Iron-Air Battery

Those of you who’ve been following the progress of renewable power integration onto our global electricity grids will no doubt be only too aware of their biggest Achilles heel – something called intermittency.

In other words, the obvious problem is that the sun doesn’t shine at night, and the wind doesn’t always blow. There are various ways to get around that challenge, including ambitious projects like intercontinental distributed smart grids that can share electrons from where they’re being generated to where they’re needed in the blink of an eye, even over distances of thousands of miles.

A grid-like that is already being built out here in Europe, but the world is probably decades away from any kind of fully integrated system. So in the meantime, we have to find ways of storing any excess energy that renewables produce so that we can use it when those renewables are dormant.

Pumped hydro does a good job in some parts of the world, and we looked at that in a previous video, but it’s limited by geography, and it’s hardly something you can just stick on the back of a truck and deliver to a new site.

Lithium-ion batteries are currently being embraced in large volumes by grid operators all over the world. They work well in principle. They’ve got relatively high energy density and efficiency; they provide instant frequency response and can discharge their stored energy into the grid for about four hours at a time.

But they’re still relatively expensive due to the scarcity of lithium metal resources and the sophisticated internal protection systems they use in order to prevent dangerous overcharging and combustion.

And four hours is not a particularly long time either, so a great deal of research and development has been going on to find cheap reliable, and long-duration energy storage solutions that also use abundant, safe, reusable, and sustainable materials.

And now, after a long period in stealth mode, a Massachusetts company has put their head above the parapet to announce to the world that they’ve developed a storage solution using one of the cheapest and most abundant elements on earth, and which can discharge power not for hours,but for days at a time.

So will this be yet another one to add to the cynics’ list of’ somewhere over the rainbow’ technologies, or could it turn out to be a realistic disrupter in the grid-scale energy sector?

The company that nails the long duration grid-scale energy storage challenge on any kind of economically viable level is likely to become a very large and very wealthy entity indeed, so it’s hardly surprising that furious research and development activity is going on in laboratories all over the world.

Form Energy Inc has been quietly working away on their own solution for about four years, and they reckon they’ve now got a product that’s ready to ramp up to megawatt levels of production by 2023.

The main two ingredients of their technology are nothing fancier than good old iron and fresh air. Both are extremely abundant, easily accessible, and dirt cheap. Good start! The iron air battery is actually a technology that’s been known for decades, but until now, there’s never been a market force strong enough to attract funding for development, partly because the batteries are very large and very heavy.

You certainly won’t be seeing iron air batteries in smartphones or electric vehicles anytime soon – they’re far too heavy for that. And lithium-ion has pretty much captured that market already anyway.

But for stationary, utility-scale, long-duration energy storage, Form’s IronAir technology looks like it could be an ideal solution. The basic principle of the technology is breathtakingly simple.

It’s something that Form refers to as ‘reversible rusting. Each individual battery is a unit about the size of a washing machine containing between 10 and 20 stacks of cells, each of which has an anode consisting of pellets of metallic iron on one side and an airbreathing cathode on the other side, all immersed in a water-based non-flammable electrolyte much like what you’d find inside a standard AA battery.

As the battery discharges, oxygen from the air reacts with the iron via the liquid electrolyte. That reaction reduces the air to hydroxide and oxidizes the iron into iron oxide or rust, releasing electrons.

To recharge the battery, an electrical current can be passed through the cells, reversing the reaction, liberating the oxygen from the rust, and turning it back into iron. One of the biggest challenges was to find a cathode material that was impervious to water but was still able to breathe oxygen.

In 2020, Form found that material at an Arizona-based battery company called Nant Energy Inc. They’d spent about ten years developing just such a membrane for a similar technology using zinc instead of iron.

Form bought all the patents and an inventory of thousands of cathodes from Nant energy, and that provided them with the last piece of their development puzzle and enabled them to greatly accelerate their program.

According to this 2019 article, the theoretical energy density of iron air batteries is around 764 Wh /kg. That’s several times greater than the best lithium-ion batteries on the market today.

Lithium-ion batteries use a process called intercalation. Lithium ions move back and forth through an electrolyte and fit into empty spaces inside the crystal structures of the anode and cathode.

That means the capacity of a lithium-ion cell is limited by the physical volume of the two electrodes. Iron air batteries don’t move metal ions between the electrodes, so they’re not limited by intercalation in available spaces in electrode lattices.

They use an electrochemical reaction that simply deposits rust onto the surface, so the electrode surface area only limits them. That greatly reduces the mass requirement of the battery and leads to that much higher theoretical energy density.

At scale, Form reckons their batteries will store energy at about a tenth of the cost of lithium-ion. However, the nickel, cobalt, lithium, and manganese minerals used in existing lithium-ion batteries translate to a cost of between fifty and eighty dollars per kilowatt-hour.

Form says that using iron instead will mean spending less than six dollars per kilowatt-hour, and even when it’s all packaged up into a full battery system the price will still be less than 20 dollars per kilowatt-hour.

At that level, the general industry consensus seems to be that renewables plus energy storage could fully replace traditional fossil fuel-burning power plants. And when I say ‘at scale’ I’m talking about warehouses full of tens of thousands of washing machine size batteries, all hooked up together to provide enormous quantities of energy storage.

Form say their least dense configuration would get one megawatt of capacity into about an acre of land. The high-density configurations reach three megawatts for the same amount of space.

By 2023, Form plans to deploy a one-megawatt demonstration battery capable of discharging continuously for more than six days, and they’re already in talks with several utility companies about potential battery deployments.

The system can be cited anywhere there’s a need, even in urban areas, and the idea is not to supersede lithium-ion batteries, which already provide a very useful function for short bursts of frequency regulation and grid stability, but to complement them by delivering about150 hours worth of continuous discharge.

According to Form CEOMatteo Jaramillo, that’s a combination that could completely displace gas power on electricity grids and enable wind and solar to provide low-cost renewable energy that can work alongside existing nuclear and hydropower plants to provide reliable carbon-free electricity all year round.

Jaramillo himself has a pretty good pedigree, having spent seven years at Tesla Motors, initially working in powertrain sales and site acquisitions and then spearheading Tesla’s move into stationary energy storage.

His industry knowledge is complemented by a team of highly experienced and very technically qualified colleagues including Professor Yet-Ming Chiang from MIT, who started working on long-duration batteries back in 2012 as part of an energy department collaboration and who co-founded a pioneering lithium-ion battery company called A123 Systems Inc.

Form is backed by Bill Gates’renewable energy investment company Breakthrough Energy Ventures and the steel-making giant Arcelor Mittal. who is one of the world’s largest iron ore producers, and who is leading a 200 million dollar funding round to get Form Energy’s technology into full production and establish collaborative links with all the major regulators and electricity generators across the United States?

There’s a saying in the building trade that the three most important factors for any project are for it to be fast, cheap, and of good quality. The saying goes that you can have any two of those factors, but you can’t have all three.

It’s a similar problem in the energy sector. The three crucial factors there are affordability, reliability, and the absence of carbon in the process. Most electricity generation can deliver any two of those factors. Still, long-duration energy storage like the Form battery looks set to help renewable energies like wind and solar deliver all three of them and actually move the world towards the sustainable future we’re all hearing so much about in the media these days.