khourygeo77
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Process to practically condense large amount of atmospheric water or dew
Any idea if such a goal is possible without much expense to spend?
There are coolants that can be made but I am not sure which are practical as they evaporate on atmospheric air.
Thanks.
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j_sum1
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This is a thermodynamics question. You need something cold - colder than the dew point (which you can look up). You need to then conduct away the heat
from the condensation. And for any kind of efficiency you need a sizable surface for heat transfer.
Devices have been invented for this. They are called air conditioners.
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LearnedAmateur
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If you look into the specific mechanics behind them, I’m sure you’d be able to gut an old fridge and use the halocarbon system to construct some
condensation device. If you’re just looking for relatively pure water though, collecting rain in a large bucket or compost bin will do the trick and
is pretty much free. If you haven’t already, studying your local climate/weather patterns will give you some insight into whether they’re feasible
ideas or not, since low humidity for a start would present issues either way.
Letting us know what your plans are would greatly help since more accurate advice can be given. Who knows, someone might even have experience with a
particular application and will be able to share some designs, or at the very least, some practical insight.
In chemistry, sometimes the solution is the problem.
It’s been a while, but I’m not dead! Updated 7/1/2020. Shout out to Aga, we got along well.
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Sulaiman
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A solar still is a possibility ? https://en.wikipedia.org/wiki/Solar_still
CAUTION : Hobby Chemist, not Professional or even Amateur
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aga
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I recall a plastic material modelled on hydrophillic/hydrophobic spots printed on the surface which mimic the surface of a desert beetle's shell.
It seems that with the right materials, water will condense from the air forming droplets as the temperature changes, which sustain the beetle.
Will see if i can find the info.
Edit:
Something like this in India:
https://www.researchgate.net/publication/282195162_Roofs_as_...
This is the beetle:
https://en.wikipedia.org/wiki/Stenocara_gracilipes
https://asknature.org/strategy/water-vapor-harvesting/#.WnTQ...
[Edited on 2-2-2018 by aga]
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Chemvironment
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Atmospheric water generators are pretty common, especially in water scarce areas that have inadequate water delivery systems(ie 3rd world countries).
They virtually all use one or more of three methods: cooling air below dew point as previously mentioned, exposing the air to a desiccant, or
pressurizing the air. Of these cooling and desiccants are the most practical obviously. In fact some systems take advantage of an environments
temperature swings (think desert day vs night) to produce potable water with almost no need for external energy sources. I studied physics and
environmental science and these were a huge part of the curriculum in one of my classes.
The earth already does this daily. Walk out in the morning when the temperature has dropped below the dew point (which depends in temperature and
pressure) and you will no doubt see earth's collection of condensed water from air. How many gallons you think condense naturally on a daily basis.
AWG units that take advantage of natural temperature swings are by far the most energy efficient.
Your mention of coolants is a little confusing to me. If you are going to use coolants they will be in a closed system (in a condenser) and not be in
contact with the atmosphere.
If your goal is to collect potable water there are more efficient ways of doing so. Rain collection is virtually free after the initial investment for
the collection system. If your goal is to dry the air dehumidifier's are fairly cheap. As an aside this is exactly what air conditioners do because
dry air is much easier to condition than humid air.
[Edited on 2-2-2018 by Chemvironment]
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Magpie
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Mechanical means (compression) are generally cheaper than those using cooling alone. A refrigerator uses both, ie, a compressor and a fan.
What is the humidity of the air (a range, or an average?) What humidity reduction do you require? What volume of air/day needs drying? How many
gallons/day of water will you generate?
The single most important condition for a successful synthesis is good mixing - Nicodem
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Chemetix
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In Melbourne recently we had humidity levels only seen in the tropics. I had to run a small portable refrigerative air conditioner to survive. The
amount of water on the floor was incredible, so I ran it for about 4hrs while collecting the water. I nearly made it to the 10 litre mark. The unit is
rated at 3kW which I don't think is right since my wall socket has 10A fuses on a 240V mains. Assume 2400W, that's quite a bit of power to get 10
litres worth of water and could only happen near the 80-100% RH levels.
Maybe use molecular sieves in a continuous chain of them that are absorbing water from the air and then be desorbed with a little heat. If the heat
was captured via a regenerator to be used in the desorbtion cycle of the next cylinder of sieve material, then it could be quite energy efficient.
Similar to the medical oxygen concentrators.
Adsorb - desorb.
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Chemvironment
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I weather seal my windows in the winter and put a container of damp rid in before I seal it off to help with the moisture. Damp rid is just a
perforated container filled with calcium chloride in the top half. It takes about two weeks for the container to fill completely with water. I live in
Oregon so humidity is almost always 80%+ which hastens the process of course.
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aga
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The corrugated plastic of my side terrace drips water in the mornings, sometimes.
It happens even in high Summer, when you'd imagine there was no possibility of dew.
