Pacific Northwest National Laboratory

902 Battelle Boulevard

Richland, WA 99352, USA

 

Solid oxide fuel cells (SOFCs), based on an oxide ion conducting electrolyte such as stabilized-zirconia, offer a clean, low-pollution technology to electrochemically generate electricity at high efficiencies. These cells operate between about 550 and 1000^oC, and some hydrocarbon fuels such as natural gas can be reformed within the cell stack eliminating the need for an expensive, external reformer. The most important need to commercialize SOFC technology is to significantly reduce the overall cost of SOFC-based power systems, while maintaining adequate performance and performance stability with time. Reduction of cell operation temperature enables use of low-cost metallic interconnects and a decrease in maintenance costs. However, at lower temperatures, greater ohmic loss due to reduced ionic conductivity of the electrolyte and reduced catalytic activity of the electrodes result in lower cell performance. To improve cell performance at lower temperatures, employing thin electrolyte and nanoscale materials in the electrodes has recently been considered. However, a crucial question that remains to be answered is whether the beneficial effect of employing nanoscale materials will persist even after long term cell operation at high temperatures, even though the initial performance may have indicated substantial enhancement. 

 

This overview focuses on the materials, processing, and performance of solid oxide fuel cells, with relative advantages/disadvantages of tubular and planar geometries. Stacks and systems built with both tubular and planar geometries are described and their operating experience discussed. Applications of such cells in stationary, mobile and military market sectors are reviewed and challenges in reducing cell and system costs are summarized. Considerable recent progress has been made in employing solid oxide fuel cells for small/portable and residential power generation applications because of their fuel flexibility and advances in materials and processing techniques; SOFCs offer important advantages over PEMFCs and DMFCs, notably their ability to use CO or liquid hydrocarbons as fuel, which makes them ideally suited for residential, portable, and military applications.