Improvement of the Performance of Direct-Generation Type Polymer Electrolyte Fuel Cells and Their Systemization

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In this research project, the direct-generation type PEFC (Polymer Electrolyte Fuel Cell) without a reformer was taken as an object of investigation among various types of PEFCs, and it was attempted to use ethanol as innocuous liquid fuel. In this case, the power generation of the PEFC was low, and therefore measures to improve the performance were examined. The power generation performance of a self-made PEEC with MEAs (Membrane Electrode Assemblies) prepared by means of the Cast Method (original making method of MEA) was measured by supplying the ethanol aqueous solution directly. As a result, an increase of about two times in output power was attained in comparison with MEAs prepared by other conventional making methods. When porous metal foam plates made of nickel were used as diffusion layers, the PEFC output power became 1.8 times larger even in the case of passive-type PEFC without any auxiliary equipment. Reaction products in the anode-side flow passage of the PEFC were analyz … More ed. C0_2 was detected but CO was not detected by gas chromatograph. Acetic acid and acetaldehyde as by-products were detected by liquid chromatograph. These results mean that ethanol is oxidized to acetic acid and acetaldehyde, and partly to C0_2. For investigating the behavior of those by-products, a three-dimensional numerical analysis model for the PEFC was composed on the basis of the original GTT method, and the flow in the PEFC was numerically analyzed. Furthermore, the flow visualization and the flow analysis by the PIV (Particle Image Velocimetry) method were carried out. As a result, it has been found that a serpentine flow passage is effective in discharging such by-products.As a hydrogen-fuelled small-size and light-weight PEFC, an original passive-type small cylindrical PEFC (named "Power Tube") which can generate a specific power of 13OmW/g has been contrived. In the case of hydrogen-fuelled PEFCs, output energy density is high but output power density is low for the power source of an electric vehicle. Therefore, it is necessary to apply a hybrid system composed of PEFCs and electricity storage devices. In this research project, a hybrid system composed of passive-type PEFCs and electric double layer capacitors was constructed for a light-weight electric vehicle. For controlling this hybrid system, an original Time-Splitting Method (TSM) which can control the power supply ratio to the motor according to running states has been contrived. As power supply modes to the motor, series and parallel modes were tested, and it has been shown that TSM can easily control the motor power in both modes. Less