An international team is planning to develop a virtual demonstration of solar thermochemical hydrogen production based on the hybrid sulfur cycle. The effort will couple DLR's diurnal two-chamber solar reactor with SRNL's continuous PEM SO2-depolarized electrolyzer. General Atomics will help integrate the two halves of the process and will contribute the SO2 separation and H2SO4 handling components. Other partners include INL, Texas Tech University, and the University of South Carolina, who will work on improved catalysts for both reaction steps, improved PEM membranes for electrolysis, and a properties model that accurately duplicates the highly non-ideal behavior of the SO2-H2SO4-H2O-SO3-O2 system. The solar acid decomposition system will be tested on-sun at DLR's solar furnace/simulator in Cologne, Germany, the electrolyzer will be tested at SRNL, and the acid/SO2 system will be tested at GA. Virtual integrated operation will be achieved by matching interface conditions between systems and utilizing process simulation models. While the scale of the demonstration is small (3 L H2), the project objective includes a detailed commercial scale design together with economic analyses to generate credible estimates for the cost of hydrogen production.