(378s) Effect of Geometry, Gas Flow Rates, and Oxygen Concentration on the Performance of Anode-Supported Planar SOFCs

The modern era is seeking highly efficient power generation systems which have minimum carbon footprints. The Solid Oxide Fuel Cell (SOFC) is an example of such a kind of device that generates power from the fuels (Hydrogen, Hydrocarbons etc.) in the presence of oxidants (pure oxygen, air) without any direct combustion. In the proposed study, a three-dimensional anode supported planar SOFC is modelled with 150 µm anode thickness, 35 µm electrolyte thickness and 50 µm cathode thickness. The length of the cell is taken to be 90 mm.

The model is studied using multiple physics at particular domains associated with suitable boundary conditions. The Navier Stokes Equation is used to compute the fluid flow in both the electrode channels. Along with this the Brinkman Equation is used to study the fluid flow in the porous electrodes, cathode and anode. Care is taken to model the mass transport in the electrodes as well as their adjacent channels. To analyse the mass transport, Stefan Maxwell Diffusion Model is applied. In the present study, cathode-electrolyte interface is taken to be at the operating voltage, the anode-electrolyte interface is taken as the electric ground, and the Butler-Volmer Equation is solved to predict the current density of the model. The overpotentials associated with SOFCs are also calculated in the present study. The general energy equation associated with conduction, convection, heat generation, viscous dissipation is analysed to study the heat transfer. Heat generation due to electrochemical reaction is also considered to analyse the heat transfer of the model. The equations are solved simultaneously at the particular domains with the help of COMSOL Multiphysics using a direct solver with a tolerance of ~10^-5.

Flow channels of bipolar plates in planar SOFCs have different geometries, such as straight or serpentine channel geometries. In the present study, the power characteristics of the serpentine geometry with two 180áµ’ bends is compared with three straight channels SOFC and it is found that serpentine geometry has higher power output. The performance of SOFCs is also analysed varying the oxygen concentration of the oxidants ranging from pure oxygen to air. The study depicts the enhancement of performance with increasing flow rate is significant up to a limit and further the performance is not enhanced significantly with the increment of flow rates for both the geometries. Further to this, a study of geometric variation is also carried out to evaluate the dependency of cell performance over various geometric dimensions of the cell. The investigation can give a direction for the optimization of flow rates of cathode and anode along with their composition.