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Water From Air
Shea Cockrum thinks that extracting water from air is the solution to the world's water shortage. Honestly, I'm not sure whether he's a nutcase, or if his theories could actually work. He claims that he was extracting one or two gallons of water an hour from an "air well" that he constructed in his backyard consisting of buried PVC pipe through which hot air was blown. One or two gallons of water an hour, if he was really getting this, isn't bad at all. And according to Cockrum, this was just the beginning. His new system is even better. Like I said, I have no idea if this could be done... though I do know that an incredible amount of dew collects in my yard every morning, which is the only reason I'm reluctant to dismiss his theory out of hand.
Free Energy
Posted by The Curator on Mon Oct 04, 2004


Well, water is H2O. Air has 20.9% oxygen, but only 0.000055% hydrogen. So, he must be getting this water from evaporated water in the atmosphere. This doesn't solve any water problems at all. It's quite easy to catch water vapor in the air.
Posted by ND  in  USA  on  Mon Oct 04, 2004  at  08:46 AM
It's quite feasible to extract water from the air - it's merely a matter of cooling the air until the relative humidity is 100% - cooling further causes dew to form. That's the way de-humidifiers work. Even air above deserts contains enough water to produce dew if it's cooled enough.
The question is how the process can be made cheap enough to make it viable - in other words how many Joules are needed to produce 1 litre of water? On the face of it, I guess that it's at least as efficient as de-salination but I suspect that it's difficult to operate on a large scale.
Posted by Lawrence Mayes  in  UK  on  Mon Oct 04, 2004  at  10:52 AM
There's already a well-developed method for extracting water from the air-- it's called rain, snow or sleet.
Posted by Big Gary C  in  Dallas, Texas  on  Mon Oct 04, 2004  at  11:55 AM
You can buy dehumidifier, which does the same thing. If you have 70-100% humidity, it will work great.
Unfortunately in a desert where water is wanted so much there is just few percent of relative humidity.
Posted by 1234  on  Mon Oct 04, 2004  at  12:46 PM
Most deserts are hot - that's why the RH is low - the RH alone doesn't tell you how much water is in the air; you need to know both temperature and RH.

It is possible for there to be more water in (hot) desert air with a low RH than somewhere cooler with a higher RH.

The important figure is the dew point - the temperature when water starts to condense - the higher this is the better.
Posted by Lawrence Mayes  in  UK  on  Mon Oct 04, 2004  at  01:08 PM
I had visions of burying a PVC pipe in my backyard and somehow being able to extract enough water from that to water my backyard for free. Somehow I don't think that's going to happen. Though maybe if I put one of these fog nets on my roof that would do the trick: http://www.fogquest.org/index.shtml
We get plenty of fog here in San Diego. But hardly any rain.
Posted by The Curator  in  San Diego  on  Mon Oct 04, 2004  at  01:56 PM
I see from the FogQuest site that we are just in time for the 3rd International Conference on Fog, Fog Collection and Dew (October 11-15 in CapeTown, South Africa).
There is at least one town in South America (Ecuador?) that gets its municipal water entirely by collecting fog on big sheets of net-like membranes. The fog gathers on the sheets and runs down into tanks. The town is situated on a mountainside that has almost perpetual fog but little or no rain (wouldn't you like to know why someone built a town there?).
The technique of collecting dew to get relatively modest amounts of water is not new at all. I remember reading instructions for this in an old wilderness survival manual (circa 1970 or before). You dig a hole, put a plastic or canvas sheet over it, and weight the center of the sheet with a rock to make sort of a closed-bottom funnel. Every morning (if there's any dew) there should be some water in the center of the sheet. If you have some kind of tube or straw, you can drink the water without having to disturb this setup every day. I don't know where you were supposed to get a big plastic sheet, a shovel, and a rubber hose in the middle of the desert, but that was the basic plan, anyhow.
Posted by Big Gary C  in  Dallas, Texas  on  Mon Oct 04, 2004  at  02:51 PM
Having grown up in Las Vegas, I know first hand how hot and dry the desert is. As we all know, water condensation is a by-product of air conditioning. In the summer, when our home central air conditioner was on, a little bit of water would drip out of an exhaust pipe at the side of the house. I placed a jar under the tube to see how much water i could extract from the dry desert air. It took me 2 days to fill up the 18oz jar. (how much is that in liters?) which isn't really bad for las vegas summers, condsidering it gets up to 120 degrees faranheit and it seems like it only rains 5 times a year.
Posted by john  in  NH  on  Mon Oct 04, 2004  at  08:53 PM
My take on his method is that it's relatively cheap to move air, so moving air through an underground (cooler) will condense out relatively cheap water. Same principle as a heat pump- using the ground as an infinite source of heat or cool.
More power to him! wink
Posted by John  in  Upstate New York  on  Mon Oct 04, 2004  at  11:20 PM
Reminds me of the dew collectors in the Dune series of books.
Posted by Kaitain  in  Not in the bathroom  on  Wed Oct 06, 2004  at  09:23 AM
I'm in Tampa, FL. Our annual rainfall in inches is usually about 30-32. Just thru September we overshot that by 76 inches. We've had 100+ inches of rain this year so far. Most of our water comes from the aquafirs & springs in the area.

