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water condensation mesh

use cold salt water to remove water from humid air
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Am interested in the idea of providing fresh water for irrigation in a mediteranean climate where there is little natural fresh water but relatively high air humdity of ave 40% going to 90% during the summer. The idea is wether it would be possible to use the large and free volumes of relatively cool sea water to pump through a radiator mesh causing the warm moist air to condense and then collect the water. Would this work and does anyone have any clues as to the returns you might get off it? All replies greatly appreciated,
dom, May 14 2005

Square One http://www.squ1.com...re/psycho-tool.html
Psychrometric chart with the absolute humidity of air, among other variables. Moisture may constitute "as much as 5% by volume" of hot air. [reensure, May 15 2005]

Tenebrionids (tok-tokkies) http://www.orusovo....debook/content6.htm
...also get their water this way. [DrCurry, May 15 2005]

(?) Fog Collection http://www.toprak.org.tr/isd/can_63.htm
[Klaatu, May 15 2005]

aerial wells http://www.opur.u-bordeaux.fr/index.htm
aerial well collection techniques from neolithic times [dom, May 15 2005]

(?) Other Methods http://www.bagelhol...icle.php/Water/350/
I haven't read the entire site & if anyone knows how to get the pictures to load I'd be interested to know how. [Zimmy, May 16 2005]

[link]






       This is essentially a solar water purification unit, only with the solar heating outside the unit.   

       Btw, this is how sequoias get their water: maybe we should just plant sequoias along the edge of the Sahara?   

       P.S. The cold water isn't exactly "free" - you've got to pay to pump it.
DrCurry, May 15 2005
  

       Have also been researching aerial wells, which follow the prnciple of collecting moisture fron air by using stone or sythetic means, see   

       The key issue would be providing the largest amount of control into the system, i appreciate that weather can be unreliable and so would like a system that can be 'geared' to harvest more or less as needed in the reservoir.
dom, May 15 2005
  

       I wonder if those old stone dew collectors worked as follows: (follow aerial wells link)   

       The stones cool during the night, and I suppose there must be some dampness to aid the cooling process. Obviously, the stones let the air diffuse through. The ground might be an additional heat sink.   

       During the day, the cold stones condense the hot humid air. Somehow, if the arrangement can be used to accelerate the air (and slightly lower its pressure)?   

       On another point, I thought about a stack, where hot air is caused to rise (by solar heating) until it's pressure reduces. When the pressure reduces, it cools down and releases vapour. But the stack would need to be very high.   

       If you want to check if sea water is cold enough, why not use an aluminium bowl and float it low down in the sea. Shield it from the Sun and see how much water condenses.
Ling, May 16 2005
  

       The in-going/out-going breezes could turn a wind mill to power an auger pump to take care of the pump power problem.
Zimmy, May 16 2005
  

       I was thinking about a similar idea - but for a different reason. In Western Australia we are facing an energy shortage and a water shortage as the urban sprawl means that there are more lawns to water and more houses to air condition. (unfortunately no one seems to be considering responsible design practices - just how to get more water and power)   

       I noticed how there is always a trickle of water from the aircon units as the humidty condenses out of the cooled air. I was wondering if there was some way to convert the latent energy in the air (heat) in to energy for the house, thereby cooling the air (providing air con) and water for irrigation (in the form of condensation from the cooled air).   

       The scary thing would be if this was sucessful and efficient enough it would be a major change to the environment - but initially, maybe just enough to undo global warming.
MikeyTheBikey, May 16 2005
  

       [Mikey] the answer's no, essentially because (and this sounds really odd, but is the simplest way to explain it) in anything we do, the net level of chaos in the universe must increase. This is referred to as the zeroth law of thermodynamics - entropy (chaos) must always increase.   

       Separating water vapour and air to produce cold dry air and water increases the level of order in the system - instead of a mixture of water vapour and air, it's neatly sorted into separate volumes of air and water. Consequently somewhere else, chaos must increase by a greater amount. In practice this means burning fuel (in power stations, or in the sun) to release enough energy to cool the air and extract the water.   

       This post makes me look like an absolute quack, but it's 100% normal physics!
david_scothern, May 17 2005
  

       Wouldn't work:   

       The coastal air temperature would be very close to the water temperature. It'd get hotter as it goes inland, but would also get drier.   

       So, to get back to dewpoint, you'd have to cool it almost COOLER than the seawater.   

       When you pipe the seawater inland, you'll introduce heat from pumping, friction, and conduction/convection in the pipes.   

       So, all told, there is very little (or zero) room for engineering to extract enough temperature difference to actually condense anything using seawater as the cooling method.
sophocles, May 18 2005
  

       There is this thing you can do in the desert for water. You dig a pit, and rip some pieces off soem vegetation. Such as a cactus. Place them in the pit, place pot in middle of pit, and cover with Plastic Wrap.   

       Then place a rock in the middle above the pot, the moisture from the vegetation will condense on the plastic underside, and will drip down into the cup.   

       Not good for mass production, or irrigation. Might save your life someday be you lost in a desert though.
EvilPickels, May 18 2005
  

       [EvilPickels] OK, but usually when I'm lost in the desert, I forget to bring Plastic Wrap. Any other handy materials that'd be good for that?
sophocles, May 18 2005
  

       [Sophocles] Perhaps instead of plastic wrap you could empty out an Evian bottle and use half of that.
weedy, May 18 2005
  

       If you're in dire need of water, please don't empty that evian bottle.
blonkm, Aug 06 2009
  

       ^^^ My vote for the most obvious statement seen on the 1/2 B. <//If you're in dire need of water, please don't empty that evian bottle//>
Custardguts, Aug 06 2009
  
      
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