19 no.3
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• pp.44-51
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• 2011

Polymer Electrolyte Fuel Cells (PEFCs) operate in wide-range changes in temperature, humidity, and electric current for automotive applications. In order to operate automotive PEFC efficiently, optimal air supply is required to adjust to these changes. This paper presents an air-supply optimization process that consists of experiments, modeling of the PEFC system, and optimization. The objective is to establish an air supply suitable for the required power for PEFC system and optimized with a Lagrange multiplier. Our simplified PEFC system model is used as a constraint for optimization problem. The result of this paper presents that efficient operation of PEFC system can be achieved by air-supply optimization.

• Journal of Hydrogen and New Energy
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• v.14 no.1
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• pp.35-45
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• 2003

Polymer electrolyte fuel cells(PEFC) have been considered to be a suitable candidate for residential, portable and mobile applications, due to their high efficiency and power density, even at low operating temperature. KIER developed a 5kW class PEFC system for residential application and operated the system for over 1,000 hours. To develop a 5kW PEFC system, performance of a cell was improved through successive tests of single cell of small and large area. Fabrication of three 2,5 kW class stacks, design and fabrication of natural gas reformer, design of auxiliary equipments such as DC/DC converter, DC/AC inverter and humidifying units were carried out along with integration of components, operation and evaluation of total system. During the development period from 1999 to 2001, MEA(membrane electrode assembly) fabrication technologies, design and fabrication technologies for separators, stacking technologies and so on were developed, thereby providing basis for developing stacks of higher efficiency and power density in the future. Experience of development of natural gas reformer opened possibilities to use various kinds of fuels. Main results obtained from the development of a 5kW class PEFC system for residential application are summarized.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2005.05a
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• pp.180-184
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• 2005

An experimental study is performed to evaluate the performance and the efficiency by humidifying MEA and by making the double-tied catalyst layers in a fuel cell system which is taken into account the physical and thermal concept. An electrical output produced by PEFC(polymer Electrolyte Fuel Cell) is measured to assess the performance of the stack and the efficiency is also evaluated according to the different situation in which is placed with and without the humidification of MEA (Membrane Electrolyte Assembly). Subsequently, It is found that the measured values of stack voltage and current are influenced by the stack temperature, humidification, and the double-tied catalyst layers which gives more enhanced values to apply for electric units.

• 한국신재생에너지학회:학술대회논문집
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• 2009.11a
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• pp.149-149
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• 2009

Generally, Nafion ionomer is used in the polymer electrolyte fuel cell (PEFC) electrodes to achieve high power density. At the high temperature operation of PEFC, however, ionic conductivity of Nafion remarkably decreased due to the evaporation of water in Nafion polymer. Recently, many researchers have focused on using the Ionic Liquids(ILs) instead of water in Nafion polymer. ILs have intrinsic properties such as good electrochemical stability, high ionic conductivity, and non-flammability. Especially, ILs play a crucial role in proton conduction by the Grottuss mechanism and act as water in water-free Nafion polymer. However, it was found that the ILs was leached out of the polymer matrix easily. In this study, we prepared membrane electrode assemblies with various contents of ILs. The effect of ILs in the electrode of each designed was investigated by a cyclic voltammetry measurement and the cell performance obtained through a single cell test using H2/Air gases. Electrodes with different contents of ILs in catalyst layer were examined at high temperature and low humidified condition.