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'No-water' hydropower turns England's hills into green and pleasant batteries
(www.rechargenews.com)
This is a most excellent place for technology news and articles.
I don't understand how that would work in this case; if this is true, I think I'd need to see a diagram.
My understanding is that they use energy to pump the liquid up during times of excess, and release it to generate energy when there's more demand.