Fresh water production from/by atmospheric air for arid regions, using solar energy: Review

Abstract

Shortage of drinking water is chronic, severe, and wide-spread in the regions of Northern Africa, Middle East, and Central and Southern Asia. Conventional processes like MSF and RO require large amounts of energy in the form of thermal energy (for MSF) or electric power (for RO). Most desalination plants using these technologies are fossil-fuel driven. This results in a large carbon footprint for the desalination plant, and sensitivity to the price and availability of oil. Decentralized water production is important for regions which have neither the infrastructure nor the economic resources to run MSF or RO plants and which are sufficiently distant from large scale production facilities that pipeline distribution is prohibitive. Many such regions are found in the developing world in regions of high incidence of solar radiation. Accordingly, the problem of providing arid areas with fresh water can be solved by extracting water from Atmospheric air. The Atmospheric air is considered a huge and renewable source of fresh water. The atmosphere contains about 12,900 km3 of fresh water, whereas liquid water resources of inhabited lands is about 12,500 km3. In this paper, atmospheric water vapor processing (AWVP) technology is reviewed. These processors are machines which extract water molecules from the atmosphere, ultimately causing a phase change from vapor to liquid. Three classes of machines have been proposed. These classes are either cool a surface below the dew point of the ambient air, concentrate water vapor through use of solid or liquid desiccants, or induce and control convection in a tower structure. The review is extended to cover different humidification and dehumidification (H-DH) techniques in which air is used as a medium to carry water in the form of vapor. The study concentrates on the extracting potable water from air especially with respect to the remote/rural arid places. Finally, different technological processes to extract water from the ambient air using solar energy as a power source are focused with discussing their strengths and limitations. © 2012 Elsevier Ltd.