[Twirrim]

The main thing of interest (to me anyway) that seems to be missing from the articles I can see on this is references to energy density. Is it equivalent to Lithium Ion? Better? Worse?

There's some tantalising research from a few years ago that suggests it could get way better energy density, but the same comes up frequently with battery technology.

[giantg2]

I don't know the specifics about their iron based battery. However, the concept of iron based batteries have existed for some time and the energy densities are pretty low. My guess is that will be the case here since they are targeting grid storage rather than vehicles or electronics.