Solid oxide electrolysis stack development and upscaling

Solid oxide electrolysis is considered an efficient technology to produce hydrogen. To deploy electrolysers at the GW scale, an increase in the individual component size (cells and stacks in particular) is required. The integration of larger cells (200 cm² active area) into 25-cell stacks has been successfully performed. Performances were in the range of –0.8 to –0.9 A cm⁻² at 1.3 V at 700°C. The number of cells has also been increased to 50 and 75 cells. For this latter 75-cell stack, the assembly of three 25-cell substacks was considered. Good gastightness and high performances were achieved, although connections between substacks add a serial resistance that affects the stack total performances. Nevertheless, a current density of more than –0.8 A cm⁻² was obtained at 1.3 V and 700°C, consistent with individual substack performances. Finally, a stack made of 50 200 cm² cells has been assembled. Although a stack deformation was visible due to individual component thickness scattering, a good gastighness was achieved and a current density of –0.9 A cm⁻² at 1.3 V and 700°C was measured. The low voltage scattering highlighted a good homogeneity of the fluidic distribution and of the electrical contacts within the stack.