Thermodynamic modeling of direct internal reforming solid oxide fuel cells operating with syngas

In this paper a direct internal reforming solid oxide fuel cell (DIR-SOFC) is modeled thermodynamically from the energy point of view. Syngas produced from a gasification process is selected as a fuel for the SOFC. The modeling consists of several steps. First, equilibrium gas composition at the fuel channel exit is derived in terms mass flow rate of fuel inlet, fuel utilization ratio, recirculation ratio and extents of steam reforming and water–gas shift reaction. Second, air utilization ratio is determined according to the cooling necessity of the cell. Finally, terminal voltage, power output and electrical efficiency of the cell are calculated. Then, the model is validated with experimental data taken from the literature. The methodology proposed is applied to an intermediate temperature, anode-supported planar SOFC operating with a typical gas produced from a pyrolysis process. For parametric analysis, the effects of recirculation ratio and fuel utilization ratio are investigated. The results show that recirculation ratio does not have a significant effect for low current density conditions. At higher current densities, increasing the recirculation ratio decreases the power output and electrical efficiency of the cell. The results also show that the selection of the fuel utilization ratio is very critical. High fuel utilization ratio conditions result in low power output and air utilization ratio but higher electrical efficiency of the cell.