Snake oil, anyone?

http://www.futureofwater.net/cost_analyst.php

They show the power consumption to be the same as a standard cooler (it simply can't be true, unless you keep your office/home at 90% RH or something), but worse, the power use estimate is the same whether you enter 4 gallons per month or 400,000 gallons per month into their calculator.

(If I can truly get 400,000 gallons of water for $3 worth of power, I'm there! :-) )

You can't cheat the second law of thermodynamics- it WILL take more energy to extract water from air than simply chilling water. (And it will certainly take a lot more energy to extract 400,000gallons vs. 4.)

Read the fine print:

http://www.futureofwater.net/commercial_03.php

"Performance based on entering air conditions of 85F(29C) and 70% RH."

In other words to get that seemingly excellent 17gallons/kwh performance you have to be in a tropical swamp.  Operating indoors, at indoor temps, that level of humidity at would be the same as 100RH @ 77F (25C):

http://upload.wikimedia.org/wikipedia/en/0/05/PsychrometricChart-SeaLevel-SI.jpg

At those humidity levels you can literally squeegee the water off the walls & windows at 75F.

You can bet it's a heluva lot less efficient at typical 30-60% RH @ 68-72F types of indoor humidity/temperature levels (so abysmally low that they probably won't publish that data when trying to sell it as a water-generator.)  The less snake-oil advertisers of these products give estimates on the order of ~2kwh/gallon, (which is 0.5gal/kwh, not 17gal/kwh.)

The only way any of these could qualify for any type of "green" status would be the dessicant-wheel enhanced versions in applications where the primary use is either latent-load (dehumidification) or full-on air conditioning, since it uses the condensate as drinking water rather than simply disposing of it.  (The dessicant wheel raises the coefficient of performance sgnificantly in very high latent-load conditions such as 70%RH @ 85F).  The rest is marketing BS. 

What this ISN'T, is a green & cost effective way to get potable water.  The drier your outdoor air, the less efficient it is- don't take one of these into the desert without a cup & sheet of plastic as "Plan-B" unless you can fit a small nuke in your backpack.

Rio: If your outdoor dewpoints regularly get above 70F for several hours/days at a time there may be some rationale to this approach as an emergency water source, but not at all if the dewpoints rarely break 60F.  You can proably find weather history data to tell if it's worth considering for any particular site.  (There's a reason nobody uses PV to run compressor-based air conditioning... )  It'll never beat the system-performance of a solar still though (it's at least a full order of magnitude behind.)

I will be building an earthbag structure in Mexico. The land that we are buying has water on it but we are planning on using plastic pipes sunk in the ground to cool the air or warm it depending on the outside temperature. The difference in temperature creates condensation which gravity feeds into a recycled 250 gallon food grade tank, covered in Grancrete and sunk into the ground. We will then pump the water to use or have a gravity feed system depending on the layout of our build. This system produces as much as three cups a minute in high humidity areas using only fans to move the air and the power of the earth to cool it. The system uses cheap replaceable filters from home depot and is easily  cleaned with a coated wire, a rag, and some food grade hydrogen peroxide.  What do you guys think of this plan? I am happy to have found this forum as I will be building these eco houses in Mexico and I know Ill need advice from time to time:)

Waterbeatsrock, that sounds like a pipe dream. Sorry for the pun ;)

What is the average soil temperature where you plan to build and at what depth? How deep do you intend to bury these pipes? What is the average relative humidity where you are building? Many parts of Mexico are arid with little moisture in the air. What kind of pipe are you using (steel, aluminum, PVC, poly, etc.) and also how large in diameter and how many linear feet of pipe?

Here is a pdf http://geoheat.oit.edu/bulletin/bull27-4/art5.pdf that has a similar system (although without the condensation collector) that was built in Africa along with all their data. My system would be at three feet depth instead of 20 inches as the extra depth does help a little. It would use multiple pipes for each room and would also incorporate solar powered attic fans to draw air from the pipes and expel heat. the pipes would need to have a low point where the water would collect into the tank. The RH of the area is high enough as it would be near the pacific @ 75 to 85 we are looking at Baja California now. The rammed earth bags would incorporate free rice husks for their class 1 insulation and we would stucco the foam roof and recycled bag walls with Grancrete and fiberglass mesh for ease of construction. I couldn't find the soil temperature map I used when devising this system but from memory the area was Ideal for cooling air with a 20 to 30 degree temperature difference between air and ground temp.