加壓型SOFC陽極支撐與電解質支撐單電池堆量測與分析

Measurements and Analyses of Anode-Supported and Electrolyte-Supported Single-Cell Stacks for Pressurized SOFCs

謝易達(Yi-Da Shie)

指導教授 ： 施聖洋

國立中央大學/工學院/能源工程研究所/碩士(2013年)

摘要

本論文使用已建立之雙腔體高壓固態氧化物燃料電池(SOFC)性能測試平台，自行組裝單電池堆(即全電池加上流道板)，分別針對陽極支撐與電解質支撐單電池堆，進行其電池性能與電化學阻抗頻譜的量測。實驗條件為固定500 sccm氫氣與400 sccm氮氣之混和氣體為陽極燃料和900 sccm空氣做為陰極氧化劑；為了探討加壓和溫度效應，我們控制不同系統操作壓力範圍(p = 1 atm ~ 5 atm)和溫度範圍(T = 700℃ ~ 850℃)，主要研究目的為探討比較兩不同支撐全電池之優劣和異同。實驗結果顯示，陽極支撐與電解質支撐單電池堆其性能皆會隨壓力與溫度增加而有所提升。例如，在T = 850 ℃與操作電壓0.7 V之條件下，陽極支撐/電解質支撐單電池堆在p = 1 atm之功率密度分別為PD = 309 / 193 mW cm-2；當p增加到3 atm時，其PD值可較迅速地增加到422 / 228 mW cm-2；而當p = 5 atm，PD值僅增加到476 / 250 mW cm-2，顯示加壓效應在1 ~ 3大氣壓時，對電池性能之影響最為顯著，其影響會隨壓力大於3大氣壓後逐漸遞減。前述提昇電池性能之實驗結果，可由電化學阻抗頻譜(EIS)量測來加以解釋和證實。
我們進一步以等效電路模組對所量測之電化學阻抗頻譜進行分析，主要結果如下歐姆極化阻抗與加壓效應無關，其僅會隨溫度增加而下降；而活化極化阻抗與濃度極化阻抗則皆會隨壓力與溫度增加而減少，此結果適用於兩不同支撐之單電池堆。經比較後，加壓效應對陽極支撐單電池堆之性能提昇比對電解質支撐單電池堆來得明顯有效，而後者對溫度效應之反應遠比前者來的敏感。整體而言，溫度效應比壓力效應對提昇電池性能來的顯著，因其可有效降低歐姆極化阻抗。本研究成果應對發展高壓SOFC與微氣渦輪機結合之複合式發電系統有重要之助益。

關鍵字

加壓SOFC ； 陽極支撐和電解質支撐單電池堆 ； 電池性能 ； 電化學阻抗頻譜 ； 歐姆和極化阻抗

並列摘要

This study applies a recently-established high-pressure double-chamber solid oxide fuel cell (SOFC) testing platform together with the self-assembled single cell stacks (a full cell with flow distributors in both anode and cathode), so that cell performance and electrochemical impedance spectroscopy (EIS) of both anode-supported and electrolyte-supported SOFCs can be measured. Fixed flow rates are used for all experiments, 500 sccm hydrogen and 400 sccm nitrogen for the anode and 900 sccm air for the cathode. To investigate effects of system pressure (p) and temperature (T), five different p varying from 1 atm to 5 atm and four different T varying from 700℃ to 800℃ are independently controlled and varied. The major objective is to compare advantages/disadvantages and similarities/differences between anode-supported and electrolyte-supported SOFC single stacks. Results show that cell performances of both anode-supported and electrolyte-supported SOFC singlel stacks increase with increasing p and T. For example, when T = 850℃ at 0.7 V, the power densities (PD) of anode-supported/electrolyte-supported single-cell stacks are respectively 309/193 mW cm-2 at p = 1 atm, values of PD modestly increase to 422/228 mW cm-2 rather quickly as p increases at 3 atm, and values of PD can only increase modestly to 476/250 mW cm-2 at p = 5 atm. These results reveal that pressurization for the increase of PD is most significant from 1 atm to 3 atm and such enhancement becomes more gradually when p > 3 atm. Furthermore, the aforesaid that cell performance results are to be explained by EIS measurements.
We use equivalent an circuit model to analyze EIS data. It is found that the ohmic polarization resistance is independent of p, but it decreases with increasing T. Moreover, both of activation and concentration polarization resistances decrease with increasing T and/or p. Such resistance results due to effects of increasing p and T are similar for both anode-supported and electrolyte-supported single-cell stacks. When compared, it is also found that the increase of PD due to pressurization is more significant in the anode-supported single-cell stack than in the electrolyte-supported SOFC single-cell stack. However, the latter is more sensitive to the temperature effect as compared to the former. Generally speaking, the temperature effect is more effective than the pressurization effect in terms of the increase of cell performance. This is because increasing T can effectively decrease the ohmic polarization resistance. The present study is important, because it is the first step toward the development of pressurized SOFCs combined with micro gas turbines for future power generation.

並列關鍵字

pressurized SOFC ； anode-supported and electrolyte-supported single-cell stacks ； cell performance ； electrochemical impedance spectra ； Ohmic and polarization resistances

參考文獻

[1] Gregor, H., Fuel cell technology hand book, CRC Press, Germany, 2003.

[2] Sammes, N. M., Du, Y., Bove, R., “Design and fabrication of a 100 W anode supported micro-tubular SOFC stack”, Journal of Power Sources 145 (2005) 428-434.

[4] M. Henke, C. Willich, C. Westner, F. Leucht, R. Leibinger, J. Kallo and K. A. Friedrich, “Effect of pressure variation on power density and efficiency of solid oxide fuel cells”, Electrochimica Acta 66 (2012) 158-163.

[5] T.-H. Lim, R.-H. Song, D.-R. Shin, J.-I. Yang, H. Jung, I. C. Vinke and S.-S. Yang, “Operating characteristics of a 5kW class anode-supported planar SOFC stack for a fuel cell/gas turbine hybrid system”, International Journal of Hydrogen Energy 33 (2008) 1076-1083.

[6] L. Zhou, M. Cheng, B. Yi, Y. Dong, Y. Cong and W. Yang, “Performance of an anode-supported tubular solid oxide fuel cell (SOFC) under pressurized conditions”, Electrochimica Acta 53 (2008) 5195-5198