Ahh...Hurricane season. It lasts from May-November. We've just passed the 'peak' of the season, but we're only thru the letter "L", I'm sure the weather could do a little more damage if it tried.
Posted by Maegan  in  Tampa, FL, USA  on  Wed Oct 06, 2004  at  12:27 PM
Hi, I'm from Singapore and here, the technology for transforming moisture in air to drinkable water is commonplace. Check out this product from a local company: http://www.hyflux.com/pdt_aquovate08.html
Posted by Alvin Kam  in  Singapore  on  Thu Oct 07, 2004  at  04:46 AM
hey alvin that is very interesting. I especially enjoyed the TV commerical!
Posted by john  in  NH  on  Thu Oct 07, 2004  at  10:34 PM
Actually belgian inventor Achille Knapen had the same idea in the 1930's,
see here:
http://www.bagelhole.org/article.php/Water/350/

The same pronciple is widely used to dehumidify walls:
http://www.humidity-stop.com/come_funziona.html

Mike
Posted by Mike Acker  on  Mon Oct 11, 2004  at  06:58 PM
Actually belgian inventor Achille Knapen had the same idea in the 1930's,
see here:
http://www.bagelhole.org/article.php/Water/350/

The same principle is widely used to dehumidify walls:
http://www.humidity-stop.com/come_funziona.html

Mike
Posted by Mike  on  Mon Oct 11, 2004  at  06:59 PM
Thank you for your responses. Is there anyone out there with a serious interest in developing this concept? I would like to build a 10,000 gallon per day demonstration model to show to municipal water suppliers.

Shea Cockrum
Posted by Shea Cockrum  on  Fri Mar 04, 2005  at  12:39 PM
With these invention my local WATER supplier "SEDAPAL" is dead.I think your system is the same as the belgian inventor but a big one. And about of your % efficience machine.
smile
Posted by JU li  in  Peru  on  Mon May 09, 2005  at  08:50 PM
Comment from: Adess Singh [Visitor]
Posted by Adess Singh  in  Chandigarh India  on  Sun Jun 26, 2005  at  01:20 PM
Dear Sir / Madam,
We would like to purchase "Water from Air" equipment for Agricaltural purpose.Please send us spec. if you have.We are waiting for help.
Thanking in advance for good cooperation.We remain.
Best Regards
A.Dalvand
Email:trade@dalvand.com
Posted by Azarnoosh Dalvand  in  Iran  on  Wed Oct 12, 2005  at  08:21 AM
I read an interesting remark from a water commissioner. "If water is scarce enough" then any source becomes feasible
Posted by Joseph Ellsworth  in  USA  on  Thu Nov 17, 2005  at  10:25 PM
There is a company that makes machines which convert air into pure drinking water. Their machines were used in Katrina. Check them out at http://www.aquair.com
Posted by John Murray  on  Thu Mar 09, 2006  at  08:15 PM
A2WH is another Air to Water harvesting unit http://A2WH.com. It produces water from air using solar thermal energy. To the best of my knowledge it is the only unit available that does not require electric power. This allows it do be deployed on a scale that is infeasible for other technologies.

After further research the buried pipe idea will work in some climates. They key is that the ground temperature has to be below the dew point. The dew point in relatively humid areas is high so it will work OK in some areas. In areas like Las Vegas the dew point is quite often within a few degrees of freezing which means that it requires special chilling technology rather than just a tube in the ground.

I ran some calculations and assuming 100% efficiency at 63.5F with 30% humidity it requires 28,856
Cubic foot of air per gallon of water. At 60% and 63.5F humidity it requires 14,229 cubic foot per gallon while and 53.5F at 90% humidity it requires 9,468 cubic foot per gallon. In North Carolina where it runs over 95F with 90% humidity during the summer it would only require 3,358 cubic foot per gallon. In the deep dry deserts where you can see 65F mornings with 15% humidity it requires 54,430 cubic foot of air. In other words it requires processing 16 times more air to get the same amount of water in the worst conditions versus the best conditions and in many instances the temperature drop to the dew point in the worst conditions is 3 to 10 times higher which means it can easily require 30 to 160 times more energy to extract water in the dry desert.

The process fundamentally requires lowering the appropriate amount of air to below it
Posted by Joseph Ellsworth  in  USA  on  Fri Mar 10, 2006  at  08:23 AM
I would like to explore the idea with Shea Cockrum about extracting water from the air. I certainly believe that with the proper technology extraction could infinite and cheap.
Please contact me.

Rafael Capella
Posted by Rafael Capella  in  Ramsey, NJ 07446  on  Fri Mar 10, 2006  at  09:38 PM
It would be interesting to try this underground cooling technique to extract water from air, within an enclosed garden environment.

