Transient operation of a solid oxide electrolysis cell

In order to investigate the transient behaviour of a solid oxide electrolysis cell, tests were carried out on a single SOEC both under steady-state and transient conditions for 600 h. Steady-state operation was performed at the reference current of −20 A, corresponding to the thermoneutral voltage (1.28 V), whereas transient tests consisted in 1800 square waves applied over 140 cumulated hours, with a current of −1 A and −20 A as well as 0 A and −20 A. Independently from the operating conditions, the measured voltage degradation rate of 5% (70 mV)/1000 h was stable for the entire experiment. Consequently, it was concluded that an SOEC can be operated under on–off conditions with no increase of the degradation rate. This result paves the way for modular operation of a high temperature electrolyser fed with intermittent electrical energy.

► Steady-state and transient operation of a solid oxide electrolysis cell at 700 °C.
► 1800 on–off cycles over 140 cumulated hours. 
►  No minimum current required under reducing atmosphere.
► No detrimental failure of the cell: no break, no crack, no delamination.
► No voltage degradation rate increase.