Science update: The iron-air battery

Some sources are reporting on a possible breakthrough in iron-air batteries. The goal is to get cost of energy storage down to about $20 per megawatt-hour (MW-h). That is enough to run about 1,000 homes for 1 hour. The idea is simple -- adding oxygen from air to iron causes the metal to rust and give off electricity. The battery is recharged by using electricity energy to remove the oxygen, converting the rust back to metallic iron. Current iron-air batteries require about 1 acre of land for 1 MW of storage, with ~3 MW/acre theoretically possible. One acre is an area of 43560 sq. ft. or about 200 x 217 feet.

Iron-air batteries are made of low cost materials. The question is can they actually be manufactured to store energy for ~$20/MW-h? If that cost point can be reached, it would mark a major milestone for humans and civilization. One could envision a drastic reduction in the need for carbon energy sources, maybe about 85-90%. 

One source comments:

They [iron-air batteries] take in power from renewable sources, storing that energy for up to 150 hours and discharging it to the grid when renewables are offline.

Each individual battery is about the size of a washing machine.

Each of these modules is filled with a water-based, non-flammable electrolyte, similar to the electrolyte used in AA batteries.

Inside of the liquid electrolyte are stacks of between 10 and 20 meter-scale cells, which include iron electrodes and air electrodes, the parts of the battery that enable the electrochemical reactions to store and discharge electricity.

These battery modules are grouped together in modular megawatt-scale power blocks, which comprise thousands of battery modules in an environmentally protected enclosure.

Depending on the system size, tens to hundreds of these power blocks will be connected to the electricity grid.

For scale, in its least dense version , a one megawatt system requires about an acre of land.

Higher density configurations can achieve 3MW/acre.

A Boston-area company involved in developing iron air batteries, Form Energy, has high powered researchers and financial backers. The Washington Post writes in an opinion piece today:

A Boston-area company, Form Energy, announced recently that it has created a battery prototype that stores large amounts of power and releases it not over hours, but over more than four days. And that isn’t the best part. The battery’s main ingredients are iron and oxygen, both incredibly plentiful here on God’s green Earth — and therefore reliably cheap.

Put the two facts together, and you arrive at a sort of tipping point for green energy: reliable power from renewable sources at less than $20 per megawatt-hour. 

Form Energy is no seat-of-the-pants outfit. Its founders include Mateo Jaramillo, former head of battery development for Tesla, and MIT professor Yet-Ming Chiang, among the world’s foremost battery scientists. Investors include Microsoft co-founder Bill Gates, Amazon founder and Post owner Jeff Bezos, the iron and steel colossus ArcelorMittal, and MIT’s The Engine, a strategic fund aimed at long-term solutions to big problems.  

According to its announcement, Form Energy has the process working well under lab conditions. The next step is to build a warehouse-size battery plant to support an electric utility in Minnesota. If successful, a one-megawatt battery will be able to power the entire utility for nearly a week between charges by 2024.

Then we’ll begin to know just how important this is.