| 摘要: | 燃料電池由於具有高能源效率、低環境污染、分散式電力來源等優點，是近年來各先進國家積極投入研發的重點項目之一。在現有已開發的燃料電池中，固態氧化物燃料電池（SOFC）屬於高發電效率的高溫型燃料電池（工作溫度範圍在650-1000oC），其中平板式SOFC具有較簡單的結構設計與製作成本、較高能源效率、較低工作溫度（800oC以下）等優點，成為目前全世界對SOFC研發的重點。當SOFC系統在運轉使用時，包括暫態快速啟動與穩態工作，隨著工作環境溫度的改變，由於不同組件間具有不同的熱膨脹係數值，加上工作環境溫度分佈的不均勻，因而會產生不可忽視的熱應力，使得熱應力成為開發一套高可靠度及高效能平板式SOFC必須考慮的重要因素之一。對陶瓷材料所製成的電解質與電極而言，熱應力可以促進陶瓷材料既存孔隙或缺陷成長為較大的裂縫造成組件的洩漏或破損，降低電池的效率，因此對SOFC電池堆的熱應力分析將是設計SOFC系統不可或缺的步驟。本研究計畫之目的，乃在配合核能研究所擬開發之平板式SOFC系統，研發適用於平板式SOFC系統的電池堆熱應力分析模式及機械性質測試技術，本期所規劃的研究內容，包括建立完整多層電池堆3-D有限元素模型並求解熱應力分佈，並對平板式SOFC的PEN板進行工作溫度環境下的耐久機械強度量測，亦將以韋伯統計模式分析機械強度試驗數據，以建立機械強度、耐久壽命與破壞機率間的關係。透過理論分析與實驗研究成果之結合，建立含有可靠度因子的平板式SOFC電池堆的最適熱應力分析及耐久壽命評估模式，作為設計SOFC電池堆組件尺寸及評估其耐久壽命之參考。 Various types of fuel cell are now being intensely developed around the world because they give higher energy conversion efficiencies, generate less pollutant emissions, and can serve as distributed electricity sources. The solid oxide fuel cell (SOFC) operates at a high-temperature range of 650 to 1000oC in a direct conversion process such that they have the highest efficiencies of all fuel cells. As planar SOFC systems have several advantages over tubular ones such as compact size, higher energy efficiency and lower operating temperature (below 800oC), most of the current research on SOFC is being focused on the planar type. The typical materials used for anode, electrolyte, and cathode (often called a positive electrode-electrolyte-negative electrode, PEN) in SOFCs are all ceramic materials and brittle in mechanical characteristics. The high-temperature operation, however, gives rise to significant thermal stresses caused from mismatch of coefficients of thermal expansion among various components and temperature gradients in the SOFC system. When a ceramic component is held under such a prolonged thermal load (stress), pre-existent pores or defects which are subcritical, i.e. less than the critical defect size for immediate failure, can grow to failure and degrade the performance of a SOFC system during service. Therefore, a comprehensive thermal stress analysis of SOFC stack is necessary for the success in design and operation of a SOFC system. The aim of this multiple-year research proposal is, by using finite element simulation, to characterize the thermal stress distribution during transients and steady operation for a planar SOFC system which is being developed at the Institute of Nuclear Energy Research (INER). It is also intended to establish a mechanical testing technique and determine the high-temperature mechanical properties of the ceramic components used in this developing planar SOFC system. In this year』s proposed work, a 3-D finite element model for a multiple-cell SOFC stack will be constructed to solve the thermal stress distribution in different stages including start-up and steady operation. In addition, mechanical testing of the high-temperature strength and durability of the PEN will be conducted in conjunction with the Weibull analysis to develop the probability of survival for the assessment of the risks related to operation of the SOFC stack when subjected to the thermal stresses. Based on the numerical and experimental results, an optimal analysis and design model, with an consideration of survival probability, for planar SOFC systems will be developed and applied to the planar SOFC system being developed at INER. 研究期間：9601 ~ 9612 |
