Long-duration batteries could free the grid from fossil fuels

Form Energy CEO Mateo Jaramillo explains the promise of iron-air batteries and why the grid needs multiple types of storage to be truly decarbonized and resilient.

An aircraft takes off from Los Angeles International Airport behind electric power lines at sunset.

Form Energy's technology sounds deceptively simple.

Photo by Patrick T. Fallon/AFP via Getty Images

Battery storage has emerged as a key technology to reach net zero.

So far, lithium-ion batteries have largely been used by utilities to store renewable energy when the sun sets or the wind stops blowing. However, existing utility-scale storage can only discharge energy for up to four hours at a time, meaning that systems can falter when the grid needs to provide widespread power for a long period of time, such as during a heat wave or major storm. To free the grid from fossil fuels that currently provide that baseload, we need long-duration batteries that provide power for at least several days at a time.

Form Energy is developing batteries that use an iron-air technology and could be poised to fill that gap. Investors certainly seem to think so. The 5-year-old company raised a whopping $450 million in its series E funding round, bringing its total investment to around $800 million. It counts high-profile VCs like Bill Gates’ Breakthrough Energy Ventures and Energy Impact Partners among its investors, as well as the steel company ArcelorMittal. The latter is also among the industrial firms that Form Energy has partnered with to acquire iron for its batteries and deploy them to provide power for notoriously hard-to-decarbonize sectors. (The head of ArcelorMittal’s investment fund said its investment leaves it “well-placed to directly benefit as the technology matures to industrial scale.”)

Form Energy signed a partnership with Georgia Power, its first with an investor-owned utility, earlier this year. The duo will work to deploy up to 15 megawatts of storage capacity. In 2020, it announced a much smaller 1 megawatt pilot project with the Minnesota cooperative Great River Energy. CEO and co-founder Mateo Jaramillo told Protocol that Form Energy will announce more contracts in the near future, and that the company is targeting late 2024 for commercial production of its batteries.

The technology sounds deceptively simple. Form Energy submerges a porous piece of iron (the anode, reminiscent of a flat and thin brick) in an electrolyte solution, and then harnesses the metal’s natural rusting process to charge and discharge energy over the course of several days. Every battery has both a cathode and an anode, which pull electrons from a circuit and push them out, respectively. But in Form Energy’s case, Jaramillo said, “the cathode is a bit of a false term.”

“The active material is not inside the battery,” he said. “It’s the oxygen in the air.”

A diagram of how Form Energy's iron-air batteries work.Form Energy submerges a porous piece of iron in an electrolyte solution then harnesses the rusting process.Image: Form Energy

The oxygen is highly controlled, entering the washer-and-dryer-sized batteries through a specialized membrane that keeps it from going out again. Once it makes contact with the electrolyte solution, a series of chemical reactions causes the iron to rust.

“Before we zeroed in on iron-air batteries, we considered what is fundamentally able to scale and what is fundamentally safe, and what is fundamentally available to us to work with,” Jaramillo said. “Iron ticks all of those boxes.”

This technology has been around for decades and was the subject of a 1970s Department of Energy study in the wake of the oil embargo and accompanying energy crisis. But in Jaramillo’s view, it is only now being commercialized because the technology is particularly well-suited to the demands of today’s grid. He spoke with Protocol about how the iron-air technology works and the importance of long-duration storage.

This interview has been lightly edited for brevity and clarity.

Can you explain exactly how an iron-air battery charges and discharges energy?

We can drive the chemical reaction that causes rusting in both directions. When you return the iron to its metallic state, you're essentially charging it and preparing it to be discharged, because iron wants to rust. But we know how to keep that from happening automatically by controlling its conditions. In its charged state, a metallic iron anode doesn't have oxygen working on it. And then in the discharged state, we're adding the oxygen to it, and in that process, it gives up the electrons.

How do iron-air batteries fit with the energy storage system?

Today, the lowest marginal cost source of electricity is renewable. There is very low-cost wind and solar, but those resources only show up when the weather permits. And when we have a weather-driven power-generation system, we need to be able to solve for the intermittency. The easy pattern to solve for is the daily cycle — the sun going down and coming back up every morning — but we also have patterns around storms and seasonality. To solve that problem, you want really low-cost batteries so you can provide storage for days at a time, and there are trade-offs to get there.

Lithium-ion batteries are very good at cycling many thousands of times. If I charge my phone a few times a day, I’m getting maybe 1,000 cycles per year out of my battery. But let’s say we have a battery that discharges for a week and then charges for a week. That means that the theoretical maximum number of cycles I could get out of my battery is 26 per year. So if I want it to have a 20-year life, we’re talking about roughly 500 cycles. If I want to keep the battery low-cost, I don’t need to prioritize thousands of cycles like I would for a lithium-ion battery.

Form Energy CEO Mateo JaramilloForm Energy CEO Mateo JaramilloPhoto: Form Energy

The trick is to make the right trade-offs in pursuit of the attributes that you really care about. On the grid today, we have great daily cycling batteries like lithium-ion, but what we don’t have are these very low-cost batteries that allow you to smooth out multiple days of intermittency associated with the power generation driven by weather. And that's what Form Energy is.

Do you have any supply chain challenges?

We certainly didn’t anticipate the supply chain problems for battery materials caused by the pandemic, but we did anticipate the scale of what we’re trying to do. And if you are competing with the automotive industry for the same materials, it's just going to be very difficult.

How have recent policy developments, such as the bipartisan infrastructure law or the Inflation Reduction Act, informed your work?

There are benefits in both of those pieces of legislation. There are specific programs in the bipartisan infrastructure act for long-duration storage, including for demonstrations. And in the IRA, the benefit to Form is direct and indirect. The biggest benefit is probably indirect, in that it is setting up a path for the energy transition broadly. If you use renewable power, you're going to want this kind of solution. But there are also direct benefits for storage in there, in particular the investment tax credit. That’s the same vehicle that's been used for solar for a very long time and has helped bring down costs, but it is calling out storage for the first time as a qualifying technology. The owner of the asset qualifies for the ITC, which would make it cheaper for both companies to develop storage technology.

What other kinds of policies would ease Form Energy’s path?

Probably most important for us at this point is that the market designs are updated to reflect where we really are today and where we want to go. Grid operators and markets were designed with an entirely different and largely combustion-driven grid in mind. There's a big push in general to acknowledge that and figure out what the right market designs are to get the system to value things like reliability and decarbonization.

For example, last year MISO came out with a report about what they called the “reliability imperative,” in which they started to articulate how the market design needs to incorporate reliability as an explicit thing that gets compensated. That is something that will have to get defined in how wholesale markets are designed so that the value that we bring as an asset is properly compensated.


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