They're a bit further along (scaling up from low-volume production, some installs in the wild) with a different approach to the use of iron (flow batteries).
ESS should not be mentioned except as an example of how prone the green news cycle is to fraud. As I detailed last year, their claims are highly dubious:
(previously I misspelled the last name of Sri Narayanan as "Narayan", for which I belatedly apologize)
And that prediction was substantiated when they were subject to a class-action shareholder lawsuit in February involving a fabricated customer which was actually a subsidiary:
Also seems worth mentioning ESS. https://essinc.com/
They're a bit further along (scaling up from low-volume production, some installs in the wild) with a different approach to the use of iron (flow batteries).