Enhanced solar evaporation using a photo-thermal umbrella for wastewater management

Abstract

Rising water demands and depleting freshwater resources have brought desalination and wastewater treatment technologies to the forefront. For sustainable water management, there is a global push towards Zero Liquid Discharge (ZLD) with the goal to maximize water recovery for reuse, and to produce solid waste that lowers the environmental impact of wastewater disposal. Evaporation ponds harvest solar energy as heat for ZLD, but require large land areas due to low evaporation rates. Here, we demonstrate a passive and non-contact approach to enhance evaporation by more than 100% using a photo-thermal umbrella. By converting sunlight into only mid-infrared radiation where water is strongly absorbing, efficient utilization of solar energy and heat localization at the water's surface through radiative coupling are achieved. The device's non-contact nature makes it uniquely suited to treat a wide range of wastewater, and the use of commercially available materials enables a potentially low cost and scalable technology for the sustainable disposal of wastewater, with the added benefit of salt recovery.

Solar passive distiller with high productivity and Marangoni effect-driven salt rejection

“…accessible to more people), robust, efficient and stand-alone (where no moving parts are present) desalination technologies able to operate even in emergency conditions have been recently designed and studied in literature. [5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21] The attention has been mainly focused on the study and design of new nano-structured materials and smart structures able to improve the solar-to-vapour conversion and the energy management. 13,[22][23][24][25][26][27][28][29] In 2018 some of the authors proposed a solar passive and multistage distiller 5 able to achieve performance beyond the thermodynamic limit of a single stage device, by recovering the latent heat of condensation.…”

Passive, high-efficiency thermally-localized solar desalination

“…To further optimize water transport, directional water pathways have also been investigated in natural wood, 49 anodic aluminum oxide (AAO), 29 and three-dimensional structures. [60][61][62] A fundamentally different front-side design is the contactless configuration, 63,64 where a solar absorber converts sunlight into infrared (IR) thermal radiation. As water is a strong IR absorber, with a penetration depth ~ 10 m in IR, most of the thermal radiation is absorbed within a thin water layer -enabling interfacial heating.…”

A Passive High-Temperature High-Pressure Solar Steam Generator for Medical Sterilization

“…Leveraging interfacial solar heat localization, improved thermal design, and enthalpy recycling, substantially higher solar-to-vapor conversion efficiencies have been reported. [12][13][14][15][16][17][18] However, these high-efficiency systems typically operate at relatively low temperatures (<50 C), which are insufficient for medical sterilization. Although high-temperature solar steam generation has been demonstrated in recent studies, their solar-to-steam conversion efficiency is limited (z 20%) due to higher heat losses at elevated temperatures (>100 C).…”