Load cycling tests of reversible solid oxide cells - Effects of current density, steam content and utilization

Four single cell rSOC tests were conducted to investigate the effect of current density, steam content and degree of utilization both upon galvanostatic SOFC and SOEC testing, and load cycling operation. Long-term degradation tests were performed at 700°C during constant galvanostatic SOFC (250 h) and SOEC (250 h) conditions followed by load cycling operation (up to 1000 h) in cycles of 16 h SOFC and 8 h SOEC. Applied current densities were 0.6 A/cm² and -1.2 A/cm²; and 0.4 A/cm² and -0.6 A/cm²; inlet gas composition i.e. p(H₂O)/p(H₂) of 90/10 and dry H₂, as well as a test applying p(H₂O)/p(H₂) of 50/50 for both modes. Furthermore, two different utilization degrees (80% and 40%) were applied. From these tests it is evident that the high current density is detrimental for the fuel electrode durability while high p(H₂O) does not seem problematic and cells sustained mechanical integrity upon load cycling.