Preparation and optimization of nanoencapsulated capric acid being as a renewable phase change material with TiO2 shell as shape-stabilized thermal energy storage material.

Novel core-shell nanostructures containing renewable capric acid (CA) core (as a high potential phase change material) and TiO2 (as a highly stable shell) were synthesized using a solgel method for thermal energy storage. Remarkably, CA, a fatty acid available in some vegetable oils, is a renewable phase change material with no undesired environmental impacts. A central composite design of response surface methodology was implemented to determine the effect of the mass ratio of CA/TNBT and the pH value on the encapsulation ratio. As the quadratic mathematical model was used to optimize the process parameters, the maximum encapsulation ratio of 56.67% was achieved, where the CA/TNBT mass ratio was 8.10, and the pH value was 2.65. The measured thermal properties indicated that NEPCMs melt at 31.1 °C with a latent heat of 88.8 J g−1 and solidify at 28.9 °C with a latent heat of 84.23 J g−1. The chemical structure and crystalline phase were measured using Fourier transformation infrared spectroscope and X-ray diffractometer. The thermal stability of the NEPCMs was analyzed by a thermogravimetric analyzer. According to the morphological images, the nanocapsules showed almost spherical shapes with an average size of 100–500 nm. The thermal cycling tests show the high thermal reliability of NEPCMs after the 50th melting/solidifying cycle. The results indicated that the prepared NEPCMs have good thermal stability and reliability for thermal energy storage; hence, they can be applied in building energy conservation and air-conditioning systems. [ABSTRACT FROM AUTHOR]