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Posted by The Natural Philosopher on December 7, 2008, 11:18 am
Please log in for more thread options John Nagelson wrote:
>> John Nagelson wrote:
>>> 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?
>> They already use water as the large weight, is anything practical?
>> Just over 1kWh from 4 tonnes lifted 100m (excluding losses).
>
> 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.
>
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.
> John
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