The cascading pressure reactor is a kW-sized test device, intended for two‑step hydrogen production, using simulated solar heat. Thermal reduction (TR) and water splitting (WS) in the reactor can be conducted under a wide range of relevant and realistic conditions, such as TR pressure (~10Pa) and temperature (1550 °C), WS temperature and steam flow, and many others. As a result, the performance of H2-production materials (oxides) can be comprehensively evaluated. The reactor uses a simulated solar flux, enabling continuous operation, material durability testing, and accelerated aging protocols.