A semi-empirical model for evaluating the fuel crossover flux of a direct methanol fuel cell

• Main Authors: Lin, Yentnig, 林延庭
• Other Authors: Chiu, Yu-Jen
• Format: Others
• Language: zh-TW
• Published: 2009
• Online Access: http://ndltd.ncl.edu.tw/handle/06252876139051225471

碩士 === 北台灣科學技術學院 === 燃料電池產業研發碩士專班 === 97 === Being one of the most representative low-temperature fuel cells, a direct methanol fuel cell (DMFC) possesses great potential for small and portable applications like consumer electronic products. However, tow major technical barriers have been confining its performance: significant anodic activation overpotential and methanol crossover phenomenon. Methanol crossover not only reduces the operating voltage, but also induces ineffective fuel consumption. It should be well managed by material design or system integration and control. Generally speaking, since the quantity of methanol crossover flux is very tiny and varies with different operating conditions, it should be evaluated by adopting delicate instrument and techniques in a laboratory. Practically, it is difficult to acquire quantitative information about methanol crossover flux in an operating fuel cell system under various conditions. The present thesis therefore proposes a semi-empirical model for evaluating methanol crossover flux that takes operating temperature, fuel concentration, and electronic loads into account. It is capable of providing in-situ estimation of methanol crossover flux to diagnose the status of the system and serve as the basis of controlling strategies. In the thesis, the effect of carbon-dioxide crossover phenomenon is considered to enhance the validity of the proposed model. According to the analysis of the corresponding parameters and variables, the results may provide suggestions on material design and system control. Finally, the degradation issue is also discussed.