Taking Advantage of Atmospheric Moisture

Psychrometric charts are widely available. Everything that is needed to operate an air/water system at ambient pressure is on them.

Hello Sapper,

I do hope you have deep pockets.

The cost for condensing water from the air, to fill a water tank is going to be very high.

Most home owners just wait for rain, or snow/ice melt from the roof, that way the process is quite effortless, and free.

Any location where you can extract water from the air to fill a rainwater tank, is going to have rain, normally within a week or so.

Please advise your location and then from the weather patterns, we may be able to solve your question.....

SparkStation,

I'm not looking to fill the tank entirely from this unit.

I'm looking for a way to use the waste energy produced by wind\solar installations.

Normally these have a dump load (Resistive load) and I would like to use, rather than waste this energy.

In Australia we have been in severe drought for several years, because the moisture is not condensing, but the humidity levels are quite often high 60-80%.

So I'm not looking to solve the world water storage, more to tinker and see if I can use what would be otherwise wasted energy on a Holiday Home system.

Sapper.

I dont think I would like to drink condensed water from air. It will be full of impurities, germs,flies. Have you ever smelt water from melted frost ice in your fridge.

Since you have "green" electricity to waste....

Perhaps it would be better to use the energy to boil impure waste water (even sea water) and condense it. Or run a reverse osmosis plant. Not as efficient, but a better product.

In Australia we have been in severe drought for several years, because the moisture is not condensing, but the humidity levels are quite often high 60-80%.

Sapper: keep your water collector temperature around 10 C and you should collect water 24/7/365 in most locations between 60 degrees South latitude and 60 degrees North latitude. Notable exceptions are the area NorthEast of the Himalayas, a small area south of the Sahara desert, and an area in west central Australia. Check weatherunderground.com and click on the dewpoint temperature button to check on the instantaneous dewpoint for most points around the world. for more information and collector design contact me at oertg@aol.com

I agree. There is no point in measuring the dewpoint. The lower the temperature, the more water you will collect, under any circumstances.

Tad

That was a good answer. You should register so you can receive responses to your posts through email.

I can cast a vote towards a good answer but you won't get any credit for it because you're not a registered poster.

Also we can have several "Guests" posting in here each response different and we can't really tell who we're responding too. Sometimes it can look like "Guest is talking to themselves.

If your humidity levels are in the 60-80% range, then what ou propose would appear feasible but not particularly cost effective (as sparkstation mentions). Are you planning on using a dehumidifier unit for condensation of the moisture or what?

I have a comment to make. I hope it comes across as intelligent. You are probably aware of the survival technique of digging a hole, covering with plastic and placing a rock in the center of the plastic (low point). As the air cools at night the vapor condenses and drops into a container (center of the hole). We could increase the return by urinating in the hole. If your waste water was applied in this manner, would the process work for you?

James

I doubt that atmospheric moisture can be turned into liquid at reasonable cost, but to answer your question, do a Google search under "water vapor saturation pressure" and/or try these web sites:

//wikipedia.org/wki/saturation_vapor_pressure

// hyperphisics.phy-astr.gsu.edu/hbase/kinetic/watvap.html

The bottom line is that there are numerous charts, tables, graphs, and equations that will provide the information you requested. Some things to keep in mind are that as soon as you have condensed some liquid water, you reduce the pressure of the vapor that remains. This means you must continue to lower the temperature to condense more water. FYI, when the dew point is 20 degrees C, there are about 1100 pounds of water per million cubic feet at 60 degrees F and one atmosphere. Another aspect of condensation is that you must provide nucleii to initiate the condensation process, or you will wind up super-cooling the vapor and get no liquid.

Hi Sapper,

There is a company in Ontario, Canada (Airwater) that makes and sell such a product which provides up to 6 gallons/day (depending on the actual meteo conditions) of drinkable water. Review this:

http://www.airwatercanada.com/e7.php

and the other pages on technology, products, etc. You might even be interested in becoming their distributor in the region.

The combination of solar/wind power with water collector from thin air is a great idea!

Good luck!

If you live in a location with high humidity you can get a gallon a day with a regular space dehumidifier.

Pennsylvania is one of these locations.

Hello again Sapper.

Of course if you are successful in your plan to extract atmospheric water, I trust you shall include for the side effects:

• Depriving people downwind of your condenser, of their share of moisture in the air.
• Reject heat from the process heating up that air which is increased for those downwind.
• Further dessication downwind, for flora and fauna.
• There will be further flow-on effects..........

