They're trying to solve the problem of 'what else can we do with these high performance batteries'. So they have some where else to put overproduction, have more buying power of raw resources due to scale, more research dollars to put into li-ion batteries responsibly, or they already have the well made hammer of li-ion batteries so everything is a nail.
1) Are prices publicly available yet? I haven't found one online, would be keen to know how much their 10kWh unit costs.
2) The cell has a finite lifespan which is analogous to cell degradation - the warranty covers up to 36,500kWh of delivered energy for the 10kWh model, which equates to 3650 full discharge cycles. This is more than lithium batteries, don't get me wrong, but they're not immortal.
3) I don't believe lithium batteries need constant cooling in most cases, especially since for bulk storage your discharge rate is going to be less than 1C.
4) Fair call, lithium batteries have some scary failure modes.
Also, the round trip efficiency of these batteries is only ~77% which is a fair bit lower than lithium (I think they're 90%+?) and represents a large loss of energy over the life of the battery.
Overall I agree that there are significant advantages to flow batteries, especially at grid scale, but they do have drawbacks too.
Instead of hideously expensive (and potentially explosive) lithium storage, solution should be synthesizing and storing some form of gas. This gas can then be produced and stored in underground locations during summer, and then spent during winter.
129MWh / 10GWh / 1M people / 12.5G people
You're right that NG plants do play an important role in the grid today, but it's a "we predict that we'll need more power generated in an hour" role.
Lithium makes sense for cars where power density is essential. But with grid scale storage, there are so many drawbacks, including
1.) High fixed cost vs. other batteries
2.) Degradation from dendrite growth
3.) Need for constant cooling
4.) Possibility of catastrophic failure in case of short circuiting
In contrast something like Zinc-Bromine flow batteries have unlimited cycling with zero loss of energy storage, and are inherently composed of fire retardant materials, making them impossible to catch fire or explode [0]. The trade off is in energy density, but that shouldn't be an issue for fixed grid-scale deployments.
This story feels like forcing a solution with the power of good marketing, not solid engineering.
[0] http://redflow.com/wp-content/uploads/2012/10/Garth-Corey-as...