 Tech-A-Wai, civil engagement lives here. And welcome to likeable science here on Think Tech-A-Wai, I'm your host Ethan Allen, glad to have you with us. Join me by phone and some video, well not video, picture today is going to be Dr. Oswath Rahman. Oswath has joined me again, he had been on the show a few years ago with the most amazing discovery I thought at the time that I had ever heard of. Dr. Rahman is a professor or assistant professor at University of Pennsylvania, also the co-founder and chief science officer of a group called SkyCool Systems, and we'll see what SkyCool is all about. Welcome Oswath. Thanks, happy to be here again. Excellent, excellent. So Oswath's background, why don't you tell us a little bit about your background and how you got started in this whole business? Sure, well I, academically at least, I became very concerned about climate change and the energy challenge that we were all facing about a decade ago now, and I decided to go get a PhD and I did my graduate school in applied physics at Stanford, which is on the west coast of the US, with a particular focus on thinking about the question of how we can better make use of light and heat, and that was sort of my entry point into this whole topic area. The research area I actually pursued is a topic known as nanoscale botanics or optics, but simply it's the idea that we can make things with features on very small length scales, so much smaller than a human hair or the wavelength of light itself, and in doing so we can induce some very unusual interactions between these artificial materials and light, and it turns out heat as well, so that was kind of my entry point into all of this, you know, in a larger sense. Right, and it was amazing what he has come up with, it almost seems like a violation of the laws of physics, although of course it isn't, but the idea is that he, Oswath has developed a surface that is highly reflective, but in a very limited band, and Oswath recently did a nice TED Talk and explains this extremely well, and in TED Talk it's well worth watching for anyone who wants to see this, but basically just as we all, anything that is visible is reflecting light, everything reflects light and reflects heat too, and Oswath cleverly manipulated matter to have that reflection just as we can paint something in a different color and it looks different, he painted as it were a surface with a structured substance such that it reflects light out in a very narrow band of I believe the near infrared that our atmosphere is very very transparent to, right, so none of this comes back in, right? Yeah, and so we can actually see that in the first slide I have, so people should be able to pull that up, it's actually not part of the spectrum that's known as the mid or far infrared, and to, yeah, to really understand this, you know, maybe just kind of stepping back, all objects, including you and I and the walls around us and the buildings, the earth itself, we all radiate heat as a kind of light that we can't see. This is a concept known as black body radiation or thermal radiation, so, you know, every object kind of naturally does this to some extent. Now, what's interesting about our atmosphere is that if you were a surface pointing yourself up towards the sky, you would send up some of you this heat as infrared light because you naturally do that because you're at a certain temperature, it's kind of a basic physical law. However, some of that heat escapes as you pointed out, and we can see that in this slide because in what we plotted is what's called a transmission window. This transmission window effectively allows some of that heat to escape and it's between 8 and 13 microns at wavelength, so this is a much longer wavelength than visible light, the light that we can see. Now, what makes all of this very exciting and interesting is that what's outside the atmosphere, so what this transmission window leads us to, is space, and if you go to the next slide, you'll see that the fundamentally enabling component of the technology I'll describe is the fact that what's outside our atmosphere is very cold and minus 270°C or minus 454°F, so that's a very cold temperature. It's the ultimate cold thing, it's the ultimate place to send heat, but what people don't realize is that we can actually access this in some way and it's as simple as literally just stepping outside and pointing yourself up towards the sky. So if you, as an individual, were to step outside right now, the top of your head is actually radiating some of its heat to space and that's just something that naturally happens all the time. Right, but the difference is at the same time during the day, of course, sunlight is pouring energy down onto the top of your head, right? And that counterbalances it. Right, exactly, and this concept, because of that, people used to call this concept night sky cooling, meaning you would only observe it at night when the sun isn't there. So this happens naturally, especially on clear night. So if you were to go and measure the temperature of your roof at night for some reason, you would see that it's actually below the air temperature because of this effect. Now, during the day, as you rightly point out, during the day, the complication is that the sun usually completely overwhelms this cooling effect so that people had traditionally thought that it was not a useful idea during the day. And technologically, this is, of course, problematic because during the day is when we need something coldest the most. Right, and this is really not, it's not brand new science. You describe in that TED talk that you do that some of the folks in the Middle East, in ancient times, would actually put out shallow pools of water on clear nights and actually be able to harvest ice from that. Yeah, it's kind of remarkable. It's, you know, before the advent of modern ice making machines, people used to have these dedicated facilities or building just to make ice. In northern parts of our world, these ice houses usually would involve just getting natural ice that formed in the winter and storing it through the summer months. Now, in many parts of the Middle East, it rarely actually got below freezing. But they were actually able to take advantage of this effect to make ice, usually during the winter still at night. And the way they did it, as you described, is you'd have these shallow pools of water and you would basically pour the water out as the sun set. And at night, you would actually, that water would freeze. And the early morning hours, the people who would run these facilities would collect the ice, chop it up into pieces, and then store it in kind of underground in these facilities that would stay relatively