Experimental study on the performance of an enhanced stepped solar still aided by PCM materials with external reflectors

Water scarcity is increasing rapidly and becoming increasingly serious in many parts of the world. Solar still is a promising desalination technology for the future. However, the solar still's productivity is relatively low and needs substantial enhancements. This study developed a low-cost simplified solar still system utilizing phase change tubes and external reflectors, based on the concept of the stepped solar still (SSS). Copper tubes were filled with paraffin wax as PCM material and placed inside the saline water in six trays inside the SSS. Three cases were studied and compared. SSS: conventional device as a reference case, PCM-SSS: SSS plus PCM material, and PCM-ER-SSS (PCM-ER-SSS): PCM-SSS plus external reflectors. All experiments were conducted in a real field under climatic conditions of Suez City in Egypt. Results revealed that the water productivity of the three cases was: 4.5 L/m²day, 7.44 L/m²day, and 8.5 L/m²day, respectively. The three cases' thermal efficiencies were 36.35 %, 66.76 %, and 89 %, respectively, achieving water production costs per liter (CPL) of $0.009, $0.007, and $0.007, respectively. Using PCM tubes and external reflectors (PCM-ER-SSS) enhanced the yield and thermal efficiency by 88.9 % and 89 %, respectively, and reduced the CPL by 22.77 % compared to SSS.