[extropy-chat] energy from osmosis
mlorrey at yahoo.com
Tue Oct 4 05:16:15 UTC 2005
--- spike <spike66 at comcast.net> wrote:
> > bounces at lists.extropy.org] On Behalf Of "Hal Finney"
> > This is a problem for Spike's invention, because the necessary
> > pressure differential for reverse osmosis will increase as the
> > becomes saltier. Therefore as he sinks his pipe lower, the
> > saltiness of the ocean will cause a greater pressure difference
> > the membrane, which will reduce the pressure needed on the fresh
> > side of the membrane. As a result, his fresh water column will not
> > as high as hoped... Hal
> True, but check this:
> If this salinity profile is correct and it stays linear, then
> the salinity at 11km is about the same or less than on the
> surface. I do have my suspicions that all is not right
> with this graph however, for I see no reason why the
> salinity up top should be higher than at 500 meters.
> Anybody have any ideas?
Yeah, atmospheric evaporation. Salinity profiles are different for
different areas of the oceans. Only the South Atlantic and the polar
regions really have significantly less salinity at the surface than at
depth, the rest have too much evaporation most of the time, but this
circulates constantly and is dependent upon currents, etc.
However, salinity generally doesn't drop below 3.2% or rise above 3.6%
at any depth. Temperature, however, can be as high as 35 C at the
surface and near freezing below a few hundred meters at the same
location. Temp differentials of 15-35 C are common in the water column.
As I mentioned earlier, if you heat your fresh water on the inside of
the pipe, a few meters above the osmosis filter, you should reduce its
density throughout the rest of the pipes water column even more, thus
creating a greater pressure differential and pushing your water higher
for a given depth.
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