Fog Harvesting (Stenocara Gracilipes)

No waterno lifeNo blue, no green.” – Sylvia Earle

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Absence of water is the major problem when talking of life in the desert. Therefore a need for obtaining water in unconventional ways exists. Fog harvesting is one of possible solutions. But can it work? And if so, how?

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A great example of natural fog harvesting is the Namibian beetle. It has a surface that consists of hydrophilic bumps and hydrophobic valleys. Tiny water droplets from the fog settle on the top of the bumps. When more droplets are attracted to the bumps, bigger drops of water form. When the latter are too big to stay on the bump, they fall down to the hydrophobic wax coated valley and rolls down to the beetle’s mouth. Research company QinetiQ has experimented with materials of different wetting qualities. The experiments have shown that a surface of little glass spheres surrounded by wax can have the same effect on fog harvesting as beetle’s skin. Pictures of the beetle show that the bumps do not form a strict grid, but rather a messy pattern that is symmetrical about the central axis of the body and tends to form circles.

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The beetle’s surface for sure is interesting but so is the body itself. The body has a figure of a drop which is an optimal shape for allowing the wind to smoothly flow around the surface (shape schemes adapted from the Source). Body’s convexity is another interesting feature that allows the water to run to any direction. Yet the beetle reasonably lifts its bottom, usually by 23°, to make most of the water run down to the mouth.

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Last spring, in March 2015, the biggest for harvesting project in North Africa became operational. 40 fog harvesting mesh panels were put at the top of Boutmezguida mountain which resulted in providing clean water for about 400 local people. The precedent shows that fog harvesting in Morocco is not only plausible but rather effective.

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The main reasons for such a success in Boutmezguida are the natural onshore breezes as well as valley breezes. Onshore breeze forms during the daytime when the ground heats and hot air rises up. Cold air from the ocean is then pressured to replace the hot air. Valley breeze forms similarly. Once the ground heats, hot air rises up, where it often condenses into a cloud.

References:

 1. Dew condensation on desert beetle skin

2. Brianna Frandrup. Namibian Desert Beetle

3. Meteorological Patterns and fog water in Morocco and the Canary Islands

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