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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

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The most advanced solar thermochemical cycles in terms of demonstrated reactor efficiencies are based on temperature swing operated receiver-reactors with open porous ceria foams as a redox material. The demonstrated efficiencies are encouraging but especially for cycles based on ceria as the redox material, studies have pointed out the importance of high solid heat recovery rates to reach competitive process efficiencies. Different concepts for solid heat recovery have been proposed mainly for other types of reactors, and demonstration campaigns have shown first advances. Still, solid heat recovery remains an unsolved challenge. In this study, chances and limitations for solid heat recovery using a thermal storage unit with gas as heat transfer fluid are assessed. A numerical model for the reactor is presented and used to analyze the performance of a storage unit coupled to the reactor. The results show that such a concept could decrease the solar energy demand by up to 40% and should be further investigated.