質子交換膜燃料電池性能最佳化之研究

A study of optimizing performance of proton exchange membrane fuel cell

程柏維(Pai-Wei Cheng)

指導教授 ： 林啟瑞 ； 蘇春熺

國立臺北科技大學/機電學院/機電整合研究所/碩士(2007年)

摘要

近年來燃料電池因高效率、低污染…等原因，相關燃料電池的技術被廣泛的提出與研究，而目前在各類型燃料電池之中，以質子交換膜燃料電池及直接甲醇燃料電池的研發潛力最被看好。質子交換膜燃料電池的優點，在於其操作溫度及操作壓力低，且具有功率密度高、體積小、重量輕、及低腐蝕性等特性，但是目前由於水、熱管理及離子傳輸上的問題，讓燃料電池的性能遲遲無法提升，如何保持薄膜內含水量以及均勻的溫度分佈是電池能否正常運轉與發揮最高效率之關鍵。所以本研究將採用實驗與模擬相互驗證的方式探討燃料電池的相關設計與參數最佳化，以提升燃料電池之效率。
本文針對25 cm2膜電極組之質子交換膜燃料電池進行研究，研究內容包括實驗與模擬兩大部分，實驗方面經由燃料電池測試平台對質子交換膜燃料電池進行實際測試，觀察不同操作參數及操作條件對於電池性能所產生的影響；而模擬方面則是參考實際的質子交換膜燃料電池使用CFD軟體建立一質子交換膜燃料電池之三維模型，模擬在不同操作參數及內部材料特性參數設定對於電池性能的影響，最後結合模擬與實驗之結果，得到一最佳化參數與操作條件設定。
結果顯示：操作參數方面，陰極之燃料流量是影響電池性能最大的關鍵，供給充足之燃料可以有效的提升電池之輸出功率，而電池最佳之增濕溫度為50∼70 oC之間，最佳操作溫度為60∼70 oC之間。電池內部水熱與氣體消耗現象方面，可知電池之最高溫度是位於陰極之觸媒層；陰極之含水量會多於陽極且出口處會有積水的現象，是電池性能下降之主因；陰極之流速與壓力差皆大於陽極。實驗結果顯示：使用最佳化操作參數，可以使電池之電流密度達到375 mA/cm2 ，最高功率達到 3.5 W。模擬計算結果發現：當觸媒層之孔隙率為0.25、熱傳係數為1.7 W/m-K、導電率為6.2 1/ohm-m、氣體擴散層之孔隙率為0.7時，可得最佳之輸出功率。經最佳化參數之模擬分析顯示，與實驗測試所用之規格相同之電池，若燃料供應充分，其輸出之最大電流密度應可以提升至1290 mA/cm2，而最高輸出功率應可以提升至7 W。

關鍵字

質子交換膜燃料電池 ； 水熱管理 ； 參數最佳化 ； CFD

並列摘要

Abstract
Title：A study of optimizing performance of proton exchange membrane fuel cell
Pages：91
School：National Taipei University of Technology
Department：Institute of Mechatronic Engineering
Time：July, 2007 Degree：Master
Researcher：Pai-Wei Cheng Advisor：Chii-Ruey Lin
Chun-Hsi Su

Keywords：Proton exchange membrane fuel cell, water and heat management, optimum parameter, CFD

Fuel cell technology has been proposed and studied extensively in recent years for its ability to lower pollution and offer higher efficiency. The research potential of proton exchange membrane fuel cell (PEMFC) and direct methanol fuel cell (DMFC) are among the best. The unique feature of these two fuel cells is their abilities to operate at low pressure and low temperature around 30 oC to 70 oC. Besides, it also has some properties such as high power density, small volume and light weight. However, water and heat management is the main issue on PEMFC power efficiency. Based on this consideration, it is crucial to maintain the amount of water remaining in the membrane and to control the temperature distribution in order to induce the highest output efficient of PEMFC. This study aims at figuring out the relatively optimal design and operational parameters by comparing experimental and simulation results order to improve the performance of the fuel cell.
The studying target, include experiment and simulation, is a single cell of PEM with an MEA of 25 cm2. Experiments were performed on a platform of fuel cell test system using different operational parameters for testing PEMFC performance. Simulations were done by using Computational Fluid DynamicTM (CFDTM) codes to create a three-dimensional model for PEMFC, then to simulate different operational parameters and material characteristic parameters on PEMFC performance. At the end, combining results from simulations and experiments is the way to reach an optimal parameters and performance.
It is found that fuel supply rate of cathode is the dominant key to determine cell performance. Offering sufficient fuel is crucial in improving the output power. In additions, the optimal fuel humidity temperature is around 50∼70 oC, and the optimal working temperature is around 60∼70 oC. Water flooding in the cathode side becomes the main reason to decrease the performance of cell. The fluid velocity and pressure in cathode are much larger than those in anode. The highest current density from the single cell is recorded as 375 mA/cm2 and the highest output power is 3.5 W. The optimal characteristic setting in porosity is 0.25, electrical conductivity is 6.4 1/ohm-m, thermal conductivity is 1.7 W/m-K for catalyst layer and porosity is 0.7 for gas diffusion layer (GDL). By these parameter settings, the cell is able to reach highest current of 1290 mA/cm2 and the highest power of 7 W.

並列關鍵字

Proton exchange membrane fuel cell ； water and heat management ； optimum parameter ； CFD

參考文獻

[49] 國家高速網路與計算中心，CFD-ACE基礎訓練課程，台灣新竹，2006。

[3] D. Chu, R. Jiang, “Comparative studies of polymer electrolyte membrane fuel cell stack and singal cell,” J. Power Sources, Vol.80, 1999, pp.226-234.

[4] D.R. Sena, E.A. Ticianelli, V.A. Paganin, E.R.Gonzalez, “Effect of water transport in a PEFC at low temperatures operating with dry hydrogen,” Journal of lectroanalytical Chemistry, Vol. 477, 1999, pp.164-170.

[5] J.S. Yi, and T.V. Nugyen, “Multicomponent transport in porous electrodes of proton exchange membrane fuel cell using the interdigitated gas distributors,” J. The Electrochemical Society, Vol. 146,1999, pp. 38-45.

[6] J.S. Yi and T.V. Nguyen, “An Along-the-Channel Model for Proton Exchange Membrane Fuel Cells,” J. Electrochem Soc., Vol. 145,1998, pp. 1149-1159.