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The thermo-physical properties of NaNO3/KNO3 (solar salt) added with Al2O3 and TiO2 nanoparticles as phase change material in thermal energy storage system were investigated. Initially the Al2O3 and TiO2 nanoparticles were added to NaNO3/KNO3 (60:40) with a concentration of 1%, 3% and 5 mass% using low-energy ball mill. The differential scanning calorimetry instrument is used to measure the thermal properties of the prepared PCM composites. It is found that the phase change temperature and latent heat capacity vary with Al2O3 and TiO2 nanoparticles loading levels. When the loading is not over 3 mass% of Al2O3, the phase change temperature drops, and the latent heat capacity increases up to 23.3%. When the loading is over 3 mass% of Al2O3, the phase change temperature increases, and the latent heat capacity drops to 14.23%. A significant increase in latent heat capacity is found around 3 mass% of Al2O3 loading. When the TiO2 nanoparticle concentration increases, the phase change temperature decreases, and the latent heat capacity increases up to 32.2%. When the TiO2 nanoparticle's concentration decreases, the phase change temperature increases, and the latent heat capacity decreases. The thermal conductivity of the composites was found to increase with the increase in the loading of nanoparticles. After adding 3% by mass of Al2O3 and TiO2 nanoparticles, the thermal conductivity was found to increase by 8.30 and 8.10%, respectively. From the characterization studies, we found that TiO2 helps to achieve the improved thermo-physical properties and heat storage characteristics for NaNO3/KNO3 which suggests their potential candidate of usage in the thermal energy storage system. [ABSTRACT FROM AUTHOR]