Well, not many of the flow batteries. The whole main concept why so many people think flow batteries are so awesome for gird storage is that you can basically

Well, not many of the flow batteries. The whole main concept why so many people think flow batteries are so awesome for gird storage is that you can basically have a tank size can scale arbitrary. The once that actually have some reasonably big pilot are Vanadium redox battery. There are multiple such batteries being developed. There are also a number of startups who try these flow batteries but try to move away from Vanadium. Li-Ion batteries are collapsing in price so fast, that they have killed of many of these ideas, like the Zebra battery. So newer startups are looking at something cheaper. But the approach of scaling many smaller ones might still work, it just basically defeats the main benefit of flow batteries in the first place.