The problem of providing arid areas with fresh water can be solved by the following methods:-
1)Transportation of water from other locations;
2) Desalination of saline water (ground and underground);
3) Extraction of water from atmospheric air. Transportation of water through these regions is usually very expensive, and desalination depends on the presence of saline water resources, which are usua
lly rare in arid regions. Atmospheric air, which contains about 14 000 km3 of water vapor , is a new and renewable water resource .The extraction of water from atmospheric air can be accomplished by absorbing water vapor from atmospheric air using a solid or a liquid desiccant, with subsequent recovery of the extracted water by heating the desiccant and condensing the evaporated water. System operation can be concluded in the three steps:-
1-At night, the bed carrying the strong desiccant is allowed to absorb water vapor from the air (glass cover open-operation of fans).
2-At morning, the evaporation and condensation happen simultaneously as shown in :
The black coated bed absorbs the incident solar radiation and consequently the bed temperature increases. As a result, the absorbed water evaporate. At this moment, evaporation of moisture from the bed with subsequent condensation on the glass surface occurs.
3-At the end of the day, the glass cover is opened and the bed is allowed to cool until the vapor pressure on its surface decreases to a value lower than that of the ambient air.
