Optimization of single-slope passive solar still using SiO₂ nanofluids

This paper comprehensively evaluates the performance of a passive solar still with a single slope using conventional water and a nanofluid comprising silicon dioxide (SiO₂). The silicon dioxide nanoparticles underwent characterization through X-ray diffraction, transmission electron microscopy, and X-ray energy-dispersive spectroscopy. Two solar stills of identical design and basin area were fabricated and tested simultaneously under identical environmental conditions to ensure uniform thermal performance. One still operated with plain water, while the other used a water-based nanofluid containing silicon dioxide at different concentrations. The findings reveal that the solar still incorporating water-based silicon dioxide nanofluid, at concentrations of 0.05%, 0.10%, 0.15%, 0.20%, and 0.25% improves the water distillate by 13.54%, 14.92%, 16.74%, 18.38%, and 17.17%, respectively, compared to a solar still using water. This underscores an optimal enhancement in output at a concentration of 0.20%. Furthermore, it is noted that the utilization of silicon dioxide nanofluids leads to a more prominent evaporative heat transfer compared to convective heat transfer.