Effect of scaling-up on the performance and degradation of long-term operated electrolyte supported solid oxide cell, stack and module in electrolysis mode

Abstract

The scale-up from single cell, to stack and integrated stack module induces an increased degradation that needs to be assessed for improving the performance and the lifetime of the high-temperature electrolyzer system. Within this work, the degradation rate of a 30-cell stack and a 90-cell module (based on similar 3YSZ electrolyte supported solid oxide cell) is evaluated with operation time of 4,224 h (−0.5 Acm−2) and 2,200 h (from −0.5 to – 0.3 Acm−2), respectively.The voltage degradation rate of the 30-cell stack is 10.5 mV/kh (0.8%/kh referring to the thermoneutral voltage of 1.3 V) including the temperature correction factor for an increase of 2 °C/kh. It is at present/currently the lowest degradation value reported for a stack of 30 electrolyte supported cells considering the thermal factor correction. This implies an increase of 5.5 mV/kh for the stack compared to the single cell. Along the steady-state phase two dynamic phases of 8,500 and 7,500 ON/OFF cycles were performed every 2 min. It has been shown that these significant load cycles do not induce additional degradation.Moving to the 90-cell module, irreversible damage occurred due to incidences related to the balance of plant; based on their analysis, propositions are made to counteract them.