Abstract

Shape Stabilized Phase Change Materials (SS-PCM) allow the Phase Change Materials (PCM) to retain the shape of the solid structure during the phase transition. Therefore, liquid phase are contained by surface forces and capillarity, providing a large area of heat transfer, also decreasing the sub-cooling and controlling changes in the volume of storage materials when the phase transition occurs. However, the real approaches in which these PCM are stabilized in the support material and its correlation with some obtaining parameters have been slightly analyzed. Therefore, the main objective of this work is to determine by Scanning Electronic Microscopy (SEM) and Infrared Spectroscopy (IRS) the stabilization form in SS-PCM obtained by sol-gel techniques based on SiO2 polymer; using Na2SO4, LiCl, LiNO3 and Li2CO3 salts as inorganic PCM. SEM images of the obtained materials permitted to analyze the influence of the nature of the salt and PCM content on the form of stabilization. Hence, three principal trends were observed in stabilization system of the SS-PCM: (1) the salt is uniformly mixed inside the SiO2 polymer crystals, (2) the PCM is inside and over the SiO2 crystals and (3) forming mixed crystals but in ones predominate the salt and in the others the SiO2. IRS confirmed the formation of the polymer and that no chemical reaction occurs between PCM and polymer, except for Li2CO3, due to was observed that the vSi-OH band (955 cm-1) disappears for this material. The melting and solidifying temperatures (Tm and Ts, respectively) of Na2SO4 SS-PCM were 887.86 and 882.95 0C, respectively. The latent heat was found 98.76 J/g for the melting and 97.15 J/g for that of the solidification (ΔHm and ΔHs, respectively); when comparing with pure Na2SO4, the enthalpy was lower due to PCM content in the final material. Similar results were obtained for LiCl and LiNO3 SS-PCM. The thermal performance of the materials demonstrated its potential as SS-PCM in medium and high temperature thermal energy storage applications.