In article , Peter Duncanson
wrote:
On Sat, 25 Jun 2011 13:33:13 +0100, "Max Demian"
wrote:


I've just invented a new kind of vacuum cleaner that uses no energy.
Just attach one end of a very long tube to a satellite in
geostationary orbit, with the other end dangling down to Earth.
There's a stopper in the bottom end which you remove to suck up all
the dust into space.

If space elevators [ http://en.wikipedia.org/wiki/Space_elevator ]
work, why not this?

It will work nicely until the pressure in the tube equals the pressure
outside the tube. Then it will stop sucking. After that you would need
to pull the tube up into space, empty it, put the stopper back in and
lower the end back to the surface.

Unfortunately, both the dangling sucker and the space elevator require
energy for their construction and use.

In one sense the 'invention' isn't a new one. I recall reading some
research studies some decades ago on something similar. The idea was,
indeed, based on a very tall 'chimney'. However it sets out to exploit the
temperature gradient.

The idea is that you 'prime' the process by deliberately warming the air in
the tall chimmey column. [1] This causes an updraft to initiate. Once this
is started the chimney keeps drawing in warmer air from the base are
letting it rise. The result is a column of lower-density warmer air at each
level compared with its surroundings. So the process continues.

You can then fit turbines to take off power.

AFAIC it is theoretically feasible provided you have a temperature gradient
with the temperature falling with height at a suitable rate. The snags are
all 'in practice' - as usual for neatly novel ideas. First build your
chimney (some kilometers high)...

In essence all it does is trap and use the convection currents that occur
anyway as the Sun warms the ground and starts updrafts. Birds and gliders
make good use of this at present. Quite a lot of power is available. But
only if you can build on a suitably grand scale. :-) People in the d-i-y
group might like to try this in their garden... if they can get planning
permission. ;-

Slainte,

Jim

[1] One way to do this is to paint the chimney black so it absorbs sunlight
and warms the air inside. This also helps the process that follows.

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