Effect of Temperature Fluctuation on Creep and Failure Probability for Planar Solid Oxide Fuel Cell

Abstract

The creep and failure probability of a planar solid oxide fuel cell (SOFC) through a duty cycle is calculated by finite element method (FEM) and Weibull method, respectively. Two sealing methods, namely, rigid seal and bonded compliant seal (BCS), are compared. For the rigid seal, failure is predicted in the glass ceramic because of a failure probability of 1 and maximum creep strain. For the BCS design, the foil can absorb part of thermal stresses in the cell by its own elastoplastic deformation, which considerably decreases failure probability and creep strain in the SOFC. The creep strength of BCS method is achieved by sealing foil with excellent creep properties. Temperature fluctuation during the operating stage leads to the increase in thermal stress and failure probability. In particular, temperature change from lowpower to highpower state results in a considerable increase in the creep strain, leading to creep failure for the rigid seal. A failure probability of 1 is generated during startup and shutdown stages. Therefore, temperature fluctuation should be controlled to ensure structural integrity, and lowering the operating temperature can decrease failure probability and creep failure.