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They're called dehumidifiers. This idea has been debunked more times than I can count.

Aromasin 3y ago
I live in a damp and dingy English cottage. I'm sure that the moisture from my 3 dehumidifiers could quench the whole county if distributed accordingly.
- tomcam 3y ago
  Okay but… do you like living in it on the whole? Sort of an Anglophile bucket list thing.
  - Aromasin 3y ago
    It is nice, albeit the old windows (listed building which means I can't replace them) let out a lot of heat. The fireplace generally heats the whole place effectively when it's on though. It's worth it for the character of the house.
    - tomcam 3y ago
      Thanks for scratching my itch. Too old now but for years I dreamt of living in a place like that.
dartos 3y ago
And yet, people with money keep throwing it at these ideas. Imo this is just an easy way to get grants from nonprofits
BobaFloutist 3y ago
I have in the past wondered about using small-scale dehumidifiers/desalination as an outlet for peak solar generation in, say, California, but water's probably still too cheap to justify it.
carimura 3y ago
what exactly has been debunked?
- realusername 3y ago
  That you can provide drinkable water in meaningful quantities from dehumidifiers. Dehumidifiers are one of the most energy intensive way to get water and if you live in a very humid region, well you already have water.
  - Turing_Machine 3y ago
    Hmm... Consider the Pacific Northwest. The difference between coastal Washington state and eastern Washington is tremendous. Seattle gets around 39 inches (~1 meter) of precipitation per year. Spokane gets less than half that. This is almost entirely due to a natural "dehumidifier". If the Cascades weren't there, there'd be much less disparity. And yeah, there's energy input, but it comes from the sun and no one has to pay anything for it.
    - realusername 3y ago
      Sure but the energy on the weather is in another scale compared to anything manmade.
- dredmorbius 3y ago
  Effectively, dehumidifiers reverse the boiling process. To boil water you've got to add the thermal heat of vapourisation to water, 540 calories/g, or about 2 kJ/g. To condense water you've got to remove that same quantity of heat. Granted that heat pumps are more efficient than adding pure heat, you're still looking at expending somewhere between 10--20% of the energy removed. Energy usage also varies with the relative humidity and ambient tempuerature. Remember that both the lower the relative humidity and the lower the ambient temperature the lower the amount of water (absolute humidity) in the air. Dehumidifiers work best when handling hot, humid air, which is not typically where water is in short supply in the first place. Attempting to dehumidify cool dry air, say, in a high-altitude desert, will be exceptionally energy intensive and produce very little output water. The condensation traps and nets mentioned in TFA work best in very-high-humidity environments. This can be useful, but again the total gains are limited, and the process remains the "un-boiling water" problem.

I live in a damp and dingy English cottage. I'm sure that the moisture from my 3 dehumidifiers could quench the whole county if distributed accordingly.

tomcam 3y ago
Okay but… do you like living in it on the whole? Sort of an Anglophile bucket list thing.
- Aromasin 3y ago
  It is nice, albeit the old windows (listed building which means I can't replace them) let out a lot of heat. The fireplace generally heats the whole place effectively when it's on though. It's worth it for the character of the house.
  - tomcam 3y ago
    Thanks for scratching my itch. Too old now but for years I dreamt of living in a place like that.

dartos 3y ago

And yet, people with money keep throwing it at these ideas. Imo this is just an easy way to get grants from nonprofits

BobaFloutist 3y ago

I have in the past wondered about using small-scale dehumidifiers/desalination as an outlet for peak solar generation in, say, California, but water's probably still too cheap to justify it.

carimura 3y ago

what exactly has been debunked?

realusername 3y ago
That you can provide drinkable water in meaningful quantities from dehumidifiers. Dehumidifiers are one of the most energy intensive way to get water and if you live in a very humid region, well you already have water.
- Turing_Machine 3y ago
  Hmm... Consider the Pacific Northwest. The difference between coastal Washington state and eastern Washington is tremendous. Seattle gets around 39 inches (~1 meter) of precipitation per year. Spokane gets less than half that. This is almost entirely due to a natural "dehumidifier". If the Cascades weren't there, there'd be much less disparity. And yeah, there's energy input, but it comes from the sun and no one has to pay anything for it.
  - realusername 3y ago
    Sure but the energy on the weather is in another scale compared to anything manmade.
dredmorbius 3y ago
Effectively, dehumidifiers reverse the boiling process. To boil water you've got to add the thermal heat of vapourisation to water, 540 calories/g, or about 2 kJ/g. To condense water you've got to remove that same quantity of heat. Granted that heat pumps are more efficient than adding pure heat, you're still looking at expending somewhere between 10--20% of the energy removed. Energy usage also varies with the relative humidity and ambient tempuerature. Remember that both the lower the relative humidity and the lower the ambient temperature the lower the amount of water (absolute humidity) in the air. Dehumidifiers work best when handling hot, humid air, which is not typically where water is in short supply in the first place. Attempting to dehumidify cool dry air, say, in a high-altitude desert, will be exceptionally energy intensive and produce very little output water. The condensation traps and nets mentioned in TFA work best in very-high-humidity environments. This can be useful, but again the total gains are limited, and the process remains the "un-boiling water" problem.