Low-cost Ca-based composites synthesized by biotemplate method for thermochemical energy storage of concentrated solar power

Highlights: • CaO/SiO₂ composites were synthesized by a low cost biomimetic process from rice husk. • CaO/SiO₂ composites are highly efficient for concentrated solar energy storage. • The composites show significantly better performance than natural limestone. • Pore-plugging is reduced by the composition and microstructure of the CaO/SiO₂ composites. - Abstract: An ever more environmentally conscious society demands the use of green, sustainable and high-efficiency renewable energy resources. However, large-scale energy storage remains a challenge for a deep penetration of power produced from renewables into the grid. The Calcium-Looping (CaL) process, based on the reversible carbonation/calcination of CaO, is a promising technology for thermochemical energy storage (TCES) in Concentrated Solar Power (CSP) plants. Natural limestone to be used as CaO precursor is cheap, non-toxic and abundant. Nevertheless, recent works have shown that carbonation of CaO derived limestone at optimum conditions for TCES is limited by pore-plugging, which leads to severe deactivation for large enough particles to be employed in practice. In our work, we have synthesized inexpensive CaO/SiO₂ composites by means of a biotemplate method using rice husk as support. The morphological and compositional features of the biomorphic materials synthesized help improve the CaO multicycle activity under optimum CSP storage conditions and for particles sufficiently large to be managed in practical processes.