 Active atmospheric water collectors have been in use since the commercialisation of mechanical refrigeration . Essentially , all that is required is to cool a heat exchanger below the dew point , and water will be produced . Such water production may take place as a by @-@ product , possibly unwanted , of dehumidification . The air conditioning system of the Burj Khalifa in Dubai , for example , produces an estimated 15 million US gallons ( 57 @,@ 000 m3 ) of water each year that is used for irrigating the tower 's landscape plantings . 
