For those who are not familiar with fog harvesting – the scope entails a nature-inspired technique (influenced by fog beetles) by which moisture can be trapped from foggy mists. This is generally achieved by expansive nets that help in trapping the vapor, and then storing the resultant water droplets (that account for a substantial volume) in a connected container. But the predicament related to most of these extending polyolefin mesh nets is that their pores are too big for adequate ‘catching’ of the water, since a high volume of the vapor passes through the perforated plastic material.

So, one of the solutions pertains to the reduction of these pore circumferences; and that is exactly what a MIT research team has achieved – thus improving the effectiveness of fog harvesting systems. When translated to figures, the newly contrived net mechanism was found to have a whopping five times more water collecting capacity than conventional systems. This equates to around 10 percent of the total water content in a mild fog, as opposed to the mere 2 percent capacity of the regular polyolefin mesh nets used for the purpose.

According to MIT’s press release –

The researchers found that controlling the size and structure of the mesh and the physical and chemical composition of this coating was essential to increasing the fog-collecting efficiency. Detailed calculations and laboratory tests indicate that the best performance comes from a mesh made of stainless-steel filaments about three or four times the thickness of a human hair, and with a spacing of about twice that between fibers. In addition, the mesh is dip-coated, using a solution that decreases a characteristic called contact-angle hysteresis. This allows small droplets to more easily slide down into the collecting gutter as soon as they form, before the wind blows them off the surface and back into the fog stream.

When seen from the perspective of practicality, this technology has the potential to do wonders for semi-arid areas that are not prone to rainfall but are affected by fogs. One such location pertains to a specific region in Chile, situated north of the capital city of Santiago. Regularly visited by camanchaca, a strong coastal fog borne by breezy winds, the area is perfectly suited to MIT’s contrivance. In fact, many conventional fog harvesting systems are already in usage along the edges of Chile’s Atacama Desert, and they make use of the localized camanchaca. But their yield only results in around 2-3 liters of drinking water per day for each square meter of mesh.

However in practical terms, Chilean experts estimate that around 4 percent of the fog’s water content capturing is feasible for the population in the zone (equating to 4-6 liters of water). To that end, MIT’s system does far better – with the researchers estimating that their fog harvesting mechanism can account for 12 liters of water per day, during certain times of the year. The good news is – these systems are already under trial for a year-long experiment. This is complemented by the fact that the zero-energy contrivances are relatively inexpensive to make and require no operating resources except for occasional maintenance (like removal of insects from the mesh).

The findings were published online in the journal Langmuir.

Source / Video: MIT NewsOffice

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