Characteristic equation development for conical active solar still with/without PVT for sustainable solution to clean water scarcity: A comparative study

To address global water scarcity and promote sustainable freshwater solutions, a novel solar distillation system has been developed and numerically analyzed. Three cases namely (a) conical solar still (CSS) consisting of partially covered PVT flat plate collectors (FPCs), (b) CSS with fully covered PVT-FPCs, and (c) CSS containing FPCs. Detailed thermal models for different cases have been developed and results are compared. An experimental validation of case (a) has been presented. The root mean square percentage deviation for water temperature, condensing cover temperature and yield are obtained as 5.30%, 4.90%, and 9.11% respectively. The conical geometry of the proposed system increases the condensing surface area and reduces shading effect, improving distillation performance. Results show that the maximum collector outlet and basin water temperatures reached approximately 99.8°C and 95.2°C, respectively at the mass flow rate of 0.04 kg/s and N = 8. Among the configurations, case (c) demonstrated the best performance, achieving a daily distillate yield of 6.44 kg and maximum instantaneous efficiency of 88.28%. However, case (c) is not self-sustainable. In comparison, cases (a) and (b) recorded yields of 4.70 kg and 3.33 kg; and maximum instantaneous efficiency of 79.76% and 25.32%, respectively. The suitability of cases (a) and (b) depends on the requirement of users. Case (a) is suitable when comparatively low electrical output and high yield are required, whereas case (b) is suitable when high electrical output and low yield are required.