Thermal optimization of a double-slope solar still using nano-enhanced PCM: a response surface methodology approach

This study explores the thermal performance enhancement of a double-slope solar still (DSSS) though the integration of paraffin wax (PCM_56) and silicon dioxide (SiO2) nanoparticles as thermal energy storage media. Experimental investigations were conducted under thee distinct configurations: a conventional system without storage, a setup incorporating only PCM_56, and a hybrid configuration combining PCM_56 with SiO2 nanoparticles. The conventional system achieved a maximum distillate yield of 1.4 kg h−1 with 36% thermal efficiency. The addition of PCM_56 increased the yield to 1.65 kg h−1 and improved efficiency to 39%. The hybrid system demonstrated superior performance, delivering 1.9 kg h−1 of distilled water with an efficiency of 45%, marking enhancements of 35.7% in yield and 25% in efficiency over the baseline. The use of nano-enhanced PCM also elevated the glass cover temperature to 86 °C, prolonging the evaporation period beyond peak solar hours. Response surface methodology (RSM) was employed for statistical optimization, identifying optimal operating conditions that produced a distillate yield of 4.13 kg h−1 and efficiency of 18.4% under solar intensities between 2200 and 2600 kJ h−1 m−2. These findings highlight the effectiveness of combining phase-change materials with nanomaterials to significantly enhance solar still productivity, offering a sustainable and efficient approach to freshwater generation in solar desalination systems.