• Journal of Hydrogen and New Energy
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• v.24 no.1
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• pp.50-60
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• 2013

High temperature proton exchange membrane fuel cells (PEMFCs) using phosphoric acid (PA) doped polybenzimidazole (PBI) membranes have been concentrated as one of solutions to the limits with traditional low temperature PEMFCs. However, the amount of reported experimental data is not enough to catch the operational characteristics correlated with cell performance and durability. In this study, design of experiments (DOE) based operational optimization method for high temperature PEMFCs has been proposed. Response surface method (RSM) is very useful to effectively analyze target system's characteristics and to optimize operating conditions for a short time. Thus RSM using central composite design (CCD) as one of methodologies for design of experiments (DOE) was adopted. For this work, the statistic models which predict the performance and degradation rate with respect to the operating conditions have been developed. The developed performance and degradation models exhibit a good agreement with experimental data. Compared to the existing arbitrary operation, the expected cell lifetime and average cell performance during whole operation could be improved by optimizing operating conditions. Furthermore, the proposed optimization method could find different new optimal solutions for operating conditions if the target lifetime of the fuel cell system is changed. It is expected that the proposed method is very useful to find optimal operating conditions and enhance performance and durability for many other types of fuel cell systems.

• The Transactions of the Korean Institute of Power Electronics
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• v.13 no.1
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• pp.46-54
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• 2008

In this paper, a low-cost impedance spectroscopy system(LCISS) suitable for modeling the electrochemical power sources such as fuel cells, batteries and supercapacitors is designed and implemented. Since the developed LCISS is composed of simple sensor circuits, commercial data acquisition board and LabVIEW software, a graphic language with powerful HMI(Human-Machine Interface), it is expected ta be widely used in substitution of the expensive EIS instruments. In the proposed system, the digital lock-in amplifier is adopted to achieve the accurate measurements even in the presence of the high level of noises. The developed hardware and software is applied to measure the impedance spectrum of the Ballard Nexa 1.2kW proton exchange membrane fuel cell stack and an equivalent impedance model is proposed based on the measurement results. The validity of the proposed equivalent circuit and the developed system is proven by the measurement of the ac power losses of the PEM fuel celt stack by the ripple current.

• Clean Technology
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• v.10 no.1
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• pp.9-17
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• 2004

Direct methanol fuel cell(DMFC) with proton exchange membrane (PEM) has advantages over the conventional power source (e.g. vehicle). DMFC, however, has a problem to be solved such as methanol crossover, high anodic overpotential and limiting current density, etc. The physicochemical phenomena in DMFC can be described by coupled PDEs (partial differential equations), which can be solved by a PDE solver. In this paper, we utilized a commercial software FEMLAB to solve the PDEs. The FEMLAB is one of the software programs available which are developed as a solver for building physics problems based on PDEs and is designed to simulate systems of coupled PDEs which may be 1D, 2D, 3D, non-liner and time dependent. We performed simulation using the Tafel equation as an electrochemical reaction model to analyze methanol concentration profile in DMFC system. We confirm that the rapid decrease of methanol concentration at anodic catalyst layer with the increase of the current density is a main reason of the low performance in DMFC through simulation results.

• Transactions on Electrical and Electronic Materials
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• v.17 no.2
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• pp.57-68
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• 2016

In this study, we present the modern hybrid system based power generation for electric vehicle applications. We describe the hybrid structure of modified current source based DC - DC converters used to extract the maximum power from Photovoltaic (PV) and Fuel Cell system. Due to reduced dc-link capacitor requirement and higher reliability, the current source inverters (CSI) better compared to the voltage source based inverter. The novel control strategy includes Distributed Maximum Power Point Tracking (DMPPT) for photovoltaic (PV) and fuel cell power generation system. The proposed DC - DC converters have been analyzed in both buck and boost mode of operation under duty cycle 0.5>d, 0.5<d<1 and 0.5<d for capable electric vehicle applications. The proposed topology benefits include one common DC-AC inverter that interposes the generated power to supply the charge for the sharing of load in a system of hybrid supply with photovoltaic panels and fuel cell PEM. An improved control of Direct Torque and Flux Control (DTFC) based induction motor fed by current source converters for electric vehicle.In order to achieve better performance in terms of speed, power and miles per gallon for the expert, to accepting high regenerative braking current as well as persistent high dynamics driving performance is required. A simulation model for the hybrid power generation system based electric vehicle has been developed by using MATLAB/Simulink. The Direct Torque and Flux Control (DTFC) is planned using Xilinx ISE software tool in addition to a Modelsim 6.3 software tool that is used for simulation purposes. The FPGA based pulse generation is used to control the induction motor for electric vehicle applications. FPGA has been implemented, in order to verify the minimal error between the simulation results of MATLAB/Simulink and experimental results.

