Standalone hybrid PV-powered double-slope solar still with automated cooling and heating for continuous freshwater production

This study presents the evaluation of a standalone modified double slope solar still (MDSSS) to produce continuous freshwater for a prolonged duration. The system is provided with a booster mirror, automatic glass cooling fans, and auxiliary DC heaters for basin water. The cooling system fitted on south-facing glass cover operates only during sunshine hours, whereas the heating system operates during non-sunshine hours to maintain basin water temperature. Eight modified cases were examined and compared with a traditional double slope solar still (TDSSS), comprising two glazing configurations, namely semi-transparent photovoltaic glass (Case 1) and conventional transparent glass (Case 2). Each configuration was evaluated with a booster mirror, firstly alone, then with cooling, with heating, and with cooling-heating combined. Case 2d was observed to be the superior one, yielding 8.02 kg/m 2 .day of freshwater, with 104.8% improvement to that of TDSSS. The basin water reached to a maximum of 56.73 °C at day-time and the non-sunshine hour stabilization was 192% higher than the TDSSS. The maximum energy efficiency, calculated by accounting for both the incident solar energy and the electrical energy consumed reached to 68.92% for Case 2d, signifying a 71.74% improvement over the TDSSS, while exergy efficiency rose from 3.27% to 6.23%. These improvements in Case 2d are due to the combined effects of cooling fans and auxiliary heaters. The total electrical energy consumption was recorded to be 1816.64 Wh. The proposed system demonstrated favourable energy, environmental, economic, and sustainability performances, to be applicable for standalone uses.