Aluminum doping of mesoporous silica as a promising strategy for increasing the energy storage of shape stabilized phase change materials containing molten NaNO3: KNO3 eutectic mixture

Efficient thermal energy storage at high temperature is necessary for both industrial waste heat utilization and continuous solar power generation. Shape-stabilized phase change materials containing mesoporous aluminosilicates and eutectic NaNO3: KNO3 (1:1 mol) molten salt mixture were obtained at 90% wt. salt. The influence of aluminum doping was studied for the first time. All samples show thermal stability up to 550 C and two distinct phase transitions corresponding to the melting/freezing of nanoconfined and interparticle salt phases. The radius and spherical shape of the nanoconfined phase were determined from the melting and freezing point depressions with respect to bulk. The enthalpy decrease was quantified in terms of surface tension and the contributions of a non-melting fraction of surface adsorbed ions. SBA-15 type aluminosilicates matrices yield composites with high latent heat storage of 76-77 Jg(-1), of which 8 Jg(-1 & nbsp;)for the nanoconfined phase and good thermal reliability. Aluminum doping is a simple and promising strategy for obtaining high temperature, efficient thermal energy storage materials due to a lack of non-melting salt fraction. The resulting shape-stabilized PCMs have a higher operating temperature range and latent heat storage, offering a 36% increase in total heat capacity over the pristine salt.