In this study, cell performance tests and measurements of the pressure drop in the anode flow channels of a micro methanol fuel cell (£gDMFC) were conducted. The effect of different operating parameters on £gDMFC performance was experimentally investigated for serpentine flow-field configuration. Experiments were conducted through a serious experiments with different operating conditions of temperature (40¡B60¡B70¡B80oC)¡Bmethanol concentration (0.5¡B1¡B1.5¡B2 M)¡Bchannel width (0.5¡B0.6¡B0.7¡B0.8¡B1¡B1.5¡B2 mm) and flow rate (10-20 sccm). Experimental results are presented in the form of polarization VI curves and PI curves under above operating conditions. The experimental results show that the pressure drop decrease with increasing current density. It has also shown that the pressure drop always increased with the methanol solution flow rates. The relationship between pressure drop and CO2 bubbles production rate would change with the current density increase. Finally, an optimal channel size of 700 £gm for the present £gDMFC could be obtained.

In this study, the flow plates of micro methanol fuel cells are designed and fabricated in-house through MEMS(Micro-Electro-Mechanical System) technology with deep UV lithography manufacturing processes (SU-8 photoresist) and micro electroforming manufacturing processes. The thesis investigates methanol and water crossover in a micro DMFC for serpentine flow field configuration. Experiments are conducted through various experiments with different operating conditions for the anode flow rate (2-10 sccm), cathode flow rate (100-500 sccm), methanol concentration (1, 2 and 3M), and temperature (25, 50 and 75¢J). Experimental results are presented in the form of polarization VI curves and PI curves under the above operating conditions. The experimental results show that the methanol and water crossover flux increases with increases in cell temperatures, methanol concentration and anode pressure drop. It is found that the fuel efficiency of the DMFC is closely related to the methanol crossover. Further examination of the relationship between the methanol crossover and cell performance reveals the possibility of reducing the methanol crossover by optimizing the anode flow rate.

The main objective of this research is to analyze the performance of micro direct methanol fuel cell (£gDMFC) and observe the bubble behavior of carbon dioxide in the anode flow channel. The flow plate adopted in this study was manufactured through deep UV lithography manufacturing and micro-electroforming manufacturing process. The geometrical configuration of the flow field is in the serpentine form. Transparent acrylic (PMMA: Polymethylmethacrylate) was used to make the terminal plate placed on both sides of the cell in order to facilitate the observation of the bubble behavior of carbon dioxide in the anode flow channel. In this experiment, Micro Particle Image Velocimetry (£gPIV) is used in order to investigate the generation / removal process of carbon dioxide from the anode of micro direct methanol fuel cell (£gDMFC) through a visualized observation method. The behavior of carbon dioxide bubbles in liquidized methanol solution and micro flowfield is also explored. Major parameters of the experiment operation that consist of flow rate of anode and cathode, density of methanol and operational temperature are used to explore their influences on the fuel cell¡¦s polarization curve and power density. The results are presented by V-I curve and P-I curve. The relation between carbon dioxide bubble movement and behavior according to the anode pressure drop are also discussed.

The micro PEMFCs were designed and fabricated in-house through a deep UV lithography technique and the SU-8 photoresist was used as microstructure material for fuel cell flow-field plates. The effect of different operating parameters on micro PEMFCs performances and electrochemical impedances was experimentally investigated for three different flow-field configurations (interdigitated, mesh, and serpentine). Experiments with different cell operating temperatures, different backpressures on the H2 flow channels as well as various combinations of these parameters have been conducted for three different flow geometries. Results are presented in the form of the polarization VI curves, PI curves and impedance spectroscopy under different operating conditions. The possible transport mechanisms associated with the parametric effects were discussed. With PI and VI curve were found that, among the three flow patterns considered, significant improvements can be reached with a specified flow geometry. With impedance spectroscopy was found that, the effect of the parameters on high frequency straight line, medium frequency, and low frequency arc. The influence in terms of impedance on dynamic response of the present H2/air micro fuel cell under different operating conditions and flow geometry can be quantitatively measured.

