Conical solar still with internal and external modifications: A comprehensive review

The global water emergency requires innovative and sustainable solutions to afford clean water especially after a rapid growing populations and industrial practices besides environmental changes. Solar desalination, particularly through conical solar stills (CSSs), presents a promising approach due to its environmental sustainability and economic viability, openly supporting the United Nations Sustainable Development Goals (SDGs), especially Goal 6 (Clean Water and Sanitation). The current paper demonstrates a thorough review of CSS technology development, signifying performance-improving modifications intend to upgrade water productivity. Several improvements have been achieved through internal modifications such as the incorporation of nanofluids with energy storage materials comprising stainless-steel balls, black glass balls and graphite fins in addition to optimized geometries utilizing egg steel trays. Referring to this review, the implementation of nanofluids has resulted in a maximum daily yield boost of 2.81 L/m2, yet stainless-steel balls have improved productivity by 95.58% and graphite fins have delivered an exergy efficiency rise by 574.1%. Also, the external modification including​ evacuated tube collectors with photovoltaic thermal systems and reflective mirrors have entailed performance improvements ranging between 33.67% and 74.14%. CSS designs demonstrate better performance than traditional systems based on optimal setups that achieve a water productivity rate of 10.26 L/m2 day and a thermal efficiency rate beyond 69%. Economically, the advantages reflected in this review signify potential and water cost reductions of more than 50% and short payback periods starting from 2.75 years. Although the development of upgraded solar water desalination delivers numerous benefits, existed difficulties pertain regarding system performance optimization and simplicity management across various environmental situations.