Hierarchically doping calcium carbonate pellets for directly solar-driven high-temperature thermochemical energy storage

Abstract

Ca-based thermochemical energy storage (TCES) system is one of the most promising energy storage techniques for the next generation concentrated solar power systems (CSP). However, it still suffers from low optical absorption, poor cycle stability, and limited energy storage density. Here, a hierarchically doping strategy is proposed to overcome above challenges and achieve high-performance energy storage under direct solar irradiation. Hierarchically doped calcium carbonate pellets, which are suitable for scalable applications, are successfully fabricated with Al-doped internal cores and Mn-rich external shells. The average solar absorptance achieves 87.15% with a 7.4% increase compared with traditionally homogeneous doping approaches. The energy storage density is still as high as 1143 kJ/kg after 20 cycles, which is enhanced by 16.6% over homogeneous counterparts. The underlying mechanism is that hierarchically doping increases contents of active CaCO3 inside pellets and absorption-enhanced substances on the outer surface simultaneously. This work presents a novel approach for the design of high-performance pellets for achieving scalable and efficient thermochemical energy storage under direct solar irradiation.