本研究主要研究對象為中溫固態氧化物燃料電池(Solid Oxide Fuel Cell, SOFC)系統，在結合不同類型之陽極尾氣回收(Anode Off-Gas Recycle, AGR)模組下，比較陽極尾氣回收對於系統電效率之影響。其中，陽極尾氣回收模組可細分為高溫陽極回收與低溫陽極回收，透過分析兩系統在電堆燃料使用率、陽極回收率與空氣燃料比等不同的操作條件下的熱電效率之差異，並利用熵增原理與可用能分析各組件不可逆之能量損失，進一步分析各組件對於系統熱電效率之影響權重，並且於論文最終提出優化設計之系統設計，達到改善與提升系統效率之功效。
為了進行一系列系統數值模擬與計算，本文透過熱力學法進行系統能量傳遞之計算並搭配第二定律熵與㶲分析，探討SOFC系統各組件之性能變化。根據數值計算之結果可知，在相同的陽極回收率、電堆燃料使用率與空氣燃料比時，高溫陽極回收SOFC發電系統的電效率皆比低溫陽極回收系統來得高，最高電效率值為63.35%。
在熵增與可用能方面，高溫陽極回收系統SOFC的熵增率較低溫陽極回收系統低一些，因此在高溫陽極回收系統有較好的可用能效率。並且可以得知組件的出入口溫差、化學反應與對外界熱傳皆會影響熵增率，尤其燃燒室入出口溫差過大時，對於熵增率的影響最大。
本文除了前述進行陽極尾氣回收系統進行效率與可用能分析外，也針對陽極尾氣回收系統進行優化設計，進而提出利用甲烷二氧化碳重組方式，將甲烷與二氧化碳部分轉換成一氧化碳與電堆所需的氫氣，除了提高3%進入電堆的氫氣濃度與氫氣流量增加10%，使電堆增加發電量與發電效率達58.63%，亦可減少進入電堆之碳氫燃氣濃度，進而避免電堆碳沉積，提升系統壽命。
最後，為了有效地利用系統剩餘尾氣，透過結合氣渦輪機與有機朗肯循環之複合發電系統以提升系統之整體效率，其整體系統效率分別提升了10%與6%左右。

This research investigates the system electrical efficiency for intermediate temperature Solid Oxide Fuel Cells (SOFC) combined different modes of anode off-gas recycle (AGR). Furthermore, anode off-gas recycle modes can be classified into high temperature anode off-gas recycle (HT-AGR) and low temperature anode off-gas recycle (LT-AGR). And we modulate different operating conditions like stack fuel utilization, anode recycle ratio and air/fuel ratio to analyze two systems’ thermal and electrical efficiency. By analyzing the weight of each component's influence on the system’s thermal and electrical efficiency with entropy increase principle and exergy. And finally proposing the optimized design of system to improving the system efficiency.
In order to numerical simulate and calculate system’s performance, using thermodynamics law and second law to analyze the change of system’s components’ energy transfer. According to the results of numerical calculations, HT-AGR SOFC system’s electrical efficiency is higher than LT-AGR’s, and the highest value is 63.35%.
In terms of entropy increase and exergy, the HT-AGR system’s stack entropy increase rate which is lower than LT-AGR’s. So HT-AGR system’s exergy efficiency is higher than LT-AGR system. And it can be known that the temperature difference between the inlet and outlet of the component, the chemical reaction and the heat transfer to the environment will affect the entropy increase rate, especially when the temperature difference between the inlet and outlet of the burner is too large, the effect on the entropy increase rate is greatest.
In addition to the aforementioned analysis of the system efficiency and exergy, also optimizes the design of the AGR system. And we propose the design by using CH4–CO2 reforming to partially convert methane and carbon dioxide into carbon monoxide and hydrogen required for the stack. This method increases the hydrogen concentration 3% into the stack and the flow rate 10%. Also increasing the stack output power and the power efficiency achieve to 58.63%. According to this result, the concentration of hydrocarbon fuel can be reduced before entering the stack that not only avoids carbon deposition in the stack but also improves the operating life.
Finally, in order to effectively use the exhaust gas of the system, the overall efficiency of the system was improved by a combined power generation system combining gas turbine (GT) and organic Rankine cycle (ORC). The overall system efficiency of combined GT and ORC which increased about 10% and 6% respectively.

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