263: A Very Magnetic Heat Pump – Julie Slaughter Interview

 Today on Still To Be Determined, we’re talking about using magnets for heat pumps. Yes. This does have a technical term. Yes. Sean has difficulty getting his mouth to say it. However, using magnets for heat pumps is of course an attractive proposition. Hi everybody. I’m Sean Ferrell. I’m a writer. I write some sci-fi.

I write some stuff for kids, and I’m just generally curious about technology and luckily for me, my brother is that Matt of Undecided with Matt Ferrell, which takes a look at emerging tech and it’s impact on our lives. And as I mentioned at the top. We’re talking in mag magnets, but it’s not actually, I can’t even say the word magnets.

Look at that. It’s not actually me doing the talking. This week, we’re sharing a long form interview that Matt has done recently. Matt had a chance to talk with Julie Slaughter from the Ames National Laboratory about their research into. Here we go. 3, 2, 1, magnetocalorics, which is of course, using magnets for heating and cooling.

So on now to Matt’s long form interview about this very interesting topic.

It’s nice to meet you, Dr. Slaughter. Um, I’m so glad to be able to kind of join me today to talk about magnetocalorics and your work in the field. It’s really nice to meet you and uh, thanks for joining me.

Thank you. It’s nice to meet you also.

One of the reasons we reached out to you is you’ve, you’ve recently had a paper that kind of came out and kind of got a lot of attention around some of the most recent research you’ve been doing. Caught my attention ’cause I’ve been looking into things like elastocalorics and then up comes your paper on magnetocalorics and it was like immediately, oh, I need to dig into this more.

So my team and I, we reached out to you, started talking to you about this. Could you just kind of gimme a little bit, before we get into that, can you gimme a little background on who you are and what led you into the study of these different calorics?

My background is actually, uh, mechanical engineering, but I’m a scientist at Ames National Lab and I’ve been here for the last oh eight and a half years or so working on both magnetocaloric and elastocaloric cooling.

Our group really started, um, with Vitalij Pecharsky and Karl Gschneidner. They, um, discovered the giant magnetocaloric effect in I think 1997. And, you know, that was kind of the, really started a lot of the room temperature, magnetocaloric cooling. If you call it revolution, you know, it really kind of garnered a lot of interest from industry in that.

But, um, there’s still been some challenges that’s been, you know, several years ago now, and, uh, it’s still not commercially, um, viable. So when we, we were brought on, you know, part of a materials discovery, I was brought on a part of a materials discovery project. Um, but my role in that was actually to work on devices and say, okay, how can we test the material in a real world situation and, and kinda move this forward to commercialization?

And I don’t know if I’ve skipped too far ahead, but No, no, I was, I was gonna say, so

your, your focus has been more on the practical, like. Yes. Making a practical application of this discovery? Yes.

Mm-hmm. Okay. Absolutely.

Yeah. And for the people that are probably watching or listening to this that are not familiar with what magnetocalorics are and what it is, could you kind of, in kind of simple terms, kind of like boil it down for, for people?

Yeah, absolutely. So magnetocaloric materials, they basically change phase in a magnetic field, so that the phase change basically from a magnetic to a non-magnetic state, typically is what um, causes a temperature change in the material. So if you apply a magnetic field to the material, if we’ll use gadolinium as an example, it’s kinda a nice baseline material.

It heats up a few degrees under a magnetic field, and then when you remove it, it cools down. And so we use that effect and then transfer, you know, transfer heat in and out of the material. As it heats up and cools down to get a, a large temperature span that’s useful for cooling or in fact heating. So it really moves heat from low temperature to high temperature.

Right. And it’s all, like you just mentioned, it’s all about the phase change ’cause like mm-hmm. My familiarity with this stuff was, you know, like you bend a piece of metal a few times, it’ll start to get warmer as you’re bending around. The idea that magnets can also have a similar effect was where my head just kind of like broke a little bit ’cause I wasn’t aware of that.

Yeah. So it is phase changes in multiple different fashions. So it’s similar to elastocalorics, but it’s just using magnets. Exactly. What’s the biggest problem that you and your team are trying to tackle right now with turning this from like research into that practical device that could actually be commercialized.

Yeah, a lot of the problem right now is not the cost of the active material, not the magnetocaloric material. It’s how do you make the magnetic fields that you need and you need fairly high magnetic fields to, to make the, to get a strong effect. The higher the fields, the stronger the effect. So if you’re limited to permanent magnets, you’re, you’re, you have a very limited amount of field that you, that you can get from permanent magnets, you know?

