Development of a vacuum double-slope solar still for enhanced freshwater productivity

[Display omitted] •A high yield vacuum-type pyramid-solar-still was investigated experimentally.•Hourly and daily productivity enhanced by 22.3 % and 63 % respectively.•Distillation and exergy efficiencies were improved by 28.7 % and 22.4 % respectively.•Incorporation of PCM with vacuum condition outperformed conventional solar stills. In this study, a solar-energy-driven high performance water purification system is designed, fabricated, and examined, which may be useful for remote areas with limited access to grid electricity and underground freshwater. This research aims to enhance the performance of a conventional solar still (double-slope type) by creating vacuum inside the chamber and using paraffin wax (PCM) as energy storage material. The performance of the modified solar still (SS) is investigated and compared with the conventional solar still (CSS) in terms of productivity, distillation efficiency, and exergy efficiency. The performance analyses show that the hourly productivity and daily cumulative productivity are increased by 22.33 % and 63 % (from 5.46 L/m2 to 7.03 L/m2) respectively for the modified still compared to the conventional still. Nearly 28.72 % distillation efficiency and 22.43 % exergy efficiency enhancement are recorded for the modified system compared to the conventional system. This study also reveals that the thermal performance of the modified system is significantly improved under vacuum condition and using paraffin wax as heat storage material, which enables the still to operate at low solar intensities. The economic analysis shows that the cost of freshwater produced per liter in the modified SS is 41.4 % less than that of the conventional SS.