Solid oxide fuel cell microstructure and performance modeling

Khalil Rhazaoui, Engineering And Physical Sciences Research Council, Claire Adjiman, Nigel Brandon
2015
The fundamental operation of Solid Oxide Fuel Cells (SOFCs) relies on the liberation of electrons at reaction sites within porous electrodes. These reaction sites, or triple-phase boundary (TPB) points, must be percolated to allow for reactants and products to flow to and from these sites. Due to the fact that electrochemical reactions in composite electrodes are dependent on the presence of TPB sites, a direct link exists between SOFC electrode microstructures and electrochemical performance.
more » ... mical performance. Recently, the development of advanced tomography and imaging techniques has allowed for this link to be better understood and quantified. This thesis presents the development of a novel effective conductivity model (ResNet) for 3D composite, anisotropic microstructures in the context of Ni-YSZ electrode characterization. The ResNet model is first used to derive the effective conductivity of simple structures, conductivities of which can be found in the literature. Good agreement was found in this initial study. The model is then used to compute the effective conductivities of more complex synthetic microstructures, comparing model outputs to those given by COMSOL Multiphysics, a commercial modeling platform. It was found that for a sufficiently high resolution, both models converge to the same results. Varying the discretization resolution allowed for an optimum discretization resolution to be determined, based on the mean particle size used for fabrication. The introduction of Volume Elements into the ResNet model is then presented, and the optimum aggregation resolution is extracted from a set of simulations. This allowed for the analysis of a real SOFC anode microstructure to be carried out, and underlined the importance of selecting a microstructure sample of a size that can be considered representative of the entire electrode. After a series of simulations on synthetically generated microstructures, several microstructural parameters are varied to carry out a sensitivity analysis on the effective conductivities and cur [...]
doi:10.25560/23301 fatcat:mlgwocd7hncqpdcc2ck252umce