Size controlled lauric acid/silicon dioxide nanocapsules for thermal energy storage

Nanoencapsulated phase change materials (NEPCMs) are a crucial part of solar energy systems due to their high thermal storage density. The particle size of the NEPCMs is especially of great importance due to its effect on heat transfer and long-term use during applications. In this paper, lauric acid (LA)/SiO2 nanocapsules with various particle sizes were prepared with a sol-gel method. The results showed that the latent heats of these nanocapsules could reach as high as 165.6 J/g, with an encapsulation ratio of 85.9%. Additionally, the latent heat values of the samples reduced slightly (less than 10%) after 1200 thermal cycles. Furthermore, an analysis of the mechanism of the size control of the LA/SiO2 nanocapsules was conducted. By analysing the size change of the samples under different synthetic conditions, it was found that the size of the nanocapsules was principally controlled by the concentration of OH-, and the encapsulation ratio of nanocapsules is affected by the cumulative percentage of emulsion droplets and the shell thickness. Thus, the optimal particle size of 340 nm for the nanocapsules was confirmed.