Manufacturing and long-term potentio-galvanostatic operation of high temperature electrolysis stacks in the 10-to-20 kWDC power range

As market penetration of high temperature electrolysis continues, demonstration systems at the MW and multi-MW scale have recently emerged. Producing solid oxide electrolysis stacks of power beyond the typical 2-to-4 kW DC is required to further upscale system power all-the-while decreasing stack manufacturing costs. Through efforts to upscale its base stack design, CEA has successively manufactured S1, a 3×25-repeat unit substack assembly with commercial 196 cm 2 cathode-supported cells, and S2, a single stack incorporating 78 cells. The stacks were both operated in potentio-galvanostatic mode until failure, S1 at −0.65 A cm −2 (12.6 kW DC ) and S2 at −0.94 A cm −2 (18.6 kW DC ), generating respectively 1.1 and 3 tons H 2 . The latter should currently constitute a record for single stack lifetime production. This experimental report shares the results of the complete test sequences, with special attention given to control loop and safety management updates required when handling high-power stacks.