Ann: Protean to Acquire 50% Stake in Flow Battery Manufacturer, page-11

Not sure when scaled to 5MW (MegaWatts) it is 'small scale', or aimed at microgrids. A vaguely stated, or hinted at feature (in the announcement) is the technology's has a longer life span than the hot to trot lithium technology, which has a lower capacity and a longer ROI.
The simple equation is: Lithium life and ROI versus, Vanadium redox life and ROI. The POW technology looks to be in front. One downside is, VRedox doesn't cut the domestic situation, Yet. I see community partnerships with one VRedox battery say, supplying a number of domestic consumers - and Soon.
The 'bullet points' in the announcement say quite a bit. They need a considered read.
IMO vanadium redox battery may (not yet) suit a domestic application but it certainly sits in a sweet spot for commercial installations where feeding back excess to the grid doesn't happen. They capture solar and just store it for internal use. At the present, in a commercial scenario, using a Lithium solutions just doesn't seem to stack up. But those guys will be working on it.