燃料電池金屬雙極板之結構設計與分析

Abstract

本文提出一系統化的方法來評估不同參數下金屬雙極板的性能。首先利用有限元素分析取得燃料電池之結構特性，如金屬雙極板和氣體擴散層之間的接觸壓力，和氣體擴散層的應變分佈，一參數化模型用於此分析上。接著，燃料電池之性能可藉由一連串有限元素分析結果的推導來評估。接觸壓力和接觸電阻的關係可用於計算燃料電池之整體電阻，而氣體擴散層的應變和有效擴散率的關係可用於估計燃料電池的極限電流密度。然後透過計算電阻和極限電流密度來推導極化和功率曲線的理論公式。最後，經由極化和功率曲線來討論燃料電池性能和結構設計參數的關係，並進行結構最佳化流程得到最適當之肋構型和鎖合壓力以提升燃料電池之性能。總結來說，本文透過有限元素分析之結果來評估燃料電池之性能，並藉由調整燃料電池結構之設計變數完成燃料電池之最佳化設計，且該系統化的性能評估方法能得到一令人滿意之結構設計結果。

This thesis proposes a systematic method to evaluate the performance of a metallic bipolar plate fuel cell with different parameters. Firstly, a finite element analysis (FEA) is used to obtain the structural responses of the fuel cell stack, such as the contact pressure between gas diffusion layers (GDL) and metallic bipolar plates, and also the strain distribution of the GDL. A parametric model with given design parameters is developed for this analysis. Secondly, the performance of the fuel cell is evaluated from the results of the FEA through a series of derivations. The relationship between the contact pressure and contact resistance is used to calculate the whole electric resistance of the fuel cell. The relationship between the GDL strain and effective diffusion coefficient is studied to evaluate the limiting current density of the fuel cell. Then, the formulations for the polarization and power curves are derived with the calculated electric resistance and the computed limiting current density. Finally, the relationship between the fuel cell performance and the structural design parameters are discussed by the formulations of the polarization and power curves. The optimum design procedure is executed to improve the performance of fuel cell with the appropriate rib shape and clamping pressure. In conclusion, this thesis studies the relationships that can transfer the FEA results to the fuel cell performance and the optimization of the fuel cell performance by modifying the design parameters of the fuel cell structure. The systematic method of the performance evaluation gives a satisfactory result in the structural design.