Not a plant to be seen, the desert
ground is too dry. But the air contains water, and research scientists have
found a {{U}} {{U}} 1 {{/U}} {{/U}}of obtaining drinking water
from air humidity. The system is based completely on renewable energy and is
therefore autonomous. Cracks permeate the dried-out desert
ground and the landscape bears testimony to the lack of water. But even here,
where there are no lakes, rivers or groundwater, considerable quantities of
water are stored in the air. In the Negev desert in Israel, for example, annual
average relative air humidity is 64 percent-in every cubic meter of air there
are 11.5 milliliters of water. German research scientists have
found a way of converting this air humidity autonomously into drinkable water.
"The process we have developed is based exclusively on renewable energy sources
{{U}} {{U}} 2 {{/U}} {{/U}}thermal solar collectors and
photovoltaic ceils, {{U}} {{U}} 3 {{/U}} {{/U}}makes this
method completely energy-autonomous. It will {{U}} {{U}} 4
{{/U}} {{/U}}function in regions where there is no electrical infrastructure."
says Siegfried Egner, head of the research team. The principle of the {{U}}
{{U}} 5 {{/U}} {{/U}}is as follows: hygroscopic brine-saline
solution which absorbs moistureruns down a tower-shaped unit and absorbs water
from the air. It is then sucked {{U}} {{U}} 6 {{/U}} {{/U}}a
tank a few meters off the ground in which a vacuum prevails. Energy from solar
collectors {{U}} {{U}} 7 {{/U}} {{/U}}up the brine, which his
diluted by the water it has {{U}} {{U}} 8 {{/U}}
{{/U}}. Because of the vacuum, the boiling point of the liquid is
lower than it would be under {{U}} {{U}} 9 {{/U}}
{{/U}}atmospheric pressure. This effect is known from the mountains: as the
atmospheric pressure there is lower than in the valley, water boils at
temperatures distinctly below 100℃. The evaporated, non-saline water is
condensed and runs down through a completely filled tube in a controlled manner.
The gravity of this water column {{U}} {{U}} 10 {{/U}}
{{/U}}produces the vacuum and so a vacuum pump is not needed. The reconcentrated
brine {{U}} {{U}} 11 {{/U}} {{/U}}down the tower surface again
to absorb moisture from the air. "The concept is suitable for
various water {{U}} {{U}} 12 {{/U}} {{/U}}. Single-person units
and plants supplying water to entire hotels are conceivable, " says Egner.
Prototypes have been built for {{U}} {{U}} 13 {{/U}}
{{/U}}system components-air moisture absorption and vacuum evaporation-and the
research scientists have already {{U}} {{U}} 14 {{/U}}
{{/U}}their interplay on a laboratory scale. In a further {{U}} {{U}}
15 {{/U}} {{/U}}the researchers intend to develop a demonstration
facility.