Solar heat integrated solid oxide steam electrolysis for highly efficient hydrogen production Günter Schiller* ,a , Michael Lang a , Patric Szabo a , Nathalie Monnerie b , Henrik von Storch c** , Jan Reinhold b** , Pradeepkumar Sundarraj b a Deutsches Zentrum für Luft- und Raumfahrt, Institute of Engineering Thermodynamics, Pfaffenwaldring 38-40, 70569 Stuttgart, Germany b Deutsches Zentrum für Luft- und Raumfahrt, Solar Research, Linder Höhe, 51147 Köln, Germany c Deutsches Zentrum für Luft- und Raumfahrt, Solar Research, Karl-Heinz-Beckurts-Str.13, 52428 Jülich, Germany * Corresponding author: Günter Schiller E-mail: guenter.schiller@dlr.de Phone: +49 711 6862635 Fax: +49 711 6862747 Abstract Water electrolysis is considered as a suitable pathway for the production of large amounts of hydrogen to be used as energy carrier for electricity storage. Among the existing water electrolysis technologies solid oxide steam electrolysis exhibits the highest electrical efficiency. Moreover, from thermodynamic considerations the efficiency can be further increased when part of the energy demand is provided by the integration of external high temperature heat to reduce the electrical energy for the water splitting reaction. This paper reports on the successful integration of solar heat into a solid oxide electrolyzer. The experimental setup of the prototype system consisting of a solar simulator, a solar steam generator, a steam accumulator and a solid oxide electrolyzer as well as first results with regard to solar steam generation and electrochemical performance of the electrolyzer are presented. Hot steam with a maxi- ** Present address: Henrik von Storch, Christianstr. 66A, 50825 Köln, Germany Jan Reinhold, Holteistr. 26, 10245 Berlin, Germany