Articles techniques et présentations

A Solid Oxide Fuel Cell (SOFC) can convert the chemical energy of a fuel (H2-rich gas mixture [1] or syngas [2, 3] or biogas [4]) in electric and thermal energies with high electric efficiency. It is composed of two porous gas diffusion electrodes and an electrolyte (Figure 1). The fuel (a H2-rich gas mixture) and air can enter in the fuel cell from the same side (co-current flows) or from the opposite sides (counter current flows) and the flow configurations affect the electrical performances in term of the polarization curves. Solid oxide fuel cell systems fed by bio-methane can be integrated with electrical energy systems from renewable sources, lithium ion batteries and a Proton Exchange Membrane (PEM) electrolyzer to obtain a poly-generative system capable of supporting pure electric or hybrid electric mobility with PEM fuel cells [5]. In this work, a model of an SOFC with the two different flow configurations is set up in COMSOL Multiphysics environment. The model includes the full coupling between the anode and cathode mass balances, the momentum balances in the gas channels, the gas flows in the porous electrodes, the ionic and electronic currents balances [6, 7]. It studies the performances of the SOFC with the two different flow configurations. The fuel cell anode and cathode electrochemical reactions are (1) and (2): anode H2+O^(2-)→H2 O+2e^- (1) cathode 1/2 O_2+2e^-→O^(2-) (2) The model includes the following processes: • Electronic charge balance (Ohm’s law) • Ionic charge balance (Ohm’s law) • Butler-Volmer charge transfer kinetics • Flow distribution in gas channels (Navier-Stokes) • Flow in the porous GDEs (Brinkman equations) • Mass balances in gas phase in both gas channels and porous electrodes (Maxwell-Stefan Diffusion and Convection). The performance of a SOFC with the co-current flow configuration was better than the performance of the same SOFC with counter current flow configuration in accordance with the results obtained in [8].