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The future of energy may be closer than we think, says Steffi Diem, an experimental plasma physicist on Climate Curious. She sits down Maryam Pasha live at TED 2025 to explain what fusion energy is, and how it could unlock a new frontier of clean energy in our lifetime, yay! Replacing fossil fuels with readily available hydrogen, Steffi shares why she’s dedicated her life’s work to ensuring this once distant sci-fi dream becomes a stunning energy-abundant reality.

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Created by TEDxLondon
Executive produced by Josie Colter
Produced by Ben Beheshty
Curated by Deesha Chandra
Hosted by Maryam Pasha and Ben Hurst
Communications by Tara Cooper and Issey Gladston

00:00 Introduction
01:09 What is fusion energy?
01:29 Fusion energy vs. traditional nuclear energy
02:08 Fusion energy and climate change
03:19 Breakthroughs in fusion energy
05:00 How we generate energy now
08:41 Challenges and downsides of fusion energy
10:11 Future vision for fusion energy
12:00 Conclusion

Transcript

[00:00:00] Introduction

[00:00:00] Ben Hurst: Welcome to Climate Quickies Bite-sized nuggets of Climate Goodness. From our TEDx London experts in under 10 minutes in this week’s climate, curious, we are getting the scoop on what fusion energy is and why [00:00:15] it could solve our fossil fuel energy woes from. Experimental plasma physicist Steffi Dean, a fusion energy researcher who studies ways to heat plasma to temperatures 10 times hotter than the sun and story in magnetic [00:00:30] bottles.

[00:00:30] Ben Hurst: For fusion energy development, Steffi shares the reason she’s optimistic about the future of nuclear energy. Think a bathtub of water, a handful of lithium batteries, and creating more energy out. Than you put in. [00:00:45] It’s all quite exciting. Let’s head over to Steffi in conversation with Marion Phar live at TED 2025 to hear more.

[00:00:53] Ben Hurst: Also, whilst I have your attention, we are going live with Climate Curious in London on the 23rd of June. [00:01:00] You can grab your tickets via the link in the description, and we hope to see you there. Stay curious.

[00:01:09] What is fusion energy?

[00:01:09] Steffi Diem: Can we just start really basic, what is fusion energy? Okay, so fusion is actually happening every day in the [00:01:15] sun.

[00:01:15] Steffi Diem: So in the core of our sun, it’s heating up hydrogen, heavy forms of hydrogen to millions and millions of degrees. It sticks together and then it forms helium, and in that, uh, process, it actually releases a ton of energy.

[00:01:29] Maryam Pasha: Yeah.

[00:01:29] Fusion energy vs. traditional nuclear energy

[00:01:29] Maryam Pasha: And this is different than like the stuff we already have like in nuclear reactors or nuclear bombs or like, like Right.

[00:01:36] Maryam Pasha: This is totally the opposite. It’s totally different. Opposite. We’re sticking thing, we’re sticking light things together. Okay. ’cause the other thing is you’re breaking them apart. Breaking apart. Yep. Okay. And this is, see I know a little bit because I’m I [00:01:45] now, yeah, you got it. This is the safer type.

[00:01:48] Steffi Diem: So this is right.

[00:01:49] Steffi Diem: Yeah. So except it happens on the sun, so there’s no runaway electric like, um, process at all. You have to impart energy to make these heavy forms of hydrogen to stick together, but if you’re [00:02:00] not putting energy into the system, it just stops. Oh,

[00:02:02] Maryam Pasha: interesting. Okay. This is very, I’m like, I’m like ready, ready to get into this.

[00:02:06] Maryam Pasha: This is good now.

[00:02:08] Fusion energy and climate change

[00:02:08] Maryam Pasha: Why, why would we be, why, what does it have to do with climate change? And like, okay, I understand that this is like a, a process that happens on the sun, but what does that have to do with us here on earth?

[00:02:17] Steffi Diem: Right? So if you, if you look at like the whole like energy resources in this reaction, we’re just talking about using heavy.

