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Three-dimensional numerical analysis of solid oxide fuel cell (SOFC) anode polarization is conducted with a microstructure obtained by a focused ion beam and scanning electron microscope (FIB-SEM). Electronic, ionic and gaseous transports with electrochemical reaction are considered in the porous anode. A sub-grid scale (SGS) model is newly developed and effectively used to consider the structural information whose characteristic scale is smaller than calculation grid size. The proposed SGS models are designed to keep the quality of the structural information which is inevitably lost by resampling process in grid generation. Through comparisons between the simulation results and the experimental data, it was found that the SGS model can either improve the simulation accuracy under a given calculation grid system or reduce computational load for the same degree of simulation accuracy. [ABSTRACT FROM AUTHOR]

Electrolyzer stacks in a bipolar architecture (cells connected in series) are desirable since power provided to a stack can be transferred at high voltages and low currents and thus the losses in the power bus can be reduced. The anode electrodes (active electrodes) considered as part of this study are single sided but there are manufacturing cost advantages to implementing double side anodes in the future. One of the main concerns with a bipolar stack implementation is the existence of leakage currents (bypass currents). The leakage current is associated with current paths that are not between adjacent anode and cathode pairs. This leads to non uniform current density distributions which compromise the electrochemical conversion efficiency of the stack and can also lead to unwanted side reactions. The objective of this paper is to develop modelling tools for a bipolar architecture consisting of two single sided cells that use single sided anodes. It is assumed that chemical reactions are single electron transfer rate limited and that diffusion and convection effects can be ignored. The design process consists of the flowing two steps: development of a large signal model for the stack, and then the extraction of a small signal model from the large signal model. The small signal model facilitates the design of a controller that satisfies current or voltage regulation requirements. A model has been developed for a single cell and two cells in series but can be generalized to more than two cells in series and to incorporate double sided anode configurations in the future. The developed model is able to determine the leakage current and thus provide a quantitative assessment on the performance of the cell. [ABSTRACT FROM AUTHOR]