固態氧化物燃料電池(SOFC, Solid Oxide Fuel Cell)具有低污染以及高能量轉換效能之雙重優點，被視為未來能源科技之發展重點項目之一。本文針對平板型SOFC之三個主要問題進行探討：1)在預熱程序中，以較完整之分析模式，進行不同預熱模式之分析，並找出最佳之預熱模式；2)在啟動程序中，嘗試不同燃料，並採用陽極再循環模式以及固定溫差之啟動機制，以試圖降低啟動所需之時間並分析其對於溫度梯度之影響；3)針對結合順從式密封技術(BCS, Bonded-Compliant Seal)，在實際操作情況下進行效能分析。
第一部份乃是建立搭配甲烷燃燒器之固態氧化物燃料電池之預熱模式。此系統包含甲烷燃燒器與燃料電池兩個部份。甲烷燃燒後之高溫氣體將導入燃料電池當中進行預熱。而此固態氧化物燃料電池分析模式包括陽極流道、陽極支撐層、陽極擴散層、陽極、固態電解質層、陰極、陰極擴散層及陰極流道等八個區域。接著並針對不同預熱模式，以及單/雙流道兩種程序進行分析。另外再針對不同甲烷燃燒器之功率，進行不同預熱程序效能之評估，以期找出最佳之預熱程序。第二部份則是建立啟動程序之分析模式，其中物理模式包含成份傳輸方程式、能量守恆方程式、化學/電化學反應模式以及電化學模式等。而探討之參數包括不同燃料、陽極再循環機制以及固定入口溫差啟動法對於啟動時間以及電池內部溫度均勻性之影響。第三部份之分析乃是針對平板型-陽極支撐式固態氧化物燃料電池，在運行之操作條件下計算其溫度分佈。接著建立有限元素分析模式，並搭配所計算出之溫度場進行熱應力分析，以評估其密封之效能。
在結果方面，單流道預熱模式所需之時間過長，對於SOFC之預熱程序而言較不實際。對雙流道模式而言，最大溫度梯度發生在預熱一開始的時候，對單流道模式而言，則是發生在預熱結束的時候。當燃燒器之功率超過10kW之後，反向模式所需要之熱能就趨近於一定值，但對於同向模式而言，其所需要之熱能則是隨燃燒器功率上升而上升。從比較分析之結果中可知，最佳之預熱模式為雙流道-反向流動模式。而在啟動之結果中發現，採用兩種不同燃料啟動時，皆會在啟動程序剛開始的時候產生最大之溫度梯度。而對於APU (Auxiliary Power Unit) 系統而言，採用甲烷啟動之時間太長。另外並發現，對於啟動而言，甲烷所進行之重組反應，其吸熱反應有助於和緩啟動瞬間之高速升溫現象，並降低電池內部之溫度梯度。陽極再循環機制對於熱應力並無顯著之影響，但能夠加快啟動之速度。固定溫差啟動機制能夠在啟動初期產生較小之溫度梯度，而在後期加速啟動之程序。在結構分析方面，採用假設之均勻溫度場會明顯低估電池及金屬外框之熱應力。另外並發現，影響熱應力之主要因素與探討區域有關。而與結合式密封技術相比，採用BCS密封技術下，溫度梯度所產生之熱應力與結合式密封技術之情況下相當。另外，熱應力會隨著電壓之降低而降低。

The SOFC (Solid Oxide Fuel Cell) meets the duo requirements of high energy-conversion efficiency as well as ultra-low pollution, and has been treated as one of the most important energy converting devices. The present study focuses on three critical issues for the development of the planar SOFC. The first one is to evaluate the performance of different heat-up modes and to identify the optimal one. The second one is to estimate the effect of the fuel type, the anode-recycling mechanism, and the fixed-temperature-difference mechanism on the start-up time and the temperature gradient. The last one is to investigate the performance of the bonded compliant seal (BCS) technique for the planar SOFC under the practical operating condition.
For the first part, it was found that from the aspect of the heat-up time, the single-channel mode leads to about 2.7 folds longer than that of the dual channel mode, making it impractical to be employed in the SOFC heat-up process. The required time for the counter-flow configuration is about 25% less than that of the co-flow configuration. From the aspect of the maximum-temperature-gradient, the slowest single-channel mode leads to the smallest temperature gradient. For the counter-flow configuration, its temperature gradient is averagely about 17% larger than that of the co-flow configuration. For both the co-flow and the counter-flow configurations, the maximum-temperature-gradient occurs at the beginning of the heat-up process, while it occurs at the end of the heat-up process for the single-channel mode. From the aspect of the required energy, it is approximately constant for the counter-flow configuration as the burner power larger than 10kW, while it gradually increases for the co-flow configuration. The total energy required for the counter-flow configuration is about 20% less than that of the co-flow configuration. The optimal heat-up approach is identified as the counter-flow configuration. Under different burner powers, the optimal counter-flow configuration results in the smallest required energy and the shortest time for the heat-up process of the planar, anode-supported SOFC at the expense of a higher maximum temperature-gradient.
For the second part, it was found that the effective maximum temperature-gradient generates at the beginning of the start-up process for both hydrogen and methane. The required time for the case using methane is 3.2 folds longer than that using hydrogen. For the APU system, a 40 minutes start-up process is too slow. For the effective maximum-temperature-gradient, the case using hydrogen is 2.2 folds larger than that utilizing methane. The statement about the endothermic internal reforming reaction generating large temperature gradient is only valid in the steady-state, while it is a positive effect on the accommodation of the temperature uniformity during the start-up process. There is no significant effect of the anode-recycling mechanism on the effective maximum temperature-gradient. However, the effect of the anode-recycling on the start-up time is significant. Comparing to the base case, i.e., without anode-recycling, the start-up time decreases by 48.58% under the condition of 70% anode-recycling. For the fixed-temperature-difference mechanism in the start-up process, a properly selected temperature difference leads to a smaller effective maximum temperature-gradient at the beginning of the start-up process and a shorter start-up time by accelerating the start-up pace at the later stage. Therefore, if the maximum sustainable effective maximum-temperature-gradient for a specific SOFC is known, the start-up process can be accelerated by choosing as high as possible fixed temperature difference, while keeping the effective maximum-temperature-gradient under the allowable threshold.
For the last part, it was found that the predictions with the assumption of a uniform temperature might underestimate the thermal-stress of the present investigated SOFC with the BCS design by 28% for the cell and 37% for the metal frame in comparison with those in practical operating conditions where the temperature is non-uniform. The dominant factor for the thermal-stress is location dependent. The contribution of the temperature gradient to the thermal-stress of the cell for an SOFC using the BCS design is comparable with that using the bonded glass–ceramic seal. With a lower voltage, the thermal-stress of the cell is relatively lower, while the contribution of the temperature gradient to the thermal-stress is higher.

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