Characteristic Equation Development for Conical Active Solar Still With/Without Photovoltaic Thermal for Sustainable Solution to Clean Water Scarcity: A Comparative Study

Abstract

Abstract. 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 photovoltaic thermal (PVT) flat plate collectors (FPCs), (b) CSS with fully covered PVT-FPCs, and (c) CSS containing FPCs have been considered. Detailed thermal models for different cases have been developed, and the 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 is obtained as 5.30%, 4.90%, and 9.11%, respectively. The conical geometry of the proposed system increases the condensing surface area and reduces the 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 a 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 requirements 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.