Thermal performance of shape-stable hydrated salt-based modified diatomite composite phase change materials for low-temperature heat storage

Hydrated salts are promising candidates for thermal energy storage (TES) in buildings because of their high energy storage density, low cost, and non-flammable nature. However, challenges such as phase separation and shape instability limit their practical application. The use of diatomite as a porous support material can effectively address these issues. This study focuses on developing cost-effective thermal composites by incorporating ternary eutectic (T.E) salt hydrates into chemically treated diatomite (D.T) via the vacuum impregnation method to create shape-stabilized phase change materials (ss-PCMs). The microstructures, chemical stabilities, thermal properties, and reliability of the composites were characterized by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR), and differential scanning calorimetry (DSC). SEM analysis confirmed the successful impregnation of the T.E salts into the diatomite pores. The resulting composites T.E1/D.T, T.E2/D.T, and T.E3/D.T exhibited latent heat values of 95.42, 119.7, and 106.13 kJ/kg, respectively. Notably, the T.E2/D.T composite demonstrated a high salt loading efficiency of approximately 68 %, indicating that the treated diatomite has the capacity to encapsulate a substantial amount of PCM. This efficient encapsulation enhances the latent heat capacity and provides excellent shape stability and thermal reliability across multiple thermal cycles. These findings underscore the strong potential of the T.E2/D.T composite for long-term TES applications, particularly in improving energy efficiency in buildings.