Compact back-side solar still for efficient vapor condensation via evaporative and wetted Janus cooling

초록

Water scarcity poses a critical global challenge, especially in remote and arid regions where large-scale desalination infrastructure is impractical. Interfacial solar steam generation (ISSG) offers sustainable freshwater production but faces limitations due to inefficient condensation and low freshwater recovery. This study proposes a compact back-side solar still (CBSS) integrating a photothermal evaporator and an optimized condenser to enhance desalination efficiency. The evaporator comprises reduced graphene oxide (rGO) embedded in melamine foam (MF), forming an rGO@MF composite, with a transparent polydimethylsiloxane (PDMS) cover to minimize vapor leakage. The condenser has a rectangular, cup-shaped copper structure externally wrapped with a chemically modified Janus fabric for efficient water transport and evaporative cooling. Cu(OH)2 nanoflowers stacked on the condenser's inner surface further boost condensation performance. Under 1 sun illumination, the rGO@MF evaporator achieved an evaporation rate of 1.4 kg m- 2 h- 1, while the PDMS-coated version maintained approximately 1.0 kg m- 2 h- 1. The CBSS successfully recovered 29 % of evaporated vapor, demonstrating a scalable, cost-effective approach for decentralized desalination. The proposed CBSS could be fabricated in a more affordable manner compared to existing desalination technologies, highlighting its potential as a portable and economically viable desalination solution. This study provides insights on effective water transport, thermal management, and condensation in back-side solar still systems, contributing to advances in sustainable seawater desalination for water-deficient regions.

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