| 摘要: | 本研究採用電化學交流阻抗圖譜法(Electrochemical Impedance Spectroscopy, EIS)來檢測由47顆單電池組成之一瓩級質子交換膜商用電堆，希望藉由此種診斷技術，找出電堆中四個特徵區段中單電池的特性差異，進而推測該區域容易發生之問題。實驗時，先將電堆依據堆疊位置均分出4個區段(分別為A, B, C 和D)，在一區段挑出位於中間之單電池進行檢測(分別以Am, Bm, Cm 和Dm代表)。電堆的A區段靠近陽極端，而D區域則靠近陰極端。藉由改變電池操作參數，量測各電池之電化學交流阻抗圖譜，所得圖譜經Z-View軟體之模擬分析，可推理出合理之等效電路，並求出電路圖中各元件數值。 實驗結果發現：活化時間的改變對商用電堆之電荷轉移阻抗(Rct)並沒有造成明顯的影響，也就是說在電堆僅需運作約1小時，觸媒的催化反應即可達穩定狀態。且當電堆運作經3小時候，在質傳阻抗(Rmt)及歐姆阻抗(Rohm)均呈現較穩定狀態。另外，當氫氣流量較低(5 L/min)時，在電堆中離氫氣端最遠的Dm電池之質傳阻抗值出現最大值(0.920 ohm)，並且隨著氫氣流量增加而使其質傳阻抗值下降，表示該電堆的流道設計恐會發生末端氣體擴散不足之問題。並且在電堆中不同區域，發現離氫氣端越遠其歐姆阻抗值越高，可能原因為末堆電池加濕不足或電堆夾持壓力不足所致。Electrochemical impedance spectroscopy (EIS) was used to conduct a non-destructive test on a commercial stack of 1.0 kW proton exchange membrane fuel cells (PEMFCs). This test provided an in-situ diagnosis of the stack to identify the different problem with the presence of unusual high impedance.The testing stack consists of 47 single cells. It was sorted into four groups (i.e., A, B, C and D) with respect to the position. Group A was at the position most closed to the anode, and departed away for the group of B, C and D so that group D with the most closed position to the cathode. The middle among the single cells in each group (i.e., denoted as Am、Bm、Cm and Dm, respectively) was focused. In the process of testing, the operation was maintained at room temperature; air was fed on the cathode at room temperature without humidification; hydrogen gas humidified at 40℃was fed on the anode. The flow rate of hydrogen gas and air was varied in the test to explore the performance of each specified single cell in every group. The experimental data were simulated with commercial software (i.e., Z-View) to estimate the magnitude of each elements in a proposed equivalent circuit. The experiment show: First, by the break-in time provide information that effect of different operating parameters, such as degree of water accumulation due to design of flow channel. Second, when the hydrogen flow rate is low (5 L / min), the end of single cell Dm response to feeding rate of hydrogen is shortage due to the design of the flow channel; and when the air flow rate is low(10 L/min), the end of single cell Am was also found the high diffusion resistance value. Third, different of stack position will cause the ohm resistance change, the phenomenon is speculation insufficient assembly pressure. |
