Form Energy filed a patent for massive ‘refuelable’ batteries – Business Insider
  • Clean-energy sources like wind and solar must be paired with grid-scale batteries to provide uninterrupted electricity.
  • The battery startup Form Energy has been working on long-lasting batteries for years. It has provided few details along the way. 
  • A patent application the company submitted last week showed that it’s developing a “refuelable battery,” likely made with an iron-based material. 
  • Iron is “dirt cheap,” one scientist said, which would allow the company to build batteries that last for days or weeks at a price that utilities can afford.    
  • Visit Business Insider’s homepage for more stories.

Renewable energy, for all its worth, has one giant flaw: intermittency.

The sun sets, the wind is temperamental, and rivers equipped with power-generating turbines don’t always flow. 

The solution is giant long-lasting batteries that can power the grid when renewable energy can’t. So it’s no surprise that the market for grid-scale energy storage is set to explode, growing by an estimated $50 billion in revenue over the next 15 years.

“There’s a big bet that long-duration energy storage is the future,” Dan Finn-Foley, an analyst at the research firm Wood Mackenzie, told Business Insider in February. “The first company that can do that is going to win.” 

Form Energy is among a handful of startups in the lead.

Form, which is headquartered outside Boston and led by a former Tesla vice president, has been working on long-duration batteries for years, promising a technology that will be 50 to 100 times cheaper than lithium-ion batteries, which are on the market today.

The startup has provided almost no information since it was founded in 2017. But a patent application filed last week offered new details about what at least one of the company’s batteries — a “refuelable battery power grid solution” — might look like.

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Electrolyte tanks of a redox flow battery.

Uli Deck/picture alliance via Getty Images

What we know: Form Energy is working on a sulfur flow battery

Lithium-ion (Li-ion) batteries in phones and electric cars do their jobs well. They’re energy-dense and relatively cheap.

The problem arises when you try to scale them up, as Li-ion batteries have a roughly linear relationship between power and cost.

At the grid scale, they’re simply too expensive.

That’s why Form is testing out other low-cost materials and technologies that get cheaper with scale, said Ertan Agar, an assistant professor of mechanical engineering at the University of Massachusetts Lowell. Agar reviewed the patent for Business Insider, but he isn’t affiliated with Form Energy.

At least one of them is a flow battery with aqueous sulfur, a cheap and abundant element. Since at least the summer, Form has been working on the flow battery in partnership with the Advanced Research Projects Agency (ARPA-E), a part of the Department of Energy.

The startup’s CEO, Mateo Jaramillo, told Business Insider that it would store power for tens of hours in a February interview

Read more: A startup run by a Tesla veteran and backed by Bill Gates is promising to build a long-duration battery that’s 50 to 100 times cheaper than lithium-ion

“Aqueous sulfur flow batteries represent the lowest chemical cost among rechargeable batteries,” Form’s ARPA-E project page said. 

Unlike a typical cell, flow batteries store an electrochemical charge in tanks of liquid electrolyte.

That means to scale up their storage potential, you just have to make the tanks bigger. This would be a problem for electronics and cars, where space and weight matters, but not for grid-scale storage. 

The other technologies Form is working on have been harder to pin down, but the patent, which Business Insider shared with three battery scientists, revealed some clues. 

An ‘air-breathing’ battery

In the application, Form refers to different configurations for a “refuelable primary battery solution that addresses bulk seasonal energy storage needs, energy demand variation, and other challenges.” 

In other words, the company is working on batteries that can replace power plants on the grid that kick in when renewables aren’t generating enough electricity.  

According to Erick White, a chemical engineer at the National Renewable Energy Laboratory, the technology mentioned in the patent is not a typical flow battery, in which a liquid electrolyte produces the charge.

In this case, the materials that interact with each other to produce charge — known as the anode and cathode — are likely either both solid or one is solid while the other is simply air.

The patent refers to the latter configuration as an “air-breathing” battery in which a certain material would generate electrochemical energy when it reacts with oxygen. 

Like in a flow battery, the electrolyte, which allows for the flow of charge between the cathode and the anode, is liquid, White said, but in this case, the electrolyte likely isn’t producing the chemical energy. 

While the specific chemistries of the configurations are harder to decipher, the scientists all said some of these batteries likely contained iron or an iron alloy, based on their review of language in the patent. 

Like sulfur, iron is reactive and “dirt cheap,” said Wesley Chang, a battery scientist at Princeton University and a former scientist at Form’s competitor Primus Power. 

“They’re really targeting just the cheapest material possible here,” he said. 

The idea to build an iron-based battery came from Jaramillo, according to what Chang heard through his research group’s online message board, while the ARPA-E sulfur flow battery was conceived by the startup’s cofounder, Yet-Ming Chiang, one of the most prolific battery inventors.

“Looks like they’re definitely working on both chemistries in their lab, so as to not put all their eggs in one basket,” Chang said. “Winner will be which, if any, actually work at scale.”

Jaramillo declined to comment on the makeup of the batteries. 

Darren Staples/Reuters

What Form means by ‘refuelable’ 

Unlike a typical Li-ion or flow battery, the technology referenced in the patent does not appear to be rechargeable per se, Chang said. 

As the battery is discharged — such as by supplying power to homes in a nearby community — the electrodes break into pieces that are “expended.”

That expended material can then be regenerated on- or off-site and used to refuel the battery, White said. 

“When they are depleted or nearing end of their useful life, the primary battery units may be identified as needing ‘refueling,'” the patent said.

This technology is not unlike a typical power plant: A fuel that contains energy, like coal, feeds a facility that converts it into electricity. 

A key difference is that the battery fuel, such as an iron material, can be regenerated — in this case, using electricity. If that electricity is produced by wind- or solar-energy sources, the battery would be emissions-free. 

What’s more, the batteries can turn a surplus of renewable energy that would otherwise be wasted into “material good,” the patent said.

When solar farms generate more power than customers can use, for example, you can funnel that power into regenerating the feedstock for these batteries.

Form’s vision of a future powered by batteries 

Ultimately, Jaramillo said, the batteries Form is working on are designed to replace coal and gas power plants on the grid.

Even in areas with renewable energy sources, fossil-fuel plants kick in when renewable production is down. 

“If you could wave a wand and get a battery that would allow you to use only renewables — wind, water, or solar — to replace that thing, that’s the biggest opportunity you can think of,” he said in February. “That’s a trillion-dollar capex opportunity. And that’s also the most meaningful thing you could do.” 

Today, the market for long-duration storage is still developing, Agar said.

It’s plotting on track with progress toward renewable-energy targets set by cities and states with deadlines in the next 1o to 30 years. 

That makes now a good time to develop long-duration storage.  

“Right now, they are trying to find the best possible option,” Agar said of Form Energy. “Once the time comes, I think they will have the answer.”


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