Investigating influences of geometric factors on a solar thermochemical reactor for two-step carbon dioxide splitting via CFD models

Solar thermochemical processes utilize inexhaustible solar energy as a thermal driving force to provide heat and motivate reactions, which offer pathways to store solar energy as chemical fuels. Some elevated temperature reactions, like thermal decomposition, gasification, and methane reforming, are anticipated in solar reactors which have the ability to provide extremely high temperatures. Presently, the dominating considerations in the design of solar reactors are heat and mass transfer with reaction mechanisms. A novel partition cavity-receiver reactor concept is proposed in this paper. In order to provide a longer pathway of interaction between the catalyst and reactants, a partition is introduced in this cavity-receiver reactor. A numerical computational fluid dynamics (CF-D) analysis is performed to study the influences of geometric factors (i.e. gap size between partition and bottom, inlets/outlets position, catalyst thickness) under both uniform and model-generated distribution of concentrated radiant fluxes. A two-step solar thermochemical redox reaction using ceria as a catalyst to split CO2 is modeled in the partition cavity-receiver reactor to investigate the relationship between geometric factors and reaction rates. Based on the comparisons and analysis of results, optimized geometric factors and corresponding operating conditions are discussed.