Experimental evaluation of an indirectly-irradiated packed-bed solar thermochemical reactor for calcination–carbonation chemical looping

The two-step calcium oxide based calcination–carbonation cycle is studied for carbon dioxide capture and solar thermochemical energy storage applications. An indirectly-irradiated packed-bed solar thermochemical reactor is experimentally evaluated using simulated high-flux solar irradiation provided by a multi-source solar simulator. Experimental runs include a single calcination reaction step as well as single and multiple (up to four) consecutive calcination–carbonation cycles. The samples are characterised using scanning electron microscopy (SEM) and X-ray diffraction (XRD). The reactor temperature peaked at 1,035°C. The average solar-to-chemical conversion efficiency, defined as the ratio of heat consumed by the reaction to radiant heat supplied to the reactor, was found to be between approximately 1.3% and 8.6% for the five performed experimental runs. The necessary advancements to the presented reactor design identified during the experimental campaign include improvements in thermomechanical characteristics of ceramic and metallic parts of the reactor to prevent fast mechanical and chemical degradation, application of more robust high-temperature reaction chamber seals, and optimisation of reactor geometry and gas flow patterns towards spatially more uniform thermal conditions and chemical reaction rates.