Hydrogen production in solar reactors

The present work summarizes the recent activities of our laboratory in the field of solar-aided hydrogen production with structured monolithic solar reactors. This reactor concept, "transferred" from the well-known automobile exhaust catalytic after-treatment systems, employs ceramic supports optimized to absorb effectively solar radiation and develop sufficiently high temperatures, that are coated with active materials capable to perform/catalyze a variety of "solar-aided" reactions for the production of hydrogen such as water splitting or natural gas reforming. Our work evolves in an integrated approach starting from the synthesis of active powders tailored to particular hydrogen production reactions, their deposition upon porous absorbers, testing of relevant properties of merit such as thermomechanical stability and hydrogen yield and finally to the design, operation simulation and performance optimization of structured monolithic solar hydrogen production reactors. This approach, among other things, has culminated to the world's first closed, solar-thermochemical cycle in operation that is capable of continuous hydrogen production employing entirely renewable and abundant energy sources and raw materials - solar energy and water, respectively - without any CO2 emissions and holds, thus, a significant potential for large-scale, emissions-free hydrogen production, particularly for regions of the world that lack indigenous resources but are endowed with ample solar energy. (C) 2007 Elsevier B.V. All rights reserved.