Scale-up of solar interfacial evaporation devices: advanced optical, thermal, and water management for efficient seawater desalination

Significant progress has been made in enhancing solar interfacial evaporation (SIE) performance at the laboratory scale, however, translating these improvements to meter-scale systems suitable for practical deployment remains limited by challenges, including material scalability, thermal losses, and non-uniform water distribution. Addressing these issues is essential for the development of modular, meter-scale evaporators as baseline units for industrial-scale desalination systems. This study presents a solar multi-stage interfacial evaporation (SMIE) device with a 1 m² active area designed to address the key limitations associated with large-scale operation systematically. The device integrates: (i) a scalable photothermal absorber layer based on Cu-CAT-1 metal-organic framework or carbon black, (ii) an inverted multi-stage configuration with optimized thermal insulation to reduce energy loss and enable latent heat recovery, and (iii) structured wicking channels engineered to maintain spatially uniform water transport. Under 1-sun illumination in a controlled laboratory setting, a 100 cm² prototype achieved freshwater production rates of 5.45 kg m-2 h-1 with deionized water and 3.9 kg m-2 h-1 with 3.5 wt% saline water. Outdoor testing of the full-scale 1 m² device yielded an average water production rate of 3.5 L m-2 h-1 (32 L m-2 day-1) and an evaporation efficiency of 345%. These results confirm that the proposed SMIE design maintains high performance at increased scales and under realistic environmental conditions. A techno-economic analysis further identifies the critical role of reducing material costs, particularly the photothermal absorber and porous membrane, to enhance economic feasibility. The work provides a scalable approach to solar-driven desalination, relevant for future modular deployment in distributed and off-grid water purification applications.