DEVELOPMENT AND VERIFICATION OF A TWO-STEP THERMOCHEMICAL PROCESS FOR SOLAR HYDROGEN PRODUCTION FROM WATER

A two-step thermo-chemical cycle process for solar hydrogen production from water has been developed. By using mixed iron-oxide-based redox systems at moderate temperatures the cycle offers promising properties concerning thermodynamics and efficiency and affords pure hydrogen without any need for product separation and without any environmentally critical emissions. The two steps are performed alternately at different temperatures. Therefore it was necessary to create a process and related hardware to enable a quasi-continuous production of hydrogen. The process was tested with a developed model reactor in a mini plant in the DLR solar furnace. A quasi-continuous, multi-cycling solar hydrogen production with a constant amount of hydrogen produced in the cycles has been successfully demonstrated over several hours of operation. The model reactor is applied to develop a basis for the continuous production of hydrogen in larger scale. The major tasks of the project include the enhancement of yield and long-term stability of the redox system, the development and refinement of an operational strategy and finally the design and development of a 100 kWth pilot reactor to demonstrate the feasibility of the process on top of a solar tower under real conditions.