Grading the Amount of Electrochemical Active Sites along the Main Flow Direction of an SOFC

A fully coupled computational fluid dynamics (CFD) approach based on the finite element method, in two-dimensions, is developed to describe a solid oxide fuel cell (SOFC). Both hydrogen and carbon monoxide are considered as electrochemical reactants within the anode. The dimensionless number of electrochemical active sites (EAS), the pore radius (indirectly proportional to the particle radius) and the active area-to-volume ratio available for methane reforming are graded, along the main flow direction, to equalize the current density distribution. Previous studies available in the open literature only considered grading in the direction normal to the main flow direction, in terms of porosity and tortuosity. It is found that grading the active area-to-volume ratio available for methane reforming increases the OCV along the main flow direction. It is concluded that an optimized graded EAS reduces the need of air flow rate with 21 %, with the same outlet temperatures as for the ungraded case.