Performance Characteristics of 100 W Carbon Fuel Cell Stack Based on SOFC Technology

Carbon Fuel Cells (CFCs) run on carbon-rich fuels such as coal and biomass. Owing to their high theoretical efficiencies, they have been studied as new stationary power generation. This work presents the fabrication and operation of a 100W SOFC-based CFC stack, consisting of 5 bundles with 6 tubular cells per bundle. 8 mol%Y₂O₃-stabilized ZrO₂ (8YSZ) electrolyte and layers of La_0.8Sr_0.2MnO₃/La_0.6Sr_0.4Fe_0.8Co_0.2O₃ cathode were coated on Ni-8YSZ anode support, with an active electrode area of 60cm² per cell. Six cells were embedded vertically on a fuel gas manifold and interconnected electrically in parallel within a bundle. Five bundles were sealed and stacked in series electrically. The stack was connected to carbon fuel chambers containing mixture of activated carbon and potassium carbonate. The carbon fuel mixture was agitated with carbon dioxide to promote reverse Boudouard reaction and thus providing carbon monoxide as stack fuel. The stack and the fuel chambers were operated simultaneously in a heating furnace. The CFC stack showed 111.5W at 850 ^oC and its average voltage degradation rate is 0.55 V/kh for 200hours. The CFC stack degradation during long-term operation was analyzed and discussed as related to microstructural change, poisoning by impurities and electrochemical cell polarization losses.