Megan Hall: Welcome to Possibly, where we take on huge problems like the future of our planet and break them down into small questions with unexpected answers. I’m Megan Hall.
When you think about batteries, you probably think about the ones in your phone, kids’ toys, or electric cars. But there’s another kind of battery that’s made of something a bit more ordinary: iron and air.
We had Leena Mudawi and Sarah Kramer from our Possibly Team look into it.
Leena Mudawi: Hi, Megan!
Sarah Kramer: Hello!
Megan Hall: Hi! So, I’ve heard these iron air batteries described as batteries that run on rust. Is that actually true?
Leena Mudawi: Surprisingly, yes. When iron rusts, it’s actually a chemical reaction that moves electrons around, and electrons are what make electricity.
Sarah Kramer: To learn how iron batteries use this process, we talked to Audrey Smith, a PhD student in chemical and environmental engineering here at Brown . She says these batteries basically take something iron already naturally does—rust---
Audrey Smith: “And now we’re just doing that on purpose, and then reversing it when we want to.”
Megan Hall: Wait, you can reverse rust?
Sarah Kramer: In this case, yes. Inside these batteries are small pieces of iron. When the battery releases electricity, that iron reacts with oxygen and turns into iron oxide—a form of rust.
Leena Mudawi: Then when you charge the battery, the process goes backwards: the rust turns back into iron, so it can happen all over again.
Megan Hall: Ok, so that’s the iron. But where does the “air” come in?
Leena Mudawi: So oxygen from the air actually moves in and out of the battery during these reactions. Audrey says you can think of the battery as “breathing”.
Audrey Smith: “So we’re sucking in oxygen on the discharge. So it’s like taking a breath in of oxygen.”
Sarah Kramer: And when the battery charges again,
Leena Mudawi: It breathes out oxygen.
Megan Hall: So why do we need a battery like this when we already have lots of other kinds of batteries?
Leena Mudawi: The big difference is how long iron-air batteries can store energy. The batteries in our cars or electronics are usually lithium-ion batteries.
Sarah Kramer: Those kinds of batteries are really efficient, but they can typically only store a few hours worth of the electricity we might need to run the electricity grid.
Leena Mudawi: But iron air batteries can provide around 100 hours—That’s more than four days.
Megan Hall: So why would we need four days of electricity?
Leena Mudawi: To address one of the biggest challenges with renewable energy- the sun isn’t always shining, and the wind isn’t always blowing. This challenge is especially true in Audrey’s home state:
Audrey Smith: “In Maine, for instance, we have long dark winters, but they are pretty windy. So there’s some maybe excess wind, or there’s not a lot of sun, and we need to store some of that electricity for a few days before we can want to use it.”
Leena Mudawi: If we can save extra electricity when it’s really sunny or really windy, we can use it days later when there’s no sun or no wind.
Megan Hall: Does that mean iron-air batteries could replace the batteries that we use right now?
Sarah Kramer: It’s not either/or, it’s both. Iron-air batteries aren't as efficient as lithium-ion batteries, but they don’t really need to be.
Leena Mudawi: Iron-air batteries are meant to do something else: sit on the power grid and store huge amounts of electricity for days at a time.
Sarah Kramer: And luckily, iron is cheap, and there’s a lot of it!
Audrey Smith: “Where lithium is a bit harder to come by, iron is one of the most abundant metals in the crust.”
Leena Mudawi: So instead of replacing the batteries we already use, iron-air batteries can add another kind of storage to our electric grid—one that helps cover those longer stretches when wind and solar aren’t producing much energy.
Sarah Kramer: And Audrey says having more ways to store electricity is going to be really important as we rely more on renewable sources of energy.
Audrey Smith: “Batteries are the key to the energy transition in a lot of ways. They allow us to put renewables on the grid cost-effectively and reliably.”
Megan Hall: So the battery might run on rust, but what it really gives us is a way to save renewable energy for when we actually need it.
Leena Mudawi: Yeah, exactly!
Megan Hall: Got it! Thanks, Leena and Sarah!
That’s it for today. You can find more information, or ask a question about the way your choices affect our planet, at ask possibly dot org. You can also subscribe to Possibly wherever you get your podcasts or follow us on social media at “ask possibly”
Possibly is a co-production of Brown University's Institute for Environment and Society, Ocean State Media and WBRU.
