Experimental Evaluation and Theoretical Validation of a Novel Solar Still Using a Modified Dunkle Model and the Application of Life Cycle Assessment (LCA) to the System

Abstract

This thesis presents the design, experimental evaluation, theoretical validation, and sustainability assessment of a novel rotating-disc solar still system developed to improve freshwater production from brackish water under solar heating. Five still configurations were investigated, including four modified systems (M1–M4) incorporating rotating desalination contactors with different geometric features and operating conditions, and one conventional passive system (M5) used as the control. The prototypes were tested side-by-side under the same climatic conditions in Beirut, Lebanon, while temperature and distillate data were collected over repeated diurnal–nocturnal cycles. The study examined the effects of water depth, disc rotation speed, and attached paddle/trough-like arms on productivity, and then compared the experimental outputs with predictions from the Dunkle model and its modified form. The results showed that the modified systems significantly outperformed the conventional still, with M1 generally achieving the highest productivity and in some cases producing between 400% and more than 1000% of the yield of M5 during the sample period. Theoretical analysis confirmed that the Dunkle model remained a useful baseline, although modifications were required to account for the rotating-disc mechanism and the enhanced evaporation surface. However, R2 value of around 0.99 between the experimental and modified Dunkle model of the M4 system demonstrates an almost perfect linear relationship. In addition, the thesis applied Life Cycle Assessment (LCA) to both M1 and M5 using OpenLCA to evaluate the environmental burdens associated with the conventional and modified still, focusing on material production and, for M1, use-phase electricity consumption. The sustainability analysis further considered economic, social, and technical dimensions, showing that the enhanced productivity of the modified design can offset its higher manufacturing complexity. Overall, the study demonstrates that rotating-disc solar stills are promising decentralized desalination technologies for water-scarce regions, provided that design optimization, environmental assessment, and cost-performance trade-offs are carefully addressed.