Revolutionizing thermochemical adsorption heat storage: An MgSO4/MgCl2/MEG composite prepared by the ball milling method for efficient and stable low-temperature heat storage

• Published in: Applied thermal engineering 2025-04, Vol.265, p.125482, Article 125482
• Main Authors: Zhang, Xueling, Xun, Haoyun, Zhou, Yingfang, Zhang, Qi, Zhang, Yeqiang, Wu, Xuehong, Jin, Tingxiang, Li, Rijie
• Format: Article
• Language: English
• Subjects: Composite heat storage material; Cycle stability; Desorption kinetic model; Heat storage density; Numerical simulation; Thermochemical heat storage
• ISSN: 1359-4311
• DOI: 10.1016/j.applthermaleng.2025.125482

•Ball milling method resulted in a 19.3 ℃ lower dehydration temperature than that of the impregnation method.•The ball milling method reduces the single-cycle stability drop rate to 0.3857%.•The reaction activation energy is reduced to 64 kJ/mol.•The heat storage density was calculated as 237.2 kWh/m3. Efficient and sustainable low-temperature energy storage are essential for thermochemical adsorption heat storage materials. This study introduces a novel thermochemical heat storage material prepared using the ball milling method for the first time. The optimised Mix@EG10 material, comprising MgSO4/MgCl2 and hydrophilic-modified expanded graphite, demonstrated exceptional comprehensive performance. It exhibited a thermal storage density of 1142 kJ/kg, thermal conductivity of 2.53 W/(m·K), retained 84.5 % of its initial heat storage capacity after 40 cycles, and the single-cycle stability drop rate was low (up to 0.3857 %). The desorption temperature of Mix@EG10 prepared by ball milling was only 100.2 °C, which was 32.4 °C and 19.3 °C lower than those of the mixture of two salts without expanded graphite and the same material prepared by impregnation (132.6 °C and 119.5 °C, respectively). This decrease was attributed to the ball milling process, which modified the microstructure, enhanced active sites, and reduced the reaction activation energy to 64.8 kJ/mol—a decrease of 46.2 % and 79.2 % compared to pure MgSO4 and MgCl2, respectively. The simulation parameters used in this study were measured for each composite. Numerical simulations validate the material’s practicality, demonstrating a maximum instantaneous exothermic power of 116.7 W and volumetric energy storage density of 237.2 kWh/m3. This study highlights the significant potential of ball-milled composite materials for advancing low-temperature heat storage applications, such as solar energy and industrial waste heat recovery.