Solid Oxide Steam Electrolysis with Integration of Solar Heat

The experimental coupling of a commercial high-temperature steam electrolyzer and a solar thermal steam generator has been realized for the first time at the German Aerospace Center (DLR). A high flux solar simulator and a solar steam receiver were used to generate superheated steam which was fed to a commercial 12-cell electrolyzer stack from an industrial supplier (SolidPower, Mezzolombardo, Italy). After optimization of the operating parameters of the different system components the system could be operated properly at 770 °C and a steam flow of 12.0 slpm (standard litres per minute), 0.58 kg/h respectively. The open circuit voltage (OCV) of the stack was 10.4 V. Approximately 8.4 slpm hydrogen was produced at a current density of -1.25 A/cm2 and a voltage of approximately 17 V corresponding to a steam conversion rate of 70%. The electrical efficiency of the electrolyzer was 93% related to the lower heating value. The experimental setup of the prototype system is presented and results with regard to solar steam generation and electrochemical performance of the electrolyzer are reported.