Fabrication of CaO pellets via polyvinyl alcohol (PVA) method for efficient CO2 capture and solar energy storage

Calcium looping (CaL) exhibits great prospects for both thermochemical energy storage and CO2 capture. The granulation of CaO into spherical pellets is a crucial step for its practical application. In this study, a PVA solution was utilized as a binder to prepare CaO spherical pellets. Two different methods including the direct method and indirect method assisted with PVA solution were employed to produce CaO pellets. The experimental results indicated that the carbonation conversion of the sorbents from the indirect method was significantly superior to those from the direct method. For energy storage, CaO pellets decomposed from calcium hydroxide using indirect method exhibited satisfying energy storage density, starting with 3200 kJ/kg at the 1st cycles and ending with a high level of ∼2400 kJ/kg over 10 cycles. In the CO2 capture performance test, CaO spheres prepared with calcium citrate as a precursor showed promising CO2 capture performance at around 700 °C. In addition, the effects of carbonation temperature on the energy storage and CO2 capture performance were also studied. It was indicated that CaO pellets exhibited better cyclic energy storage performance at 750 and 800 °C, and that performed best when carbonated at 700 °C for cyclic CO2 capture. Besides, the pellets also demonstrated good mechanical properties such as satisfactory long-term anti-attrition ability, further supporting the practical viability of CaO pellets for both thermochemical energy storage and CO2 capture applications.