Nanosilicon dioxide hydrosol as surfactant for preparation of microencapsulated phase change materials for thermal energy storage in buildings

Abstract

Microencapsulated phase change materials (MEPCMs) have been recognized as potential energy storage materials for applications such as balancing of heating and cooling loads in buildings. However, current MEPCMs do suffer from low thermal conductivity and low mechanical strength thus limiting their full potential. Past investigations have shown that nanomaterials could be used as a surfactant for the preparation of O/W emulsion and for thermal enhancement in encapsulation processes of phase change materials. For that reason nanosilicon dioxide hydrosol was selected as a surfactant for the encapsulation of samples of n-octadecane due to its excellent thermal stability and good combination properties with both organic and inorganic phase change materials. To this end, the focus of the study was on the synthesis and characterization of the fabricated MEPCM samples. Analysis of the results did show good particle dispersion and shell integrity with the best fabricated sample (MF-2) achieving a significant increase in thermal stability temperature by approximately 78°C (i.e. from 133°C to 211°C) and also higher core material content ranging from 8% to 25% in comparison with other samples. However, there was a reduction of about 17% in the energy storage capacity and a slight reduction of 0.57°C in its melting temperature when compared with the original sample of n-octadecane. The results also revealed that the nucleating agent (ammonium chloride) did affect the morphology, particle size distribution and the content of the base materials. Further enhancement studies are therefore encouraged.