Obtaining Drinking Water from Air Humidity
Not a plant to be seen, the desert ground is too 1 . But the air contains water, and research scientists have found a 2 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 desert1 in Israel2, 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 such as thermal 3 collectors and photovoltaic cells, which makes this method completely energy-autonomous. It will therefore function in regions 4 there is no electrical infrastructure, says Siegfried Egner, head of the research team. The principle of the 5 is as follows: hygroscopic brine saline solution which absorbs moisture runs down a tower-shaped unit and absorbs water from the air. It is then sucked into a tank a few meters 6 the ground in which a vacuum prevails4. Energy from solar collectors heats up the brine,, which is diluted by the water it has 7 .
Because of the vacuum, the boiling point of the liquid is 8 than it would be under normal atmospheric pressure. This effect is known from the mountains: as the atmospheric pressure 9 is lower than in the valley, water boils at temperatures 10 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 continuously produces the vacuum and so a vacuum pump is not needed. The reconcentrated brine runs down the tower surface 11 to absorb moisture from the air.
The concept is suitable for various water 12 Single-person units and plants 13 water to entire hotels are conceivable, says Egner. Prototypes have been built for both sys-tem components- air moisture absorption and vacuum evaporation-and the research scientists have already 14 their interplay on a laboratory scale. In a further step the researchers in-tend to develop a demonstration 15 .
练习：
1. A dry B dirty C sandy D clean
2. A path B way C channel D road
3. A oil B wood C coal D solar
4. A when B what . C where D who
5. A promise B progress C prospect D process
6. A of B with C off D below
7. A absorbed B attracted C allowed D affected
8. A wetter B hotter C lighter D lower
9. A close B there C beyond D nearby
10. A gradually B distinctly C necessarily D possibly
11. A again B too C either, D more
12. A users B owners C providers D producers
13. A using B obtaining C supplying D cleaning
14. A repaired B sold C copied D tested
15. A tank B method C facility D tool
答案：ABDCD CADBB AACDC