Long-term operation stability tests of intermediate and high temperature Ni-based anodesʹ SOFCs directly fueled with simulated biogas mixtures

Long-term operational tests under direct biogas feeds of intermediate and high temperature solid oxide fuel cells (SOFCs) with Ni-cermet anodes, based respectively on gadolinia doped ceria (GDC) and yttria stabilized zirconia (YSZ) solid electrolytes are presented. Both biogas SOFCs seem to operate stably in a variety of biogas compositions, including poor-, equimolar- and rich-quality biogases, for a long period of time (for about 200 h at each condition, more than 600 h total operation for each cell). The only exception concerns the case of the intermediate temperature SOFC, when operated with poor biogas feed (i.e., CH4/CO2<1), where a systematic attenuation of cell performance is observed, resulting practically to its deactivation after ∼100 h. Details on cells output characteristics under all operating conditions are presented and discussed.