[00:02:25] Steffi Diem: Forms of hydrogen and then it puts out helium. Um, [00:02:30] and I’m gonna do a comparison for like how much energy you need to power your whole entire lifetime, right? Okay. So let’s go with, um, coal. You need to burn 280 tons of coal to provide energy for your lifetime. This is your car, your house, all [00:02:45] your electronics and things like that.

[00:02:46] Steffi Diem: And that gives off 380 tons. Of greenhouse gases. It’s a lot, a lot. Um, to get equivalent amount of energy from fusion energy, you need the amount of heavy hydrogen found in [00:03:00] two bathtubs full of water, and six, the lithium from six laptop batteries and no greenhouse gases are released. Right. So it’s kind of like mind blowing numbers.

[00:03:12] Maryam Pasha: Yeah, it is mind blowing numbers. Um, [00:03:15] I’m gonna come back to those numbers in a second. I almost like need a minute to like absorb timing.

[00:03:19] Breakthroughs in fusion energy

[00:03:19] Maryam Pasha: I have seen in the news like in the last like 12, 18 months, some like little bits around how we’re making breakthroughs, right? Yeah. With this kind of fusion energy we are we at with it?

[00:03:31] Maryam Pasha: What’s like, how close are we to actually being able to do something with this? Is it still really researched? Like where are we?

[00:03:38] Steffi Diem: That’s a, that’s a really great question. So for a while it was just like. We were doing research to like, create [00:03:45] the conditions for, for hydrogen diffuse here on Earth. And it requires temperatures, um, over a hundred million degrees, which is 10 times higher than the sun.

[00:03:53] Steffi Diem: So we That’s excellent. Excellent. This sounds,

[00:03:55] Maryam Pasha: it’s extremely simple Exactly.

[00:03:57] Steffi Diem: Engineering at the, the extremes. Um, we [00:04:00] either use lasers that we focus to, uh, implode and get it to fused together, or I use. I create very large magnetic bottles that capture it and hold onto it so it gets hot enough and long enough to fuse.

[00:04:13] Steffi Diem: And so in [00:04:15] 2022, um, was when the first time scientists on earth demonstrated for the first time that could actually create more energy out than they put in to actually get the hydrogen diffuse. Wow. Yeah. Right. [00:04:30] And so once you demonstrate that’s possible, yes, that was the major breakthrough. Okay. Um, now we’re working on.

[00:04:35] Steffi Diem: Like materials that can withstand those extreme environments and extracting the energy. Because at the end of the day, a lot of the way we generate [00:04:45] electricity or energy is, um, cleaner ways to boil water, to generate steam.

[00:04:51] Maryam Pasha: This is, I

[00:04:51] Steffi Diem: think,

[00:04:51] Maryam Pasha: okay. Yeah. And I’m not, my brain wants to really go down this tangent of asking like the about the materials.

[00:04:56] Maryam Pasha: ’cause I keep thinking, whoa, could you possibly build that? Could hold that? But I’m not [00:05:00] gonna do that.

[00:05:00] How we generate energy now

[00:05:00] Maryam Pasha: Because I think the more interesting thing I’ve realized in having this conversation is I probably don’t really understand how we make energy now. I.

[00:05:08] Steffi Diem: Yeah,

[00:05:08] Maryam Pasha: and, and how this is different. So can you just give us like a little like crash course on that?

[00:05:13] Steffi Diem: So a lot of what we do [00:05:15] right now is through chemical reactions that happen at like thousands of degrees, and we’re just burning things to generate steam, to turn a turbine to then generate electricity. And so we’re replacing that burning part. That’s like what, that’s [00:05:30] like, is that like the combustion engine?

[00:05:32] Steffi Diem: Is that like basically what It’s, in a way it’s, it’s, it’s a little bit different ’cause the combustion engine is like, has pistons and things like that. Oh, okay. Okay. This is like, this is like you just. You have steam come out, turns a [00:05:45] turbine, and then that creates electricity in there in through the, the movement of the turbine.

