Tubular Solid Oxide Fuel Cells

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Fuel cells are silent, modular and an efficient source of electricity (50-60%). They could be used for remote power, home heating, power plants and backup power for hospitals and manufacturing plants. When used reversibly, they can provide load leveling for renewable energy. When excess power is available, they can be used in electrolysis mode to provide energy storage via fuel. Combining dry reforming of methane with a fuel cell can eliminate CO2 while producing both electricity and CO, a valuable industrial raw material. High temperature solid oxide fuel cells (SOFCs) offer two main advantages over the low temperature versions: expensive catalysts can be avoided and a variety of fuels can be accommodated. The tubular design has some significant advantages over the planar configuration including low temperature sealing, superior mechanical properties, rapid start-up and higher volumetric power density if small diameter tubes are used. The main drawbacks are lower power output mainly due to the long current path for the inner electrode and, as for the planar design, redox cycling (occurs when air enters the anode chamber) causes structural damage. In an effort to overcome these drawbacks, by using a combination of calcined powders, pore formers and slip casting, we have fabricated a robust tubular fuel cell with exceptional redox cycling resistance. It has infiltrated nanostructured electrodes which lead to greatly improved power output. The nature of anode microstructure (phase distribution, porosity, pore size distribution) will be related to cell performance as we have carried out recently for the cathode. Such a study might help understand the microstructural changes occurring in reversible cells (alternate between fuel cell and electrolysis modes). Optimum microstructures could then be identified. The main problems restricting commercialization are inefficient electrode infiltration, unacceptable current collection and degradation (gradual loss of power with time). Each will be studied. Solution composition, slurries and rapid heating could lead to better and faster infiltration. Current collectors will be evaluated as to conductivity, mechanical properties, form (solution, paste, wire, mesh, etc.) and stability. The main causes of degradation which are coarsening of nanostructures, delamination of current collectors and diffusion will be correlated with operating temperature, current density and gas flow rates (fuel utilization). Applications including energy storage as fuel and CO2 elimination will be concurrently considered. Building on our recent success overcoming redox cycling and improving power output, this research should improve understanding of SOFC behaviour and move tubular cells closer to commercialization. Whether for traditional power generation or unique uses, Canada will benefit as both a major supplier of fossil fuels and a large CO2 emitter.