One to one and a half Tesla are about the maximum that you can expect. And with that, you know, it costs a lot to put permanent magnets in. So you actually have more permanent magnet in an actual cooling device than you have of the magnetocaloric material. So that becomes the most costly component, and that’s really a limiting factor on that.

And what makes, what makes this approach so appealing compared to the other forms, like, like I keep bringing up elastiocalorics, but there’s also electrocalorics, like what makes magnetocaloric so appealing that people are focusing on it?

One thing is, it’s, it’s it’s efficiency. I mean, the phase change in the material is nearly lossless, so, so you really have the potential to be much more efficient than vapor compression or elastocalorics and not as familiar with electrocaloric, but I think it, it has that potential to be much more efficient than today’s technology. It’s also, you know, I say it’s expensive to create magnetic fields, but it’s also not that difficult to create magnetic fields.

I mean, you have permanent magnets and, and that that’s an actual easy way to do that. And there’s a lot of history in permanent magnet motors that, that we have to build on.

You, yeah. You actually just, you, you just touched on something, the fact that it’s, it’s not just that we’re getting away from potential fluids that might be greenhouse gas issues mm-hmm.

For the climate. Yeah. But it’s, these technologies are potentially just way more efficient. Potentially. Yes. Um, which is another reason why we just be looking at these because it’s gonna take what we currently do today and make it even better. Would it be fair?

Absolutely. And yes, that that’s fair. And you know, and to, to go back to that, absolutely.

Getting rid of the greenhouse gases and some of the other problems with today’s technology is, is a good thing, but there’s also, um, you don’t need the high pressure. So right now when you have, you know, vapor compression, you’re actually forcing a phase change. You need really high pressure to do that. So when we’re, we have a low pressure, heat transfer fluid, so eventually, once this is more mature, it should be even more reliable too than today’s technology.

Yeah. Yeah. That was gonna be one of my questions. It seems like, because it’s a slightly, and I’ll put this in air quotes, simpler system, in a way, it seems like it would be more reliable over a longer period of time for whatever the machine is that you’re using. It seems like it would probably be more reliable overall, unless I’m not understanding it completely.

Yeah, I, I think it has the potential to be, I think, you know, at the lab scale, you know, obviously the first thing you build is very complicated, if any, anything. So the early prototypes are, are much more complicated than they need to be. Yeah. Than they’ll be eventually. So

yeah. One of the other things I, I find fascinating when I was looking into this is the different designs of what the systems actually look like.

And yours, if I remember correctly, it kind of has a spinning magnet system in the middle of it. Yes. Um, and it reminded me very much of an electric motor. That’s just the way, the basic structure of it. So is, is that, is it not that far off from an electric motor? Basic, the basic premise of that central magnetic section,

it’s similar.

I, I, I think there’s definitely some analogies and I think it, you know, I can see future designs moving that direction toward, you know, what you would see for, for a motor, but it’s not quite there yet because we actually use a motor to spin the magnets, so we, we don’t generate that. Yeah. Electromotive force, you know, inside.

But, but, uh, but yeah, I can see definitely there, there’s some very close analogies and a lot we can learn from what electric motors, you know, they’re designs and being compact and, and using magnets very creatively to, uh, to get the fields where we need them. And,

and so that, that section, is that the part that’s called the, uh, AMR?

So the permanent magnets are what apply the magnetic field. The active magnetic regenerator is where the active, uh, magnetocaloric material fits. And then, you know, the, the magnets spinning is really to get that change from high field to low field. So you need that alternating magnetic field on the active material and then we transfer fluid in and out of that active magnetic regenerator bed.

So it’s a porous structure in there. Um, and we use that heat transfer fluid to carry the heat away.

And you were mentioning before that one of the materials you used was gadolinium. Um, what was the other material that you used that you’ve also found good results with?

Right. And, and this is something we just looked at theoretically in our, in our paper, but, uh, there are better materials that high of a higher magnetocaloric effect and lanthanum, iron and silicon.

That family of materials is one that’s very well known. Um, there, there are others too, but really, um, there’s a very limited commercial availability of any of these materials. But lanthanum, iron, silicon has been around quite a while and it has quite a bit of studies or research that’s been done on that.

Okay, so you had mentioned that cost wouldn’t be necessarily a factor, like as this becomes commercialized for some of the basic components, but like you just mentioned just now, it sounds like some of them may not be readily available, so there may not be a supply chain that’s available to produce this at scale at this point.

