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.
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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.
Unfortunately in a desert where water is wanted so much there is just few percent of relative humidity.
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.
We get plenty of fog here in San Diego. But hardly any rain.
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.
More power to him! 😉
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.
The same pronciple is widely used to dehumidify walls:
The same principle is widely used to dehumidify walls:
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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
Please contact me.
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
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.
You can find ample of details at http://en.wikipedia.org/wiki/Atmospheric_water_generator
Its a wikipedia initiative.
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:
I read about the vote you where talking about. Quite frankly I would also be hesitant to accept sewage that has been treated with membrane technology.
Producing 1,000 liters per day is fairly easy with our solar thermal powered [No Ads Please] system. There are also options that would allow us to use local waste water to increase local air humidity which would dramatically lower the energy cost and hence the capital cost for the A2WH system operating in your area.
In your area the ground temperatures are not cool enough to work with the simple buried pipe approach that Shea first recommended. For your area we have only two choices to increase the humidity in the air or reduce the air temperature. A2WH uses solar thermal energy to chill the air sufficient to reach the dew point. We can also use your ground temperatures as a heat sink which is particularly effective whenever the air temperatures are more than 10 degrees above ambient.
[No Ads Please]
I was under the impression that Australia has large aquifers containing salt water. Our patent pending water distillation technology can purify the brackish water for potable use and it is quite a bit cheaper to desalinate than to extract water from air.
There may be a significant opportunity in your area to treat grey water for use in small gardens and we would love to work with you in your local market to test this concept.
for more details you can visit: http://www.ad.com
THIS IS NOT AN ADVT PLEASE!!!
PS: Moderator. How are people interested in the topic supposed to exchange contact information when no emails are included and you remove contact information from responses?
Thank you for taking the time to respond with advice and info
Of course, as you see above, the military has this ability, but they keep it a secret. All mere mortals can do is pray for crumbs - maybe someday you will notice that some of the top spies have bought up half the land in the Western U.S., and if you rush to join in with them before the price maxes out you might make a few dollars. Then you'll know some commercial gadget might be coming out (can't wait to see the restrictions and hidden spy features)
I can obtain the IP for a Night radiant system which uses blackbody radiant cooling techniques to condense water out of the night air. The new design is expected to produce more water on more nights and will work in a broader range of environmental conditions than previous dew harvest designs. It is unclear if there is sufficient market demand to justify moving the technology into large scale production. This design is specifically targeted at humid regions where temperature at 10:00PM averages 0F to 8F above the ambient dew point.
How low do manufacturing costs need to be before it becomes attractive? Which market segments would be the most viable? In which geographical areas? At what cost points? Why will buyers in those markets be interested at that price point?
The Night Radiant A2WH system is manufactured in 100 square foot packages. In ideal weather conditions 100 square foot will produce between 2 to 3.5 gallons. At what price point will these become attractive and in which markets? The problem with this particular technology is that to obtain reasonable production costs production must be ramped up into the range of 100,000 square foot per month and it is unclear if there is sufficient market to consume that amount of product.
The night radiant design is self contained and requires no external fuel or electricity. It uses a small amount of PV energy to operate an on board micro controller and some low power fans. The PV panels approx 15 watts per 100 square foot are included.
Comparable electricity driven systems would be combined with sufficient PV solar panels to provide all needed power. The Electric systems claim to consume between 0.6 and 2KWh per gallon of water produced. At 0.6KWh per gallon it would require 1.8Kwh to produce 3 gallons. Assuming a 6 hour sunlight day 300 watts worth of solar panel should provide 3 gallons of water per day. I am very interested in cost and actual energy consumption feedback from people who have field tested the electric systems using PV for power.
Rather than running air under the ground which has some obvious scaling and cleaning issues how about changing your design to use a geothermal ground loop which circulates fluid which is chilled by the ground. The geothermal tubing is pretty inexpensive and comes in 1,000 foot rolls ideal for large scale thermal exchange
Use the chilled fluid in the geo loop circulated through a water tank which chills the tank. The heat exchange into the water tank could be as simple as coiling several loops of the geo loop tubing inside the water tank.
Then use cause your air flow to go through a heat exchanger submerged in the chilled tank.
In this way you have to circulate relatively little fluid in the ground loop which uses less power and is cheaper than pipes large enough to carry sufficient volumes of air and you don't have to worry about mold and other things growing in the buried pipes.
It ought to be pretty fast to install a few thousand foot of the geo loop with a standard trencher.
The air condenser would be submerged in the tank where fluid to condenser contact will give a good thermal exchange. The air flow path is only the length of the tank which will minimize fan power and the condenser is above ground where it can be easily accessed for cleaning.
I am using some of these concepts in the A2WH night radiant system but in some areas it might work without the night radiant chillers
it is exactly, exact by the rocks...???
Does anyone that has engineering experience have
a reaction? Thanks, Grandma Coledust
Total cost of water is that of the energy consumed to produce it.
EG: around Aud $ 15cents Ltr.
But there are many out there which will produce 100- 200- 300Ltrs and more per day.
Price per ltr will be a little less than ours.
There are many manufactures of these machines....
just google ...water from air machines ..or air water generators etc...
You should find a supplier in your location
Knapen's air well in Trans-en-Provence produces only five liter condensed water each night, following