• Current Industrial and Technological Trends in Aerospace
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• v.7 no.2
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• pp.95-105
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• 2009

Fuel cells are applied to the propulsion system of aircraft based on environmental-friendly characteristics with low noise and zero emission of CO2, currently many kinds of UAV and small manned aircraft equipped with fuel cells are being developed. Fuel cells for aircraft typically classified into PEMFC(Proton Exchange Membrane Fuel Cell) type and SOFC(Solid Oxide Fuel Cell) type and the system is developed to adapt missions and operational conditions of aircraft. For UAV, various types of aircraft mostly based on PEM fuel cell technology are investigated for military or commercial uses, and the stability and endurance of system will be improved. For small manned aircraft, many researches are carried out to substitute the propulsion system by fuel cell, also some developments for the higher performance of APU of large commercial aircraft to apply fuel cells are in progress. In the future, a fuel cell aircraft will be expected to improve the reliability and efficiency with higher power density.

• Journal of Electrochemical Science and Technology
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• v.1 no.2
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• pp.92-96
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• 2010

A new synthesis method for the preparation of Pt electrocatalysts on carbon nanofibers (CNFs) is reported. In this method, Pt electrocatalysts are loaded onto 2-naphthalenethiol (NT) functionalized CNFs. The noncovalent functionalization of CNFs by NT is the effective way for better distribution of Pt particles and higher electrocatalytic activity in polymer electrolyte membrane fuel cells. It was found that the presence of NT acts as a poison to catalysts. Therefore, it is necessary to remove NT through the heat treatment at $400^{\circ}C$.

• 한국전기화학회:학술대회논문집
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• 2003.07a
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• pp.283-288
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• 2003

• Transactions of the Korean hydrogen and new energy society
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• v.25 no.5
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• pp.491-499
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• 2014

It is important to accurately measure and control the relative humidity of humidified gas entering a PEM (polymer electrolyte membrane) fuel cell stack because the level of humidification strongly affects the performance and durability of the stack. Humidity measurement devices can be used to directly measure the relative humidity, but they cost much to be equipped and occupy spaces in a fuel cell system. We present soft sensors for predicting the relative humidity without actual humidity measuring devices. By combining FIR (finite impulse response) model with PLS (partial least square) and SVM (support vector machine) regression models, DPLS (dynamic PLS) and DSVM (dynamic SVM) soft sensors were developed to correctly estimate the relative humidity of humidified gases exiting a planar-type membrane humidifier. The DSVM soft sensor showed a better prediction performance than the DPLS one because it is able to capture nonlinear correlations between the relative humidity and the input data of the soft sensors. Without actual humidity sensors, the soft sensors presented in this work can be used to monitor and control the humidity in operation of PEM fuel cell systems.

• 한국신재생에너지학회:학술대회논문집
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• 2008.05a
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• pp.558-559
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• 2008

본 논문은 미 일리노이 주립대 어바나-샴페인 캠퍼스에서 주로 군사용 응용 관련하여 개발 중인 마이크로 PEM 연료전지 시스템 개발에 대한 논문이다. 본 연구는 수소 저장 장치까지 포함하여 1 $mm^3$의 초소형 연료전지 시스템을 목표로 진행 중이며 본 논문은 이러한 진행 과정 중 화학적 하이드라이드 기반의 수소 발생기와 10 $mm^3$의 시스템 개발 과정에 대해 보고한다.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.58 no.1
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• pp.35-41
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• 2009

This paper proposes a stand alone type single-phase fuel cells micro-source with a voltage sag compensator for compensating the ac output voltage variations (sag or swell) of micro-source. The proposed micro-source is consist of a PEM(polymer electrolyte membrane) fuel cells simulator, a full bridge de converter, a 60Hz PWM(pulse width modulation) VSI(voltage source inverter), and a voltage sag compensator. Voltage sag compensator is similar to the configuration of hybrid series active power filter, and it is directly connected to micro-source through the injection transformer. Compensation algorithm of a voltage sag compensator adopts a single phase p-q theory. Effectiveness of the proposed the system is verified by the PSIM(power electronics simulation tool) simulation in the steady state and transient state which the proposed system is able to simultaneously compensate the harmonic current and source voltage sag or swell.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.41 no.10
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• pp.788-795
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• 2013