So. Do you think that this is kind of like where the bottlenecks might start to hit for trying to commercialize this kind of technology where it’s like the supply chain isn’t there enough as it starts to kind of ramp up?

I think the supply chain is growing. Um, there’s actually a, a, a small company in Europe that is trying to commercialize magnetocaloric technology.

But there are also, um, a couple of companies that are working on the materials and the active regenerators supplying those components. So I think, but supply chain can easily catch up to where it needs to be if the applications start to, to become realistic and, and grow.

I keep talking, I’m talking about the challenges ’cause those are the ones that keep popping in my head, but like Sure.

Some of the engineering challenges that you’re, you’re trying to do to try to make this more practical commercializable device. What are some of the biggest like challenges in trying to make it smaller, cheaper, and more efficient?

That’s a great question. Um,

there’s, there’s probably like a thousand different answers to that question too.

There are. The paper that, that, that, uh, you referred to earlier. We, we were really focusing on making the permanent magnets and all the ferro-magnetic parts, all the parts that just carry magnetic flex but don’t generate it. So steel, iron, silicon, those types of materials to making all those components as small as we possibly could.

Um, because you know, to be frank, if you don’t weigh less than a compressor, you’re never going to cost less than a compressor. So, um, that, that was our approach to that. So that was one of the big challenges we’re facing. And then as you go to higher and higher power. We need to have better materials, so better magnetocaloric materials that have a higher effect in a lower magnetic field.

So we, we kind of compete at the low end of the power spectrum, but we don’t yet compete at the high end of the power spectrum.

One of the terms I wasn’t completely familiar with until I read your paper, which was the system power density, the SPD, that use to kind of calculate things. Um, could you kind of walk through what that is and why?

It’s kind of important to kinda look at that, to understand where a technology like this kind of sits in commercialization.

A lot of times when, um, people are talking about magnetocaloric or elastocaloric material, they talk about how many watts per gram of cooling power that the material, the active material can generate.

Well, that’s. That’s one piece of it. But now you have to look at from a system wide, from a device level. Um, so that’s what we were calling our system power density. So we looked at all the magnetic components, so the magnetocaloirc material in its active regenerator form, the permanent magnets and the magnetic steel.

We considered that our system mass. So that’s where that came from. And then it’s really how much cooling power, and we tried to keep everything on a level playing field. So we had the same temperature span when we were comparing compressors and all the other magnetocaloric devices that we looked at.

And then we looked at just the device level mass, and then how much cooling power that mass, device mass produced. So that was our system power density definition that we use.

Right? Because, because I’m familiar with like, like when you’re talking about an HVAC system, what’s the coefficient to performance?

And so this was a different way of looking at something similar.

Right? And we made the assumption in our paper that we could be equivalent on coefficient of performance because there have been devices that have shown similar coefficient of performance between a magnetocaloric device and a vapor compression device.

So we just made that baseline assumption that performance was the same. How much did it weigh to get that same performance? How much mass did that take?

Now, based on your experience with the research that you’ve been doing as well as your knowledge of other companies, what they’re doing around the world, because you’ve already mentioned a couple of them.

This is the million dollar question. And I know this is kind of a loaded question, but how close do you think we are to seeing a magnetocaloric device like in our home refrigerators or air conditioners or some kind of device that consumers can finally get their hands on?

Right, and I think there’s probably different stages of this.

I think the early adopters are going to be more niche applications where they have some pain point that needs to go, you know, that there’s a reason they can’t use vapor compression. There’s a reason they can’t use something else. So I think that’s gonna be the early adopters, and we’re starting to see that now with some of the companies that are out there.

And some of the projects we’re, we’re working with and companies we’re talking to. Um, so that’s gonna be early adopters, but then I think we’re probably gonna move into small appliances first. So home appliances, refrigerators, and, um. You know, perhaps even water heaters, but, but that, you know, small scale devices and then it’s going to move more into the HVAC systems as we get higher and higher.

Because I think right now the, the space where it’s more competitive is at that low end, you know, one kilowatt and below for, uh, cooling power. But I think as the materials improve and systems improve, we’ll get up to that home, home heating and cooling system level.

So we’re still a ways off, but those early adopters are gonna be the ones that are gonna basically be funding the continuing development of this.

Yes, and I think the early adopters, we’re going to see that grow in the next, I would say, three to five years, really, where there are some examples, very good examples of devices out there working in the, in the field. So

I know you already, you, you have a lot of experience with elastocalorics too. How do you think this work compares to what’s happening in the elastocalorics space?

