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World's largest sodium-ion battery goes into operation - Energy Storage
(www.ess-news.com)
This is a most excellent place for technology news and articles.
The main issue with using batteries for load balancing is the massive resource investment required for them at a grid level, BUT that's more of a concern with lithium based batteries due to a number of factors. Sodium batteries use way more easily accessible and abundant materials.
NGL I'm hella fuckin hyped about sodium batteries vs lithium batteries.