Simulation and Fabrication of a Microtubular Solid Oxide Fuel Cell Stack with Novel Anode Current Collection and Enhanced Thermofluidynamics

This PhD deals with the development of Microtubular Solid Oxide Fuel Cells (µT-SOFC) at the cell and sub-stack level. The study provides a body of work as a basis for future development in the field. The information has been acquired and interpreted empirically and numerically. µT-SOFCs are suited to a broad range of applications with power demands ranging from a few watts to several hundred watts. µT-SOFCs possess inherently favourable characteristics over alternate configurations such as high thermo-mechanical stability, high volumetric power density and rapid start-up times, lending them for particular value use in portable applications. Efficient current collection and interconnection constitute a bottleneck in the progression of the technology and addressing this was the focus of this study. An empirical study to determine the effect of varying current collector position and number was conducted. A mathematical model with its underpinnings in a resistance path model was constructed to interpret the empirical findings. A multiphysics CFD model mirroring the experimental setup was constructed to build on the insight provided by the mathematical model. The model was validated and fitted with experimental data and was reliable for prediction of µT-SOFC performance within set parameters. Contacting of each electrode is most simply and most typically achieved from the cell exterior at the expense of available active cell area and durability. Building on the knowledge gained in the empirical and numerical studies, a novel method of internal current collection was proposed; collecting current from multiple points along the inner wall of the anode supported cell. The current collector also acted as a flow turbuliser, enhancing the flow and thermal distribution within the fuel cell. To reduce the contact resistance of the internal current collector, a contacting technique was identified, namely brazing. Brazing enabled the formation of multiple, physical joints along the interior of the µT-SOFC. The brazing improved the current collector performance and durability. The study featured the development of a novel braze and braze application technique. CAD and CFD were used for the optimisation of a 4-cell µT-SOFC manifold, stack, and operating conditions. The stack design used data from the experimental testing of cells with the novel, brazed internal current collector. Two 4-cell stacks with two current collector variations, both using the novel, brazed internal current collector design, were fabricated and electrochemically tested. Data from performance and durability testing of the stacks was presented and the best design identified