Imagine a person residing on 100th floor. When new TV was brought by him to 100th floor, energy was spent & converted to potential energy.

Now the TV weighing 20kg (say) needs to be disposed of. Rather than taking it downstairs through escalator, it is descended through a rope-pulley system connected to generator & battery charger. It is a public system, that can be used by all residents of 100th floor at their convenient timings.

The trash collecting area is vertically below the pulley system. The rope doesn't have open ends. So a small part of energy would be spent for its upward movement while the trash is being lowered. When the trash reaches ground floor, rope is removed & knot is tied by the person waiting there. After disposing of few objects, there would be multiple knots on the rope loop. This would be made in a bundle & descended to ground floor using new rope. Of course, the pulley is designed to take care of knots in the rope.
-- vedarshi, Nov 05 2006

Why not just use regenerative braking on the elevator? They already use counterweights, so little energy was wasted anyway.
-- kevinthenerd, Jan 24 2010


kevin has you on all accounts there.
-- WcW, Jan 24 2010


Well, for a minute there I thought this was an idea to burn junk in a generator.
-- ye_river_xiv, Jan 25 2010



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