Performance investigation of LiCl·H2O-γ-Al2O3 composite materials for low-grade heat storage

Abstract

In this study, the influences of nano γ-Al₂O₃ on the thermal storage performance of LiCl were experimentally investigated. The XRD results show that a complex of lithium aluminium oxychloride (LiAlOCl₂) was formed through the LiCl·H₂O and γ-Al₂O₃ composites preparation process. The in situ diffuse reflectance infrared Fourier transform spectroscopy measurement reveals that the addition of γ-Al₂O₃ accelerated the hydration rate of LiCl composites, concentrated the spectrum utilization range, and promoted the desorption rate of physical adsorbed H₂O and low-frequency structural –OH in the materials. The highest specific surface area of the composite is 34.5 times higher than that of pure LiCl. The addition of γ-Al₂O₃ can increase the conversion rate of LiCl·H₂O to approximately 100% at the hydration time of 1 h and the addition content of γ-Al₂O₃ at 15 wt%. A maximum heat storage density (HSD) for the LiCl·H₂O-γ-Al₂O₃ composite can reach 714.7 kJ kg_LiCl·H2O⁻¹ in 1 h when the addition content of γ-Al₂O₃ was 15%_wt and its water uptake can reach 0.26 g g⁻¹ in 1 h. It also can be found that the addition of Al₂O₃ in LiCl resulted in a decrease of the activation energy from 90.89 kJ mol⁻¹ to 79.76 kJ mol⁻¹. However, the thermal conductivity of the LiCl·H₂O-γ-Al₂O₃ composite slightly decreased with the increase of nano γ-Al₂O₃ content.