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195

Penn Engineers Discover a New Class of Materials That Passively Harvest Water from Air (blog.seas.upenn.edu)

submitted 2 days ago by [email protected] to c/[email protected]

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[–] [email protected] 6 points 2 days ago (1 children)

That seems like it would violate the law of entropy by turning a high entropy state (water vapor mixed into the air) into a lower entropy state (water in liquid form), but I'm probably just missing something.

[–] [email protected] 10 points 2 days ago* (last edited 2 days ago) (1 children)

I don't at all understand why the second law of thermodynamics is being invoked. Nonetheless, capillary condensation is already a well-studied phenomenon. As the scientific article itself notes, the innovation here over traditional capillary condensation would be the ability to easily remove the water once it's condensed.

Re: Entropy:

Entropy is a statistical phenomenon that tends to increase over time averaged across the entire body, i.e. the Universe. Not literally every part of the Universe needs to increase its entropy as long as on average it is increasing. You're evidence of that: your body is a machine that takes entropy and pushes it somewhere else.
Water vapor is a high-energy state compared to liquid water. What you're saying therefore is the opposite of how the second law works: water vapor's energy tends to spread out over time until it eventually cools back to a liquid. Liquid water is a higher entropy state than water vapor.

[–] [email protected] 1 points 2 days ago (1 children)

The entropy of a little water mixed with air is higher. As with anything that mixes a little.

[–] [email protected] 1 points 2 days ago

Condensation is exothermic, though, so the material will heat up slightly