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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.
Supposedly it's exactly that, but stabilized by a polymer to keep it in suspension for up to 60 days without mixing. https://online.flippingbook.com/view/1025707592/10/#zoom=true
Edit: I've concluded it's likely calcium carbonate.
rotor blades are going to love this