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. chris_va · 1790789235 · focus · HN ↗

      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)

      1. jaggederest · 1790797332 · focus · HN ↗

         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.

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