Enhancing Water Harvesting through the Cascading Effect

Abstract

Harvesting water from high humidity conditions is an attractive strategy toward strengthening water security due to its cost-effective and zero-energy mechanism. To facilitate this process, bio-inspired microstructures with heightened water accumulating ability are typically affixed onto atmospheric water harvesters. However, because of this surface morphology type harvester design, there is an inherent partition of regions with different water accumulating abilities: the active water harvesting region (AWHR) and passive water harvesting region (PWHR). Most of the water harvested by such water harvesters is usually attributed to the AWHR, while a large amount of uncollected water is present in the PWHR as numerous small water droplets that are prone to re-evaporation. This lack of PWHR utilization may be considered as the Achilles’ heel toward optimal water harvesting. Hence, in this work, a cascading effect was proposed with a microstructure design to induce water harvesting from both AWHR and PWHR. The “clearing” of PWHR columns was demonstrated via a cascading effect, contributing to ca. 3 times more water harvested as compared to the unmodified water harvester. The successful demonstration of this cascading effect highlights the necessity of considering PWHR in the future water harvester designs so as to achieve efficient water harvesting.

Fiber-Based Composite Meshes with Controlled Mechanical and Wetting Properties for Water Harvesting

“…However, this is only one possibility. There are research studies in which different types of strips, wires, harps or mechanisms to mimic nature have been applied. , Additionally the microstructure effect on the coalescence of water droplets responsible for improving water harvesting from poly­(dimethylsiloxane) (PDMS) films have also been investigated . Water condensation performance according to the hierarchical roughness on metallic coatings was also analyzed in terms of water drops adhesion and nonwetting effects .…”

Tailoring silicon for dew water harvesting panels

“…From the perspective of practical applications in future, the utilization of proposed metasurface in combination either with grooves (Bintein et al, 2019) or with surfaces holding cascading effect (Ang et al, 2019) may lead to optimum water collection performance and get closer to the ultimate limit of ''zero pinned water''. Considering the remarkable optical emissivities of Black Silicon extending to the infrared in atmospheric window waveband (Sarkar et al, 2019), a 1 m 2 such metasurface panel can predictably provide more than 1 L of water per night in a passive manner with zero energy consumption, which is quite considerable for whether drinking or irrigation demands, and is significant to the regions with freshwater scarcity or water pollution issues.…”

Directional Droplet Transport on Functional Surfaces with Superwettabilities

“…[ 5b,43 ] In addition to these anisotropic surfaces, modified SLIPS was also introduced to water collection. [ 102 ] The precious capability of SLIPS was its lossless droplets transport, which guaranteed the efficiency of water collection. Although SLIPS qualified the requirement that directional droplet transport, it is difficult for liquid nucleation aggregating into droplets on the same surface.…”