Enhancing the performance of conical solar stills through optimised flint stone placement on absorber

Abstract

Water shortage is a significant global issue, necessitating the development of sustainable, energy-efficient desalination technologies. This study aims to determine the optimal spacing of 2 cm diameter flint stones to enhance the efficiency of conical solar stills. Three identical stills were tested over two days: the first had no stones, the second had stones spaced 3 cm apart (61 stones), and the third had stones spaced 4 cm apart (41 stones). On the second day, the first still remained stone-free, while the second and third stills had stones with 5 cm (25 stones) and 6 cm (13 stones) spacing, respectively. The results indicated that the system with 3 cm stone spacing achieved the highest water productivity, yielding 8600 g/m2, significantly surpassing the other configurations: 4 cm (7850 g/m2), 5 cm (7400 g/m2), 6 cm (6900 g/m2), and the baseline system (5600 g/m2). The optimal distance of 3 cm resulted in a 53.57 % improvement over the conventional system. Performance analysis further revealed enhancements across thermodynamic indicators, with the system at 3 cm spacing exhibiting a 56.68 % increase in efficiency, a 190.64 % improvement in exergy efficiency, and a 163.03 % rise in exergy production compared to the baseline. These improvements are attributed to better heat retention and optimized heat transfer dynamics from closer stone placement. The study concludes that using flint stones with a 2 cm diameter and a spacing of 3 cm significantly enhances system performance, offering a scalable and low-cost solution for solar-powered desalination in arid regions.