• Journal of ILASS-Korea
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• v.22 no.2
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• pp.69-79
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• 2017

When designing a redox flow battery system, compression of battery stack is required to prevent leakage of electrolyte and to reduce contact resistance between cell components. In addition, stack compression leads to deformation of the porous carbon electrode, which results in lower porosity and smaller cross-sectional area for electrolyte flow. In this paper, we investigate the effects of electrode compression on the cell performance by applying multi-dimensional, transient model of all-vanadium redox flow battery (VRFB). Simulation result reveals that large compression leads to greater pressure drop throughout the electrodes, which requires large pumping power to circulate electrolyte while lowered ohmic resistance results in better power capability of the battery. Also, cell compression results in imbalance between anolyte and catholyte and convective crossover of vanadium ions through the separator due to large pressure difference between negative and positive electrodes. Although it is predicted that the battery power is quickly improved due to the reduced ohmic resistance, the capacity decay of the battery is accelerated in the long term operation when the battery cell is compressed. Therefore, it is important to optimize the battery performance by taking trade-off between power and capacity when designing VRFB system.

• Journal of Hydrogen and New Energy
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• v.27 no.5
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• pp.503-509
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• 2016

Fuel cell is a device for producing electricity by using the hydrogen produced by the fuel processor. At this time, CO is also created by the fuel processor. The resulting CO enters the stack where is produce electricity and leads to the adsorption of anode catalyst, finally the CO poisoning occurs. Stack which occurred CO poisoning has a reduction in performance and shelf life are gradually fall because they do not respond to hydrogen. In this paper, experiments that using a PROX reactor to prevent CO poisoning were carried out for removing the CO concentration to less than 10ppm range available in the fuel cell. Furthermore experiments by the PROX reaction was designed and manufactured with a water-cooling heat exchange reactor to maintain a suitable temperature control due to the strong exothermic reaction.

• Journal of Hydrogen and New Energy
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• v.35 no.4
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• pp.370-376
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• 2024

Load variations reduce the lifespan of polymer electrolyte fuel cells (PEFCs). To analyze the impact of load variations on durability of PEFCs, two stacks were built and operated continuously for 400 hours, one under load variations and the other under constant current condition with the same energy output. Using the example model provided by Mathworks, we obtained load variation data for the experiments. The performance curves were measured every 100 hours and analyzed by current interruption method and electrochemical impedance spectroscopy. The degradation comparison shows a much larger decrease in performance under the load variation. The activation resistance, electrical resistance, and mass transfer resistance are all found to increase more.

• 한국신재생에너지학회:학술대회논문집
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• 2010.11a
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• pp.87.2-87.2
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• 2010

The steady and dynamic process model for an internal reforming molten carbonate fuel cell power plant is discussed in this paper. The dominant thermal and chemical dynamic processes are modeled for the stack module and balance-of-plant, including cathode gas preparation, heat recovery, heat loss (Each heat loss amount for the stack and MBOP is obtained from real plant data) and fuel processing. Based on dynamic model and control demand, PID controllers are designed in the whole system. By applying these controllers we can obtain temperature balance of stack and control system depending on changing steam to carbon ratio, air feed amount, and transient condition.

• 한국신재생에너지학회:학술대회논문집
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• 2007.06a
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• pp.180-183
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• 2007

CO in the reformed gas for proton exchange membrane fuel cell(PEMFC) has a strong tendency to adsorb on the surface of the catalyst and thus to block the sites that hydrogen needs for reactions. Even part per million levels of CO can cause serious poisoning. This CO poisoning can overcome to bleed trace amounts of air into the anode. In this study, we indicated the alteration of stack performance in various CO concentration and then bled a small amount of air. The performance of stack was reduced by increasing CO amount, and recovered by air bleeding. But the air-bleeding have an impact on performance of anode should be further explored.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2015.11a
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• pp.338-338
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• 2015

