Flow batteries have been in the news every year but I've yet to see a deployment other than this one. If they're so simple what is holding large scale implementation back?
Usually, just turning down some fossil fuel plant is a better option.
Using the electricity via demand response comes after that.
A long wire to somewhere else that can use it and send you back some of their excess is next.
If you really can't use that power for anything lithium batteries are cost efficient as long as you regularly cycle them (e.g. daily solar peaks).
So you need to get into storing power for long periods of time before they have a niche. Which is on its way, but isn't here yet. So building more renewables makes more sense. (Do enough of that and eventually you'll want some more storage options).
That happens over and over for each house that gets solar installed and the grid is not trusted, or is badly overpriced (as in many places with nukes).
If you scroll down there's a table 32.7 about Projects in China. A number of which, according to that table, are completed.