The huge environmental awareness emerging last years by reason of global warming and greenhouse effect, on one hand, and the need of finding other sources of energy production and conversion due to the declining of fossil resources and the increasing cost of this kind of energy resource, on the other hand, both have led position renewable energies as a powerful alternative on the energy production and conversion. PV-systems have emerged at an exponential rate in recent year as the main candidate and a satisfactory possibility with respect to environmental and economic sustainability. Nowadays, the large volume on photovoltaic market is currently dominated by four types of solar cells, divided by the semiconductor material used to absorb light and convert the energy into electricity: (1) crystalline silicon (monocrystalline and polycrystalline), (2) amorphous silicon, (3) CIGS and (4) cadmium telluride; and among them, monocrystalline silicon and CIGS technologies are installed on the building 45 of the University of Gävle, at the south face of the laboratory. In this context and with the motivation to contribute knowledge on PV field, a comparison between single crystal solar technology and thin film CIGS technology has carried out through f ratio and performance ratio procedures in order to perform an assessment of the energy conversion of each one under field conditions. A logger monitors the power conversion from the PV modules since June 2014 while two pyranometers monitor global and diffuse solar radiation since March 2016. It must take into account that only clear sunny days have been considered during a period from 8:00 to 14:00 in order to avoid shadows effect on the PV systems. The results come to conclude that single crystal silicon modules present a better behavior with respect to energy conversion under no shadows effect conditions by two reason: (1) f ratio, relationship of PV conversion per kW (PV yield) between CIGS and single crystal silicon, is about 87.25% with some variations along a day due to ambient temperature, cell temperature and incidence angle; (2) PV module's performance ratio of monocrystalline silicon modules is higher than thin film CIGS ones during a sunny day about 87.56% and 76.38%, respectively; and they are consistent with usual performance ratio values between 80% and 90% since 2010 onwards. In light of the outcome and in order to confirm these conclusions, it intends to launch a project with the objective of evaluating the data collected and compare the performance of the module after a year of measurements outdoors by the PV module's performance ratio procedure. Along the same lines, the next step of the University of Gävle will be to launch a project with the objective of evaluating the potential to be self-sufficient.

