Long term behaviour of solid oxide electrolyser (SOEC) stacks

Abstract

The paper reports and compares the long term operation behavior of a solid oxide electrolysis (SOEC) stack in electrolysis and reversible SOFC/SOEC operation. The 30-cell stack with electrolyte supported cells (ESC) was supplied by Sunfire GmbH (Dresden/Germany) as part of the German funded project “Reversible Solid Oxide Cell" (RSOC). The stack was operated for 3370 h in SOEC and for 2000 h in reversible SOFC/SOEC operation mode at 70 % steam conversion and 70 % fuel utilization, respectively. After the initial performance test, current-voltage (jV) characteristics and electrochemical impedance spectra (EIS) were recorded regularly. The degradation of the electrochemical properties, e.g. open circuit voltage (OCV), electrical stack power, electrical stack efficiency and the resistances of the repeat units (RU), during SOEC and reversible SOFC/SOEC long term operations are compared to each other and discussed.