[extropy-chat] energy from osmosis

Mike Lorrey mlorrey at yahoo.com
Sun Oct 2 18:17:57 UTC 2005

One other thing: You still need to preserve the 240m pressure
differential at the filter, you know, even when the pipe is full of
fresh water, which creates its own pressure. However, your proposal can
explain how you can get pressure out of an artesian well even at the
top of a mountain: the rock is denser than the water, so it pushes the
water out. In oil wells, there is typically oil and salt water, with
the oil being forced out by the salt water, as the oil is less dense,
which of course creates a pressure differential with lower deposits to
refill the reservoir...

--- spike <spike66 at comcast.net> wrote:

> > bounces at lists.extropy.org] On Behalf Of Mike Lorrey
> > Subject: Re: [extropy-chat] energy from osmosis
> > 
> > ... We could then hook up a water wheel and
> > > have a perpetual motion machine. Now we know
> > > something is seriously wrong, but what?
> > 
> > What is the pressure limit of the osmotic membrane?
> I don't know, but it is high.  Seawater is currently
> desalinated by pumping it thru osmotic membranes.

Sure, at the ~240m pressure equivalency. I've got a clay osmotic filter
I use for camping. I doubt it would stand up to the pressure of the
depths (also gotta figure out embrittlement from the cold of the depths
> > 
> > Okay, here goes:
> > Until you reach 240 m, you are trying to sink the pipe which is
> likely
> > positively bouyant.  You can either force it down by some mechanism
> that
> > is anchored to the bottom, or else ballast it down with weights...
> No issue, fill it with fresh water.
> > The walls of the pipe will need to get progressively thicker as you
> sink,
> > so this automatically adds weight as well (and of course energy to
> > refine the materials used in making the pipe)...
> OK.  Ordinary modern steel alloys could carry the 
> weight if we weld in thicker wall steel at the top
> of the pipe.  Do the calcs Mike, you know how.  {8-]  The
> density of steel is close enough to 8g/cc for
> this calc.  Ordinary steel can go 400 megaPascals
> tensile, and you know the maximum compressive pressure 
> on the pipe is 2.4 mPa, which is nothing to small
> diameter pipe.  Submarines can down that far.
> ...
> > 
> > There is nothing wrong with what you propose, though, because the
> > energy differential between fresh and salt water is a real
> potential,
> > which you can use in the reverse in a riverine tidal zone at the
> > salinocline (provided you have a dam or dyke built there) to draw
> > electric power out of the ion influx, which is the more typical
> > application of osmotic filters for this purpose.
> > 
> > Mike Lorrey
> OK I figured out the solution this morning; Mike's
> post kinda hinted me there.  I went crazy last night
> trying to figure it out.  I will post what I think
> is the right answer in about a little later.  The hint that
> Mike posted is in the comment "There is nothing wrong
> with what you propose..."
> spike
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Mike Lorrey
Vice-Chair, 2nd District, Libertarian Party of NH
Founder, Constitution Park Foundation:
Personal/political blog: http://intlib.blogspot.com

Yahoo! Mail - PC Magazine Editors' Choice 2005 

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