Self-Filling Water Bottle Condenses Humidity From The Air Into Drinkable Water

Engineer here. Lemme give you the practical numbers. Condensing moisture from humidity into water requires 9000 BTU/gal, if the air's already at the dewpoint, 100% humidity. 17 fluid ounces requires 1195 BTU to condense. If this were the efficiency of a central air conditioner, this would use 92 watt-hrs of electricity. But we're surely talking about Peltier solid-state cooling, which has not advanced significantly in 25 years or so. If it did, it would be huge news. Peltiers are like 10th the efficiency of R134a systems. And the performance curve is really critical- if the heatsink gets significantly warm, the performance drops precipitously. Heatsinks have to be huge to actually dissipate the wattage while not being particularly warm themselves. So you'd need about one kilowatt-hr to make 17 ounces of water in 100% humidity conditions. Just so you know, a fit person pedaling a generator for long periods without going anywhere will generate about 200W, so you'd need 5 hrs of work. Solar panel tech is about 14.5 watt per sq ft. So to generate 1KW in 4 hours of decent sun a day, that would require over 17 sq ft of solar panels to produce the 250W output to condense 17 oz with a Peltier over the course of the day. This doesn't make a lot of sense, you would not have that much sunlight in 100% humidity conditions. What that shows is "moisture farming" is fantastically energy-intensive. If you were going to condense water out of the air, you'd use conventional R134a/R410a refrigeration and counterflow heat exchangers. The performance will be an order of magnitude better, but the bottom line STILL makes no sense. If you had that much power, you'd probably find something better to do with it than making a few oz of water. Water is a thing, but not THAT critical, and if it were, you would not have the means to be doing this sort of huge "solution". Well if you're in a desert with no means of support and dying of thirst, yes 17 oz of drinking water is a big thing, but a massive, expensive solar array would not make any sense as a solution. You need far more water than that to live and farm. In any case, the proposal does not add up. Nothing that size can condense 17 oz of water a day from solar, even under the most ideal conditions, however unlikely they may be.

-/u/oznog99

/r/Futurology Thread Link - hydrationanywhere.com