Friday, February 1, 2013

Fog Cloth Waters Desert





This is important. It gives us a cheap and easy way to precipitate humidity at night and then drive it directly into a downward sloping collector tube after sunrise to feed a buried porous earthen pot to hold the water for a day or more. The canvas does not need to be tied against the wind either which implies scant maintenance.

As I have already posted, watering the desert is about extending the zone of one hundred percent humidity inland step by step and that entails supporting and protecting the full hydrological cycle. It may need to be established at tidewater with mangroves but inland it consists of the Eden cycle in which some water can be added artificially from the atmosphere in order to support the respiration of the adjacent plants. These will be obviously trees of some sort.

This technology fits the model rather well and can also be dirt cheap and easily maintained by the stakeholder.

The key has always been to get enough water from the atmosphere at night and to recover it in the morning to feed the adjacent tree. The difficulty was not doing it as doing it cheap enough to facilitate implementation. Obviously a hanging flag from a horizontal spar shifting in the wind or some other clever geometric shape will grab the moisture. That moisture should wick down into a collection tube easily enough also when the sun comes out.

I am thinking the Sahara Desert of course, but the coastal Mediterranean is superb for all this as it restores the original ancient cover enjoyed here and ample manpower exists to cause it all to happen fast.

Cotton with special coating collects water from fogs in desert

by Staff Writers

Eindhoven, Netherlands (SPX) Jan 23, 2013



Researchers at Eindhoven University of Technology (TU/e) together with researchers at the Hong Kong Polytechnic University (PolyU), have developed a special treatment for cotton fabric that allows the cotton to absorb exceptional amounts of water from misty air: 340 % of its own weight.

What makes this 'coated cotton' so interesting is that the cotton releases the collected water by itself, as it gets warmer. This property makes of the coated cotton materials a potential solution to provide water to the desert regions, for example for agricultural purposes. The results of this research will be published next month in the scientific journal Advanced Materials.

The researchers applied a coating of PNIPAAm, a polymer, to the cotton fabric. At lower temperatures, this cotton has a sponge-like structure at microscopic level.

Up to a temperature of 34C it is highly hydrophilic, in other words it absorbs water strongly. Through this property the cotton can absorb 340 % of its own weight of water from misty air - compared with only 18% without the PNIPAAm coating.

In contrast, once the temperature raises the material becomes hydrophobic or water-repellant, and above 34C the structure of the PNIPAAm-coated Beetles in desert areas can collect and drink water from fogs, by capturing water droplets on their bodies, which roll into their mouths.

Similarly, some spiders capture humidity on their silk network. This was the inspiration for this new coated-cotton material, which collects and releases water from misty environments simply as the temperature changes throughout the day.

This property implies that the material may potentially be suitable for providing water in deserts or mountain regions, where the air is often misty at night. According to TU/e researcher dr.

Catarina Esteves a further advantage is that the basic material - cotton fabric - is cheap and can be easily and locally produced. The polymer coating increases the cost slightly, but with the current conditions the amount required is only about 12%. In addition, the polymer used is not particularly costly.

Fine-mesh 'fog harvesting nets' are already being used in some mountains and dry coastal areas, but these use a different principle: they collect water from misty air, by droplets that gradually form on the nets and fall to the ground or a suitable recipient. But this system depends on a strong air flow, wind. The coated cotton developed the research team can also work without wind.

In addition, cotton fibers coated with this polymer can be laid directly where the water is needed, for example on cultivated soil. The researchers are also considering completely different applications such as camping tents that collect water at night, or sportswear that keeps perspiring athletes dry.

The research was led by professor John Xin at PolyU and dr. Catarina Esteves at TU/e. They now intend to investigate further how they can optimize the quality of the new material.

For example they hope to increase the amount of water absorbed by the coated-cotton. Moreover they also expect to be able to adjust the temperature at which the material changes from water-collecting to the water-releasing state, towards lower temperatures.

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