For instance, what if you piped household greywater into an enclosed garden area (earthship concept), and used the plants to transpire the water into the air as humidity. Perhaps you could reclaim that very same water with this air-to-water idea?

The air temperature in these types of enclosures easily gets to 95F or higher on a daily basis, even in winter. Also, the Relative Humidity is always very high.

The high temperature and humidity levels, combined with the stable 58F temperature of the earth (below frost line), essentially make these expensive, energy-hogging methods of cooling the air to the dew point unnecessary. So all that is required is air movement, which is relatively easy.

Or am I mistaken? I am unsure of what the Dew Point would be, for 95F or higher air, at 90% or higher Relative Humidity.

If this idea actually worked, it could possibly recover a significant percentage of water used in homes on a daily basis. Would be a pretty neat way to recycle water.

Earthship Website: http://earthship.com
Posted by Edwin  on  Wed Mar 29, 2006  at  02:48 PM
The dew point for 95F at 90% humidity is 91.6F and every 3,358 cubic foot of air will contain 1 gallon of water. If you can your ground stays at 58F the system as described should work quite well.
Posted by Joe Ellsworth  in  http://a2wh.com  on  Thu Mar 30, 2006  at  10:53 PM
Excellent. Thanks for the info. Now all that needs to be calculated is how much electricity it takes to move 3,358 cubic ft of air.
Posted by Edwin  on  Sun Apr 02, 2006  at  11:51 PM
It is a little more complex than just moving the air. First you need to determine what how long and what diameter of pipe you will be using which depends heavily on the pipe's thermal transmission characteristics. The tradeoff is that smaller pipe gives better surface area to chill the air and more condensing surface which improves the efficiency of humidity capture. A smaller pipe also adds more air resistance which increases the energy cost of pushing the air through the pipe.

You need to make sure the pipes slope down to a pumping location where a liquid pump can extract any fluid. You will also need some way of periodically sterilizing the these pipes or you will have a very nice mold culture. I suspect that a set of smaller pipes buried at least 10 pipe diameters apart will give the best results but that is only a guess.

One caveat is that the size of the system will have to be sized to match the humidity production capacity of the greenhouse and if you want to fully optimize the system then you need to have sufficient ground loop to cool the entire greenhouse without having to vent any of the valuable moisture with the traditional large vent fan. Ground is a fairly good conductor of heat over time but in the short term is a pretty good insulator so you will need the loop to be long enough to give the ground long enough to conduct the heat load away otherwise local heating will increase the ground temp to above the dew point.

Incidentally the same solar thermal motors we use for our EEDRT product would be ideal for this kind of application. Stirling motors would also work. They both have a higher capital cost than an electrically driven fan but they have zero energy costs so it works out over time. I think the biggest cost issue will be the cost of the buried pipe and the excavating costs.

I have not done the calculations so this guess could be way off but a starting point is that you need to calculate a factor which is degrees of cooling needed multiplied by CFM of flow which I will call CFM-Heat-flow. You will need something in the range of 15 to 20 foot of 2 inch PVC pipe per CFM-Heat-flow unit. Take that number and reduce by 8% for every 8F the average buried ground temp is cooler than the calculated dew point. You can run these pipes in parallel to get higher gross air flow as long as they are separated by 10 pipe diameters and as long as the minimum air run length is something over 20 foot times the pipe diameter in inches.

One last point is that there will be non trivial air resistance in this system so a two stage centrifuge blower will be a better choice than typical radial fan. One of the harder design aspects will be designing the manifold to ensure average airflow across the entire system is consistent and that you do not get any one leg where the air flow is substantially higher than the other legs.
Posted by Joseph Ellsworth  in  USA - UTAH  on  Mon Apr 03, 2006  at  12:35 AM
In India there is a company that makes machines that extract water from air.

See http://www.watermakerindia.com
Posted by Ashvidia  in  India  on  Sun Apr 23, 2006  at  06:55 AM
Guys,

You can find ample of details at http://en.wikipedia.org/wiki/Atmospheric_water_generator

Its a wikipedia initiative.
Posted by Ashvidia  on  Sun Apr 23, 2006  at  07:04 AM
Mr. Cocrum's theory of the Lo TEG appears to be plausable. I would be interested in discussing the possibility of funding its research.

Currently I am working with an entity to provide North African nations with potable water. The 50 mile wide stip along the medateranian sea is very hot and very humid most days of the year. Additionally, the area is always breasy or windy which helps generating power by wnidmills.

We think of Capturing humidity in those areas by domestic type dehumidifiers that have much bigger components and, thereofe, much higher capacity. With the use of windmills, cost of needed power should not be an issue. We invite suggestions and ideas. The door is also wide open for any form of cooperation including the design and manufacture of a very large dehumidifier prototype. I can be contacte by email:
Posted by Tawfik  in  Chicago, USA  on  Sat Jul 15, 2006  at  12:40 PM
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