RE: Question ???11 Aug 2018 13:09
MiddleEastMoney
the amount of Vanadium is proportional to the battery energy storage capacity (MWh) not its power (MW) which is the reason why you can get longer storage times (the hour, h, in MWh) by simply adding more electrolyte and leaving the power stacks completely untouched.
This is what gives Flow Batteries sublinear scaling of cost vs Storage capacity (double the capacity and the cost goes up less than double) which is the key feature that makes flow batteries idea for mega and gigascale energy storage systems.
The amount of Vanadium required is 5000 tonnes per GWh - this makes about 40,000 tonnes of electrolyte once you mix it with water and acid.
The point of the Vanadium flow battery is that it has exactly the same electrolyte on either side of the battery so it does not matter if you get a little transmission of electrolyte through the membrane that keeps positive and negative electrolyte apart in the flow cells. No other element can do this.
There is little engineering point in coupling a Vanadium Flow battery with any other technology - a VRFB can switch from charge to discharge in less than a millisecond and there is essentially only a single state of charge (SoC) for the entire battery, unlike solid state batteries where every cell could be in a different state of charge, and of degradation, and needs to be individually tracked (inelegant to say the least, a nightmare to say the most).
There is an economic sense to pretend that your 100MW Vanadium Flow Battery is actually a 200MW battery by tacking on a short duration 100MW Lithium ion battery to it only if the regulator in your territory doesn't know that batteries are not like power stations and are only defined by their power rating. We used to do that in the UK before the Capacity Market derating rules came in which reduced what people could get paid for installing short term Lithium ion battery systems, which is the right thing to do.
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