Abstract Global water scarcity has reached a critical threshold in the 2026 UN‐declared era of “water bankruptcy, ” with agriculture consuming 72% of freshwater resources and 2. 1 billion people lacking safe drinking water. Conventional passive single‐basin solar stills (SBSS) suffer from low daily productivity (2–5 L/m 2 /day), severe diurnal intermittency, and limited thermal efficiency, rendering them inadequate for scalable, off‐grid desalination. This review proposes a novel material‐augmented passive solar still strategy centered on twin‐wedge solar still (TWSS) and double‐slope configurations, synergistically enhanced by capillary wick materials (cotton or bamboo), sensible heat storage (manufactured sand), and a latent nano‐PCM (nano‐Al 2 O₃/graphene oxide composite PCM), together with graphene‐nanoplatelet‐coated absorbers. Experimental outcomes from four interconnected 2025–2026 studies demonstrate that the optimal TWSS + cotton wick + M‐sand configuration achieves 5. 84 L/m 2 /day (235% higher than baseline SBSS), while the nano‐PCM/wick variant reaches 6. 133 L/m 2 /day (139% improvement), delivering energy efficiencies of 58%–67%, exergy efficiencies of 4. 3%–5. 3%, evaporative heat transfer coefficients up to 236 W/m 2 ·K, a sustainability index of 1. 06, and a levelized cost of water (LCOW) of 0. 012/L with a 4. 6‐month payback. These advancements, combined with broader integration of evacuated‐tube collectors, PVT cogeneration, and hybrid membrane processes, significantly reduce greenhouse gas emissions (50%–90%) and pave the way toward SDG 6, 7, and 13 targets, while highlighting remaining gaps in AI‐optimized controls and socio‐economic life‐cycle assessments for full commercialization.
Md Atiqur Rahman (Fri,) studied this question.