Bloomberg - Big Battery Bonanza, page-6

It will be interesting as they learn more from it to see whether flow batteries will be incorporated. I can see that most of the time lithium makes sense with its higher round trip efficiency for day-to-day price arbitrage, but when a generator goes out, if there’s a bank of fully charged flow batteries underpinning the lithium bank that sit there in standby mode, you could run them flat first, and protect the lithium ones. It wouldn’t surprise me if a hybrid plant springs up.