Dataset for the paper "Enhancing Calcium-Looping Materials for Thermochemical Energy Storage: Alkali Chloride Modification for Improved Cycling Stability and Moisture Resistance"

This study explores the impact of alkali chloride additives on the performance and durability of CaO-based materials obtained from natural limestone for thermochemical energy storage through the calcium-looping process. The investigation was carried out using CaCO3 of different particle sizes derived from natural limestone as the base material. An alkali mixture, extracted from biomass ash and predominantly composed of KCl, was used as additive. The composite materials were prepared in varying proportions (1 and 5 wt%) and tested in thermal cycling experiments that simulate energy storage operation conditions, in order to assess their multicycle reactivity and storage behavior. Key experimental findings demonstrate that a limited alkali addition (1 wt%) slightly decreases conversion during the fast carbonation stage but significantly enhances multicycle stability, achieving conversion values up to 0.40 after 20 cycles for fine particles (60-100 µm) compared to 0.25-0.30 for unmodified materials. This improvement is attributed to accelerated diffusion-controlled carbonation. Furthermore, the use of alkaline salts has a positive effect on inter-cycle storage stability by preventing moisture-induced degradation, as the salts inhibit hydroxylation of CaO under humid conditions, which would otherwise reduce the stored energy. Thus, it has been observed that alkali modification extends the time to full conversion to Ca(OH)2 by up to 700% under 32% relative humidity conditions. The optimized composition (1 wt% alkali) effectively balances conversion efficiency, cyclic and storage stability, making this approach particularly viable for industrial energy storage applications such as concentrated solar power systems where materials may undergo extended storage periods between operational cycles.