Continuous direct solar-driven thermochemical energy storage via funnel-shape falling-particle reactors

Direct solar-driven thermochemical energy storage offers a promising pathway to bridge the mismatch between intermittent solar availability and continuous thermal energy demand, owing to its high energy density and long storage duration. However, existing thermochemical energy storage reactors are usually constrained by intermittent operation, limited controllability, and low solar-to-chemical conversion efficiency. Here, we demonstrate continuous and efficient direct solar-driven thermochemical energy storage via a funnel-shaped falling-particle reactor. By dynamically regulating particle residence time, the reactor enables optimized matching between solar energy transport, reaction kinetics, and particle flow, providing a flexible operating window to balance conversion and throughput. Under direct solar irradiation, the reactor achieves a system efficiency of 26.63%–34.20% and a calcium carbonate conversion of 74.4%–95.5%. Numerical analysis further suggests that a 25% reduction in thermal losses, which is a reasonably achievable target through insulation upgrades and optical optimization, could increase the system efficiency to 40.72%. This work opens new routes for the design of direct solar-driven thermochemical energy storage reactors that enable continuous, efficient, and tunable operation, and promotes their scalable applications.