A magnesium bipolar plate whose surface was protected by thinly deposited silver layer was investigated as an alternative to existing graphite bipolar plate of PEM fuel cells. Thin silver layer of $3{\mu}m$ was deposited on a magnesium alloy substrate by physical vapor deposition (PVD) method in an environment of $180^{\circ}C$. A number of tests were conducted on the fabricated magnesium based bipolar plates to determine their suitability for use in PEM fuel cell stacks. The test on corrosion resistance in the same pH condition as in a PEM operation demonstrated the layer protected the magnesium alloy substrate, while unprotected substrate suffered from severe corrosion. The contact resistance of the fabricated bipolar plate was less than $20m{\Omega}-cm^2$ which was superior to the conventional bipolar plates. A single cell was constructed using the fabricated bipolar plates and power output was measured. Due to the enhanced conductivity caused by low contact resistance, slight increase was observed in current density and output voltage. With low density of the magnesium substrate and ease on machining, the weight reduction of the stack of 30~40 % is possible to produce the same power output.

• Carbon letters
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• v.8 no.4
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• pp.326-334
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• 2007

In this study, graphite composites were fabricated by warm press molding method to realize commercialization of PEM fuel cells. Graphite composites have been considered as alternative economic materials for bipolar plate of PEM fuel cells. Graphite powder that enables to provide electrical conductivity was selected as the main substance. The graphite powder was mixed with phenolic resin and the mixture was pressed using a warm press method. First of all, the graphite powder was pulverized with a ball mill for the dense packing of composite. As the ball milling time increases, the average size of particles decreases and the size distribution becomes narrow. This allows for improvement of the uniformity of graphite composite. However, the surface electrical resistivity of graphite composite increases as the ball milling time increases. It is due to that graphite particles with amorphous phase are generated on the surface due to the friction and collision of particles during pulverizing. We found that the contact electrical resistivity of graphite particles increases as the particle size decreases. The contact electrical resistivity of graphite powders was reduced due to high molding pressure by warm press molding. This leads to improvement of the mechanical properties of graphite composite. Hydrogen gas impermeability was measured with the graphite composite, showing a possibility of the application for bipolar plate in fuel cell. And, I-V curves of the graphite composite bipolar plate exhibit a similar performance to the graphite bipolar plate.

• Journal of Korean Society of Environmental Engineers
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• v.32 no.2
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• pp.113-120
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• 2010

Air-cathode microbial fuel cell consisted of 4 unit cells were operated under batch condition and electricity generation and microbial community structure variation were investigated, depending on separator types and cathode characteristics: A) PEM(Proton Exchange Membrane)-30% Wet proofing Carbon Cloth(WC), B) AEM(Anion Exchange Membrane-WC, C) CEM(Cation Exchange Membrane)-WC, D) PEM-No Wet proofing Carbon Cloth(NC). Maximum power densities of PEM-WC, AEM-WC and CEM-WC were 510.9, 522.1 and 504.8 $mW/m^2$, respectively. But PEM-NC showed relatively lower maximum power density of 218.3 $mW/m^2$. And PEM-WC, AEM-WC and CEM-WC showed similar internal resistances(20.0-28.2 ${\Omega}$). PCRDGGE, PCA and diversity indices showed that uncultured bacteria which reported in previous MFC studies were detected in suspended growth bacteria and attached growth bacteria would be affected not by separator type but by cathode characteristic. Thus, cathode characteristic can be one of the critical factors for power generation in air-cathode MFC using PEM, AEM, and CEM as separator.

• 한국전기화학회:학술대회논문집
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• 2005.07a
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• pp.323-328
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• 2005