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Old Dec 21st 2016, 08:06 PM   #1
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Does anyway use escalators to generate electricty

I was at a large baseball stadium today and they had escalators to bring everyone up to the upper levels at the beginning of the game. At the end of the game, when everyone was leaving, the escalators were shut off and blocked off and everyone was walking down ramps to exit. I was thinking it should be possible to have everyone take the escalators down and the motors could be used as generators to generate electricity to sell back to the electric company. Does anyone do this? Is there a practical reason why this wouldn't work?
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Last edited by MartinL; Feb 23rd 2017 at 11:50 PM.
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Old Dec 22nd 2016, 06:06 AM   #2
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Originally Posted by MartinL View Post
I was at a large baseball stadium today and they had escalators to bring everyone up to the upper levels at the beginning of the game. At the end of the game, when everyone was leaving, the escalators were shut off and blocked off and everyone was walking down ramps to exit. I was thinking it should be possible to have everyone take the escalators down and the motors could be used as generators to generate electricity to sell back to the electric company. Does anyone do this? Is there a practical reason why this wouldn't work?
Using the weight of the people to push the escalator down? I would think that would be unstable and very dangerous.
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Old Dec 24th 2016, 08:33 AM   #3
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Nice Idea, but...

Sounds like a nice idea,
but I think the control system, to do it safely, would be too difficult.
The control system will have to continuously adjust for the varying number (and size) of the people on the elevator;
otherwise the speed of the elevator will be continuously varying (not safe).
This would also mean that the electricity generated would be very variable, which is undesirable.
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Old Jan 3rd 2017, 12:38 PM   #4
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I'm not aware of anyone doing this, but I think it's less an issue of it being too difficult than it is an issue of not being economically practical. It seems like such an obvious thing, there must be a reason no one's doing it, and so ran a few back-of-the envelope numbers:

The energy that could be captured through a controlled descent of going down hill is:
Delta PE = mgh

If we assume the average person is 80 Kg and the height of the escalator is 50m then the energy that could be captured (if the machinery is 100% efficient) is

Delta PE = 80 kg x 9.8 m/s^2 x 50 m = 39,200 N-m = 39,200 watt-seconds.

If there were 10,000 attendees at the ball game, the total energy produced would be 3.92 x 10^8 watt-seconds. Which sounds like a lot, but convert to kilowatt-hours and it's only 109 kWh. The price of electricity varies, but a reasonable average number is 20 cents/KWh. So in theory the baseball stadium could sell the energy from one ball game for about ... $22. Obviously the investment for the special machinery to make this happen would be in the tens of thousands of dollars, so unfortunately this wouldn't pay off. That's why no one does it.
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