Winter desalination enhancement using paraffin wax and lauric acid as phase change materials with twin-tubular solar stills in semi-arid climates

Conventional solar stills produce only 2–4 L/m² per day of freshwater; consequently, they cannot satisfy the daily freshwater demand, even for a single family. Literature indicates that tubular solar stills (TSSs) are more effective, although they encounter challenges such as heat loss and reduced productivity in winter due to lower heat flux. This necessitates advancements in the TSSs to address these challenges. The present research investigates the effectiveness of a double-tubular solar still when loaded with phase change materials (PCMs), such as paraffin wax and lauric acid, in producing more freshwater. The developed solar stills were tested with PCM containers in strategic locations to store and release heat. This compensated for the fact that solar irradiation was lower in the winter months. The results revealed a significant increase in distillate production (15.2 % with paraffin wax and 11.4 % with lauric acid) compared with the baseline (i.e., no PCM). Thus, paraffin wax was found to be better for storing heat and boosting production. The results showed that integrating the PCM improved the distillation efficiency. This study provides vital information for selecting and arranging PCM to optimise the performance of solar stills in semi-arid areas prone to winter weather.