Developing 3-D Model of Intermediate-Temperature SOFC with GDC Electrolyte

SOFCs with GDC electrolytes present challenges for stack modeling due to the variation in conductivity and chemical activity of GDC as a function of effective oxygen partial pressure PO2, which varies significantly down the channel in SOFC anodes with increasing fuel utilization. This paper presents a 3-D model for an intermediate-temperature SOFCs with GDC electrolytes, Ni/GDC anodes, and LSCF/GDC cathodes. The model uses fitted kinetics to capture, internal reforming and water-gas-shift in the anode as well as variations in open circuit voltage and activation overpotentials as a function of flow composition and temperature along the length of the channel. The model is validated against button cell data. The results show that for 600 and 650°C inlets, super-equilibrium concentrations of CH4 remain after 5 cm of channel. For the same fuel stoichiometry and cell voltage, humid H2 provides over 30% more power than reformate with more than 5% CH4.