[extropy-chat] energy from osmosis

The Avantguardian avantguardian2020 at yahoo.com
Tue Oct 4 03:50:27 UTC 2005

--- Hal Finney <hal at finney.org> wrote:

> This is a problem for Spike's invention, because the
> necessary
> pressure differential for reverse osmosis will
> increase as the water
> becomes saltier.  Therefore as he sinks his pipe
> lower, the increased
> saltiness of the ocean will cause a greater pressure
> difference across
> the membrane, which will reduce the pressure needed
> on the fresh water
> side of the membrane.  As a result, his fresh water
> column will not grow
> as high as hoped.

Yes, but the osmostic pressure is directly
proportional to the temperature. That is to say that
the osmotic pressure increases with salinity and
decreases with temperature. So what's important is
whether, as one decends down into the abyss, it gets
saltier faster or slower than it gets colder. It is a
race between the slainity gradient and the temperature
gradient essentially and they are equally important in
this regard since their product multiplied by a
constant (the ideal gas constant) is the osmotic
pressure that must be overcome for the device to work.

The Avantguardian 
Stuart LaForge
alt email: stuart"AT"ucla.edu

"I don't want to achieve immortality through my work. I want to achieve it through not dying." - Woody Allen

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