Thread

1. jedberg · 1790786161 · focus · HN ↗

   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?

   1. jawns · 1790788105 · focus · HN ↗

      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.

      1. jedberg · 1790790512 · focus · HN ↗

         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.

         1. OneDeuxTriSeiGo · 1790791202 · focus · HN ↗

            As long as the water is being locally used and locally discharged (i.e. via a drainage field) it shouldn't seriously have an impact. The water would return to the water table and either be used by plants or get wicked back into the air via capillary action from evaporation on the surface.

            1. clickety_clack · 1790824441 · focus · HN ↗

               I guess technically you’d be adding water to the water table since the water was in the air before you pulled it out.
         2. mrguyorama · 1790801744 · focus · HN ↗

            In places with low ambient humidity, harvesting water from the air is an atrocious process. The physics have not changed since people came up with this idea the last time, and the time before that.

            For reasons of thermodynamics, pulling water out of the air uses more energy than desalination, and that's before the fact that you have to have a large fan to move a large volume of air to get a few drops of water.

            It is on the order of using 60X as much energy to dehumidify air if you are trying to produce bulk water, rather than just desalinating water through a method like reverse osmosis

            1. RobGR · 1790805341 · focus · HN ↗

               When these systems are designed for low ambient humidity areas, they use a desiccant based first stage, where desiccant wheel or loop captures water from the low humidity air, and then is heated in a chamber to "regenerate" it and drive off the water into a 100% humidity chamber where the condensation can happen.

               The applications of condensate water sources typically aren't in areas where desalination is the competing technology -- usually the competition is piping water in from far away via a utility system.

      2. roughly · 1790791015 · focus · HN ↗

         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.)

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