Creating Water from Thin Air

Iphtashu Fitz writes "In order to provide the U.S. Military with water in places like Iraq, the Defense Advanced Research Projects Agency gave millions of dollars in research funding to companies like LexCarb and Sciperio to try to extract water from the air. Amazingly, a company that DARPA didn't fund, Aqua Sciences, beat them all to the punch by developing a machine that can extract up to 600 gallons of water a day from thin air even in locations like arid deserts. The 20 foot machine does this without using or producing toxic materials or byproducts. The CEO of Aqua Sciences declined to elaborate on how the machine works, but said it is based on the natural process by which salt absorbs water."

Comments

They did this in ancient times in the middle east

[spun]

I recall reading an article about ancient rock mounds, where the rocks were loosely lumped with plenty of space in between. Air filtered through and encountered the cool rock faces of the interior of the mound. Water condensed on the interior rock faces and trickled out the bottom. I'll see if I can find a link.

hm

[inKubus]

Sounds like they probably use a hydroscopic compound such as calcium chloride and then you some type of ion replacement to recover the water (precipitate calcium metal and some other non-soluable salt, such as Fe(III)Cl.

Re:hm

[c4miles]

The word you're looking for is Hygroscopic. From the article you linked to:

The similar sounding but unrelated word hydroscopic is sometimes used in error for hygroscopic. A hydroscope is an optical device used for making observations deep under water.

A related word, deliquescent, refers to substances so hygroscopic they will dissolve themselves using water absorbed from the air.

Re:hm

[Big Bob the Finder]

Calcium bromide (CaBr2) is slightly more hygroscopic, absorbing moisture down to 16% RH (Handbook of Chemistry and Physics); it's also a hexahydrate- it sponges up a lot of moisture. Right below that is lithium chloride, which continues to absorb down to 11% RH.

Most likely it's a system where prilled or powdered salt is tumbled through dry air to absorb moisture; it's then roasted to release the moisture, captured under reduced pressure to reduce the amount of energy required, and returned to its anhydrous state. It'll be clumpy and chunky, so it'll have to be re-ground into a fine powder before reuse.

The $.30 a gallon is probably largely from the amount required in the removal of the water from the hydrate; distillation of water runs ~$.25 a gallon (assuming no recycling of the waste heat from condensation to pre-heat water going into the boiler) at $.10/kwh. Using gasoline or diesel would be considerably more expensive- thus the reduced pressure.

Distilled water from air- not too shabby. I've thought about trying the same here in the desert (where it's routinely ~10% RH in Phoenix), but it's just not worth it.

Linky link

[spun]

Here we are, as promised. About a third of the way down the page. Ignore the Reichian weirdness, the wells were built near the ancient Byzantine city of Feodosiya. There were 13 large conical tumuli of stones, each about 10,000 feet square and 30-40 feet tall, on hilltops. Russian engineer Friedrich Zibold calculated they would each produce more than 500 gallons daily. These theories have been disputed by some archeologists (who don't seem to like it when engineers discover cool archeological stuff and make up theories about it) but the mounds do all have numerous terra-cotta pipes around the base, presumeably to collect the run off

I know a SERE instructor...

[rampant mac]

I hang out with a SERE instructor and do a lot of camping / hiking / ORV riding where I'm sometimes far away from reliable potable water. He gave me some pretty cool information about how to obtain water from your surroundings:

1) Water from plants is always drinkable. I'm talking about water from the root system, not some stagnant water you could slurp out of a recess between branches. The easiest way is to take a large trash bag, grab a cluster of branches and put the bag around them (make sure the open end of the trash bag is tightly sealed to prevent air from going into the enclosed bunch). It forces the tree to "sweat" water from its root system. After about 24 hours you can slit the bottom of the bag and drain it into a nalgene bottle. You can only do one group of branches per 24 hour period, so you need to use different trees to gather water. I tried it out when I was in Eastern Oregon (which, for all intents and purposes, is an inland desert) and averaged about 1 liter of water per 24 hours. I had 6 trash bags that I normally have in my hiking ruck, so I could feasibly harvest 6 liters per day if I was SOL somewhere.

2) A cluster of birch trees usually means there's water underground.

3) Any multi-celled berry (ie: raspberry) is edible.

Anyway, I thought it was pretty cool shit, and informative. :)

Solar Still

[David Off]

A solar still produces water in the desert and uses no external energy source other than sunlight (there is plent of that in the desert)

Re:And remember kids...

[erice]

It's only an issue if water is permanently removed from the environment, which it generally won't be. Water was in the air and in a few hours, it is back again.

This is actually much better than trucking in water from afar or pulling it out of deep wells. In that case, you are altering the environment. Water not previously in the environment is being added.