Regenerative hydrogen production relies on water or biomass as raw materials in the long term to ensure a carbon dioxide free or carbon dioxide neutral process. One prominent method is the Hybrid Sulfur (HyS) Cycle, which produces hydrogen from water via electrolysis of sulfur dioxide to form sulfuric acid, and oxygen through the thermal decomposition of sulfuric acid. DLR has been active in developing a solar interface for the HyS cycle, mainly for the endothermic high temperature decomposition of sulfuric acid. The development included materials investigation and selection, energy integration, numerical system models, experimental validation and scale-up studies . Also the integration of the key components into a solar process and its energetic assessment were crucial parts of this work. After realizing small scale components and testing decomposer prototypes on-sun in a solar furnace, the most recent step of development addresses the scale-up and demonstration of the technology at DLR’s solar tower in Julich. For that purpose a solar sulfuric acid decomposer is being designed in a hundred kW range and will be tested on-sun as part of a virtual demonstration plant.