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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