• Title/Summary/Keyword: Polymer electrolyte membrane

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Geometrically Inhomogeneous Random Configuration Effects of Pt/C Catalysts on Catalyst Utilization in PEM Fuel Cells (연료전지 촉매층 내 촉매활성도에 대한 탄소지지 백금 촉매의 기하학적 비등방성 효과에 관한 연구)

  • Shin, Seungho;Kim, Ah-Reum;Jung, Hye-Mi;Um, Sukkee
    • Journal of the Korean Society for Precision Engineering
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    • v.31 no.10
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    • pp.955-965
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    • 2014
  • Transport phenomena of reactant and product are directly linked to intrinsic inhomogeneous random configurations of catalyst layer (CL) that consist of ionomer, carbon-supported catalyst (Pt/C), and pores. Hence, electrochemically active surface area (ECSA) of Pt/C is dominated by geometrical morphology of mass transport path. Undoubtedly these ECSAs are key factor of total fuel cell efficiency. In this study, non-deterministic micro-scale CLs were randomly generated by Monte Carlo method and implemented with the percolation process. To ensure valid inference about Pt/C catalyst utilization, 600 samples were chosen as the number of necessary samples with 95% confidence level. Statistic results of 600 samples generated under particular condition (20vol% Pt/C, 30vol% ionomer, 50vol% pore, and 20nm particle diameter) reveal only 18.2%~81.0% of Pt/C can construct ECSAs with mean value of 53.8%. This study indicates that the catalyst utilization in fuel cell CLs cannot be identical notwithstanding the same design condition.

A Study on the Protective Function Performance Evaluation of Grid-Connected Power Conditioning System for Residential Fuel Cell System (가정용 연료전지시스템 계통연계형 전력변환장치의 보호기능 성능평가에 관한 연구)

  • Lee, Jung-Woon;Seo, Won-Seok;Kim, Young-Gyu
    • 한국신재생에너지학회:학술대회논문집
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    • 2009.06a
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    • pp.341-344
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    • 2009
  • In this paper, protective function evaluation was conducted to determine the performance and safety of a power conditioning system(PCS) for 1kW residential fuel cell system. It is essential to have a power quality, grid-connection and safety of PCS. Even though it is under 500ms by KGS-A410 standard, it is shown a rapid response time of 25ms from input under-voltage test. In terms of output over/under-voltage test, it is shown 29.15 and 79.4ms. Especially using anti-islanding test, it is shown all times under 100ms for combination cases of real and reactive power. We confirmed a rapid response characteristics and safety of PCS. The results of this evaluation are being used to develop a new test protocols of PCS.

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Operating characteristics of an air cooling PEMFC for portable application (이동 전원용 공랭식 고분자 연료전지의 제작 및 운전 특성 연구)

  • Sohn Young-Jun;Park Gu-Gon;Yang Tae-Hyun;Yoon Young-Gi;Lee Won-Yong;Yim Sung-Dae;Kim Chang-Soo
    • New & Renewable Energy
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    • v.1 no.1 s.1
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    • pp.72-78
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    • 2005
  • Optimal design and proper operation are important to get aimed output power of a polymer electrolyte membrane fuel cell (PEMFC) stack. An air cooling fuel cell stack is widely used in sub kW PEMFC systems. The purpose of this study is to analyze operating conditions affecting the performance of the air cooling PEMFC which is designed for portable application. In portable applications, air cooling stack is difficult to maintain well balanced operating conditions. The importart parameters are the relative humidity, the temperature of the stack, the utilization of reactant gas and so on. in this study, a 500W air cooling PEMFC was fabricated and tested to evaluate the design performance and to determine optimal operating conditions. Moreover, basic modeling also is carried out. These results can be used 3s design criteria and optimal operating conditions for portable PEMFCs

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Electrocatalytic activity of Carbon-supported near-surface alloys (NSAs) for Electode reaction of Fuel cell (연료전지 전극 반응을 위한 카본 담지 표면 합금의 전기촉매 활성)

