26-minute listen/watch | 16-minute read | 1-minute teaser
Cooling is energy-intensive, with air conditioning consuming a significant portion of electricity in homes and commercial buildings, while also contributing to greenhouse gas emissions and climate change. This creates a cycle of increasing energy demand for cooling. However, innovative materials that cool when strained offer a promising, sustainable solution for various applications.
Transcript
Herschel Pangborn
We can create technologies that instead of using fossil fuel energy to provide cooling, we can create technologies that harvest energy that's already out there, and use that to provide cooling. That can make a big dent in our fossil fuel consumption. It can really help to mitigate climate change. And so that's really the end goal here, is to harvest energy instead of generate energy that comes from nonrenewable sources.
Host
Welcome to Growing Impact, a podcast by the Institute of Energy and Environment at Penn State. Each month, Growing Impact explores the projects of Penn State researchers who are solving some of the world's most challenging energy and environmental issues. Each project has been funded by the Institute's seed grant program that grows new research ideas into impactful energy and environmental solutions. I'm your host, Kevin Sliman.
Cooling is an energy-intensive process. Whether it's your home or the food in your refrigerator, that cooling takes a lot of energy. In fact, air conditioning accounts for about 19% of electricity consumption in U.S. homes. In commercial buildings, air conditioning accounts for about 14%, but the energy needed to circulate that air consumes an additional 18%.
In addition to energy consumption, cooling also emits greenhouse gases, which are impacting the climate, which requires more cooling. It's a vicious cycle. But what if there was a way to harness existing energy to cool? A research team at Penn State is exploring materials that cool their environment when they're strained. This technology could provide a sustainable way to cool everything from a building to a laptop.
Welcome to Growing Impact. I really appreciate you taking time coming on the show and talking about your research. Would everyone go around and can you introduce yourselves?
Wenjie Li
My name is Wenjie Li, currently an associate research professor at the Department of Materials Science and Engineering at Penn State University. My first research focus is mainly on developing functional and structural materials and devices for sustainable and environmentally friendly energy applications, such as the elastocaloric cooling technology that we are going to talk about today, as well as like thermoelectric power generation and cooling and hydrogen storage materials.
Herschel Pangborn
My name is Herschel Pangborn. I'm an assistant professor of mechanical engineering here at Penn State. I also have a courtesy appointment in the Aerospace Engineering Department. And my research broadly is at the intersection of energy systems and autonomy. So we look at how do you model the energy dynamics in a range of different systems, ranging from hybrid electric aircraft to robots to microgrids. And then once we understand what the behavior of those systems is, then we try to exploit that knowledge to make them more efficient, higher performing, safer. And that really involves using the theory of autonomy and decision making to make those systems operate themselves better.
Na Liu
My name is Na Liu, currently a postdoc research fellow in materials science and engineering in Penn State University. And so my background was about scanning probe force microscopy characterizing the functional materials. Since I joined the Penn State team, my background changed to use the phase change materials such as shape memory alloy, or, vanadium oxide, those kind of oxide materials to do some thermal management objectives, generally speaking, to convert waste energy to useful energy.
Kaelea Hayes
My name is Kaelea Hayes. I'm an undergraduate student researcher in the Department of Mechanical Engineering. And my research is primarily on simulation and modeling of dynamic systems. So in the past, I've done research, modeling vehicle dynamics of some autonomous robots. And currently I've ventured into thermal simulations a bit with this project.
Herschel Pangborn
We should also acknowledge Andrew Thompson, who's a Ph.D. student in my lab and has been working closely with Kaelea throughout the last year or so. Andrew’s had a really exciting internship this summer. So he's not joining us here, but he has been very involved in the project and has been a great mentor as a graduate student.
Host
You're working on a facet of elastocaloric cooling. Can you explain first what is elastocaloric cooling. And then could you share about how it works?