[00:05:51] Steffi Diem: And then that goes to the power grid. I can kind of imagine this. Yeah. Yeah. I can kind of

[00:05:53] Maryam Pasha: imagine this. Yeah. And so that’s what, that we do that in various fancy ways. Yes. And this is [00:06:00] about, actually this is different because you are, it’s way hotter, way hotter. Wait, and you’re bringing things together and you’re fusing them together.

[00:06:06] Maryam Pasha: Yeah. And that and that. Yeah. That releases a lot of energy. It’s such, it’s such an, it’s, I think it’s like one of those things where as a, like a lay person, the idea of putting things [00:06:15] together and it releasing energy feels like very counterintuitive. It would feel like if we stick things together, it would just sticks, sticks things together.

[00:06:20] Steffi Diem: Right. That’s a really great question. Um, Einstein’s equation equals mc squared. Right. Our, our

[00:06:26] Maryam Pasha: favorite of equation. We’re going

[00:06:27] Steffi Diem: back to that one. Okay. [00:06:30] What it really means is that ener like mass is not lost. It’s just transferred Yes. Into energy. Right. You

[00:06:36] Maryam Pasha: don’t ever lose anything.

[00:06:37] Steffi Diem: Exactly. So if you measure what went into the, the fusion reaction and then you compare it to the weight of the [00:06:45] helium, it looks like it lost weight.

[00:06:47] Steffi Diem: It’s lighter. It’s lighter, but that, that small amount is actually directly, it’s, it’s transferred to energy. Right. Okay. So it’s like, yeah, it’s,

[00:06:55] Maryam Pasha: I understand this is, I mean, I, I do understand, actually, I’m hoping others understand. Um, well, [00:07:00] we

[00:07:00] Steffi Diem: very rarely talk about what, what Einstein’s equation is. Yes.

[00:07:04] Steffi Diem: Right. And practical uses of it.

[00:07:07] Maryam Pasha: It’s, and so let’s talk about that practical uses. What do you, what’s a hope here? Like what does, what could this mean? So

[00:07:14] Steffi Diem: this couldn’t, [00:07:15] what does this mean? That’s why a lot of what I do is trying to realize it and make it economical and approachable for everyone, is that if you have a, a form of energy that’s based on hydrogen that’s available to everyone around the world, that could be [00:07:30] transformative because a lot of our geopolitical tensions and wars are around access to energy and energy resources.

[00:07:39] Maryam Pasha: Do you, is it cheap to do this? Like, and this is a silly question ’cause obviously right [00:07:45] now there’s loads of technology that needs to be developed. But I guess what I mean is it feels like extractive energy sources are finite. Like we only have so much oil. We only have so much gas, but we have like renewable is [00:08:00] more.

[00:08:00] Maryam Pasha: I guess infinite in, in a way with, with this kind of energy. Like how is it something we would run out of? Is it, is it is the, is the thing, are the things that go into it really cheap? Like, tell me a bit about that. So

[00:08:13] Steffi Diem: that’s, that’s a really great [00:08:15] question. Um, even renewables, they rely on finite materials.

[00:08:20] Steffi Diem: And minerals here on earth, right? Yes. Yes. And so, um, part of what we’re looking at in the fusion space is we know that lithium we also use Yes. In fusion. [00:08:30] Um, and so kind of looking at projections of how much we would need and how much other markets would need. Okay,

[00:08:35] Maryam Pasha: that makes sense. And, and how sense, how would

[00:08:36] Steffi Diem: plan like lead to scaling up and things like that.

[00:08:39] Maryam Pasha: This sounds very good.

[00:08:41] Challenges and downsides of fusion energy

[00:08:41] Maryam Pasha: What are some downsides?

