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 follows3: 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 100oC. 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 reconcentrated5 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 system 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 intend to develop a demonstration 15 .

　　詞匯：

　　autonomous adj.獨(dú)立的 thermal adj.熱的 permeate v.遍布 photovoltaic adj.光電的 hygroscopic n.吸濕的

　　infrastructure n.基礎(chǔ)設(shè)施

　　brine n.鹽水 interplay n.相互作用 saline adj.含鹽的

　　注釋：

　　1. Negev desert：內(nèi)蓋夫沙漠(位于以色列南部的沙漠地區(qū)，占以色列國土面積一半以上)。

　　2. Isreal：以色列 3. as follows：如下

　　4. in which a vacuum prevails：水箱里是真空狀態(tài)。Which 指代的是前半句的 tank。 Prevail 意為“占上風(fēng)”。

　　5. reconcentrated：重新濃縮的。