Nano-enhanced PCM-assisted solar stills: A systematic review of performance, economics, and sustainability

Abstract

Abstract Freshwater scarcity is an escalating global challenge, particularly in arid, remote, and off-grid regions where conventional desalination technologies remain energy-intensive and costly. Solar stills provide a simple and sustainable desalination option; however, their broader application is constrained by low freshwater productivity, intermittent operation, and limited thermal efficiency. In recent years, nano-enhanced phase change materials (NEPCMs) have emerged as a promising thermal energy storage solution for overcoming these limitations by improving heat storage capacity, thermal conductivity, and heat release during non-sunshine hours. Despite this progress, the available studies remain fragmented across different nanoparticle types, still configurations, and reporting conventions, which makes their findings difficult to compare directly. This study presents a PRISMA-based systematic review of NEPCM-assisted solar still technologies reported between 2020 and 2026. The review critically synthesises recent developments in NEPCM compositions, hybrid solar still configurations, and integrated heat and mass transfer enhancement techniques. Reported findings indicate that NEPCM integration can significantly improve solar still performance, with freshwater productivity increases of about 50–300%, thermal efficiency improvements of 20–150%, and exergy efficiency gains of up to 230% relative to conventional systems. Techno-economic analyses further show reduced water production costs, in some cases as low as 0.010–0.015 USD L −1 , together with short payback periods of approximately 3.9 months. Environmental assessments also reveal considerable mitigation potential, with annual CO 2 emission reductions reaching about 47 tonnes in some configurations. These improvements are mainly associated with high-conductivity nanoparticles, such as CuO, Al 2 O 3 , Ag, and graphene-based additives, as well as synergistic integration with wick materials, corrugated absorbers, reflectors, fins, condensers, and multi-stage designs. Overall, NEPCM-assisted solar stills are a promising and increasingly practical pathway towards efficient, cost-effective, and environmentally sustainable freshwater production, provided that long-term material stability and standardised performance reporting are addressed in future work. Graphical Abstract A Pathway to Sustainable Water: Nano-PCMs Boost Solar Still Productivity and Economics.