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This may be baked... But I haven't found it yet.
An elevator uses a counterweight to move passengers up and down. This weight is usually 40% of the max load. When an elevator is 40% full, then the motor only has to overcome frictional forces. Any other occasion is a chance for optimization, though.
My
proposal is for a dynamic counterweight system where the elevator registers the load and selects its counterweights accordingly. This would make the motor more efficient. Counterweights would be interspersed throught the shaft, with a mechanism for attaching to the chain based on input from the elevators ouput data. Hopefully, random processes would keep each interval of the shaft equipped with a sufficient number of counterweights.
Patent WO2004039716
http://v3.espacenet...DX=WO2004039716&F=0
An autobalancing roping and drive arrangement for elevators which continuously balances the weight of an elevator cab and the weight of a counterweight [xaviergisz, May 17 2005]
[link]
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I think this needs some maths and/or
modelling.At the moment, I'm sitting on
the fence:
Downside
argument: my gut feeling is that you're
going to wind up having to restore the
counterweights to their original
positions at some point, and the energy
you save on the one hand, you will
waste by having to re-juggle your
counterweights. Unless you have
hundreds of weights to ride the
averages over the day.
Upside
argument: what this is leading to,
fundamentally, is a system for
averaging the load over several
journeys. Since everyone who goes up
must eventually come down, any such
time-averaging should help (net
passenger load lifted over 24hrs=zero).
So, this could lead somewhere.
Extrapolation from the
above: maybe it makes more sense to
use water as the variable counterweight.
It's easier to add and remove, and a
large water-tank in the roof could act
as a buffer. |
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Water is a nice element to this idea. Its sooo.... continuous... Then again, the floors are discrete, the load is discrete... not that quantifiability has anything to do with the soundness of an idea. |
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I believe my idea (especially with water) deviates from the patent sufficiently. |
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[BasePair], I'd be a fool not to hang around the fence, especially on my own ideas. But, you're reading my mind, and that scares me. |
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[Pa've], I think the 40% number should be a clue that gains can be achieved. Its shows compromise in design, and compromise is always cutting yourself short. |
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rather than the additional counterweights being added from the elevator shaft, could you instead slide weights across from the elevator onto the counterweight cable (and then back again when needed)? The counterweight cable would have hooks at regular spacing to hold the counterweights... |
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Unless all the occupants are jumping out of windows, they must be returning to the ground floor. |
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Use regenerative braking to recover the excess power used to lift them in the first place. |
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Using variable counterweights is too halfbaked... |
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The trouble with using counterweights
that you pick up and drop is that lift use
in office blocks is quite 'tidal': lots of
people going up in the morning, lots of
people coming down in the evening. |
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In a 10-storey building with a limit of
100 people per floor you'd need at least
65 tonnes of counterweight to fill the
building with people. That's about 8
cubic metres of metal. |
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If you're willing to live with that weight
spread about the building and a limit to
how many people you can bring into the
building then I think you've got a goer. |
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[Ling], I'll take it as a compliment! |
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[st3f], That is mostly true. At some point in the day, you will have a maximum amount of PE in the people, and it will have to have come from the counterweights. Considering the "tidal" aspects of the office, this weight will be large, but are you sure that number is too large? |
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Are the counterweights distributed amongst the floors? In other words, does each shaft have a cache of counterweights on each floor? |
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Because the total delta P.E. over the course of a day is zero, this cache issue should not be a problem. But, I do see how all the weights collect somewhere and can't be used for the desired lift. |
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The water idea would require two buckets, one of them counterweighting the load. The other one will be the buffer. the buffer dumps into the counter until it matches the load. When the load is coming back down, the counter pours the water back into the buffer thereby retrieving the P.E. of the raised load. |
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//But, you're reading my mind, and that
scares me.// I knew you'd say that. |
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If water is to be used, rainwater could be
collected at the roof for this purpose. |
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