harvesting electricity from humidity

[InterestedEngineer]

https://www.sciencedaily.com/releases/2023/05/230524181948.htm

Applicability to space habitats, comets, anywhere there's water available.

And yes, the net energy input has to be the sun or some other heat source, to evaporate the water in the first place.   For space purposes it's more of a competitor to solar cells or thermo-electric.

I wonder if would be more efficient than the 10% thermoelectrics are getting of RTGs.

[redneck]

John Galt in Atlas Shrugged?  Written before I was born and I'm old.

[InterestedEngineer]

I think the idea suffers from the fact that there has to be a humidity gradient, and the proposal doesn't clarify how the dry side is going to stay dry.

(the wet side staying wet is easy).

It'll take energy to dry out the dry side.   Thus you now have something like a classic Carnot cycle setup, with a humidity gradient instead of a temperature or pressure gradient.

For an RTG, it's pretty easy to see the humidity loop - the RTG evaporates the water from the dry side of the gradient. radiators cool it to concentrate the humidity to something like 99%, and the device works as is in the middle of this loop.   Conversion efficiency compared to Thermal-Electric (TEG) devices is what I"m curious about.

EDIT:  Or a combined cycle with TEG devices, where the waste heat from the TEG is first used to evaporate water in the humidity loop.