A simple model for interconnect design of planar solid oxide fuel cells

Abstract

Two geometries of solid oxide fuel cells (SOFCs) are currently under development, tubular and planar. Both types of cells are configured in a stack using an interconnect, which electrically connects the anode of one cell to the cathode of the adjacent cell, while also physically isolating fuel from oxidant. Proper design of the interconnect in conjunction with single-cells is critical to minimizing the overall stack resistance. This work quantitatively examines the dependence of total SOFC stack resistance as a function of interconnect contact spacing, interconnect contact area, cathode thickness, electrolyte thickness, anode thickness, and transport properties associated with each region and at interfaces (charge transfer resistance). Both one-dimensional (channels) and two-dimensional (dimples) symmetries of interconnect geometry are analyzed for planar cells. Analytical expressions are derived for the area-specific resistance (ASR) of a repeat unit consisting of a cell and interconnect, for both geometries, as a function of cell parameters, interconnect contact area and interconnect contact spacing. It is found that the one-dimensional interconnect symmetry leads to lower values of stack-repeat unit area-specific resistance (ASR) than the two-dimensional symmetry. Thus, based on the analysis presented here the one-dimensional interconnect geometry is preferred over the two-dimensional one.