Thermal reduction of iron–manganese oxide particles in a high-temperature packed-bed reactor for solar thermochemical energy storage

The reduction of iron–manganese oxide particles in a high-temperature packed-bed solar thermochemical reactor isinvestigated using an advanced transient three-dimensional computational fluid dynamics model. The model couplesthe conductive, convective, and radiative heat transfer, reaction kinetics, and fluid flow in the bed with packed particlesand interstitial sweep gases to obtain a detailed description of the transport phenomena in the bed. A reactor prototypethat features a reaction tube confining the packed particles and a surrounding diffuse reflective cavity is tested undersimulated high-flux solar irradiation to validate the model. The numerically predicted temperature profiles and oxygengeneration rates are in good agreement with the experimental data. The validated model is applied to evaluate thethermochemical performance of the reactor. The calculated temperature profiles indicate that uniform temperaturedistribution in the reactive packed particles is achieved from the onset of the reaction. An energy rate balance analysisshows the instantaneous peak solar-to-thermochemical energy efficiency reaches 9.3%. The optimal operationconditions for the reactor are explored in a parametric study of the sweeping gas velocity and the concentration ratio ofincident solar radiation.