質子交換膜燃料電池堆設計方法、性能分析與特性

Design, Performance Analysis and Characteristics on Proton Exchange Membrane Fuel Cell Stacks

周泊賢(Po-Hsien Chou)

指導教授 ： 蘇艾

元智大學/工程學院/機械工程學系/博士(2009年)

https://doi.org/10.6838/YZU.2009.00131

摘要

質子交換膜燃料電池是目前普遍認為最快商業化的燃料電池，燃料電池堆則是運用在許多產品上都是商業化產品最終的型態，因此燃料電池堆相關的研究就相當重要。然而，目前世界上對於燃料電池堆原理的相關文獻相對較少，且對於關鍵技術與研究通常掌握在工業界，在此篇論文中將會對於工業界在燃料電池堆上無法公佈的研究加以討論。燃料電池堆在設計方式及性能現象方面，由於電池堆與單電池二種特性相差甚遠，因此在燃料電池單電池方面的設計與現象討論無法運用在燃料電池堆。在此論文中對於燃料電池堆的設計方式以及運作原理將會在加以分析、討論。
研究成果方面，燃料電池堆中有一型態為微型燃料電池堆，這種電池堆可用於攜帶式的產品。在研究中對於此2瓦微型燃料電池堆做了許多測試，研究中發現此種自然呼吸式燃料電池堆在操作過程中，電池堆對於周遭的環境影響很敏感, 二端的電池有較大的溫度變化。當周遭的空氣流動較好時，可以幫助改善電池堆的電壓不均勻性。若將電池堆的型態放大到200瓦的電池堆，在實驗中發現當燃料電池堆在做極化曲線時，由高電流量到低電流比由低電流量到高電量的性能來得要好。另外也發現當燃料電池堆在做模擬交通載具的電流瞬間拉載測試時，在高電流拉載的條件下，燃料電池堆的陰極在開啟背壓時的電壓會比在陽極增加氫氣供給量還來的高，這將有助於防止燃料電池堆在長期反覆電流操作時對於MEA的傷害。在燃料電池堆中的主流道是相當重要的設計之一，在研究中利用氣體速度分析儀來量測燃料電池堆中的主流道氣體的分佈性，在實驗中發現若燃料電池設計的流場壓降過小，將會造成氣體在大流量的操作條件下入口的部份電池會有負氣壓的現象發生，這將會造成燃料電池堆的性能不均勻並且整體的電池堆性能無法提升。若將電池堆中的單一電池(unit cell)來探討的話，在研究中使用多區型燃料電池來研究，且此多區型燃料電池也可視為平板式燃料電池堆。研究中發現當燃料電池操作在低加濕的情況下，下游區所產生的電流會高於中、上游區，若將燃料電池的入出口對調的話，將可使每區的性能均勻化，這樣的操作條件將可避免燃料電池在長時間操作下時MEA的老化不勻均。在燃料電池堆中，水的影響是非常大的，利用可視化燃料電池搭配高速攝影機可拍下液態水在流道裡的流動方式以及各種肉眼無法觀察到的現象，在實驗中發現液態水不管是在流動或是聚集狀態，由於肋條表面相較於氣體擴散層是親水性質，因此液態水大部份會與流道中的肋表面接觸。另外，也觀察到燃料電池在操作過程中的排水現象，在中、下游的部份水不一定沿著流道流動反而是穿過肋條下方的氣體擴散層而直達下一條流道。

關鍵字

質子交換膜燃料電池 ； 燃料電池堆 ； 主流道燃料分佈 ； 區域型電池 ； 微型燃料電池

並列摘要

PEMFC (Proton Exchange Membrane Fuel Cell) is admitted for the fast-commercial product in fuel cells, and fuel cell stack is also the finial type in many kinds of the commercial product. Therefore, the research of fuel cell stack is important. However, the reference of research on fuel cell stack is relatively less than others, and the key technology and research usually own by industry. In this study will discuss and analyze some of the key technology which industry will not announce in public. As for the design method and performance analysis on stack, the character between stack and single cell are totally different. Therefore, the design and phenomenon discussion on single cell can not be used on stack. In this study, there is some research of analysis, discussions, design and operating condition on fuel cell stacks.
One of the fuel cell stack type is micro stack, this type of stack can be used for portable product. There is a series test of 2 W micro stack in this study. In the stack operating, this air-breathing fuel cell is sensitive for the surrounding temperature. There is higher temperature difference at both sides of cells. When air flow is added on the cathode, it can improve the non-uniform voltage in the stack. In the result of 200 W stack, the scan current from high to low has a better performance than scan current from low to high in the polarization curve. In the dynamic load response, when the stack was operated under high current condition, the stack voltage which is operated under back pressure in cathode will have higher voltage than the operating condition of higher hydrogen supply. This result can prevent the degradation of MEA which is during repeatedly long term operating. The header design plays an important role on fuel cell stack, and this study uses PIV (Particle Image Velocimetry) to measure the gas distribution in each cell. In the research, when the pressure drop of flow field is lower in high flow rate operating, there is minus pressure in the gas inlet of cells which is close to gas inlet of header. This result will cause in the non-uniform gas distribution, and lower performance in whole stack. In the research of unit cell in stack, segment fuel cell was used for research, and it is also the “plate-type” stack in fuel cell. When the segment fuel cell was operated under low humidity condition, the down-stream segment will have higher current than up/mid-stream. In the counter flow situation, the performance is uniform between all segment cells. This operating condition can prevent the non-uniform degradation in MEA during long time operating. Water influence is enormous in a fuel cell stack, using transparent fuel cell and high speed camera can capture some phenomena of water droplet which naked eye cannot be observed. In the experiment, when water droplet flooding or emerging, droplet will contact the surface of rib because of the hydrophobic compare to gas-diffusion-layer (GDL). Additionally, in this experiment also capture some unusual result; part of water flowing in the mid/downstream will not flow along the channel, contrarily the water will underneath the rib to next channel.

並列關鍵字

PEM fuel cell ； fuel cell stack ； stack header ； fuel distribution ； segment fuel cell ； micro stack fuel cell

參考文獻

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