Granular porous calcium carbonate particles for scalable and high-performance solar-driven thermochemical heat storage

Calcium carbonate is promising thermochemical heat storage material for next-generation solar power systems due to its high energy storage density, low cost, and high operation temperature. Researchers have tried to improve energy storage performances of calcium carbonate recently, but most researches focus on powders, which are not suitable for scalable applications. Here, novel granular porous calcium carbonate particles with very high solar absorptance, energy storage density, abrasive resistances, and energy storage rate are proposed for direct solar thermochemical heat storage. The average solar absorptance is improved by 234% compared with ordinary particles. Both cycle stability and abrasive resistances are excellent with almost no decay of energy storage density over 25 cycles nor apparent particle weight loss over 24 h of continuous operation insides a planetary ball mill. In addition, the decomposition temperature is reduced by 2.8%–5.6% while the reaction rate of heat storage is enhanced by 80%–205% depending on the CO₂ partial pressure. The decomposition process of doped granular porous CaCO₃ particles is found to involve three overlapping processes. This work provides new routes to achieve scalable direct solar thermochemical heat storage for next-generation high-temperature solar power systems.