  • Park, In-Su;Lee, Kug-Seung;Choi, Baeck-Beom;Sung, Yung-Eun
    • 한국신재생에너지학회:학술대회논문집
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    • 2006.11a
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    • pp.316-319
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    • 2006
  • There is a worldwide interest in the development and commercialization of Polymer Electrolyte Membrane Fuel Cells (PEMFCs) for vehicular and stationary applications. One of the major objectives is the reduction of loaded electrode materials, which is comprise of the Pt-based noble metals. In this paper, a novel chemical strategy is described for the preparation and characterization of carbon-supported and surface-alloys, which were prepared by using a successive reduction process. After preparing Au colloid nanoparticles, the deposition of Au colloid nanoparticles occurred spontaneously in the carbon black-dispersed aqueous solution. Then nano-scaled active materials were formed on the surface of carbon-supported Au nanoparticles. The structural and electrochemical analyses indicate that the active materials were deposited on the surface of Au nanoparticles selectively and that an at toying process occurred during the successive reducing process The carbon-supported & surface-alloys showed the higher electrocatalytic activity than those of the particle-alloys and commercial one (Johnson-Matthey) for the reaction of methanol and formic acid oxidation. The increased electrocatalytic activity might be attributed to the effective surface structure of surface-alloys, which have a high utilization of active materials for the surface reaction of electrode.

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The Performance Evaluation of Metallic Bipolar Plates of Fuel Cells for a Small Reconnaissance UAV (소형 정찰 UAV를 위한 연료전지 금속 분리판의 성능 평가)

  • Kim, Ki-In;Lee, Jong-Kwang;Kwon, Se-Jin
    • Proceedings of the Korean Society of Propulsion Engineers Conference
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    • 2009.11a
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    • pp.278-281
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    • 2009
  • The performance of aluminum bipolar plates was evaluated for the lightweight fuel cell system as a power source for a small reconnaissance UAV. Higher performance per weight was obtained from aluminum bipolar plates than the graphite bipolar plates. To check the influence of operating temperature, the performance of a single cell using aluminum bipolar plates was evaluated at 40 / 50 / $60^{\circ}C$. When dry hydrogen and air were used, the finest performance was obtained at $40^{\circ}C$, a lower operating temperature compared with usual operating temperatures.

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A Study on the Mass Flow Effects to the Performance of PEMFC (고분자 전해질형 연료전지내의 질량유동이 성능에 미치는 영향)

  • Park, Chang-Kwon;Jo, In-Su;Oh, Byeong-Soo
    • Transactions of the Korean hydrogen and new energy society
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    • v.18 no.4
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    • pp.422-431
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    • 2007
  • Polymer electrolyte membrane fuel cell(PEMFC) is very interesting power source due to high power density, simple construction and operation at low temperature. But it has problems such as high cost, improvement of performance and effect of temperature. These problems can be approached to be solved by using mathematical models which are useful tools for analysis and optimization of fuel cell performance and for heat and water management. In this paper, the present work is to develop an electrochemical model to examine the electrochemical process inside PEM fuel cell. A complete set of considerations of mass, momentum, species and charge is developed and solved numerically with proper account of electrochemical kinetics. When depth of gas channel becomes thinner, diffusion of reactant makes well into gas diffusion layer(GDL) and the performance increases. Although at low current region there is little voltage difference between experimental data of PEM fuel cell and numerical data. When the porosity size of gas diffusion layer for PEM fuel cell is bigger, oxygen diffusion occurs well and oxygen mass fraction appears high in catalyst layer.