Are there kinda like lessons or crossovers between the two at all?

Yeah, I think there’s a lot of, a lot of lessons in crossovers. I think. A lot of what we’ve learned about the systems and how to design them for magnetocaloric are are directly, directly translatable to elastocalorics. Elastocalorics is really more in its infancy. It’s kind of a little bit of a wild west out there right now because people are, are, everyone’s got new and exciting ideas and it’s still kind of settling down into what, what is the best approach. Um, magnetocalorics has a little more history and I think there’s a fairly straightforward way to design a device.

They’re not all gonna look diff the, the same between different research groups, but, but it’s very similar. So I think, elastocalorics can learn from what we’ve done for, you know, the fluid pumping, the, the valving, the timing and and and things like that. So I thought there’s a lot of crossover and I think they’re gonna have different application areas.

’cause I think magnetocalorics is always going to be more efficient than elastocalorics. But maybe heat pumping, maybe water heating is a better application for elastocalorics. So I think they definitely have their niches.

Yeah, finding those niches is gonna be where they come by land. Yeah. Makes a lot of sense.

Yeah,

definitely.

And if, and if you could, if you could wave, if you could like wave a magic wand and accelerate one aspect of your research, what would that be?

I think it would be right now making the active regenerator, because right now packed particle beds are kind of the standard, what’s been used or parallel plates, and we have to be able to manufacture something that’s more robust and has better heat transfer and, and lower fluid flow pressure drops. So I think there’s a lot to be done in the active regenerator space right now. Now you can’t separate that from magnetocaloric materials because you have to have to materials that are not brittle and they’re able to withstand the processing that it takes to form it into the right shape.

So getting that forest structure with very small features and good heat transfer is, I see a big challenge right now.

And what excites you most about where this could lead?

I think just. The applications are, are endless for it. I mean, when, you know, you can replace anywhere a compressor is using, you use the, um, you know, the harmful gases that are in refrigerants, you know, um, I think that that’s really just, I, I see the applications are just enormous for this.

So I think it’s just, room for so much more research and development and seems exciting.

Well, one thing that just popped in my head, would the side effect also be, not only is it better in that regard, but would it be quieter than having a compressor system? I.

It, it can be, it depends on, you know, some of these other things.

It needs valves, it needs some things like that. But it should be because we don’t, you don’t have the compressor cycling on and off, which I agree is a very annoying thing to have in your refrigerator, in you and your hotel room. So, so absolutely. I think that’s an aspect of it that has been talked about that has never been proven.

So yeah, I think that’s definitely something we need to, to evaluate at some point?

Well, one, my final question, I always like to ask every person I talk to people like with your experience, is for students or young researchers or people that are just kind of getting into these kind of fields, uh, what kind of advice, what advice would you give them?

Yeah, that’s a great question. When you’re looking at what you want to research or what you want to do, don’t, don’t look at what you know the, the next exciting big thing is look at, look at what you’re interested in, what’s going to have an impact, what’s, what’s going to really excite you as a researcher and, you know, find somebody who’s passionate about what they do and, and learn from the experts in the field too.

I think that’s really the best advice I can give is try to surround yourself with people who are good at what they do and are passionate about what they do.

Love that. Well, I I appreciate your time. Thank you so much for talking to me. I really, I, I’m so glad you talked to me about your work ’cause it’s, it’s very interesting stuff and when I read your paper I was immediate like, I gotta dig, dig into this ’cause it sounds so cool.

So thank you so much.

Alright, well thank you Matt. I appreciate it. It was nice to meet you and uh, this have been great.

Thanks to Julie Slaughter for sitting down with Matt, and thanks to all of you for taking the time to watch or listen. What did you think about this conversation and what do you think about this technology?

Uh, was there an element about this that stood out to you or is there something about it that you wish had been answered in the video? Drop it in the comments below, and maybe Matt will be able to follow up or provide answers to your questions. As always comments, liking, subscribing, sharing with your friends, those are very easy ways for you to support the channel. Believe it or not, simply liking and commenting does tremendous things for us, so please jump in even if all you’re gonna say is magnets. Or Sean can’t say the word magnets. We appreciate it. So thank you. And if you wanna support us directly, you can go to still tbd fm, click the join button there, or you can click the join button on YouTube.

Both of those allow you to throw coins or magnets at our heads, and we appreciate the welts. Thank you so much everybody, for taking the time to watch or listen. We’ll talk to you next time.