Na Liu
What is elastocaloric cooling? It's kind of a new technique. So we want to use it to replace the traditional, like, refrigerator cooling because it has a lot of advantages. So what is that? The concept is that there's a technology that is the property of certain materials. We are talking about shape-memory alloys in this project, which is a phase change material.
So we want to use this kind of certain material to create a cooling effect through some kind of external mechanical stresses such as bending, compression, or tension, or stretching. So all those kind of forces can some somehow generate, apply the force, and then the material can generate the delta T in order to cool the surrounding atmosphere.
Host
So this material, when manipulated, compressed in some way, some kind of force is put on it, it actually creates a cooling effect. It cools off instead of warms up.
Na Liu
It warms first and then cools down. So, this is shape-memory material. We are using so-called memory alloy, which is the metal for our elastocaloric application. So I want to just introduce this material a little bit. They are not new. So all the kind of applications are due to this two important effects.
First is shape memory effect. So shape memory effect is this material you can easily bend it. For instance, at room temperature, you bend the material and the material just deforms, like significantly. And this deformation will not go back to its original state. But you can apply the heat and then this material just go back to the initial shape. So this is called shape memory effect.
Another very important item is called super elastic effect which is used for this elastocaloric cooling technology. So that effect is so at room temperature, for instance. That's all because this transformation temperature below the room temperature and the super memory effect is the transformation temperature above the room temperature. This is how these two are different from each other.
So for the shape memory elastic... for the super elastic effect, when the transformation temperature is below the room temperature. So you are bending the material, and it can be deformed significantly. But when you release the force without additional like heating, it can go back to the initial shape. So we are using this material for our application.
Herschel Pangborn
One way to think about this is, fundamentally all cooling technologies for things like HVAC, it's about trying to move heat in the opposite direction from where it wants to go. Right? Heat wants to make the cold things hotter. Right? But when you're trying to cool something and trying to make something that's already cooler or even colder than its environment, so you're trying to pump heat against its gradient.
So traditional systems like our refrigeration cycle, right. You use a big compressor and fans that consume a lot of electrical energy, and you use that to change the phase of a refrigerant, and you use that to pump the heat across its gradient. But we're trying to do is take mechanical energy, right, that, you know, vibration or compression and use that through this material to create that gradient that can drive heat, in the direction you need it to go for cooling.
Wenjie Li
The purpose of this project is trying to utilize this material’s device and technology for the future smart building applications, which requires ideally even a small, mechanical pressure is applied on the materials, it should be able to trigger this elastocaloric-cooling effect. But one of the challenges right now is like a lot of like materials, it requires a certain amount of pressure to trigger this elastocaloric cooling.
So far for the material scientist, one challenge is how we can lower the threshold of this applied force to trigger this cooling effect. So yeah, generally speaking, it can be used in the various applications, not only the smart buildings, but primarily for this specific project, we are targeting all the smart buildings.
Herschel Pangborn
I would think about any context in which you have some kind of mechanical force that is right now not being used to harvest energy. So that could mean people walking on a floor where, you know, right now they're their footsteps just going to the ground and don't go anywhere. But could you use that energy to actually provide cooling?
All right. Or you could think about a compressor and a refrigerator or a fan. Right. Something that already they have mechanical dampening. They have springs under that compressor that's designed to take its really, you know, strong vibrations and dampen those out. So it's not shaking the whole building. Instead of just trying to dissipate that energy again where it doesn't go anywhere, can you harvest it and use it for cooling?
You could use this in vehicles like aircraft that undergo, you know, mechanical stresses as they fly, where you can try to use that to provide cooling to the components in the aircraft, or you have all kinds of batteries and electronics, and another things that need that cooling. So there's a lot of places where you could potentially harvest energy, where right now it's it's not being used, and this would be able to utilize that to provide some benefit.
Wenjie Li
Yeah. And also maybe another very simple example that I just we just had a very brief discussion with Na earlier today about the, the lab, for example, the laptop.
