Characterization and performance analysis of SrCl2 impregnated activated alumina composites for solar thermal energy storage

The utilisation of solar energy has the potential to reduce the dependence on fossil fuels. But it often faces a mismatch between supply and demand. As a result, the thermal energy storage technology, especially the thermochemical energy storage technology based on hydrated salts has attracted great attention. Among the materials, SrCl ₂·6H ₂O has an impressive energy storage density of 667 kWh/m³ and a dehydration temperature below 130 °C, making it particularly suitable for energy storage in buildings. However, pure hydrated salts typically suffer from problems such as poor heat and mass transfer performance and low cyclic stability. To solve these challenges, a series of SrCl ₂/Al ₂O ₃ composites have been synthesised using vacuum impregnation. The adsorption experiments showed that the composite prepared with 25 wt% SrCl ₂ solution (AS25) had the highest adsorption capacity, with an energy storage density measured at 150.5 kWh/m³. Furthermore, the activation energy values of SrCl ₂·6H ₂O and AS25 were obtained by fitting the Kissinger equation, which indicated that AS25 had a lower activation energy, representing a faster dehydration rate compared to SrCl ₂·6H ₂O. Finally, the experiments were conducted to assess the adsorption and desorption performance of AS25 in a lab-scale reactor. The results demonstrated that AS25 exhibited an energy efficiency of up to 93.8 % and stability of at least 10 cycles, indicating potential applications in solar energy chemical energy storage systems.