Effects of Clamping Load on the Thermal Stress Distribution in a Planar SOFC with Compressive Sealing

The objective of this study is, by using finite element analysis (FEA), to characterize the effects of clamping load on the thermal stress distribution in a prototypical planar solid oxide fuel cell (pSOFC) stack with compliant mica-based seal gaskets. A three-dimensional (3-D) FEA model was constructed for a multiple-cell stack to perform comprehensive thermal stress analyses at steady operation and shutdown stages. The constructed 3-D FEA model consists of complete components in a practical pSOFC stack, including positive electrode-electrolyte-negative electrode (PEN) assembly, interconnect, nickel mesh, glass-ceramic seals, and compressive mica seals. Five different compressive loads (0.06, 0.1, 0.6, 1, and 6 MPa) were applied in the modeling to clamp the given integrated pSOFC stack. Simulation results indicate that increasing the applied clamping load from 0.06 to 0.6 MPa could eliminate bending deformation in the PEN plate and its supporting frame. For a further increase of the applied clamping load to 1 and 6 MPa, the critical stresses in the glass-ceramic and mica sealants increased to a potential failure level. In this regard, a 0.6-MPa clamping load is considered an optimal assembly load that can both eliminate bending deformation in the PEN-frame assembly plate and maintain acceptable critical stresses in the glass-ceramic and mica sealants.