Na Liu
So imagine you have this material which is inserted in your computer, and then you are typing your keyboard while you are using a computer. So that is kind of a very... that is kind of mechanical force you are applying like in our daily life quite often. Imagine you can use that kind of force then to cool your computer.
Host
So this already sounds like this has multiple potential places where this could actually show up from a keyboard to an airplane to the floor of a building.
Wenjie Li
Yeah, from small scale to the large scale.
Host
Why is elastocaloric cooling a technology that deserves more attention and investment? And is there data or background on this that talks about the technology or shows how the technology is superior to maybe other cooling technologies? Or if it is, I guess maybe that's a discussion point, like is it actually superior to other cooling technologies, and if so, how so?
Wenjie Li
So, generally speaking, the reason why the elastocaloric cooling deserves more attention investment is that it can simply provide an efficient and environmentally friendly alternative to the traditional cooling system, such as vapor compression technique.
So first of all, it has a positive environmental impact. So traditional cooling system, you often use refrigerants that inevitably generates greenhouse emissions, leading to the climate change, which is harmful to the environment. Where this elastocaloric cooling technique just potentially eliminates the need for those harmful chemicals. Secondly, this technology can be more energy efficient compared with conventional cooling methods.
And also relatively, it represents a novel approach to the cooling and utilizes existing mechanical force, which is everywhere around our life. There is some preliminary research has shown that this technology can convert some mechanical work directly into the cooling with minimal energy loss, and thus reduce the energy cost for the cooling application. And according to the very recent report from the Department of Energy, this elastocaloric effect shows the greatest energy saving potential among the various caloric cooling, and also compared to the conventional cooling technologies that can reach more than 40% of energy consumption saving over the conventional way.
Maybe the last, but not least, is in terms of the performance and the scalability. So it provides rapid cooling cycles because we are targeting to use alloys, which has a high thermal conductivity, so they can benefit a very precise temperature control, so that for can further extend the application of this technique to even, for example, the wearable devices to monitor your body's conditions and also make the people feel cool and comfortable during the hot summer.
What we want to do is to develop new materials and design systems for the scalable and practical device in the future.
Herschel Pangborn
So one thing I would say in terms of the, you know, the broader impact here, something around 30% of our energy consumption in the US goes to buildings and somewhere around 40% of the energy used in buildings is for heating, ventilation, and cooling. Right. So it's a huge chunk of the total energy that we produce goes into heating and cooling. So most of that energy is coming from nonrenewable sources and it's coming from fossil fuels.
So we can create technologies that instead of, you know, using fossil fuel energy to provide cooling, we can create technologies that harvest energy that's already out there and use that to provide cooling. That can make a big dent in our fossil fuel consumption. Right. It can really help to mitigate climate change. And so that's really the end goal here, is to harvest energy instead of generate energy that comes from nonrenewable sources.
Na Liu
So this is elastocaloric cooling. We can incorporate this technique with some other like technology. For instance the 3D metal printing and also the AI. This kind of technology can be included and incorporated in order, we can print any kind of sizes or shape of other devices and which are potentially used in any kind of scenario.
Host
Can we talk about your project and its objectives and what you're hoping that will a) what you hope to do at the end of the seed grant as it comes to a close here and then maybe even moving forward, what that could potentially looks like?
Wenjie Li
We are trying to develop the shape memory alloys and related device to address the challenges from both manufacturing and the simulation studies.
So first of all, we have developed different shape memory compounds with a large latent heat, low mechanical hysteresis, good thermal connectivity, and high recoverable strain. So all these compounds can cover a broad temperature span that can be utilized for the different applications with a specific temperature requirement. And secondly, we have developed a miniature device using the shape memory alloy tubes showing that we can demonstrate quick temperature response and the large temperature difference capability.
