Solid Oxide Electrolyzer System Operational at the H₂ Refueling Station of Karlsruhe^†

The tenth H₂ refueling station of the German federal state of Baden-Württemberg was commissioned on September 6, 2017. The Karlsruhe H₂ refueling station, located at the multi-fuels station of Total, is the first one equipped with an onsite hydrogen production using a solid oxide electrolyzer (SOE) system. In the present work, details about the SOE system equipment are reported. Electrical consumption of the integrated stacks module (ISM) and the hot balance of plant (BoP) for steam generation and inlet gas pre-heating, was monitored during 240 h of steady-state operation under 100% steam. The average cell voltage of the 90 cells composing the ISM was 1.35 V at 0.4 A cm⁻² current density. ISM efficiency was around 91.5% HHV_AC considering 100% faradaic efficiency and including the conversion of the AC/DC power supply. Due to the consumption of the hot BoP and system auxiliaries for safety and control, achieved overall system efficiency was 61.4% HHV_AC. Independently from electric steam production, around 10% reduction of the ISM electricity consumption could be feasible with the optimization of the inlet air flowrate. Indeed, adapting the inlet air flowrate as function of the outlet hydrogen flowrate would allow reducing the electricity need for inlet air pre-heating.