# Storing wind-generated energy as gravitational potential energy?

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Posted by John Nagelson on December 7, 2008, 3:31 pm

Not so great with wind-generated energy is the fact that you need a
battery bank, and batteries are expensive.

So why not store the energy as gravitational potential energy?

E.g. make the generated energy lift a large weight, controlled in such
a way that it falls when you need it to, yielding just the amount of
electrical power you need?

??

Parts would need replacing far less often than batteries.

John

Posted by Andy Burns on December 7, 2008, 3:41 pm

John Nagelson wrote:

They already use water as the large weight, is anything practical?
Just over 1kWh from 4 tonnes lifted 100m (excluding losses).

Posted by John Nagelson on December 7, 2008, 3:52 pm

True that (mass) x (g) x (height) = (required power) x (time) gives
large figures for (mass) x (height).

But maybe with concrete or old cars?
Or maybe store some as elastic potential energy?
I'm only thinking about at a domestic level.

John

Posted by Vortex3 on December 7, 2008, 3:56 pm

True that (mass) x (g) x (height) = (required power) x (time) gives
large figures for (mass) x (height).

But maybe with concrete or old cars?
Or maybe store some as elastic potential energy?
I'm only thinking about at a domestic level.

John

____

Take a read of chapter 4 of Prof David Mackays fantastic book on sustainable
energy: http://www.inference.phy.cam.ac.uk/sustainable/book/tex/cft.pdf  (10
meg download)

I think actually harvesting sufficient wind energy in the first place is
problem zero.

D

Posted by The Natural Philosopher on December 7, 2008, 4:18 pm
John Nagelson wrote:

When you look at energy density, for any form of storage of usable
energy, you find a scale, and the lowest on the scale is mass times
height systems.

Much better is mass times velocity squared, and heat. Both of those can
be large in small spaces and volumes. At moderate heats too.

Then comes chemical energy, liquid fuels, batteries and the like. Things
start to get pretty compact. Self contained portable power units of
sensible dimensions become possible.

At the top of the scale is nuclear energy.

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