Experimental study of a solar still with heat pipe solar collector and selected phase change material for wastewater treatment and simultaneous hot water generation

In this study, a hybrid system comprising a single basin solar still and an evacuated tube collector has been designed, where palmitic acid was used as a phase change material filled inside the evacuated tubes. The system was run at a 5 LPH flow rate and two wastewater depths (2.8 cm and 3.2 cm). At a larger wastewater mass, the highest productivity of 5700 mL/m².d was achieved, which was 196.875% higher than the traditional system. Based on distillate output and hot water productivity, the energy and exergy efficiency were computed. The highest value of energy efficiency was 34.53% in terms of hot water productivity and 33.7% in terms of distillate output at 3.2 cm wastewater mass. When analysed for hot water productivity, the highest exergy efficiency came out to be 22.39%, and for distillate output, it was 2.86% at 3.2 cm wastewater mass. The use of palmitic acid enhances the extension period of the system by 2–4 h. This designed system can also produce hot water that may be used for a variety of domestic tasks for consecutively 8.5 h and 11.5 h at wastewater masses of 2.8 cm and 3.2 cm, respectively. The hybrid system effectively removes total dissolved solids, chemical oxygen demand, and biological oxygen demand with removal efficiencies of 90.97%, 94.58%, and 97.03%, respectively.