Synthesis and Determination of The Thermal Properties of a Waste Silica Gel Based Composite for Latent Heat Storage Applications

In this study, polyethylene glycol (PEG1000) was infused into the porous structure of moist silica gel at a concentration of 45% by weight using a direct impregnation method. The waste silica gel, as a porous material, was subjected to a series of drying and grinding processes. The chemical structure and morphology of the silica gel/PEG1000 (45% by weight) composite were determined using fourier transform infrared spectroscopy (FT-IR) and scanning electron microscopy (SEM), while differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) techniques were used to determine its heat energy storage and thermal resistance properties. DSC results showed that the prepared composite stored 52.8 J/g of heat energy at 30.3 °C. It was observed that the chemical structure and energy storage properties of silica gel/PEG1000 did not change even after the thermal cycling process was repeated 1000 times. The obtained TGA data showed that the prepared composite is highly suitable for thermal energy storage (TES) applications. The thermal conductivity (TC) value of the synthesized composite was determined, and the TC values were improved by doping carbon nanotubes (CNTs) in different amounts (1%, 3%, and 5%) by weight. Additionally, the effect of adding CNTs to the prepared composite on heat storage and release times was investigated. In summary, the composite material prepared in this study has the potential to be used safely and for a long time in temperature control applications such as building air conditioning and waste heat storage, thanks to its latent heat storage capacity.