• Composites Research
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• v.29 no.5
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• pp.243-248
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• 2016

Although thermoset carbon fiber composite bipolar plates not only have high mechanical properties but also high corrosion resistance in acid environment, high manufacturing cost and low bulk electrical conductivity are the biggest obstacle to overcome. In this research, thermoplastic polymer is employed for the matrix of carbon composite bipolar plate to increase both the manufacturing productivity and bulk electric conductivity of the bipolar plate. In order to increase the electrical conductivity and strength, plain type carbon fabric rather than chopped or unidirectional fibers is used. Also nano particles are embedded in the thermoplastic matrix to increase the bulk resistance of the bipolar plate. The area specific resistance and the mechanical strength of the developed bipolar plate are measured with respect to the environmental temperature and stack compaction pressure.

• International Journal of Computer Science & Network Security
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• v.22 no.3
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• pp.37-44
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• 2022

Plug-in Hybrid electric vehicles (PHEV) show great potential to reduce gas emission, improve fuel efficiency and offer more driving range flexibility. Moreover, PHEV help to preserve the eco-system, climate changes and reduce the high demand for fossil fuels. To address this; some basic components and energy resources have been used, such as batteries and proton exchange membrane (PEM) fuel cells (FCs). However, the FC remains unsatisfactory in terms of power density and response. In light of the above, an electric storage system (ESS) seems to be a promising solution to resolve this issue, especially when it comes to the transient phase. In addition to the FC, a storage system made-up of an ultra-battery UB is proposed within this paper. The association of the FC and the UB lead to the so-called Fuel Cell Battery Electric Vehicle (FCBEV). The energy consumption model of a FCBEV has been built considering the power losses of the fuel cell, electric motor, the state of charge (SOC) of the battery, and brakes. To do so, the implementing a reinforcement-learning energy management strategy (EMS) has been carried out and the fuel cell efficiency has been optimized while minimizing the hydrogen fuel consummation per 100km. Within this paper the adopted approach over numerous driving cycles of the FCBEV has shown promising results.

• Journal of the Microelectronics and Packaging Society
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• v.30 no.1
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• pp.79-89
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• 2023

Development of efficient and stable electrocatalysts for oxygen evolution reaction (OER) under acidic conditions is desirable goal for commercializing proton exchange membrane (PEM) water electroyzer. Herein, we report iridium-doped hydrogenated titanate (Ir-HTO) nanobelts as a promising catalyst with a low-Ir content for the acidic OER. Addition of low-Ir (~ 3.36 at%) into the single-crystalline HTO nanobelts with large exposed {100} facets significantly boost catalytic activity and stability for OER under acidic conditions. The Ir-HTO outperforms the commenrcial benchmark IrO₂ catalyst; an overpotential for delivering 10 mA cm^-2 current density was reduced to about 25% for the Ir-HTO. Moreover, the catalytic performance of Ir-HTO is positioned as the most efficient electrocatalyst for the acidic OER. An improved intrinsic catalytic activity and stability are also confirmed for the Ir-HTO through in-depth electrochemical characterizations. Therefore, our results suggest that low-Ir doped single-crystalline HTO nanobelts can be a promising catalyst for efficient and durable OER under acidic conditions.

• Korean Chemical Engineering Research
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• v.52 no.6
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• pp.720-726
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• 2014

PEM fuel cell vehicles have been getting much attraction due to a sort of highly clean and effective transportation. The onboard fuel processor, however, is inevitably required to supply the hydrogen by conversion from some fuels since there are not enough available hydrogen stations nearby. A lot of studies have been focused on analyses of ATR reactor under the assumption of thermo-neutral condition and those of the optimized process for the minimization of energy consumption using thermal efficiency as an objective function, which doesn't guarantee the maximum hydrogen production. In this study, the analysis of optimization for 100 kW PEMFC onboard fuel processor was conducted targeting various fuels such as gasoline, LPG, diesel using newly defined hydrogen efficiency and keeping simply synthesized heat exchanger network regardless of external utilities leading to compactness and integration. Optimal result of gasoline case shows 9.43% reduction compared to previous study, which shows the newly defined objective function leads to better performance than thermal efficiency in terms of hydrogen production. The sensitivity analysis was also done for hydrogen efficiency, heat recovery of each heat exchanger, and the cost of each fuel. Finally, LPG was estimated as the most economical fuel in Korean market.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.36 no.2
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• pp.161-170
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• 2012

There are many factors to consider when attempting to improve the efficiency of fuel cell operation, such as the operation temperature, humidity, stoichiometry, operation pressure, geometric features, etc. In this paper, the effects of the operation pressure were investigated to find the current density and water saturation behavior on a cross section designated by the design geometry. A two-dimensional geometric model was established with a gas channel that can provide $H_2$ to the anode and $O_2$ and water vapor to the cathode gas diffusion layer (GDL). The results from this numerical modeling revealed that higher operation pressures would produce a higher current density than lower ones, and the water saturation behavior was different at operation pressures of 2 atm and 3 atm in the cathode GDL. In particular, the water saturation ratios are higher directly below the collector than in other areas. In addition, this paper presents the dependence of the velocity behavior in the cathode on pressure changes, and the velocity fluctuations through the GDL are higher in the output area than in inlet area. This conclusion will be utilized to design more efficient fuel cell modeling of real fuel cell operation.