Effect of Ag, Au, TiO2 metallic/metal oxide nanoparticles in double-slope solar stills via thermodynamic and environmental analysis

In recent years the use of nanoparticles in solar desalination is an emerging approach for improving the performance of systems. Utilizing nanoparticles in black paint of solar stills employed by some researchers but the number of studies in this context is limited. In all previous studies researchers usually utilized a single type of nanoparticle. In the present study silver (Ag), gold (Au), and titanium dioxide (TiO₂) with 0.1 wt% of concentration were utilized in three double-slope solar stills. Performance of the systems from energetic, exergetic, economic, exergoeconomc, enviroeconomic, CO₂ reduction, and energy matrices are examined. Findings revealed that the thermal efficiency of Ag-based solar still is calculated by about 33.68% which shows an improvement around 7.6%, 20.7%, 38.2% compared to Au, TiO₂, and conventional system while overall exergy efficiency of Ag-based system with 2.34% is higher by about 7.3%, 32%, 70.5% in comparison with aforementioned systems respectively. The exergoeconomic results based on energy and exergy from highest to lowest were obtained by Ag, TiO₂, conventional, and Au-based solar stills. Moreover, the economic assessment showed that the lowest and highest cost of distilled water with 0.0065 $/l.m⁻² and 0.0289 $/l.m⁻² were produced by Ag-based and Au-based solar stills. The rate of CO₂ mitigation for the systems with Ag, Au, TiO₂, and conventional was calculated by about 10.82, 10.02, 8.87, 7.7 t/y respectively. The energy payback time (EPBT) for all systems was less than 3 years. It can be concluded that using silver nanoparticle regarding the amount of improvement and the cost, is the most effective particle while the gold nanoparticle due to its high cost is not appropriate for use in solar stills.