 Another type of atmospheric water collector makes use of desiccants which adsorb atmospheric water at ambient temperature , this makes it possible to extract moisture even when the relative humidity is as low as 14 percent . Systems of this sort have proved to be very useful as emergency supplies of safe drinking water . For regeneration , the desiccant needs to be heated . In some designs regeneration energy is supplied by the sun ; air is ventilated at night over a bed of desiccants that adsorb the water vapour . During the day , the premises are closed , the greenhouse effect increases the temperature , and , as in solar desalination pools , the water vapour is partially <unk> , condenses on a cold part and is collected . 
