Master Degree / Yüksek Lisans Tezleri
Permanent URI for this collectionhttps://hdl.handle.net/11147/3008
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Master Thesis Hydrogen Production From Water Using Solar Cells Powered Nafion Membrane Electrolyzers(Izmir Institute of Technology, 2007) Aksakal, Ziya Can; Şeker, ErolThe aims of this thesis are two folds; to construct single and multi cell proton exchange membrane electrolyzers and to evaluate the performance of these electrolyzers powered by solar panels on Iztech campus. All other parts, except the purchased membrane electrode assemblies, were designed, manufactured and assembled in our labs.In the construction of single and multiple cell proton exchange membrane electrolyzers, Nafion-117 based membrane electrode assemblies were used. Graphite bipolar plates, end plates, current collectors and gaskets were machined on institute.s computer numerical controlled lathe. In the first stage, a single cell electrolyzer with 20cm2 available electrolysis surface areas was examined with a direct current power supply by varying current density (0-500mAmp/cm2), water flow rate (0.05 to 0.5g/cm2min), and temperature (30-50oC). It was found that average cell voltage decreases from 2.18V at 30oC to 1.97V at 50oC when the current density is 500mAmp/cm2. Since cell gaskets were softened and stick to the membrane above 50oC of operating temperature, temperatures higher than 50 oC could not be tested. Five cell electrolyzer stack was constructed according to the final single cell design. It was observed that the stack could generate 388ml/min hydrogen under 500mAmp/cm2 and 10.09V of the operating condition at 41.5oC. When the stack was directly coupled with a solar array, voltage of the stack was found to vary from 7.5V to 12.5V and the current density changes from 0 to 1000mAmp/cm2 with respect to the solar radiance of the day. This results in a voltage efficiency ranging from 98.7% to 60% based on the higher heating value of hydrogen. Electrolyzer powered by solar cells can generate up to 750ml/min hydrogen and total daily production could be as high as 350L per day but weather condition greatly affects the production rate. Together with the losses inside the electrolyzer, another important energy loss is due to voltage mismatches between PV array and electrolyzer in low solar irradiance during sunrise and sunset.Master Thesis Determination of Preparation Conditions for Membrane Electrode Assembly of Pem Electrolyzer(Izmir Institute of Technology, 2013) Düzgören, Derya; Şeker, ErolThe aim of this thesis is to investigate the effect of preparation conditions of Membrane Electrode Assembly (MEA) on the hydrogen production of a single cell Proton Exchange Membrane (PEM) electrolyzer operated at room temperature and atmospheric pressure. In the first part of the thesis, the catalyst ink, without the metal catalysts, coated membrane (MEA), with the 16 cm2 active area, were produced. For the proton exchange membrane Nafion-117 membrane was used. An experimental design (Small Central Composite Design) was done in order to investigate the optimum preparation conditions (such as temperature, pressure and holding time in the hot press) for MEA of PEM electrolyzer. The responses were water vapor permeability and the surface resistance of the catalyst ink coating. The optimum conditions that gave maximum permeability and lowest surface resistance were found at 135°C of the hot press temperature, 5000 pound of pressure and 3 minute of holding time. In the second part, Membrane Electrode Assembly containing Pt and Pt/Ru metals in the catalyst ink was produced using the optimum conditions found in the first part. Then the prepared MEA was compared with the commercial MEA containing Pt and Pt/Ru metals using our home made single PEM electrolyzer.