Optimal Design of Permeable Fiber Network Structures for Fog Harvesting

Abstract

Fog represents a large, untapped source of potable water, especially in arid climates. Numerous plants and animals use textural as well as chemical features on their surfaces to harvest this precious resource. In this work, we investigate the influence of surface wettability characteristics, length scale, and weave density on the fog harvesting capability of woven meshes. We develop a combined hydrodynamic and surface wettability model to predict the overall fog collection efficiency of the meshes and cast the findings in the form of a design chart.Two limiting surface wettability constraints govern re-entrainment of collected droplets and clogging of mesh openings. Appropriate tuning of the wetting characteristics of the surfaces, reducing the wire radii, and optimizing the wire spacing all lead to more efficient fog collection.We use a family of coated meshes with a directed stream of fog droplets to simulate a natural foggy environment and demonstrate a five-fold enhancement in the fog-collecting efficiency of a conventional polyolefin mesh. The design rules developed in this work can be applied to select a mesh surface with optimal topography and wetting characteristics to harvest enhanced water fluxes over a wide range of natural convected fog environments.

Testing Water Yield, Efficiency of Different Meshes and Water Quality with a Novel Fog Collector for High Wind Speeds

“…However, Feld et al (2016) also reported substantially higher (62% to 178%) yield of Enkamat meshes as compared to Raschel. They also pointed out that based on hydrodynamic theory (Rivera, 2011;Park et al, 2013), their smaller fiber radius and higher mesh fiber spacing is consistent with greater collection efficiencies. The comparably lower Raschel yields in our study may be partly explained by the rigid supporting grid to which the meshes are connected at regular intervals.…”

“…While not depending on the position of a mesh inside the linear fog collector, the relative yield and ranking of nets varied considerably from event to event, possibly depending on the wind speed and fog parameters (cf. Park et al, 2013;Fernandez et al, 2016). Overall, highest yields in our study were obtained by the meshes Hail dual set, Spacer fabric and Hail net.…”

“…Hydrodynamic models can be used to derive efficiency ratings for different processes involved in fog collection (e.g., fog interception efficiency, aerodynamic collection efficiency, capture efficiency (Rivera, 2011)) and may also lead to improved materials or arrangements. The study of Park et al (2013) is an example for optimizing meshes at the laboratory scale with the help of a combined hydrodynamic and surface wettability model. Field tests of different materials are rather scarce and were performed by Shanyengana et al (2003), Abdul-Wahab et al (2007b), Fernandez et al (2016) and Feld et al (2016).…”

Symbiotic offshore energy harvesting and storage systems

“…Note the average speed of the Gulf Stream is about 1.8 m/s with a top speed near the surface of up to 2.5 m/s 1 . Most offshore wind farms will have probably not be located in such strong currents, but if they are, it could make sense to mount underwater turbines onto the structure that supports the wind turbine as shown in Figure 1.…”

“…However, a large flat panel can be a great water-gathering device from rainfall or even fog. In the case of the latter its not just gathering water from fog condensing on the panels but fog condensing on other structures placed among the solar field [1]. Collected water can be stored and used sparingly over the course of many months for cleaning the cells.…”