34 comments

MostlyStableabout 11 hours ago
Cool concept. As they mention, more work needs to be done on long term durability, although they saw no degradation in their (very short) testing period. To me, the humidity control seems more worthwhile/useful than the power generation, although that could be a useful solution for small IoT devices like door and window sensors that don't need much power.

I like it as a proof of concept, would love to see a more serious engineering effort to demonstrate what real world costs, durability, and aesthetics might look like (if significant portions of indoor walls are going to be covered in this stuff, it needs to be able to look decent).

jedbergabout 12 hours ago
I've thought for a while that it would be interesting to have micro dehumidifiers on my roof that supplement my water supply from humidity.

Turn myself into a moisture farmer if you will.

But then I wonder, would it be a problem if everyone did it? Would it cause humidity to drop in a bad way?

chris_vaabout 11 hours ago
oo, fermi estimate time!

Typical 50% RH at ground level is ~7g/kg air, air is roughly 1kg/m^3, so between the surface and the planetary boundary layer (let's say 1km) is about 7L of water per m^2 of surface. Moving along at ~3m/s means 21L/s passes by each meter of fence line.

PBL probably mixes after about 50km, so it takes ~5 hours to normalize after you pull out water at ~5 knot wind speed. If you want to not make a dent, means you can pull less than 1L per m^2 per hour, or about 8m^3 pear, which is about 8x the yearly requirement for farmland.

So, you can irrigate a farm and your neighbors would mostly be fine.

(math not checked)

jaggederestabout 9 hours ago
Absolutely can pull the water you need for e.g. household purposes out of the air - somewhere north of $0.10 a gallon or so, spendy, but close to trucked water - maybe $1k a month, give or take. People pay that much for trucked water, though a well is rapidly cheaper if it's available.

For a farm, say growing almonds (notably water intensive, but a reasonable first pass), you need about 4 acre-feet per acre per year, which would cost... hmm, somewhere in the very rough ballpark of $200k / yr.

That might put the economics of almond farming substantially in doubt, given that an acre of almonds might yield a value (revenue, not profit) of, say, $10k on a good year.

jawnsabout 12 hours ago
In humid regions, there is no practical limit that would cause any noticeable effects on the humidity of outdoor air. There is just so much water in the air that even if you were running dehumidifiers across all available land area, the air is still going to feel humid.
roughlyabout 11 hours ago
The other side of that is that a big problem we're going to have moving forward is dealing with increased humidity - the climate change angle isn't just heat, heat + high humidity (the wet bulb temperature) is the actual health risk and the thing that takes a heat wave from inconvenient to a genuine crisis. Turning high humidity into drinkable water is two birds with one stone, if you do it right.

(To your point, it's almost impossible to imagine we'd be able to operate it at a scale that makes a genuine impact, but these are all chaotic systems and a couple percent here and there can compound to keep things on the right side of the phase shift.)

jedbergabout 11 hours ago
True but in those areas it also tends to rain a lot so it's less necessary. I'm thinking about Mediterranean and desert climates.
RobGRabout 11 hours ago
There are commercially available systems that do that now, one that seems popular in my area is https://www.aquaria.world/ .

As to your question, would it be a problem if everyone did it -- it depends obviously on your definition of "problem", but consider that most people doing this have no way to dispose of the water they take from the air except by putting it back in the air. It might increase regional power consumption, and smooth out nightly shifts in atmospheric humidity, but unless there is a new river running to the sea, the average atmospheric humidity will remain the same.

largbaeabout 11 hours ago
This is fun, thank you! I wonder why home HVAC units couldn't just capture the drain water to accomplish something similar for "free".
NewJazzabout 12 hours ago
It would probably depend on how you use the water. Watering plants (including via gray water systems) would mean a lot of the water would evaporate or transpirate. Flushing it down the drain means it exits the system.
cyberaxabout 9 hours ago
> I've thought for a while that it would be interesting to have micro dehumidifiers on my roof that supplement my water supply from humidity.

Hi! This is friendly neighborhood energy conservation law speaking!

You can't just get moisture out of the atmosphere without investing energy. This device works backwards, it exploits the difference in humidity between the indoors and the outdoors. The source of this difference is ultimately the stored energy in food. Humans burn the food and release water vapor as a result, raising humidity inside the building.

dinkblamabout 11 hours ago
> A 1596-unit array powers a wireless keyboard and simultaneously reduces indoor humidity from 38% to 32%,

isn't below 40% "bad"?

ortusduxabout 11 hours ago
Depends on your region, house, and preferences:

https://midwesthvacpro.com/what-should-indoor-humidity-be-a-...

Carrokabout 11 hours ago
Bad by what metric?
robinsonb5about 10 hours ago
Bad as in your lips will be prone to chapping, you'll get frequent random static zaps, and your guitar top will split?
fodkodraszabout 8 hours ago
Meanwhile I'm struggling to increase humidity as it is unhealthily dry at my place... (and ultrasonic evaporators are a no-go)
bix6about 12 hours ago
That’s impressive humidity drop for a small panel area. Curious how big the room was.

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