Sustainable solar desalination through interfacial evaporation: Integration of chitosan aerogel-impregnated graphene nanoplatelets solar evaporator and phase change material

Solar energy offers several advantages for desalination, including affordability, eco-friendliness and sustainability. However, certain factors have influence on the evaporation rate and result in low yield. These factors include a low solar absorption rate, slow temperature rise, and insufficient heat trapping. To address these challenges, we integrated chitosan aerogel-impregnated with graphene nanoplatelets (CAGNPs) as a photothermal absorber (PTA) and soy wax (SWAX)-based thermal energy storage material (TESM) into spherical solar stills (SSS). This innovative combination enhances solar absorption rates and enables energy storage, thereby enabling all-day, all-weather freshwater production. Waste beverage aluminum cans were utilized to fill the phase change material (PCM) for storing thermal energy. Three identical SSSs were fabricated and their performance was examined from March to August 2023. This comprehensive evaluation demonstrated the effect of photothermal absorption and energy storage, elucidating their collective impact on system efficiency over this period. The test showed that the conventional SSS achieves a freshwater productivity of 1.6 L/m2 over 9 h. The integration of SWAX gives rise to 3.0 L/m2, significantly improving freshwater production compared to the conventional SSS. Moreover, the combined effect of CAGNP and SWAX into SSS results in substantial enhancement, yielding a freshwater productivity of 4.1 L/m2. The obtained exergy efficiencies for the conventional SSS, SSS-PCM, and SSS-CAGNP-SWAX were 1.21 %, 1.69 %, and 1.85 %, respectively. Furthermore, the use of SWAX facilitates the effective storage and release of thermal energy, enabling all-day, all-weather freshwater production.