Single step co-sintering is proposed as a method to minimise the time and cost of fabricating solid oxide fuel cells (SOFCs). Such a methodology is attractive but challenging due to the differing sintering behaviours and thermal mismatch of the constituent materials of the anode, cathode and electrolyte in solid oxide fuel cells. As a result it is likely that compromises are made for one layer with respect to optimising another. The single chamber solid oxide fuel cell (SC-SOFC) has not seen widespread adoption due to poor selectivity and fuel utilisation, but relaxed some of the stringent SOFC requirements such as sealing, and the need for a dense electrolyte layer. Thus, to initiate the study into single step co-sintering, the single chamber SOFC is earmarked as the first candidate. The effect of single step co-sintering on cell performance is also an attractive area to investigate. Therefore, in this study, a new co-sintering process (single step co-sintering) was applied to fabricate three different types (in terms of the supporting structure) of planar SC-SOFCSs (the anode, cathode and electrolyte supported planar cells) and anode supported wavy types of SC-SOFC in order to reduce fabrication cost and time owing to effective fabrication process. In addition, their performances were tested to establish functionality of the sintered specimens as working electrochemical cells as well as to investigate the maximum performance possible with these cells under single chamber conditions. Moreover, it is also aimed to improve the performance of SC-SOFCs by extending TPB (Triple phase boundary) via wavy type. This study presents a single step co-sintering manufacturing process of planar and wavy single chamber solid oxide fuel cells with porous multilayer structures, consisting of NiO-CGO, CGO and CGO-LSCF as anode, electrolyte and cathode respectively. Pressure of 2 MPa, with the temperature at 60˚C for 5 minutes, was deemed optimal for the hot pressing of these layers. The best result of sintering profile was obtained with heating rate of 1˚C min-1 to 500˚C, 2˚C min-1 to 900˚C and 1˚C min-1 to 1200˚C with 1 hour dwelling; the cooling rate was 3˚C min-1. Hence anode supported SC-SOFC (thickness: 200:40:40 µm, thickness ratio: 10:2:2, anode (A): electrolyte (E): cathode (C)) was fabricated via a single co-sintering process, albeit with curvature formation at edges. Its performance was investigated in methane-oxygen mixtures at a temperature of 600˚C. Maximum open circuit voltage (OCV) and power density of the anode supported planar cell were obtained as 0.69 V and 2.83 mW cm-2, respectively, at a fuel-oxygen ratio of 1. Subsequently, anode thickness was increased to 800 µm and electrolyte thickness was reduced 20 µm (thickness ratio of cell 40:1:2) to obtain curvature-free anode-supported SOFCs with the help of a porous alumina cover plate placed on the top of the cell. The highest power density and OCV obtained from this cell was 30.69 mW cm-2 and 0.71 V, respectively, at the same mix ratio. In addition, the maximum residual stresses between cathode end electrolyte layers of anode supported cells after sintering were investigated using the fluorescence spectroscopy technique. The total mean residual stresses along the x-direction of the final anode supported planar cell after sintering were measured to range from -488.688 MPa to -270.781 MPa. Determination of optimum thickness and thickness ratio of the cell with the defined ideal hot pressing and sintering conditions for single step co-sintering were carried out for cathode and electrolyte supported planar cells using similar fabrication processes. Their performance changes with thickness ratio were examined. The results show that the cathode and electrolyte supported planar cells can be obtained successfully via single step co-sintering technique with the help of alumina cover plates, as with the anode supported cell. In addition, an anode supported wavy SC-SOFC was fabricated via single step co-sintering and its performance was also investigated. The maximum power density and OCV from the final curvature free cathode supported planar cell (thickness: 60:20:800 µm, thickness ratio: 3:1:20, A:E:C) was measured to be 1.71 mW cm-2 and 0.20 V, respectively, at a fuel-oxygen ratio of 1.6. Likewise, the maximum OCV and power density were found to be 0.55 V and 29.39 mW cm-2, respectively, at a fuel-oxygen ratio of 2.6, for the final electrolyte supported curvature free planar cell (thickness: 60:300:40 µm, thickness ratio: 3:15:2, A:E:C). Furthermore, a maximum OCV of 0.43 V and power density of 29.7 mW cm-2 were found from the final anode supported wavy cell (thickness: 800:20:40 µm, thickness ratio: 40:1:2, A:E:C) at a fuel-oxygen ratio of 1. In essence, this study can be divided into five chapters. The first chapter addresses the overview of the research background, problem statement, aims and objective of this study as well as that of novelty and impact. In the second chapter, fundamental information is provided regarding SOFCs and SC-SOFCs in terms of working principles, main components including electrodes electrolytes, advantages and disadvantages, types, material used for each cell components, losses in the system, and so forth. Moreover, the second chapter also contains essential sintering information in order to understand how to approach sintering of ceramics or cermet to fabricate SC-SOFCs. The overall methodology of this study is explained in detail in the third chapter while experimental works are described in the chapter 4, chapter 5, chapter 6, chapter 7 and chapter 8. Chapter 5 also contains background for the fluorescence spectroscopy and a modelling technique for residual stress measurement between ceramic layers. The results of experiments with discussion session are also in the same chapter. The last chapter presents conclusions and the possible routes for future works of the study.

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京都大学 / 新制・課程博士 / 博士(工学) / 甲第24644号 / 工博第5150号 / 新制||工||1983(附属図書館) / 京都大学大学院工学研究科化学工学専攻 / (主査)教授 河瀬 元明, 准教授 中川 浩行, 教授 外輪 健一郎 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DFAM

Das Betriebsverhalten eines elektrischen Turboladers zur Bedruckung des Kathodengassystems eines automobilen Brennstoffzellensystems wird unter Berücksichtigung der feuchten Brennstoffzellenabluft untersucht. Basierend auf den Komponentenkennfeldern von Elektromotor, Leistungselektronik, Lagerung und Turbomaschinenkomponenten werden stationäre und transiente Betriebslinien berechnet, anhand derer eine Betriebspunktverschiebung gezeigt wird. Diese kann auf die Einflüsse der Gaszusammensetzung und Kondensation in der Turbine zurückgeführt werden. Anhand von drei stationären Betriebspunkten wird die Zusammensetzung der Verluste innerhalb der Maschine gezeigt. Die Verzögerung wird zudem als kritisches Manöver im transienten Betrieb durch signifikante Abnahme des Pumpgrenzabstands identifiziert. / The performance of an electric turbocharger for the cathode gas supply system of an automotive fuel cell system is investigated considering moist air off gasses. Based on the component performance maps of electric motor, power electronics, bearings and turbomachinery, steady state and transient operating lines are calculated and a shift of operating points is shown. These can be traced back to the influence of gas composition and condensation within the turbine. Based on three operating points, losses inside the machine are characterized. Furthermore, deceleration is identified as the most critical transient operating scenario due to a significant decrease of the surge margin.

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