This work deals with microstructural characterisation, modelling and simulation of SOFC electrodes with the goal of optimizing the electrode microstructures. Methods for a detailed electrode analysis based on focused ion beam (FIB) tomography are presented. A 3D FEM model able to perform simulations of LSCF cathodes based on 3D tomography data is shown. A model generating realistic, yet synthetic microstructures is presented that enables the optimization of microstructural characteristics.

This work deals with microstructural characterisation, modelling and simulation of SOFC electrodes with the goal of optimizing the electrode microstructures. Methods for a detailed electrode analysis based on focused ion beam (FIB) tomography are presented. A 3D FEM model able to perform simulations of LSCF cathodes based on 3D tomography data is shown. A model generating realistic, yet synthetic microstructures is presented that enables the optimization of microstructural characteristics. This work was published by Saint Philip Street Press pursuant to a Creative Commons license permitting commercial use. All rights not granted by the work's license are retained by the author or authors.

Solid oxide fuel cells (SOFCs) are promising electrochemical power generation devices that can convert chemical energy of a fuel into electricity in an efficient, environmental-friendly, and quiet manner. Due to their high operating temperature, SOFCs feature fuel flexibility as internal reforming of hydrocarbon fuels and ammonia thermal cracking can be realized in SOFC anode. This book presents an overview of the SOFC technology with a focus on the recent developments in new technologies and new ideas for addressing the key issues of SOFC development. This book first introduces the fundamental principles of SOFCs and compares SOFC technology with conventional heat engines as well as low temperature fuel cells. Then the latest developments in SOFC R&D are reviewed and future directions are discussed. Key issues related to SOFC performance improvement, long-term stability, mathematical modelling, as well as system integration/control are addressed, including material development, infiltration technique for nano-structured electrode fabrication, focused ion beam – scanning electron microscopy (FIB-SEM) technique for microstructure reconstruction, the Lattice Boltzmann Method (LBM) simulation at pore scale, multi-scale modelling, SOFC integration with buildings and other cycles for stationary applications.

Three-phase porous composites containing electrolyte (ionic conductor), electronic conductor, and porosity phases are frequently used for solid oxide fuel cell (SOFC) electrodes. Performance of such electrodes is microstructure sensitive. Topological connectivity of the microstructural phases and total length of triple phase boundaries are the key microstructural parameters that affect the electrode performance. These microstructural attributes in turn depend on numerous process parameters including relative proportion, mean sizes, size distributions, and morphologies of the electrolyte and electronic conductor particles in the powder mix used for fabrication of the composites. Therefore, improvement of the performance of SOFC composite electrodes via microstructural engineering is a complex multivariate problem that requires considerable input from microstructure modeling and simulations. This dissertation presents a new approach for geometric modeling and simulation of three-dimensional (3D) microstructure of three-phase porous composites for SOFC electrodes and provides electrode performance optimization guidelines based on the parametric studies on the effects of processing parameters on the total length and topological connectivity of the triple phase boundaries. The model yields an equation for total triple phase boundary length per unit volume (LTPB) that explicitly captures the dependence of LTPB on relative proportion of electrolyte and electronic conductor phases; volume fraction of porosity; and mean size, coefficient of variation, and skewness of electrolyte and electronic conductor particle populations in the initial powder mix. The equation is applicable to electrolyte and electronic conductor particles of any convex shapes and size distributions. The model is validated using experimental measurements performed in this research as well as the measurements performed by other researchers. Computer simulations of 3D composite electrode microstructures have been performed to further validate the microstructure model and to study topological connectivity of the triple phase boundaries in 3D microstructural space. A detailed parametric analysis reveals that (1) non-equiaxed plate-like, flake-like, and needle-like electrolyte and electronic conductor particle shapes can yield substantially higher LTPB; (2) mono-sized electrolyte and electronic conductor powders lead to higher LTPB as compared to the powders having size distributions with large coefficients of variation; (3) LTPB is inversely proportional to the mean sizes of electrolyte and electronic conductor particles; (4) a high value of LTPB is obtained at the lowest porosity volume fraction that permits sufficient connectivity of the pores for gas permeability; and (5) LTPB is not sensitive to the relative proportion of electrolyte and electronic conductor phases in the composition regime of interest in composite electrode applications.

This book presents methodologies suitable for the optimal design of control and diagnosis strategies for Solid Oxide Fuel Cell (SOFC) systems. One key feature of the methodologies presented is the use of modeling tools with an ideal balance between accuracy and computational burden. Particular emphasis is given to the useful combination of models within a hierarchical framework to reduce the experimental efforts required for characterization and testing. Such tools are proven to be highly effective for SOFC systems destined for both residential and transportation applications. Throughout the book, optimization is always conceived in such a way so as to allow the SOFC systems to work efficiently while guaranteeing safe thermal operation, as well as an extended lifetime. This book is aimed at scientists and engineers involved in the design of marketable SOFC systems. It gathers the knowledge and experience derived from other research and industry practice for which control and diagnosis have proven to be the main keys to success and market penetration.

This book fills the need for a practical reference for all scientists and graduate students who are seeking to define a mathematical model for Solid Oxide Fuel Cell (SOFC) simulation. Structured in two parts, part one presents the basic theory, and the general equations describing SOFC operation phenomena. Part two deals with the application of the theory to practical examples, where different SOFC geometries, configurations, and different phenomena are analyzed in detail.

This work presents a numerical FEM framework, capable of predicting SOFC performance under technically relevant, planar stack contacting conditions. A high level of confidence in the model predictions is supplied by using exclusively experimentally determined material/kinetic parameters and by a comprehensive validation. The presented model aids SOFC stack development by pre-evaluating possible material choices and design combinations for cells/interconnectors without any experimental effort.