Stack performances in high temperature steam electrolysis and co-electrolysis

Abstract

High Temperature Steam Electrolysis (HTSE), based on solid oxide electrolysis cells (SOE) is a promising way to produce massively hydrogen with high efficiencies. This technology also allows producing syngas (H2 + CO) by co-electrolyzing a mix of steam and CO2. This syngas constitutes the basis to obtain further synthetic fuels. For both HTSE and co-electrolysis, durability and cost are still key points, but additionally for co-electrolysis the outlet H2/CO gas composition has to be tailored to fit with the targeted fuels. Previous works have been carried out to develop a stack design suitable for both applications. Here experiments at stack level in both electrolysis and co-electrolysis modes have been carried out. A 10-cell stack and a 25-cell stack have been tested in electrolysis mode, respectively producing 0.6 Nm3/h and 1.7 Nm3/h of hydrogen at 800 °C below the thermoneutral voltage (1.3 V) for all the cells and a steam conversion around 50%, with a small scattering between the different cells. Gas tightness of the stacks has also been evaluated. Moreover, the operation in co-electrolysis has been validated. Finally a cost analysis of this stack design has been performed and shows all the economical potentialities of this technology.