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j_sum1
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My point is that even at its most saturated, a cubic metre of air just doesn't contain a lot of water. And if you are going to condense it you need to
move some heat energy around. Sure this happens naturally through weather cycles. But if you are after a device (a) they exist and (b) it is not a
practical or cost effective means for obtaining water.
There has been a recent glut of fraudulent crowd-funding efforts of late with purported goals to extract water from air as a practical source of
water. Thunderf00t has debunked a number of there. Look up his channel on yt. In his own rambling way he explains the processes quite well and you
will find all the answers to your questions.
[edit]
My apologies if I came across as a bit snarky. I strongly object to fraudulent activity and I have seen a bit in this context.
[Edited on 2-2-2018 by j_sum1]
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Chemvironment
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Dew isn't uncommon on hot summer days as long as you live in a relatively humid environment. For example if the relative humidity is 60% and the temp
is 90°f the dew point will be somewhere just under 75°f. If it doesn't get below 75°f where you live you should move because thats disgusting lol.
Also its pretty common for dew to form on surfaces that are not in contact with the ground. They of course tend to be colder than surfaces or
materials that do contact the ground. Being corrugated increases surface area which would provide more area for condensation to occur as well I
assume.
I just remembered my professor was very excited about some new AWG technology that will/does use foil condensers. If I recall India has some huge
collectors that harvest upwards of 200 liters of water a night during peak "dew season." I believe they have proposed even larger ones that would be
located next to the coast to condense dew and fog.
I agree with Jsum that these devices aren't very efficient. The very act of condensing water raises the surrounding temp due the release of latent
heat which works against our desired goal. Though I'm not completely in agreement that this process isnt at all practical. One of the biggest issues
is that the places where these devices tend to work best are usually places that already have an abundance of water.
[Edited on 2-2-2018 by Chemvironment]
[Edited on 2-2-2018 by Chemvironment]
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roXefeller
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It's called a thunderstorm. It convects massive amounts of moisture rich air and deposits it upon the surface. If you need to store it a rain
barrel will suffice. I only say that to drive home the point that water needs to be there in sufficient quantities for a person to draw it out in
large quantities. And having a large mass of moist air will naturally dehumidify by precipitation.
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WangleSpong5000
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A dew covered grassy field at twilight; in certain regions, is a good visual example of the role surface area plays in the physical properties of
matter within a system. Works for activated charcoal... not condensation.. Surface area...
Sorry... I've been thinking about surface area a lot lately... hahaha Jesus
Hyperbole be thy name
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Morgan
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Tidbits
http://www.theweatherprediction.com/habyhints/260/
http://www.theweatherprediction.com/habyhints/40/
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annaandherdad
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I have wondered if it would be practical to use the cool water of the deep ocean to condense moisture from air extracted at the surface.
Any other SF Bay chemists?
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unionised
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https://edition.cnn.com/2016/11/18/africa/fog-catchers-moroc...
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Melgar
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Am I the only one here who's wondering why he doesn't just go the hardware store and get a dehumidifier? Set it to run only at night, using a timer.
No need for anything complicated if it's unnecessary.
If is goal is to spend very little money, then look on craigslist. Lots of people end up with some water leak that floods a room in their house, then
buy a dehumidifier to dry it out. Often, they don't have a use for it after that, so there should be plenty of used ones out there.
[Edited on 2/20/18 by Melgar]
The first step in the process of learning something is admitting that you don't know it already.
I'm givin' the spam shields max power at full warp, but they just dinna have the power! We're gonna have to evacuate to new forum software!
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Panache
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Yeah its called a succulent, a class of plant relying on the atmosphere primarily for water rather than the soil. There is an inherent problem, they
tend to be spikey (how is that word spelt).
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Sulaiman
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First you should determine how much water is available,
a psychrometer https://en.wikipedia.org/wiki/Hygrometer will indicate RH%
To condense water from air usually requires the removal of heat,
so the 'best' option is to use the excess heat,
so one option is to use an air heat exchanger/pump to heat your living space.
If you are in a country that needs air-conditioning then just collect the condensate from the air conditioner - its a free by-product.
Air de-humidifiers are a good stand-alone option,
but you would need 'fresh' air not room air,
because if it works, the humidity level will be low !
If starting from scratch, then excessive cooling is to be avoided for thermodynamic efficiency,
so a refrigeration unit that does not go below 0oC is preferable.
==============================
On average, people that do not have access to fresh water do not have access to electricity,
with electricity water can be pumped,
so I do not see a major application for this technology.
If this technology is for industrial/agricultural use,
then sucking all of the moisture from the air is not neighbourly,
so please do not assist this technology.
CAUTION : Hobby Chemist, not Professional or even Amateur
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Rogeryermaw
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too bad luke's aunt and uncle got wacked by the empire...they had giant condensers and robots to run them.
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