Synthesis and Study of Pt/MWCNTs Catalysts by Using Microwave Assisted Polyol Method for PEM Fuel Cells (마이크로파-폴리올법을 이용한 고분자 전해질 연료전지용 Pt/MWCNTs 촉매의 제조 및 이의 특성분석)

  • Lee, Tae Kyu;Hur, Seung Hyun
    • Journal of the Korean Electrochemical Society
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    • v.15 no.4
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    • pp.264-269
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    • 2012
  • In this study, highly loaded(50 wt%) and very stable Pt/MWCNT catalysts for Polymer Electrolyte Membrane Fuel Cells(PEMFCs) are synthesized in short time scale by microwave assisted polyol method with different microwave irradiation time. The XRD and TEM results show that the Pt size becomes bigger as the microwave irradiation time increases. The mean Pt sizes of fabricated catalysts are 4.1, 4.9 and 8.5 nm when the microwave are irradiated for 10, 20 and 30 min, respectively. When compared with Pt catalyst made by conventional polyol method, it shows better long term durability due to the better Pt dispersion on the MWCNT surface.

The effect of PEMFC stack performance at air supply condition (공기공급 조건이 스택성능에 미치는 영향)

  • Park, Chang-Kwon;Oh, Byeong-Soo
    • Transactions of the Korean hydrogen and new energy society
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    • v.19 no.3
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    • pp.232-238
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    • 2008
  • Research has been proceeded on fuel cell which is fueled by hydrogen. Polymer electrolyte membrane fuel cell (PEMFC) is promising power source due to high power density, simple construction and operation at low temperature. But it has problems such as high cost, temperature dependent performance. These problems could be solved by experiment which is useful for analysis and optimization of fuel cell performance and heat management. In this paper, when hydrogen flows constantly at the stoichiometry of ${\xi}=1.6$, the performance of the fuel cell stack was increased and the voltage difference between each cells was decreased according to the increase of air stoichiometry by 2.0, 2.5, 3.0. Therefore, the control of air flow rate in the same gas channel is important to get higher performance. Purpose of this research is to expect operation temperature, flow rate, performance and mass transportation through experiment and to help actual manufacture of PEM fuel cell stack.

Analysis of Part Load Performance of a Hybrid PEMFC System (하이브리드형 고분자전해질 연료전지 시스템의 부분부하 성능해석)

  • Ji, Seung-Won;You, Byung-June;Kim, Tong-Seop;Sohn, Jeong-Lak;Lee, Young-Duk;Ahn, Kook-Young
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.32 no.11
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    • pp.849-855
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    • 2008
  • The paper addresses modeling and analysis of the part load performance of a hybrid fuel cell system integrating a polymer electrolyte membrane fuel cell(PEMFC) and a gas turbine(GT). The system is a pressurized one where the working pressure of the PEMFC is higher than the ambient pressure. In addition to the two major components, the system also includes auxiliary parts such as a steam reformer, a humidifier, and afterburner and so on. Based on design analysis, component off-design models are incorporated in the analysis program and part load operation is simulated. The mode for the part load operation of the PEMFC/GT hybrid system is a variable rotational speed operation. The operating characteristics and variations in the system efficiency and component performance parameters at part load are analyzed.

The Effect of a Bypass Flow Penetrating through a Gas Diffusion Layer on Performance of a PEM Fuel Cell (가스확산층을 통과하는 반응가스 우회유동이 고분자 연로전지의 성능에 미치는 영향)

  • Cho, Choong-Won;Ahn, Eun-Jin;Lee, Seung-Bo;Lee, Won-Yong
    • 한국신재생에너지학회:학술대회논문집
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    • 2007.11a
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    • pp.147-151
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    • 2007
  • A serpentine channel geometry often used in a polymer electrolyte membrane fuel cell has a strong pressure gradient between adjacent channels in specific regions. The pressure gradient helps some amount of reactant gas penetrate through a gas diffusion layer(GDL). As a result, the overall serpentine flow structure is slightly different from intention of a designer. The purpose of this paper is to examine the effect of serpentine flow structure on current density distribution. By using a commercial code, STAR-CD, a numerical simulation is performed to analyze the fuel cell with relatively high aspect ratio active area. To increase the accuracy of the numerical simulation, GDL permeabilities are measured with various compression conditions. Three-dimensional flow field and current density distribution are calculated. For the verification of the numerical simulation results, water condensation process in the cathode channel is observed through a transparent bipolar plate. The result of this study shows that the region of relatively low current density corresponds to that of dropwise condensation in cathode channels.

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