Potential and challenges of improving solar still by micro/nano-particles and porous materials - A review

Solar still (SS), being one of the convenient solar desalination systems, has been widely studied in terms of their productivity, efficiency, and economics during the last decades. Recently, to overcome the bottleneck of conventional SS and improve its performance, optimizing the solar evaporation process based on micro/nano-materials has been proposed as a promising strategy. In this review, the recent developments for achieving high-performance SS and solar evaporation by micro/nano-materials were discussed. The reviewed studies have indicated that the enhancement of productivity and efficiency depends on many factors, such as particles concentration, materials type, systems configurations, solar intensity, and so on. It has been found that thermal conductivity and solar absorptivity of the utilized micro/nano-particles are the most important factors. On the other hand, porous structure, surface property, and thermal design are the key factors for porous materials. The paper also discussed the potential of using machine learning to predict the SS performance and analyze the importance of different factors of systems and materials. Moreover, several important points for challenges of SS and solar evaporation investigations were also discussed. These challenges included: the erosion and corrosion of components by micro/nano-particles, complexity-productivity trade-off, salt rejecting, the durability of porous materials, mechanism of water phase change, and so on. The objective of this paper was achieved by highlighting the materials and systems design for the effective use of micro/nano-materials in SS.