Experimental insight into the enhancement of productivity in a single-slope passive solar still through optimization of TiO2 nanofluid concentration

This study experimentally investigates the influence of TiO2 nanofluid concentration on the yield of a single-slope passive solar still. The work aims to determine the optimal nanofluid concentration that maximizes freshwater yield, addressing a gap in existing research where the effects of concentration are seldom examined comprehensively. Two identical solar stills were made, one operating with simple water and the other with a TiO2 water nanofluid prepared through the combination of magnetic stirring and ultrasonication. The TiO2 nanoparticles were characterized using X-ray diffraction (XRD), transmission electron microscopy (TEM), and energy dispersive spectroscopy (EDS), while nanofluid stability was confirmed via zeta potential analysis (− 32.9 mV). Experiments were performed for TiO2 nanofluid concentrations of 0.05, 0.10, 0.15, and 0.20 vol%. Results revealed that a concentration of 0.15 vol% yielded the highest improvement in distillate water, 19.81% higher than that of the conventional still. The addition of TiO2 nanoparticles enhanced both the temperature distribution and heat retention capacity of the working fluid, resulting in a pronounced increase in evaporative heat transfer compared to convection. The findings confirm that the optimum TiO2 nanofluid concentration (0.15 vol%) offers a significant performance enhancement while maintaining water quality within acceptable limits, providing valuable insights for the design of sustainable solar desalination systems.