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atmospheric water generator

A project log for Silly hardware wishlist

Too simple for a project page & which may never happen.

lion-mclionheadlion mclionhead 08/09/2021 at 04:280 Comments

The lion kingdom has pondered the implications of living off grid in Fl*rida, as regards the water supply.  Unless you're very lucky in the stonk market or in business, no career yields enough to retire in a cozy municipality.  The lion kingdom is going to have to move to the middle of nowhere eventually.

People living off grid in Calif* have seen their wells dry up for years or been banned from using them, in order to preserve the city water supplies.  There probably will be a similar story in Fl*rida.  The lion kingdom lived through 1 drought in Fl*rida which entailed water conservation & a burn ban.  Environmental laws are going to get more strict as more New Englanders move down.

The leading solution is extracting water from air.  It's not as cheap as trucking it in, but it's convenient & more reliable than trucking it in.  During the summer, even the drought years in Fl*rida have far more humidity than anywhere else.  Winters in Fl*rida have similar humidity to Calif*.  Humidity always peaks at night, but the air has to be much colder at night to extract water.  The most efficient process is to condense water from air during the hottest time of day, when the dew point is highest.  Water could also be collected from the house air conditioning.

Commercial atmospheric water generators are all pretty bad.   No-one really knows how they work.  They're just air conditioners.  They don't have any attachment for bringing in outside air, so people run them in their living rooms where the air is dry & it recirculates doing nothing.  They filter all the water in expensive filters & require water to clean their air filters.

In exchange for $3500 & 1500W, they generate 10 gallons/day.  Lions need over 40 gallons/day to wash their manes.  The mane advantage of a water generator over an air conditioner is it doesn't need to output any cold air.  The air & water exiting its heat exchanger is just above freezing.  It can be used to cool down another heat exchanger or cool down the condenser.  The other improvement would be filtering only some of the water for drinking.  It might be more efficient to store solar power in a battery until the hottest time of day.

All the DIY water generators are on the gootubes.  They all use peltier coolers.  Helas, they don't have any optimizations like using the cold output products to cool the peltier module or a 2nd stage heat exchanger.  The trick is passing just enough air over the heat exchanger to get it just above freezing, then pass the nearly frozen water & air to a 2nd heat exchanger to extract more water, then pass all the products to the peltier module's heat sink to aid the fan.

The condensation can be improved by 1st collecting water from a large area in a dessicant, then heating the dessicant to release the water in a small chamber where a conventional air conditioner can condense it.  This is more useful in a place with low humidity.

There are more passive water generators which radiate heat at night, then retain their cooler temperature in the day to condense water.  This could be done with water as a working fluid, but it always requires a lot of space.

In reality, the lion kingdom would suffer with trucking in water for a long time before ever investing in atmospheric water generation, but there are some unused solar panels & a battery which could be used in a very small proof of concept.

The media has slowly latched onto atmospheric water generators, better late than never.  The official story claims a minimum 30% humidity & 50F ambient temperature, but your luck will vary.  There are several high & dry days in winter when the temperature never gets above 50F in Fl*rida.  The 2 mane workarounds are moving air faster through a smaller collecting area or making a bigger collecting area for slower moving air.  The winner depends on what's cheaper.

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