15 December 2009

A Cold Drip: Emergency Water from the Air

Posted by Michael McFadden

Flash back to a sultry New Orleans evening a few years ago. I’m sitting on a porch with a bottle of beer sweating into my hands. The chug-chugging air conditioner mounted precariously in a second story window drips stale water into my hair.

There’s water in the air all right. And as shown at GC21A: Water Supply Management and Security I posters, we already know how to get it into a form we can drink. One way is cloud seeding: shooting tiny particles into the air that water vapor can stick to and form droplets heavy enough to fall out of the sky.

Cloud seeding sounds like bit of snake oil salesman myth, but it’s been practiced in the state of California in some form or another since 1948. It was also used to keep the skies clear for the opening ceremony of the 2008 Beijing Olympics. It’s not in widespread practice because there isn’t much scientific evidence that cloud seeding actually works well enough to be useful.

Another method to get water from air, one that we know works, is to use modified air conditioners to condense airborne moisture. It’s not a new idea, but a poster describes company in Florida called Aquaventus which received money from the Naval Research Center to develop a more efficient, safer way to do so. The portable version of the device they developed is about the size of a cooler for a tailgating party. It weighs 140 lbs, half as much as New Orleans Saints defensive end Will Smith.

The Aquaventure device can produce up to 80 liters of water per day. But any thermodynamics professor will tell you that artificial cooling is inherently energy-intensive. The amount of water the device produces and the energy it takes to do so depends heavily on the temperature and humidity of the air. It’s most efficient in muggy climates, such as those in Florida and New Orleans.

The device needs electricity and chemical coolants to run, and the water that’s produced has to be cleaned to make it safe to drink, so it’s not practical for all situations. But it could be useful in a disaster situations like the Katrina aftermath, when downed water pipes and disabled treatment facilities make clean drinking water hard to come by.

–Sandra M. Chung, UCSC Science Communication Graduate Student