Energy, Exergy, and Economic Assessment of a Modified Double‐Slope Solar Still Using Low‐Cost Heat‐Storage Materials

ABSTRACT In many arid and water‐scarce regions, the need for new methods of desalination that are inexpensive and environmentally friendly remains high as access to drinking water continues to be insufficient. Solar stills offer a viable solution, but their widespread use is limited due to low freshwater production and poor thermal performance. The current research investigates a traditional single‐slope solar still (TSS), a double‐slope solar still, and four modified double‐slope solar stills (with iron scraps, black Kanchey, shaving blade fins, and pebbles as thermal energy storage, respectively) (MSS‐1, MSS‐2, MSS‐3, MSS‐4, MSS‐5). In the study, MSS‐1 was the unmodified double‐slope system. The daily water yield in mL/day for various stills was recorded as follows: TSS: 1330, MSS‐1: 1890, MSS‐2: 2370, MSS‐3: 2450, MSS‐4: 3150, and MSS‐5: 2250. The MSS‐4 system (shaving blades) outperforms TSS, presenting the highest yield, increasing productivity by 136%. The peak energy efficiency for different solar stills was as follows: TSS: 29%, MSS‐1: 36.6%, MSS‐2: 46.5%, MSS‐3: 49.5%, MSS‐4: 52.5%, and MSS‐5: 38.3%, with MSS‐4 achieving the highest value of 58.5%. The maximum exergy efficiency recorded was TSS: 10%, MSS‐1: 11.5%, MSS‐2: 15.5%, MSS‐3: 19.6%, MSS‐4: 23.7%, and MSS‐5: 17.4%. According to the economic evaluation, the lowest cost of freshwater production for the modified solar stills was for MSS‐4 (Rs. 0.98/L), and was less than Rs. 1.85/L for TSS, which is a reduction of about 46.2%. The findings demonstrate that integrating a double‐slope configuration with thermal energy storage materials and an enhanced heat‐transfer surface area leads to a substantial improvement in freshwater yield.