Performance enhancement of stepped double slope solar still by using nanoparticles and linen wicks: Energy, exergy and economic analysis

This work aims to improve the thermal and economic analysis of stepped double slope solar still (SDSSS) that integrated with linen wicks (LWs) and carbon black nanoparticles (CBNs). The LWs and CBNs were used to increase the evaporation surface area and enhance heat transfer of basin saline water. The SDSSS with LWs and LWs with CBNs were evaluated, and compared with traditional solar still (TSS). The energy and exergy for convection and evaporation and exergy efficiency for different modifications were analyzed, and its costs were discussed. Results indicated that adding LWs and CBNs to SDSSS increased the freshwater productivity and energy efficiency by 80.57 and 110.5%, respectively, compared to TSS. The SDSSS fractional exergy of evaporation was the highest in the case of integrating LWs and CBNs with the solar still due to the high basin water temperature. This modification caused the highest exergy efficiency for SDSSS because of enhanced photothermal properties of CBNs, and heat storage characteristic of LWs. Economic analysis indicated that the total costs per liter of produced freshwater for SDSSS without any modifications, SDSSS with LWs, SDSSS with CBNs, and SDSSS with LWs and CBNs were lower than TSS by 13.73, 19.91, 23.83, and 47.22%, respectively.