Exploring synergistic sintering factors and nanopore regeneration of calcium-based thermochemical energy storage materials

Abstract

Calcium-based thermochemical energy storage is essential for high-temperature solar energy utilization. However, performance decay is inevitable in repeated calcination/carbonation cycles, even for modified materials. In this study, the effects of synergistic sintering factors on performance decay are investigated, including chemical reaction, temperature and CO2 atmosphere. More importantly, rather than complicating the initial preparation process of the anti-sintering composites to achieve higher stability, a regeneration method is proposed to repair the nanopores of sintered composites and recover their performances. After using citric acid to dissolve materials with heavily sintered morphologies and reconstruct their porous structures, the energy storage densities of both the co-doped and benchmark materials increase by 2–4 times. The regenerated Al/Mg co-doped composite also shows high cyclic stability in subsequent long-term cycles. Furthermore, DFT calculations illustrate the strong atomic interaction between CaO and dopants. The economic analysis reveals that the regeneration costs of the co-doped composites are approximately one-half of their synthesis costs, making them a cost-efficient choice for long-term industrial application. This work expands the limited perspectives of current modification research on improving cyclic stability. It can guide the actual industrial applications of thermochemical energy storage, thus enhancing material reutilization and realizing costs reduction.