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Picture a largeish, but very shallow body of water in a
climate subject to winter freezing and summer thawing.
The body is in fact shallow enough that the entire body
freezes. Perhaps a very large kiddie pool. Let's make it
cylindrical-shaped for simplicity.
Floating on the surface of this
large body of water is
Maxwell's demon, resting comfortably on a beach chair
on
top of a floating 'lid,' which covers the entire surface of
the kiddie pool and basically seals it. Connected to the
lid
is a piston arm which apply the upward motion induced
by
the freezing of the pool water into some potential energy
which is then converted in your method of choice.
Perhaps
hydraulic displacement or whatever. Effectively we have
a large, squat
cylinder which expands and contracts with the weather
and
supplies some power in doing so.
Despite resting easy on his beach chair, the demon is
perplexed as to how to balance his energy books and
explain matters to his head gargoyle who doesn't like to
be trifled with when joules come up missing.
Liquid density&pressure
https://www.enginee...pressure-d_309.html
[bs0u0155, Jan 10 2018]
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hmmm, water gets about an 0.5% volume change between
4-15C which is better than the ice-water system because
the phase change is a real energy suck. Also, 4-15 is
totally feasible on a day/night cycle in many parts of the
world. |
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So say you had some 10m tall tubes with pistons in,
between min/max temp you would get a 5cm throw,
which isn't great, but workable. The energy output would
be the throw * the force. How large can the force be?
well, liquids are non-compressible, so effectively
infinite??? It's here that I faced a fork in the road, free
energy Youtube video one way, self education the other. |
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Self-education yielded another high-school science lie,
liquids compress, there's curves and everything <link>. So
the energy output would, rather boringly, be limited to
the low grade thermal energy input extracted very slowly
and probably inefficiently. Sort of a Sterling engine,
without all the fuss. |
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Make the vessels rigid and conical, with a float on the top. |
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Ambient energy harvesting from a negative temperature differential - nice. |
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If you extrapolate those data points, the bottom of your
garden variety oceanic trench is worth a 5% density
increase, which should make it a little easier to float to the
surface should you find yourself there unexpectedly. |
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// the demon is perplexed // |
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And I'm confused. Is the demon perplexed as to where his potential energy has come from? Surely it comes from the water, as it freezes? |
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I suppose the water, when freezing and thus lifting
the
demon, must do some work under pressure, and
thus
freezes a tad slower than when not under any more
pressure than 1 atm. |
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bs0u, I’m most interested in the potential from the
phase
change. Forget the min max temp differential, the
9% ice
expansion here is what’s interesting, where a
reduction in thermal energy results in a potential
energy rise. |
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//I suppose the water, when freezing and thus lifting the demon, must do some work under pressure, and thus freezes a tad slower than when not under any more pressure than 1 atm. // |
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Quite so. And, reciprocally, you can melt ice by compressing it. |
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I'm pretty sure entropy is involved somewhere, but me and entropy have never seen eye to eye. |
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Don't worry, it'll approach your level of disorder
eventually... |
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