Thermal energy storage performance of magnesium-based hydrated salts impregnated with activated alumina

• Published in: Energy sources. Part A, Recovery, utilization, and environmental effects Recovery, utilization, and environmental effects, 2023-10, Vol.45 (4), p.10487-10504
• Main Authors: Zhang, Xueling, Gu, Junheng, Ye, Qiang, Zhang, Yeqiang, Zhang, Qi, Cheng, Chuanxiao, Xun, Haoyun, Jin, Tingxiang, Liu, Jianxiu, Wu, Xuehong
• Format: Article
• Language: English
• Subjects: adsorption; porous matrix; Salt hydrate; thermochemical heat storage; vacuum impregnation
• ISSN: 1556-7036; 1556-7230
• DOI: 10.1080/15567036.2023.2244457

A new thermochemical heat storage composite was prepared for the first time by vacuum impregnation using activated alumina (AA) as the porous matrix and magnesium sulfate (MgSO 4 ) and magnesium chloride (MgCl 2 ) as the heat storage material. The salt content of composites obtained by the vacuum impregnation method was 8.31% higher than that of atmospheric impregnation method. The adsorption and heat storage performance were investigated, the AA − 20 wt% MgSO 4 (AS-20) and AA − 20 wt% MgCl 2 (AC-20) were outstanding from the single-salt-impregnated composites, especially AS-20 with the heat storage density (HSD) increased by 20.7% compared with atmospheric immersion method. Morphological tests and composition analyses were indicated that the hydrated salt was evenly impregnated into the uniform spherical particles AA matrix. A binary mixed-salt (MgSO 4 -MgCl 2 ) impregnated AA composites were also prepared, and the sample with the MgSO 4 :MgCl 2 mass ratio of 20:80 in the 20 wt% solution (ASC-20) exhibited the better performance. The adsorption capacity of ASC-20 was 0.301 g/g, the kinetics constant (k s ) was 0.01 s −1 , and the HSD was 554 kJ/kg, which were higher than those obtained by single-salt composite and atmospheric impregnation methods. In particular, the k s value of ASC-20 was increased by more than 10 times compared to previous studies. After 10 cycles of testing, the HSD of ASC-20 decreased by 12.5%, and no fracture occurred in the globular particles, showing good thermal stability and structural stability. The new composites obtained by this method is conducive to system application.