For the last decade, the U.S. Army has invested millions of dollars in research to develop a practical device that could extract water from the air. In the last five years several of these devices were developed, but none has yet proved suitable for wide use in a combat zone. The latest one can reliably produce 2,000 liters (500 gallons) a day from one 20 foot shipping container size device. The down side is that this system uses a liter of fuel for each five liters of water produced. In addition, even with sound-proofing, this system is very noisy. But this device means you don’t have to run as many truck convoys (carrying water) through hostile territory.
An older system uses salts, and can produce water for less than 30 cents a liter. This system also can fit into a standard twenty foot long shipping container and turns out 600 gallons a day. But the developer has run into a number of technical problems that kept the system from wide use by the military. Most of these devices need at least 20 percent humidity to function, and all but the most arid deserts can supply that.