Water scarcity is an escalating global concern, particularly in arid and semi-arid regions where access to fresh potable water is limited. Conventional desalination technologies, while effective, are often energy-intensive and economically prohibitive. Solar desalination systems, especially solar stills, offer a sustainable and low-maintenance alternative by mimicking the natural hydrological cycle—evaporating water using solar radiation and condensing it to produce distilled water. However, their productivity remains relatively low, typically yielding 2.5–3 kg/m²/day under average conditions.
This study presents an experimental investigation into enhancing the performance of solar stills through the use of bitumen and metallic filings (iron, copper, aluminum), combined with black-painted aluminum coatings. The objective is to develop a cost-effective and thermally efficient desalination system by integrating six novel material configurations into a modified solar still (MSS), benchmarked against a conventional solar still (CSS). Both systems were constructed with identical geometries and tested under natural conditions in Mansoura, Egypt, from September to November 2022, with a fixed water depth of 4 cm.
The MSS configurations included bitumen alone and bitumen mixed with iron or copper filings, with and without black-painted aluminum coatings. Key performance indicators—temperature distribution, water productivity, energy and exergy efficiencies, and economic analysis—were evaluated. The most effective configuration, comprising bitumen with copper filings and aluminum coating, achieved a daily water yield of 2.48 L/m², representing a 76.16% increase over the CSS. Thermal efficiency improved from 21.2% to 30.19%, and exergy efficiency rose from 1.39% to 2.42%. The cost per liter of distilled water decreased from $0.081 (CSS) to $0.051 (MSS), with annual production reaching 841.5 L compared to 477.7 L for the conventional system.
The findings underscore the significant impact of thermal additives and surface coatings on solar still performance. Previous research has demonstrated similar improvements using absorptive materials such as cotton wicks, sponge cubes, black granite gravel, jute cloth, charcoal cloth, and black rubber matting. Innovations like thermoelectric modules and phase change materials (PCMs) have also shown promise, with productivity gains ranging from 35% to over 100%. Nanotechnology has further advanced the field, with nano-sized particles like Al₂O₃, CuO, TiO₂, and graphene oxide enhancing heat transfer and distillation efficiency.
This study contributes to the growing body of research aimed at optimizing solar desalination systems through material innovation. By leveraging bitumen and metallic filings, the modified solar still offers a practical and scalable solution for low-cost freshwater production, particularly in regions facing acute water shortages.
(Source: Science Direct)