On Wed, 24 May 2017 13:57:19 +0100, Tim Streater
wrote:

In article , Brian Gaff
wrote:

Maybe its cheaper just to flood old mines and use turbines to generate power
then pump them out when there is little demand. Is it any less efficient
than a bleedin big battery which needs to then be converted to AC in any
case?

Flood them with what?

Something liquid at room temperature and quite dense would be preferable.
Mercury would appear an optimum choice. As for finding an old mine with a
shaft still usable and with roadways still inctact then you are ****ed before
you even start.

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