Energy Storage Systems Technology (ESS Tech Inc), the star child of flow battery industry, one of the few flow battery companies to ever go public, a technology with raw materials so cheap that you could buy them for pennies. This is the company I looked up to for 3 months, the ingenuity in their technology. Of course, a battery of iron is the way to go, its an economic masterstroke.
But I was missing something, if it was so easy to build, why wasn't everyone doing this. All Iron redox flow battery should be easy, if any Indian or Chinese manufacturer knew about this technology, they would reverse engineer it in 1 year.
But I was wrong, not only because they hold a LOT of patents (103 granted, 214 filed), but also because physics doesn't give free lunch. So here are the roadblocks I ran headfirst into, while trying to copy ESS.
1. The Stack
As I mentioned in the
last post, charging an Iron Redox Flow Battery is like electroplating, it requires slow charging, which means lower current density, around 25-40 mA/cm2 , for months I was trying to find ways to increase it to 60 mA/cm2, but every research paper I read, every ESS Inc patent I analyzed said the same thing. The moment you increase the current density above 50 mA/cm2, your battery efficiency crashes below 60%. A battery which stores 40% of its initial electricity, is not a battery, its a joke.
If you accept lower currents, that means as an iron manufacturer you have to make more stacks than your Vanadium competitor. Because Vanadium current density is minimum 80 mA/cm2, so you need to make 3x more cells. Same materials, 3x the cost of cell stacks.
Congrats !!!! Whatever money you managed to save on electrolyte by using Iron, you used up in making 3x more stacks than VRFB.
2. Complex Manufacturing
Let's say you will mass manufacture your cell stack in such large quantities that its cost comes down to same as that of VRFB, this technology fundamentally relies on plating of solid iron on negative side. This plating will inevitable form dendrites, in order to facilitate these dendrites you have to manufacture precisely machined flow fields, in different patterns. Here take a look -
Fascinating for an art project, not for a factory that has to produce 1000 machined plates in 1 hour. This inevitably increases the cost of cell stack manufacturing, so much so that a Vanadium Battery cell stack becomes cheaper
3. The Dealbreaker - Efficiency
Until I knew this number, I was extremely optimistic about Iron Redox Flow Batteries. The total cell efficiency of Iron batteries in the best possible conditions in lab is drumroll please🥁🥁🥁
65 %
A battery that is so complex to manufacture, so big to make, with its cell stack more expensive has lower efficiency than the incumbent it is supposed to replace.
For comparison, a Li- ion cell and has >95% efficiency, a VRFB or vanadium battery has ~80%.
You can't replace a superior technology with an inferior but cheaper technology. Everyone expects the newer tech to be better than the older one.
And just for reference, when you connect a battery to the grid, its efficiency goes down by at least 7-10% because of inverters, transformers, wires and other unavoidable efficiency losses. So if a lithium battery gives 85% of its energy back, a Vanadium one gives 70% of it back, an All Iron one gives only 50% of it back.
That's terrible.
I didn't have the knowledge to analyze 103 patents, and the case for All Iron battery was going down. So I was back to square one.
Until I remembered something, Gemini used to make a fundamental mistake. Every time I started a new chat with Gemini and told it I was making an Iron Redox Flow battery, it always assumed Iron-Chromium battery (typical dumb AI mistake), then I had to correct it and explicitly say All Iron Hybrid Redox Flow Battery.
I wonder if it really was a dumb mistake......
But more on that in the next post
None of this is AI generated, so feel free to fact check me and looking forward to your views and help.
Mayank Jately
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