Enhancement of solar desalination using a passive parabolic trough integrated tubular solar still through experimental investigation

Conventional solar stills are constrained by low productivity and limited thermodynamic efficiency. This study experimentally investigates a passive parabolic trough-assisted tubular solar still (TSS-PTC) and compares its performance with a conventional tubular solar still (TSS) under identical climatic conditions. A passive parabolic trough reflector is integrated to enhance solar concentration without external energy input, achieving an effective concentration ratio of 2.33 and improving solar energy absorption. Experiments conducted over five consecutive days under peak and average solar irradiance of 970 and 641.5 W/m2 indicate improved thermal behaviour. The TSS-PTC showed increases in basin water and cover temperatures of 3.84°C and 1.9°C, respectively, leading to a 23.10% rise in the evaporative heat transfer coefficient. Consequently, freshwater productivity increased, with a 54% rise in peak hourly yield and an average productivity improvement of 91.3% compared to the conventional system. The maximum thermal efficiency reached 45.2%, while the conventional one still produced 26.1%. In addition, thermal and exergy efficiencies increased by 59.43% and 91.30%, respectively. Overall, daily distillate output from the TSS-PTC was more than twice that of the conventional still, indicating its suitability for efficient, decentralised solar desalination applications.