SOFC modeling at the cell scale including hydrogen and carbon monoxide as electrochemically active fuels

Fuel cells are promising for future energy systems, because they are energy efficient and able to use renewable fuels. A fully coupled computational fluid dynamics (CFD) approach based on the finite element method (with the software COMSOL Multiphysics) in two-dimensions is developed to describe an intermediate temperature solid oxide fuel cell (SOFC) single cell. Governing equations covering heat, gas-phase species, momentum, ion and electron transport are implemented and coupled to kinetics describing internal reforming and electrochemical reactions. Both hydrogen and carbon monoxide are considered as electrochemically active fuels within the anode. The activation polarization in the electrodes and the ohmic polarization due to ion transport in the YSZ material are found to be the major part of the potential losses. The activation polarization is the most significant and it is smaller within the cathode compared to the anode for this study. The ion current density and the activation polarization are the highest at the electrolyte-electrode interface and decrease rapidly within the electrodes as the distance from the interface increases. However, the ohmic polarization by ion transfer increases for the positions away from the interface. The addition of the electrochemical reaction with CO as fuel increases the current density. It is concluded that the temperature and current density are strongly integrated and when any of them is changed, the other follows, and the change is accelerated. (Less)