Annual overall energy, exergy and efficiency analyses for conical solar still consisting of flat plate collectors with/without PVT: A comparative study

Solar stills are vital, low-cost, and sustainable devices for converting brackish/saline water into drinkable water. They are particularly essential in arid/remote regions, serving as an eco-friendly and energy-intensive desalination technique to overcome water scarcity. However, if the conventional designs are modified to enhance the solar still's performance, - a detailed, combined, and comprehensive analysis is required to optimize design parameters, improve water yield, and ensure the system is economically viable for market use. Thus, this work focuses on an annual energy, exergy, and efficiency analysis of modified configurations of conical active solar stills to provide sustainable solutions to the contemporary issue of freshwater scarcity and to support the UN's Sustainable Development Goals. Three configurations are considered, namely N-P-PVTFPC-CSS: conical solar still (CSS) with N partially covered photovoltaic-thermal (PVT) flat-plate collectors (FPC); N-F-PVTFPC-CSS: CSS with N fully covered PVTFPCs; and N-FPC-CSS: CSS with N conventional FPCs. The data for New Delhi's climate is obtained from the Indian Meteorological Department. The thermal model is experimentally validated for N-P-PVTFPC-CSS. The computation of annual yield, energy, exergy, overall energy, overall exergy, and various efficiencies for the three cases is carried out using MATLAB to compare the results. Overall, annual energy is higher by 2.20% and 4.69%, and annual exergy is higher by 29.26% and 54.83% for N-F-PVTFPC-CSS than for N-P-PVTFPC-CSS and N-C-FPC-CSS, respectively. N-P-PVTFPC-CSS has higher overall energy efficiency by 8.59% and 23.98% than N-C-FPC-CSS and N-P-PVTFPC-CSS, respectively, whereas N-F-PVTFPC-CSS has higher exergy efficiency by 22.66% and 31.41% than N-P-PVTFPC-CSS and N-C-FPC-CSS, respectively.