Three-dimensional open architecture enabling salt-rejection solar evaporators with boosted water production efficiency

Abstract

Direct solar desalination exhibits considerable potential for alleviating the global freshwater crisis. However, the prevention of salt accumulation while maintaining high water production remains an important challenge that limits its practical applications because the methods currently employed for achieving rapid salt backflow usually result in considerable heat loss. Herein, we fabricate a solar evaporator featuring vertically aligned mass transfer bridges for water transport and salt backflow. The 3D open architecture constructed using mass transfer bridges enables the evaporator to efficiently utilize the conductive heat that would otherwise be lost, significantly improving the water evaporation efficiency without compromising on salt rejection. The fabricated evaporator can treat salt water with more than 10% salinity. Moreover, it can continuously and steadily work in a real environment under natural sunlight with a practical solar-to-water collection efficiency of >40%. Using the discharged water from reverse osmosis plants and sea water from the Red Sea, the evaporator demonstrates a daily freshwater generation rate of ~5 L/m2, which is sufficient to satisfy individual drinking water requirements. With strong salt rejection, high energy efficiency, and simple scalability, the 3D evaporator has considerable promise for freshwater supply for water-stressed and off-grid communities.

Ion‐Transfer Engineering via Janus Hydrogels Enables Ultrahigh Performance and Salt‐Resistant Solar Desalination

“…By rationally utilizing the heat of the Janus‐IS hydrogel evaporator, its evaporation rate of 6.86 kg m −2 h −1 in 15 wt% reaches a record‐high value among the reported evaporators (Figure 3f). [ 20–35 ]…”

“…By rationally utilizing the heat of the Janus-IS hydrogel evaporator, its evaporation rate of 6.86 kg m −2 h −1 in 15 wt% reaches a record-high value among the reported evaporators (Figure 3f). [20][21][22][23][24][25][26][27][28][29][30][31][32][33][34][35] Salt-resistant performance was tested by a continuous longterm operation in 15 wt% brine (Figure 3g). Under one-sun irradiation, the stable evaporation rate of 2.17 g h −1 (6.70 kg m −2 h −1 ) over a six-hour running indicates that the evaporator is not damaged by salt crystals.…”

Recent advances in interfacial solar vapor generation: clean water production and beyond

“…12(d). 261 The distinct evaporator contains a plethora of vertically aligned mass transfer bridges, through which excessive salt can flow back via diffusion and convection. Moreover, the vertical bridges separate light-absorbing surface and bulk water, forming a 3D open space to confine conductive heat in the upper position and facilitate additional water evaporation.…”

Polyoxometalates-Modulated Hydrophilic-Hydrophobic Composite Interfacial Material for Efficient Solar Water Evaporation and Salt Harvesting in High Salinity Brine

“…[7][8][9][10][11] Owing to the ultra-low diffusivity of salt in water (10 -9 m 2 s -1 , and the diffusivity of water vapor in air is about 10 -5 m 2 s -1 ), [12] the salt inevitably crystallizes and precipitates on the surface of the photothermal material as the water vapor continues to escape rapidly. [13,14] This problem severely hinders the light absorption, water transport and water vapor escape in the continuous water evaporation process, significantly degrading the performance of SVG and terminating the operation of the device. Thus, the development of photothermal water evaporation materials with both efficient water evaporation performance and self-cleaning/anti-salt fouling properties is a key issue to drive SVG from the laboratory to large-scale practical applications.…”