Extract drinking water out of the air

Thrud

Richard Proenneke
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Looks too good to be true....

Cut and pasted from comments section on the link...


""Condensing moisture from humidity into water requires 9000 BTU/gal, if the air's already at the dewpoint, 100% humidity. 17 fluid ounces requires 1195 BTU to condense.

If this were the efficiency of a central air conditioner, this would use 92 watt-hrs of electricity.

But we're surely talking about Peltier solid-state cooling, which has not advanced significantly in 25 years or so. If it did, it would be huge news.

Peltiers are like 10th the efficiency of R134a systems. And the performance curve is really critical- if the heatsink gets significantly warm, the performance drops precipitously. Heatsinks have to be huge to actually dissipate the wattage while not being particularly warm themselves.

So you'd need about one kilowatt-hr to make 17 ounces of water in 100% humidity conditions. Just so you know, a fit person pedaling a generator for long periods without going anywhere will generate about 200W, so you'd need 5 hrs of work.

Solar panel tech is about 14.5 watt per sq ft. So to generate 1KW in 4 hours of decent sun a day, that would require over 17 sq ft of solar panels to produce the 250W output to condense 17 oz with a Peltier over the course of the day. This doesn't make a lot of sense, you would not have that much sunlight in 100% humidity conditions.

What that shows is "moisture farming" is fantastically energy-intensive. If you were going to condense water out of the air, you'd use conventional R134a/R410a refrigeration and counterflow heat exchangers. The performance will be an order of magnitude better, but the bottom line STILL makes no sense.

In any case, the proposal does not add up. Nothing that size can condense 17 oz of water a day from solar, even under the most ideal conditions, however unlikely they may be."

Basically, they're generating a bunch of money from crowd-sourcing and are going to split without ever shipping the imaginary device.
 

peter.robinson

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it's so jolly humid at the moment, I wish it were possible - dehumidify the house, use the resulting water, it sounds good
 

Aussie123

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From my quick read its not actually "condensing" water from the air, its using a hydrophobic "filter" (coating I guess) to extract the water vapour from the air (when the humidity is suitably high ... like near a large body of water or otherwise humid etc)

A "filter" comprised of hydrophobic nanoparticles (my guess about what this is) doesn't really need the same grunt as a peltier cell or AC unit; it is passive.
I think the reason they demo it with a bike and solar is that the forward motion of the bike can be simulated using a small fan (which can run on solar). By constantly moving air over the filter, the moisture is "rammed" through it and into the bottle.

By getting the right mix of hydrophobic and ultra-hydrophobic particles to form a filter, it should be possible to literally filter water from thin air. Kool stuff and experiments have been around since at least the 80's ...

Think of it like vacuuming up ping-pong balls (where the balls are water particles):
- If you suck air through a pipe, you get a mix of air and balls.
- If you put a filter in front of your pipe, you could get the air to pass through, and the balls (water droplets) to collect on the surface of the filter;
- With a bit of imagination you could get the balls to run down to a collection bin, once they hit the filter .... and there you have it !

(No affiliation and no real knowledge or research about this product)
PS - this could be mumbo-jumbo happy to be corrected !
 
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MongooseDownUnder

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I imagine it will have a very low yield especially in most parts of Australia. Nanotech is quite capable of achieving this I think but it's expensive and not very reliable. I certainly would not be putting my life on the line by relying on this contraption.
 

Aussie123

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I imagine it will have a very low yield especially in most parts of Australia. Nanotech is quite capable of achieving this I think but it's expensive and not very reliable. I certainly would not be putting my life on the line by relying on this contraption.
I think I saw that it needs 35% relative humidity ... I'm not sure how an increase in humidity would affect the yield (double the humidity does not necessarily = 2x the yield ?)

Today the filter would work in most parts of the country (nothing below 30%):
http://www.bom.gov.au/watl/humidity/
 

MongooseDownUnder

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That sounds quite good, I wonder how much water you actually get per hour though. I was looking at the bike version I imagine the yield will be much lower than your actual water requirements.
 

Aussie123

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That sounds quite good, I wonder how much water you actually get per hour though. I was looking at the bike version I imagine the yield will be much lower than your actual water requirements.
I also wonder how robust / long lived / easy to clog it is ....

None the less, plenty of people spend $ on all sorts of equipment on the basis that some is better than none.

I was thinking about using it at sea, where there's plenty of humidity, but not much fresh water
 

Aussie123

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I was reading about the Namib Desert and read about the Fogstand Beetle and immediately recalled this discussion.

A bit more googeling and found this article:

http://www.bbc.com/news/technology-20465982

You just can't beat nature when it comes to high technology !

.... another article talked about manufacturing high tech "tents" to harvest water, I suppose they were talking figuratively not literally, but imagine if you did make a tent or tarp
out of this material, you could wake up every morning to a replenished water supply.

... or a vehicle paint. You can have a permanently full water tank in your car.
... new hat ? A jacket ? The walls of you house, or a farmer's fence line (to provide water to a dry paddock) .... lots of potential applications ....
 
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