Evaporation rate far beyond the input solar energy limit enabled by introducing convective flow

Solar-driven interfacial evaporation for desalination is regarded as one of the most promising technologies to relieve global freshwater scarcity due to its high efficiency, sustainability and low cost. However, the evaporation rate, as one of the decisive factors of the throughput of evaporative water, has been severely restricted due to heat loss and insufficient vapor diffusion in the conventional evaporators. Herein, we demonstrate that a carbon nanotubes (CNTs) and airlaid paper-based 3D wavy evaporator not only facilitates the double-surface evaporation, but also can effectively diffuse the suspended vapor assisted by the convective flow, so as to reverse the heat loss and continuously harvest additional energy for efficient evaporation. An evaporation rate as high as 5.55 kg m(-2)h(-1) is achieved under one sun illumination coupled with convective flow of 5 m s(-1), well beyond 278% of the input solar energy limit, presuming 100% solar-to-vapor energy conversion. More importantly, the 3D wavy evaporator can consistently evaporate for 24 h in the natural environment, with the outdoor evaporation up to 53.72 kg m(-2) and no salt deposition. Furthermore, theoretical simulations of convective flow velocity and distribution, as well as relative humidity distribution, are remarkably compatible with experimental results. The realization of such a high evaporation rate provides a new inspiration for designing the around-the-clock and high-throughput evaporation system that can be practically applied.

Automated summary

The solar-driven 3D wavy evaporator, combining carbon nanotubes and airlaid paper, achieves high evaporation rate and can continuously evaporate for 24 hours in natural environment without salt deposition.