[00:08:42] Steffi Diem: Some downsides? I mean, it’s [00:08:45] really hard to do. It’s really, it’s really hard to do. I think right now that’s, that’s one of the bigger downsides. Okay. Right. The other downside is, um, anytime you have, um, minerals and resources that go into building these machines, [00:09:00] you have to think about where you’re resourcing that from ethical.

[00:09:05] Steffi Diem: Mining practices, labor practices Right. And things like that. And any waste generation.

[00:09:11] Maryam Pasha: One

[00:09:11] Steffi Diem: of the things

[00:09:11] Maryam Pasha: I know because I watched a film about it, is that the problem with [00:09:15] traditional nuclear, other energy like fission.

[00:09:18] Steffi Diem: Mm-hmm.

[00:09:20] Maryam Pasha: I’m very impressed that I remember this is a waste. Right. What about the waste of infusion?

[00:09:25] Maryam Pasha: What, what is that and is that as dangerous?

[00:09:27] Steffi Diem: So, that’s a great question. Um, there’s [00:09:30] danger in everything. You’re just gonna be, um, so. Fission, um, has high level waste. Radioactive waste is where it’s radioactive for thousands of years, right? Yes. Um, this, so fusion does produce some low level [00:09:45] activation radioactive waste,

[00:09:46] Maryam Pasha: okay?

[00:09:47] Steffi Diem: And that would have to be stored for about a hundred years. Okay? So, um, a lot of researcher researchers are looking at. How do we design the systems to really minimize that right before we fully design the system?

[00:09:59] Maryam Pasha: [00:10:00] That’s very smart. And I guess the idea is that everything does have waste and yeah, thou a hundred years feels like a much more manageable amount of time than thousands of years.

[00:10:07] Maryam Pasha: Yeah. Okay. Thank you for this science lesson. This has been very cool. Yeah.

[00:10:11] Future vision for fusion energy

[00:10:11] Maryam Pasha: So my final question then for you is, if we get this right Yeah. What is the potential for. Climate change for addressing climate change, for energy, access, justice, globally. What’s your vision?

[00:10:25] Steffi Diem: So the vision is. All of our base load power right now, [00:10:30] or most of it, I would say about 80% is carbon based.

[00:10:33] Steffi Diem: It’s giving off a ton of pollution. Also, we’ve done little to decarbonize manufacturing, and so we’re also looking at, a lot of people talk about fusion energy for electricity, but you can [00:10:45] also look at using it for. Decarbonizing desalination, processed heat in manufacturing, district heat and things like that.

[00:10:53] Steffi Diem: A lot of sectors that haven’t had something come in to displace the carbon based.

[00:10:59] Maryam Pasha: Yeah. [00:11:00] That’s awesome. I love that. It’s, it sounds like, I think it’s really cool because just what you said earlier around how you, you’ve been doing this for 20 years and just this like. Real breakthrough moment. So recently it feels like it is actually gonna mean that, do you [00:11:15] imagine that this is something, you may not be able to answer this, but do you imagine that this is a kind of energy we might have access to in our lifetime?

[00:11:23] Steffi Diem: That’s my goal. That’s what I’m trying to do and that’s what a lot of governments are doing right now. Um. A lot of them [00:11:30] are based on like a 10 year plan to build a demonstration power plant that can generate electricity. And from that it’ll take a while to actually commercialize that.

[00:11:40] Maryam Pasha: Right.

[00:11:41] Steffi Diem: But I hope we’re getting close to being able to say within our lifetime.

[00:11:44] Maryam Pasha: That’s [00:11:45] awesome. Yeah. I. Kind of hope. I hope this podcast is going in 10 years and I hope that we can have you back and you can tell us about this demonstration. Okay. That would be amazing. Thank you so much for taking the time, step. So nice to meet you. Thank you. Good to you. [00:12:00]

[00:12:00] Conclusion

[00:12:00] Ben Hurst: Thanks for listening to this quickie.

[00:12:02] Maryam Pasha: This episode was created by our superstar podcast team at TenX London. Until next time,

[00:12:07] Ben Hurst: stay curious.