Comparative Analysis of Thermal and Redox Cycling for Microtubular SOFCs

One of the key problems of SOFCs is their poor cycling performance which can arise due to thermal expansion or redox stresses. In some instances, one redox cycle is sufficient to destroy a planar Ni/YSZ anode supported cell. Microtubular SOFCs appear to be more resistant to cycling because the thermal and redox gradients are smaller (1). The purpose of this paper is to compare the cycling performance of microtubular SOFCs under both thermal and redox conditions. The objective was to cycle in temperature from ambient to the operating condition several times at high ramping rates up to 8000 degrees C/min to measure the degradation rate per cycle. Then this degradation was compared with that measured under redox cycling conditions. The relative expansion of the cells was also determined by dilatometry. The conclusion was that redox cycling was more damaging than thermal cycling because much larger expansion and degradation took place.