Solar-driven collaborative thermochemical energy storage and fuel production via integrating calcium looping and redox cycle

To better utilize solar energy and reduce CO₂ emissions, this study proposes a novel idea of solar-driven thermochemical energy storage and fuel production via integrating calcium looping and redox cycle. Such integrated system design not only can realize solar energy storage and CO₂ capture based on thermochemical reversible reaction of CaO/CaCO₃, but also can achieve fuel production through thermochemical conversion of captured CO₂ into CO based on redox cycle. More interestingly, the temperature required for CaCO₃ calcination of calcium looping matches the temperature for the oxidation reaction of redox cycle, which means a good connection between calcium looping and redox cycle. Additionally, a solar-driven thermochemical reactor system and its comprehensive thermodynamic model of calcium looping and redox cycle are developed to present the performance of integrated system. Results indicate that such integrated system can achieve a 43.54 % of solar energy converted into chemical energy (40.53 % obtained by calcium looping and 3.01 % obtained by redox cycle) even after 100 cycles. Moreover, the solar-to-chemical efficiency can reach 57.69 % and solar-to-fuel efficiency can reach 32.76 % after 100 cycles, when the heat recovery is considered (heat recovery effectiveness is assumed to be η_recovery = 70 % in this work). This study presents a promising path to simultaneously achieve solar energy storage, CO₂ capture and renewable fuel production.