Not as an individual thing, as grid-scale storage. Buffers for solar and wind farms.
I've suggested before that some site such as Electrek have a monthly column, "1, 5 and 10 years ago in battery announcements", so we can look back at the hype. There are so many of these "sort of maybe works in the lab, trillion dollar industry next year" announcements. Usually with videos full of stock photos and talking heads.
Where I live, consumers sometimes end up with solar installations, whose economic feasability relies on the compensation paid by energy companies in the case of overproduction. Which happens in the summer during daylight hours. In the winter, you buy energy at whatever rate the energy company sets. Where I live, these prices are regulated.
You can imagine that there is appeal to being able to store energy year-round, not having to deal with price regulation and energy companies.
My point is, a situation can arise where people want nothing to do with the grid unless there is no other way. Back in the day, running a steam turbine with coal in your backyard was not practical. So was dedicating an entire room for a mainframe computer. When things get miniaturized, running them in your home becomes possible.
If these flow cells, which have been around for a very long time, would somehow be practical in a scaled down form, I can see it work in a one-per-building configuration, assuming those buildings have solar panels.
However it may be preferred to either run the flow cells on a centralized grid as you suggest, or to provide it a more local level, e.g. one installation per residential block. Because people in apartments also need power.
I've suggested before that some site such as Electrek have a monthly column, "1, 5 and 10 years ago in battery announcements", so we can look back at the hype. There are so many of these "sort of maybe works in the lab, trillion dollar industry next year" announcements. Usually with videos full of stock photos and talking heads.