Dynamic Simulation of the Anodic Side of an Integrated Solid Oxide Fuel Cell System

A new dynamic SOFC model was integrated with the simulation modules of other system components (i.e.: reformer, anodic off-gas burner, anodic ejector) to construct a system model that could simulate an integrated 250 kW SOFC hybrid system. This work describes the preliminary results obtained for the anodic loop, which was studied in order to obtain a complete time characterization of its time-dependent behavior. The new dynamic model was then compared with an existing model for an integrated planar pressurized Solid Oxide Fuel Cell at the steady state. The two models differed due to their levels of complexity and calculation times: the first one was meant for real-time applications, hence retaining the basic dynamic information but including relevant simplifications in the internal information on fuel cell behavior; the second one was used for more accurate predictions at the steady-state, but required longer simulation times. The unsteady-state tests with the new dynamic model showed that the characteristic voltage transient due to changes in SOFC hydrogen concentration had a time scale that was of the order of fractions of seconds while the characteristic temperature transient was of the order of hours. The frequency characterization of the anodic loop with phased oscillations in the fuel flow and stack current enabled us to correlate the inner SOFC anode features with the anodic loop response, thus providing useful indications for designing robust anodic loop controllers.