<p>This study examines the improvement of a double-slope solar still by incorporating thermal energy storage (TES) materials to boost its desalination efficiency. The research investigates the incorporation of Phase Change Materials such as paraffin wax to capture surplus thermal energy during high solar radiation and to discharge it during periods of low sunlight, guaranteeing a consistent and stable distillation process. Experimental studies evaluate the performance of solar stills that incorporate TES materials versus those that do not, showing a notable rise in water production. The results indicate that incorporating TES materials leads to increased freshwater output by sustaining higher temperatures and minimizing dependence on direct solar energy. This study advances the optimization of solar desalination methods, especially for regions with limited water resources and in remote locations, by providing a sustainable and effective approach for producing drinkable water.</p> Graphical abstract <p></p>