VRFB(Vanadium Redox Flow Battery)는 바나듐계 이온을 전해질로 사용하는 레독스 흐름 전지로, 전해질의 양이 전지의 용량을 결정하기 때문에 주로 대용량의 전력이 필요한 플랜트 등에서 주로 사용하는 전지이다. 이 VRFB내에는 Current collector의 부식 방지용으로 두꺼운 Graphite판을 BP(Bipolar plate)로 사용한다. 플랜트에서는 대용량 전지를 필요로 하여 Single stack으로는 사용되기 어렵고, Multi stack으로 주로 사용한다. Multi stack의 경우, 수 백장의 BP가 들어가 전지의 부피가 매우 커지게 되고, 이에 본 연구에서는 BP의 두꺼운 Graphite를 얇은 $TiO_2$ 기판으로 교체하여 성능을 비교하는 연구를 진행하였다. Ti 금속기판을 양극산화법으로 $TiO_2$ 나노튜브 구조를 만든 후, $TiO_2$의 전도도 향상을 목적으로 $IrO_2$를 코팅하였다. 결과적으로 기존의 Graphite에 비해 전기화학적 특성이 향상되었음을 확인하였으며, Cell test를 통해 VRFB의 성능을 평가하였다.

• ETRI Journal
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• v.38 no.5
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• pp.903-910
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• 2016

We propose a novel multi-stack (MS) technique for a compact and wideband electromagnetic bandgap (EBG) structure in high-speed multilayer printed circuit boards. The proposed MS technique efficiently converts planar EBG arrays into a vertical structure, thus substantially miniaturizing the EBG area and reducing the distance between the noise source and the victim. A dispersion method is presented to examine the effects of the MS technique on the stopband characteristics. Enhanced features of the proposed MS-EBG structure were experimentally verified using test vehicles. It was experimentally demonstrated that the proposed MS-EBG structure efficiently suppresses the power/ground noise over a wideband frequency range with a shorter port-to-port spacing than the unit-cell length, thus overcoming a limitation of previous EBG structures.

• Proceedings of the KIPE Conference
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• 2014.07a
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• pp.435-436
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• 2014

최근 대용량 PCS(Power Conditioning System)는 신재생에너지, 에너지저장장치 등의 다양한 산업 분야에서 수요가 증가하고 있다. 본 논문에서는 신재생에너지 분야에서 대용량 시스템으로 발전용 에너지원으로 사용되는 2.8MW 연료전지 시스템의 수랭형 PCS 개발을 위하여 수랭식 IGBT Stack 및 냉각 장치를 설계, 제작하여 열적 안정성을 실험을 통하여 검증하였다.

• Journal of Hydrogen and New Energy
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• v.35 no.2
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• pp.168-174
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• 2024

The electrochemical hydrogen compressor was run under diverse operating conditions in order to probe its capabilities and limitations. It was found that, unlike single-cell operations, the electrochemical hydrogen compressor stack performance improved with a rise in temperature. This improvement in performance was attributed to the gradual weakening of the electro-osmotic drag over time, impacting membrane resistance. As a result of these experiments, compression levels, up to an impressive 120 bar, using the electrochemical hydrogen serial stack were achieved.

• 한국신재생에너지학회:학술대회논문집
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• 2005.06a
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• pp.339-344
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• 2005

A PEMFC system model for FCEV was constructed and simulated numerically to examine the heat/water flow of the system and air/fuel humidification process for various operation conditions (ambient pressure /temperature/humidity, operating temperature, power load). We modeled PEMFC stack which can generate maximum electricity of about 80 kW. This stack consists of 400 unit cells and each unit cell has $250cm^2$ reacting area. Uniform current density and uniform operating voltage per each cell was assumed. The results show the flow characteristics of heat and water at each component of PEMFC system in macro-scale. The capacity shortage of the radiator occurred when the ambient was hot $(over\;40^{\circ}C)$ and power level was high (over 50 kW). In spite of some heat release by evaporation of water in stack, heat unbalance reached to 20kW approximately in such a severe operating condition. This heat unbalance could be recovered by auxiliary radiators or high speed cooling fan with additional cost. In cold environment, the capacity of radiator exceeded the net heat generation to be released, which may cause a problem to drop the operating temperature of stack. We dealt with this problem by regulating mass flow rate of coolant and radiator fan speed. Finally, water balance was not easily broken when we retrieved condensed and/or unused water.