Performance Enhancement of a Pyramid-Type Solar Still Using a Fresnel Lens and Thermoelectric Coolers: An Experimental Study

This study experimentally investigates the performance of a pyramid-type solar still under four operating configurations: a reference system, a thermoelectric cooling (TEC)-assisted system, a Fresnel lens-assisted system, and a hybrid configuration combining Fresnel concentration with TEC cooling. The study evaluates the effects of enhanced evaporation and condensation mechanisms on the thermal behaviour and freshwater productivity of the solar still. The reference system produces 3.19 L/m2day of distilled water. The TEC-assisted configuration increases the daily yield to 3.78 L/m2day, corresponding to an improvement of 18.3%, while the Fresnel lens-assisted configuration achieves 4.81 L/m2day, representing a 50.4% increment compared with the reference system. The hybrid Fresnel + TEC configuration achieves the highest freshwater productivity of 5.19 L/m2day, corresponding to an improvement of 62.6%. The experimental outcomes highlight that Fresnel concentration effectively enhances evaporation by increasing basin-water temperature, whereas TEC cooling promotes condensation by reducing the glass-surface temperature. Energy analysis further shows that the Fresnel-only configuration provides the highest overall energy efficiency, at roughly 41.7%, while the hybrid configuration maximises freshwater production but requires additional electrical energy for TEC operation. Overall, the results demonstrate that optical concentration and TEC can effectively improve different stages of the solar distillation process, with their combined application providing the highest freshwater yield among the investigated configurations. From a sustainability perspective, the findings demonstrate the potential of solar-driven desalination to support decentralised freshwater production, while also highlighting the importance of minimising auxiliary electricity consumption in actively cooled configurations.