Numerical study on thermal stresses of a planar solid oxide fuel cell

A three-dimensional (3D) finite element model consists of positive electrode-electrolyte-negative electrode (PEN) and metallic interconnect (MIC) assembly is constructed by using commercial finite element software Abaqus. With the simulated temperature profile in the planar solid oxide fuel cell (SOFC), the finite element method is employed to calculate the thermal stress distribution in a planar SOFC. The effects of temperature profile, electrodes and electrolyte thickness, and coefficients of thermal expansion (CTEs) mismatch between components are characterized. The value and distribution of thermal stress are the functions of the applied materials CTEs, applied temperature profiles and thickness of anode and electrolyte. The calculated results can be applied as the guide for SOFC materials selection and SOFC structure design. The anode is subjected to large tensile stresses and the electrolyte is subjected to large compressive stresses during the first cooling from the sintering temperature. The chemical reduction of NiO to Ni in the porous anode lowers the absolute stress level in the PEN structure by 20%. The large tensile stresses in the anode and the large compressive stresses in the electrolyte relax partly when the SOFC operates at high temperature. Cracks could probably appear in the anode structure when the PEN structure is cooling to room temperature after the sintering.