成果報告書詳細
管理番号20110000000977
タイトル*平成22年度中間年報 固体酸化物形燃料電池システム要素技術開発 基礎的・共通的課題のための研究開発 機械的解析による劣化機構の解明、加速試験方法の確立
公開日2011/10/12
報告書年度2010 - 2010
委託先名国立大学法人東北大学大学院環境科学研究科
プロジェクト番号P08004
部署名新エネルギー部
和文要約和文要約等以下本編抜粋:1. 研究開発の内容及び成果等
(1) 緒言
本研究は、固体酸化物形燃料電池(SOFC)の機械的損傷を伴う劣化の発生機構を解明し、各種セルの短期・長期信頼性を評価する手法を提案することを目的としている。SOFC で用いられる酸化物は、酸化・還元や通電によって物理化学的・機械的特性が複雑に変化する。ところが従来の構造解析ではこれらの因子が十分に考慮されておらず、また必要な基礎データも公表されていなかった。そこで、昨年度までにこれらを取り入れたモデリング手法と模擬セルによる検証法を策定し、基礎データの取得(実施項目3)から模擬セル試験(実施項目2)、実セル解析(実施項目1)に亘る階層的な評価体系を構築してきた。本年度は、データの拡充、解析法の改良を進めるとともに、特に機械的な損傷が問題となりやすいセルタイプを抽出し、苛酷条件での損傷の発生機構を特定することを試みた。
英文要約Development of Systems and Elemental Technology on Solid Oxide Fuel Cell (SOFC)
/Basic Research for Improving Durability and Reliability
/Research on Mechanical Degradation and the Accelerated Test Method
FY 2010 in the project of FY2008 ~ FY2011 Tohoku University
This work aims at understanding the mechanism of mechanical failure of SOFCs, and establishment of the
test methods for their reliability in short- and long-term operations. At the beginning of this project,
methods and the data required were lacking for quantitative analysis of SOFC under real operation
conditions. Thus, efforts have been paid for data acquisition, development of a numerical model, and
experimental verification of the model. In this fiscal year, the results were applied to understand
important or common features of the failure mechanism in SOFCs that are under development in this project.
(i) Chemically and thermally induced stress in a planar type cell and stack
The asymmetric nature may cause mechanical failure when the planar type cell is constrained flat during
operation. The acoustic emission measurement for a stack module of planar cell showed accidentally
generated large temperature gradient can cause a mechanical damage. Accelerated test with single cells
confirmed the results.
Furthermore, stress condition measurements with in-situ Raman spectroscopy revealed that the periphery of
the single cells were under tensile stress during operation. In order to understand those behaviors of
the planar cells, numerical calculation was carried out using the newly developed code that can treat
the ionic-electronic mixed conductivity and oxygen nonstoichiometry of the materials together with the
complicated mictrostructure of the electrode using homogenization method.
The calculation showed in all cases that the oxygen vacancy formation in the electrolyte under reduced
atmosphere caused high tensile stress at the cathode side, especially, around the periphery of the cell.
This stress is further enhanced when temperature at the center is increased, which might happen when high
current density is extracted, or the cell stack is cooled quickly from the side of the cell.
(ii) The effect of cell deformation in a weakly constrained cell stack
The flat tubular cells, with the electrolyte on one side and the interconnect on the other side, may bend
during the operation due to its asymmetric feature. Furthermore, the interconnect and the electrode
materials are known to have oxygen nonstoichiometry and show chemical expansion under certain atmospheres.
In order to check the effect of the deformation on the integrity of the cell-to-cell connection, in-situ
observation of the cell shape was carried out using a model cell. The cell showed complicated bending
behavior in heating and fuel flow operations. Acoustic emission measurement of the stack of those cells,
however, showed stable operation is possible during quick heating and cooling cycles except for the initial
cycles.
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