Yazar "Selamet, Omer Faruk" seçeneğine göre listele

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    Development and testing of a highly efficient proton exchange membrane (PEM) electrolyzer stack
    (PERGAMON-ELSEVIER SCIENCE LTD, 2011) Selamet, Omer Faruk; Becerikli, Fatih; Mat, Mahmut D.; Kaplan, Yuksel
    Integrated with the renewable energy resources such as wind and solar energy, a Proton Exchange Membrane (PEM) water electrolyzer is one of the important methods for hydrogen production due to its high efficiency, compact structure, releasing no harmful emission and possibility to store the product hydrogen directly to high pressure tanks. In this study, development stages of a highly efficient PEM electrolyzer stack are presented. First, a single cell is developed and its performance is improved from 74% to 87% through design and materials enhancement. Then a 10-cell stack is developed and its operating parameters are optimized for high efficiency. The 10-cell stack produces 5 l/min hydrogen at 1.35 A/cm(2). The single cell is tested for 2000 hours continuously and an acceptable degradation rate of 1.5 mu V/h is measured. Copyright (C) 2011, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.
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    Investigation of gas generation in regenerative fuel cells by low-energy X-rays
    (ELSEVIER SCIENCE BV, 2015) Selamet, Omer Faruk; Deevanhxay, Phengxay; Tsushima, Shohji; Hirai, Shuichiro
    Gas generation and discharge behaviors in an operating regenerative fuel cell (RFC) are investigated using low-energy X-ray radiography. In situ visualization at high spatial and temporal resolution reveal dynamic and inhomogeneous behaviors of the gas generation in the membrane electrode assembly (MEA) in the RFC. Temporal and spatial variation of the gas thickness in the MEA is quantitatively discussed and shows an intermittent and periodic discharge processes of the gas generated by electrolysis, suggesting that the reaction sites in the catalyst layer and the discharging path of gas bubbles are well established in the MEA for the electrolysis. Larger gas accumulation and discharge in the gas diffusion layer (GDL) under the ribs are identified in comparison with those under the channels, which is attributed to the relatively longer path for accumulated gas under the ribs to be discharged into the flow channels. (C) 2015 Elsevier B.V. All rights reserved.
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    Mathematical modeling and dynamic Simulink simulation of high-pressure PEM electrolyzer system
    (PERGAMON-ELSEVIER SCIENCE LTD, 2016) Yigit, Tevfik; Selamet, Omer Faruk
    PEM electrolysis based hydrogen generator system model is developed by using Simulink in MATLAB. The model covers the following system components: PEM electrolyzer stack, water pump, cooling fan, storage tank, water tank, power supply, control unit and sensors. In simulation, PEM electrolyzer stack model is the most complex component and consists of four parts; anode and cathode modules, membrane and finally voltage calculations module. Efficiency drops and voltage losses in the PEM electrolysis stack are estimated. The overpotentials are investigated as anode and cathode activation, electronic and ionic ohmic resistances. In addition, the loss of the other components is considered. The model is tested against the dynamic changes and it responded with quick outputs. The cell and stack behavior under different conditions (i.e. ranging of temperature and pressure) are examined. The loss of each system component at different current densities is added to the simulation. The study shows that the loss of stack dominates the losses of other components at higher current densities. The simulation counts that the stack and system model can run with different cases and scenarios. It is run for the scenario that it consumes constant power for a high pressure operation. Results show that current drawn by the stack decreases as the voltage increases because of the increasing pressure. The model is also compared with the experimental results and the model is found to be consistent with the experimental data. (C) 2016 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.