And also we have done some preliminary 3D printing of the shape memory alloys. And we just found out today that it shows a large latent heat of the materials. Since I talk about this latent heat concept a couple times, so I want to briefly bring the idea of what exactly it is. So the latent heat indicates the amount of the heat required to change the state of substance without changing the temperature, which means specifically for the elastocaloric materials, the larger latent heat your materials have, and the more heat you can absorb from its surroundings before it goes through the phase change and deform. And then we transfer this heat to other places in order to make our surrounding cooler.
Herschel Pangborn
Ultimately, 3D printing, what it allows you to do, one of the things it lets you do, is fabricate parts that would be very hard to build by any other means, right? Other manufacturing processes. And so, where that ties into some of the modeling we've done is that through the models Kaelea’s created, we can predict things like what would the efficiency of the device be with different thicknesses and different lengths and different diameters? And if that optimization tells you a particular diameter might be best, you know, we either have to find a way to manufacture that component or go out and buy it on the on the market somewhere. And that can be hard to do. Right? Suppliers of these materials... Right. It may not be exactly the right chemistry. It may not be exactly the right form factor, but we can do with additive manufacturing as we can print exactly the ideal part that our models tell us is going to make the best device out there. So that's where we've been able to use this modeling to inform what we manufacture and then use 3D printing to actually manufacture it and test it out.
Host
Kaelea, can you talk a little bit about the modeling part of it?
Kaelea Hayes
Yeah, sure. So basically, the way that we’re modeling this is we're using some basic assumptions and knowledge about how heat transfer works. So knowledge about how stresses and materials work and knowledge about the specific SMA (shape memory alloy) materials to create an equation-based model that lets us simulate how a hypothetical device, or even an individual like piece of the material would behave under certain conditions.
So you can pick room conditions, room size, ambient temperature, basically environmental factors, and you can adjust that. So you can say, okay, we have this kind of device that we'd like to look at. How would it perform under these conditions? And then in slightly different conditions, you know, what are your tradeoffs. And we can also use it to do some design parameter adjustment as well.
So for example, okay, like at what point is the thickness of this device too much where the benefits tend to be outweighed by, you know, some other effects that you might not have predicted. So the model is really valuable in that it helps us hone in on these parameters more precisely than just guessing or doing calculations, especially because you can save a lot of calculation time.
So rather than doing these things by hand, or estimating or guess and check, you can sweep over a range for a parameter and say, okay, this is the value we're looking for. So this is the value we're going to choose. Yeah. So that's basically the point of the simulation is that it lets us pick design parameters more precisely for this device than we might have been able to without it.
Herschel Pangborn
We have the folks you're hearing from here are really, you know, world-leading experts on the material science. And at Penn State, we have facilities and testbeds that allow us to characterize materials. You know, using the latest and greatest methods that are out there. And so, you know, these experts are able to tune in exactly, you know, what's the best alloy, what are the best materials, do the testing to characterize their properties. And then in that same week, we're able to take that test data and plug it into the models that that Kaelea’s developing and understand what are the device level and the system level impacts of those improvements in the material properties and that ability to translate from, you know, the fundamental material science into the system-level understanding and the dynamic understanding. I think that is really unique about this project and how multidisciplinary it is, and it's also a unique thing about Penn State: the fact that we have this range of expertise, and we have mechanisms like these seed grants that can give us the opportunity to collaborate in that way.
Host
What kind of groups and/or, you know, whether it's organizations or people that could potentially benefit from this knowledge and application?
Wenjie Li
This can simply benefit a wide range of like industries and stakeholders as well as the general public, just by offering the improvement in efficiency, sustainability, performance. So, I'll just maybe give you a couple examples, like for the HVAC, the heating, ventilation and air conditioning manufacturers and consumers for just for more efficient, environmentally friendly products or just reduced... bring you the reduced energy bills for your house.
And also like Herschel just mentioned earlier, like in electric and maybe the hybrid vehicles, this technology can be used for, like efficient battery thermal management and also the climate control systems. Also like in the electronics and IT industries, it's just another thing about this topic that it can be improved cooling solutions for the data centers and consumer electronics, preventing overheating and extending the lifespan of the device.
