3D-printed mineral limestone structures for calcium looping thermochemical energy storage: reactivity and performance across cycles

This work presents a proof of concept for the use of 3D-printed CaCO₃ structures, prepared from low-cost and widely available mineral limestone, as an innovative approach for thermochemical energy storage (TCES) via the calcium looping (CaL) process in a fixed-bed reactor. These structures offer significant advantages in terms of reaction efficiency, gas flow control, structural stability, and maintenance. These factors are critical for achieving uniform reaction surface distribution and effective thermal management. The 3D structures were fabricated by robocasting and subjected to various debinding and calcination conditions. They maintained their structural integrity and exhibited high reactivity over multiple carbonation-calcination cycles. Under scheme 1 conditions (calcinations in nitrogen), the printed structures retained a CaO conversion of 0.44 after 50 cycles, corresponding to an energy density of 1.39 MJ kg −1 CaO, outperforming the powdered sample, which reached a conversion of 0.32. Advanced characterization techniques, including thermography, scanning electron microscopy, and X-ray computed tomography, highlight the internal structural advantages of the 3D structures. Overall, this study demonstrates the potential of 3D-printed CaCO₃ structures as scalable and efficient TCES materials, offering a promising route toward improving the performance and practical deployment of solid-state thermochemical energy storage systems. 3D CaCO₃ structures were fabricated via robocasting using mineral limestone particles The 3D CaCO₃ structures were tested at calcium looping conditions for energy storage The 3D structures exhibit higher reactivity than CaCO 3 powders over multiple cycles X-ray tomography reveals structural integrity retention of the novel 3D structures The results highlight the potential of 3D CaCO 3 structures for thermochemical storage