Design of solar evaporator with well-aligned and multi-scale fluid channels based on convection tuning for stable and efficient brine desalination

Abstract

Desalination based on interfacial solar evaporation is emerging as one of the most promising water treatment technologies. However, the inevitable salt-accumulation at the evaporation interface is still a major challenge facing the long-term application. Herein, a salt-resistant evaporator (SRE) is proposed under the guidance of computational fluid dynamics simulation. Theoretical simulation clearly suggests that well-aligned multiscale channels represent the optimal geometry of the photothermal evaporator, as they contribute high hydraulic conductivity and diffusion flux and derivate strong convection. During solar evaporation, these channels provide the pathways for the rapid transfer of bulk brine, which excretes the salt and self-regenerates the evaporator in real time. Rattan naturally features regular multiscale channels. Consequently, this sustainable biomass material is employed to carbonize and assemble the desired SRE. This rattan-based evaporator exhibits a high evaporation rate (1.47 kg m−2 h−1) and efficiency (91 %) in a highly concentrated brine (20 wt% NaCl) under 1 sun. Owing to the convection effect tuning, its performance is kept constant during a continuous week operation, indicative of the long-term stability of the system. Moreover, convective effect tuning can be generalized to other photothermal materials, which opens up the possibilities for large-scale application of solar desalination of high salinity brine.