Mechanism-based engineering review of solar still enhancement strategies: Thermal performance, design trade-offs, and practical implications

Solar stills show great potential for decentralized water desalination, but low production and thermal performance limit practical use. This paper reviews studies published from 2020 to 2026, focusing on design, thermal enhancement, material and optical properties, operating conditions, climatic conditions, and hybrid integration. This review differs from previous studies that evaluate modifications in isolation by comparing enhancement strategies based on their thermal mechanisms, conceptual design trade-offs, and practical implications. The results reveal that performance arises from the interplay among solar absorption, heat transfer, energy storage, and evaporation-condensation processes. The structural and optical modifications provided over 150% improvement in some configurations, while PV/T integration helped enhance the productivity by up to 52%, and coupling with reverse osmosis resulted in a 14.54% enhancement in freshwater recovery. At a constant solar radiation level, changes in thermal efficiency were ascribed to ambient temperature (73.5%), wind speed (14.3%), and dew point temperature (12.2%). Performance depends upon operating conditions, design objectives, simplicity, and economics—no one improvement is always best. Important research gaps include a limited number of comparisons under standardized conditions, incomplete thermodynamic analyses, and insufficient economic and environmental evaluations. Thus, the present review provides a mechanism-based framework to guide the selection of solar still enhancement strategies focusing on thermal performance, viability, and design compatibility.