This transcript has been edited and condensed for clarity.

Grist reporter Jesse Nichols traveled to a factory in Oregon, that’s building a new type of battery.

Sitting in a row outside of the factory, these giant batteries are the size of freight containers. Powered by vats of iron and saltwater, they’re called iron flow batteries. And they’re part of a wave of cleantech inventions designed to store energy from the sun and the wind, and solve a problem that has stumped the energy world for more than 150 years.

The problem is described in a Scientific American article from 1861.

Grist thanks its sponsors. Become one.

“One of the great forces nature furnished to man without any expense, and in limitless abundance, is the power of the wind,” the article says. “Its great unsteadiness, however, is causing it to be rapidly superseded for such purposes by steam and other constant powers.”

To unlock the potential of wind and solar power, you need some kind of energy storage device. That could be batteries, hydrogen, or the device proposed in the Scientific American article.

Grist thanks its sponsors. Become one.

When it was windy, the device would crank these heavy iron balls up this marble chute. Then, when the wind stopped blowing, they could release the balls to get energy when they needed it. 

Unsurprisingly, wind energy did not take off. And fossil-fuels dominated.

Fast forward to the 1970s, when diplomatic tensions led to an infamous oil shortage in many countries around the world. In the United States, people were scrambling to conserve extra energy, wherever possible. 

And guess who had a big plan to solve that problem? NASA! That’s right, after putting a man on the moon, NASA set its sights on a new terrestrial challenge: to reimagine the battery.

Their plan was to develop a giant battery that could store extra energy that’d otherwise go to waste. It could also contribute to the use of more then-emerging technologies like solar and wind. NASA’s invention was called the flow battery. 

Here’s how it works: All batteries have three basic components, that are sort of like a peanut butter and jelly sandwich. There are the two main ingredients — one that wants electrons, another that wants to get rid of electrons, and, like the bread in a sandwich, a component that brings those two ingredients together to produce electricity.

In a typical lithium ion battery — the kind in your phone — those ingredients are spread out in thin layers, just like a PB&J. If I want a battery that lasts longer, I need more peanut butter and jelly. But because of the design of lithium batteries, I can’t do that without adding more bread. And that bread costs money.

That’s where the flow battery is different. Instead of only storing the ingredients in the sandwich, the flow battery stores its peanut butter and jelly in big tanks. Those ingredients are pumped into the sandwich to produce electricity.

If I want to increase a flow  battery’s life, I just add more peanut butter and jelly to the tank. And I can save money by not paying for more bread. This makes it easy and cheap to scale up to the size of battery I’d need to store energy on the grid.

So NASA had its battery. From there, scientists started searching for the best chemicals to use in them. Eventually, a young midwestern scientist named Bob Savinell came up with an idea for a flow battery made of iron.

Now, iron is appealing for a few reasons: Unlike other elements used in batteries — like titanium, vanadium, or the lithium that now powers our phones and laptops — iron is one of the most abundant elements on earth. And that means it’s cheap, and generally more environmentally friendly to mine. A flow battery powered by cheap iron would make energy storage even more accessible.

Savinell and his team built a prototype, but the timing wasn’t quite right. The battery ran into some technical problems with corrosion. And, as the energy crisis came to an end, scientists lost interest in these heavy, utility-scale batteries.

That is, until recently, thanks to two chemical engineers from Oregon: Craig Evans and Julia Song. Around 2010, they were starting to notice a big change in the world of energy. Wind and solar power were getting cheaper, and people were starting to put a lot of it onto the grid.  Evans and Song could see it was only a matter of time until people needed batteries to store all this renewable energy. So they decided to get into the battery business, founding a company called ESS.

And they knew that if their battery was gonna catch on, it’d need to be cheap. 

“​​And really the only way to do that is to use earth-abundant materials,” Song said. “So that kind of helped us to narrow down our search.”

Then they found it: That 30 year-old battery design from Savinell. 

“As we started looking at the numbers — just the cost of the electrolyte — it is so inexpensive it makes perfect sense,” Song said.

And, like that, iron flow batteries were back in business. ESS had found their materials. Next, they needed to build them. They were awarded a grant from ARPA-E, a government program to fund big, out-there ideas in clean energy. After years of research, they designed a new iron flow battery that didn’t suffer from the corrosion problems that had stumped Savinell. Over the next decade, they moved from a garage into a full-on factory. And finally, late in 2021, shortly after I visited, they went public on the New York Stock Exchange. 

According to the National Renewable Energy Lab, grid-scale battery storage could grow by more than an order of magnitude in the coming decades. And right now, lithium ion batteries are leading in this field. But ESS is hoping that scalability can be their secret weapon.

For a battery that lasts just a few hours, lithium is cheaper than iron. But after the four hour mark? ESS claims their battery is cheaper than lithium, all the way to 12 hours — which is the limit on their current battery system. 

The iron flow battery has a lot of strengths. But the world of energy storage is crowded — full of all sorts of technologies that can store energy on scales short and really long. And the battery market is only going to grow.

A startup called Form Energy made headlines for a 100-hour battery design that uses iron and air. Even Savinell, the battery scientist who worked on that original iron battery during the energy crisis, has gotten back in the iron battery game. He’s designed an iron flow battery that can be scaled up forever. That means, in theory, you could run it for four hours, 12 hours, a day, or a week, just by adding more juice to the tank. 

To get off fossil fuels, we’re going to need lots of different energy storage technologies. Whichever technologies succeed, it’ll be a dream that’s a long-time coming.