Volumetric Absorption of Direct and Indirect Radiation in Porous Redox Structures for Solar Fuel Production

In order to reduce the dependency on fossil fuels and thereby the emission of greenhouse gases, the large-scale production of renewable chemical energy carriers plays an important role. Here, the production of green hydrogen via solar thermochemical redox cycles presents a promising pathway. In order to develop and improve reactor concepts that utilize this approach, the usage of numerical models is essential. The volumetric radiation absorption within porous redox structures is often simplified or neglected within such models. Furthermore, the setup of redox structure and radiation source is often limited to the direct collimated irradiation of flat structures. Therefore, a Monte-Carlo ray-tracing model is developed to simulate the volumetric radiation absorption within porous redox structures of different geometries and reactor boundary conditions. In addition to the direct irradiation of a flat geometry with collimated solar radiation, the indirect diffuse irradiation of a cylindrical redox structure is evaluated. The model setup and resulting absorption profiles are presented here and will serve as an input to material models for heat transfer simulations.