Thermal Performance Enhancement of Double-Slope Solar Still Using Phase Change Material: Numerical Investigation and Energy Analysis under Casablanca Climatic Conditions

This study presents a comprehensive numerical investigation of a double-slope solar still integrated with phase change material (PCM) under the Mediterranean climate of Casablanca. A five-node transient thermal model was developed using Python, incorporating detailed geometrical parameters (1.0 m² basin area, 0.05 m water depth, 0.02 m PCM thickness, 33° glass inclination) and validated heat transfer correlations. The model simulated 24-hour operation for both conventional and PCM-enhanced configurations using meteorological data from peak solar intensity days. Results demonstrate that paraffin wax PCM (melting point 60°C) effectively regulates thermal dynamics, reducing peak water temperature by 13°C from 89°C to 76°C while maintaining operational stability. The PCM exhibited a 14-hour phase transition cycle, enabling significant thermal energy time-shifting that increased overall daily productivity by 10.5% from 3.8 to 4.2 kg/m². Most notably, nocturnal distillate yield increased by 180%, extending productive operation from 12 to 18 hours daily and shifting 28% of total evaporative energy to post-sunset periods compared to only 8% in conventional operation. The study provides validated evidence that simple PCM integration transforms solar stills from intermittent to continuous producers, offering enhanced reliability for remote applications. The computational framework establishes a robust foundation for optimizing PCM-based thermal storage in solar desalination systems, demonstrating practical pathways for performance improvement without mechanical complexity.