With your project, as with all projects, it is good to remember that if the project is successful, it cannot be universally applied.

There was an interesting SF short story "A Pail of Air" I read years ago, where the air froze, the whole story is on-line, and please refer to part of it (Full story is on-line), here:

http://www.baen.com/chapters/W200501/0743498747___6.htm

"A Pail of Air" is a story about survival in the face of desperate circumstances, and there are no ifs, ands or buts about it. There is no atmosphere . . . bitter cold . . . only way you can breathe is to dig up a pail of liquid oxygen and heat it . .

Pa handled the pail of air in a twist of cloth. Now that it was inside the Nest, you could really feel its coldness. It just seemed to suck the heat out of everything. Even the flames cringed away from it as Pa put it down close by the fire.

Yet it's that glimmery white stuff in the pail that keeps us alive. It slowly melts and vanishes and refreshes the Nest and feeds the fire. The blankets keep it from escaping too fast. Pa'd like to seal the whole place, but he can't—building's too earthquake-twisted, and besides he has to leave the chimney open for smoke.

Pa says air is tiny molecules that fly away like a flash if there isn't something to stop them. We have to watch sharp not to let the air run low. Pa always keeps a big reserve supply of it in buckets behind the first blankets, along with extra coal and cans of food and other things, such as pails of snow to melt for water. We have to go way down to the bottom floor for that stuff, which is a mean trip, and get it through a door to outside.

You see, when the Earth got cold, all the water in the air froze first and made a blanket ten feet thick or so everywhere, and then down on top of that dropped the crystals of frozen air, making another white blanket sixty or seventy feet thick maybe.

Of course, all the parts of the air didn't freeze and snow down at the same time.

First to drop out was the carbon dioxide—when you're shoveling for water, you have to make sure you don't go too high and get any of that stuff mixed in, for it would put you to sleep, maybe for good, and make the fire go out. Next there's the nitrogen, which doesn't count one way or the other, though it's the biggest part of the blanket. On top of that and easy to get at, which is lucky for us, there's the oxygen that keeps us alive. Pa says we live better than kings ever did, breathing pure oxygen, but we're used to it and don't notice. Finally, at the very top, there's a slick of liquid helium, which is funny stuff. All of these gases in neat separate layers. Like a pussy caffay, Pa laughingly says, whatever that is.

Hope you enjoyed reading the complete on-line short story....

What I am saying is that even if everyone tried a projects similar to your proposed one, the consequences are sometimes/often unforeseen.

Kind Regards....

Hi to all,

this water collection was invented by the pine trees of Gran Canaria some million years ago: using the needles to collect the fine droplets of fog on mountain slopes.

In Chile some people have stretched fine plastic nets high up on the coastal mountain where the air has cooled down to form clouds or fog. This is very effective and whole communities can rely on this water if the winds are continuous.

To provoke condensation you need either the temperature down or the pressure or both.

As the solubility of water in air is very much temperature dependent it is much more effective to start with warm air - as moist as possible.

The principles can be extracted from any book on thermodynamics, there is a "Molliier i,x diagram" included , from this you can define a starting point (pressure, temperature, humidity and an endpoint and read how much excess humidity is in your air in the form of fog, mist nebula, droplets. To collect these you have to blow this mixture through a structure that separates the droplets from the air by centrifugal action. I am sure you will find this diagram in the internet.

May be instead of the centrifugal extractor there is a chance of converting a high voltage electrostatic filter to do the job.

I would like this to be developed into a 1kg unit for use in remote deserts!

RHABE

Liquid water might be harvested from fog, but not from moist air because the water is present as a gas. You can not separate oxygen from nitrogen by centrifugal force. Same applies to water vapor. Incidently, about 200 years ago, Dalton demonstrated that gases function independently of each other. If this is still true, the implication is that the presence of water vapor in air is independent of the properties of the air. The same water could exist in a vacuum, or in other gases. It's only the partial pressure of water vapor that determines the dew point. I have a feeling that using refrigeration to condense water from the atmosphere will prove to be expensive, but if one has waste energy to use, it may be practical.

Thanks everyone for you input.

Since this is more an accessory to a Solar\Wind system it will be relatively small and unlikely to impact anyone else, if I get more than 20litres a day I will be a happy camper and have achieved my goals. Even 10litres would be good.

The unit is only likely to be a 1meter cubed so as to avoid being an eyesore or worse still a birdsnest and fire hazard.

Thanks again for all your comments & links; they have been very helpfull.

Regards,

Sapper.