Also, as we just bring out the topic earlier, that it can be beneficial to the portable medical cooling devices for the medication, which requires very precise temperature control and improving the patient comfort and care qualities. Also for the, maybe for the larger scale, it can enhance energy efficiency and reduce environmental impact of the refrigeration and like in the units like the supermarkets or food processing and storage facilities and so on.
And also we covered a little bit, I would say for the more like frontiers of the advanced science, this technology can benefit, the stakeholders for like the renewable energy sectors such as, solar power system, by managing the heat more efficiently and also for like for the geothermal systems, so the efficient heat exchange mechanisms. Also like in the aerospace or defense area, it is interesting for people who want to utilize this technology in the aircraft for the more efficient and lightweight, climate change system to ensure the proper functioning of the onboard electronic systems and equipment by like thermal management doing the whole like long-term space explorations.
Herschel Pangborn
Another thing we do, and I think this is why a lot of us choose to be in academia, is we train students to be the next generation of leaders in the space. Part of what we've had the opportunity to do through this project is to work with Kaelea and Andrew Thompson who I mentioned is a PhD student and train them in and how to do this multidisciplinary research.
And for me, you know, that is a huge part of the value of what we do. My hope is that they will take what they've learned through this project and go on to do, you know, way cooler and greater and better things than anything we do in our careers. And I think they're set up to do that.
Kaelea Hayes
So it's been interesting to see how a research project like this can really develop over a longer timescale, like a year as opposed to two months, and it's also given me a lot of opportunities to improve some like technical writing skills that I didn't really have before, and a lot of communication stuff too, that you don't really get from anywhere except just doing it.
So I presented a poster about my work on the simulation for this project. And that's a really cool opportunity to get used to putting my work out there that I wouldn't have otherwise if I wasn't on this project.
Host
You have 20 seconds with industry leaders, some world leader, whatever it is, you have 20 seconds to talk about your project. What do you tell them about this project and why it's important?
Wenjie Li
Elastocaloric project is pioneering and innovative and environmental friendly and energy-saving technology to achieve efficient cooling by cyclically pressing and releasing the shape-memory materials. So this technology is providing solution for sustainable development with potential benefits for the environmental economy, workforce development, and promoting the energy security and independence.
Herschel Pangborn
A double-digit percentage of our energy goes into heating and cooling in buildings. That is emissions, that's cost. And so rather than, you know, take energy off the grid in order to provide this cooling, let's try to take the energy that's already out there that's not being used. Right. And the same way that we use solar panels, that we use wind turbines, right, to obtain renewable energy, this is a way of extracting mechanical energy from motion and turning that into cooling in buildings as a, as a new way of, you know, providing almost think of it as free energy, in a sense, energy that's there that we're just making use of in a new way.
Host
Thank you so much for being on Growing Impact. I really appreciate it. Na, Kaelea, Wenjie, Herschel, thank you so much. It was great talking with you about this. And I learned a lot because this is something that's amazingly complex, and I really appreciate you guys working on it. So thank you for being on here and talking about it.
Wenjie Li
Thank you for your coordination.
Herschel Pangborn
Yeah. Appreciate it. Thank you for the opportunity.
Na Liu
Thank you.
Kaelea Hayes
Thank you.
Na Liu
Have a nice one.
Host
This has been season five, episode nine of Growing Impact. Thanks again to Wenjie Li, Herschel Pangborn, Na Liu, and Kaelea Hayes for speaking with me about their project. To watch a video version of this episode and to learn more about the research team, visit iee.psu.edu/podcast. Once you're there, you'll find previous episodes, transcripts, related graphics, and so much more.
Our creative director is Chris Komlenic, with graphic design and video production by Brenna Buck, marketing and social media by Tori Indivero, and web support by John Stabinger. Join us again next month as we continue our exploration of Penn State research and its growing impact. Thanks for listening.