cool all the way into the summer months. So you could, you know, have ice cream in the summer in ancient Persia. So people were pretty ingenious. And, you know, I have to emphasize, it's very unlikely that folks that were building these necessarily understood the science behind it, but they understood the effect. They saw it happen. Someone really observed it naturally happening and said, Hey, why don't we, you know, I see frost form on the ground. Why don't we use this to make a lot more ice, you know, more systematically. Yeah. And it's, I love the story also that you told building your first nanostructured surface and putting it out on the roof of building in Stanford. You talk about that in that in that TED talk, and realizing when you when you touched it after it had been out there for a while, that it was cooler than the surrounding air. Exactly. So the, you know, when I started working on this is around 2012 or 2013. And the whole idea was that, well, I actually kind of started from a basic question, which was, why, you know, why wasn't this actually being used as a technology? Like, what was the fundamental kind of scientific roadblock here? And one thing I realized was an issue immediately was that it didn't work during the day. And so that kind of led to the advent of the school project. And we eventually came up with a design of an artificial material or structure that we could use conventional technologies that already exist to actually deposit and fabricate. And the funny thing about this kind of lab experiment is that you can't actually do it in a lab, you actually have to go outside and, you know, face the sky to see if it's actually doing what it's supposed to do. So these kinds of experiments are pretty funny, because you basically go on a rooftop somewhere, and you know, put your material out there to face the sky, and then you see what its temperature is. So that's very first time, you know, I was, it was the first time I was actually running the experiment. So I wasn't sure it was actually going to work. I figured there'd be some problem or thing I hadn't thought about. But amazingly enough, the, you know, I just left it for half an hour, I came back up on the roof. And here, as a scientist, you're probably not supposed to do this, but I decided to just touch it. And it was, you know, very cool to the touch immediately. And I figured, Hey, this is probably working. So that was pretty exciting. It was probably one of the best, you know, research moments I've ever had in my career. Yeah, because because that does does seem up to break in a common sense, sense. The basic, everything that sits in the sun gets warm. I mean, we know this from our common experience. There is nothing that gets cold when it sits in the sun, right? Yeah, so it was, it was really counterintuitive. And, you know, I would do this, I would do this demo for people where I would essentially, you know, shade it. And you would think, Hey, it'll get cooler, but it would actually start warming up. Counterintuitive. Amazing. Yeah. And yeah, it's one way to think about what we did was we essentially, it's like we took the sun out of the picture. And it was like we were basically returning to what would happen at night, because we were reflecting almost all the sun's incident energy. So we avoid this getting heated up by the sun. So that was kind of the, you know, the moment of insight and the kind of the thing I think that we thought made this technology really compelling, because now we had something that got cold below the air temperature throughout the day. And there's very few things out there like that. This is utterly amazing technology indeed. Oswath, we're gonna have to take a short break here, one minute break. And for our viewers out there, I'm Ethan Allen, host of think of likeable science here on thick tech. My guest is Dr. Oswath Rahman from the University of Pennsylvania and sky cool systems. And we'll be back in one minute. Are you tired of sleep walking through life? Are you dreaming of a healthier, wealthier, happier you? You're not alone. And that's why thousands of people tune in each week to watch RB Kelly on out of the comfort zone Tuesdays at 1pm. Make a change, get the help you need and stop sucking at life. The army were going to go live. Hello, it's 1pm on a Tuesday afternoon. And I'm your host, RB Kelly. Welcome to out of the comfort zone. Aloha. My name is Reg Baker, and I'm the host of business in Hawaii. We broadcast every Thursday from two to 230. And we highlight successful businesses in Hawaii. Hawaii has some challenges. Most places do. But we have businesses here that have figured out how to make it work. And we learn their secrets and we learn how they have made it successfully in Hawaii. Occasionally, we'll have organizations that come on and explain how they help these businesses to be successful. And we find that there's an awful lot of resources out there available to anybody in business to help them do better. So please tune in every Thursday from two to 230 here at the think tech studios and get educated. Aloha. And you're back here on think tech Hawaii. Another episode of a likeable science with your host, me, Ethan Allen, and my guest joining us from the University of Pennsylvania today is Dr. Aswath Rahman, who has developed this utterly astounding coating or material that reflects so much of the incoming radiation from the sun that it actually gets cooler than the surrounding air when it sits in the sun. And we want to now look a little more deeply into sort of how it does this, why it does this, but even more importantly, where does this lead us, Aswath? Where do we're going to go with this? Yeah, that's a great question. And it's actually something we thought a lot about many years ago as well, especially once, you know, we got it to work. I think there's there are a few kind of interesting observations. You know, just thinking about it from the technological perspective, what is this technology strength? Well, it works 24 hours a day, it can get passively cooler than the air temperature. And it doesn't require any water. So it's non evaporative. And, you know, to the extent that people care about this, it's it's also silent. So it's not a noisy machine. It just is just sits there and it gets cold. When we when we saw the kind of the advantages of the technology, we started thinking about how we might actually use it to tackle the specific problem of air conditioning and refrigeration. And that became the focus of a lot of our efforts. Right, because you point out that air conditioning and refrigeration systems involve a huge amount of energy expenditure from our country and from the world around us, something like 15, 18% of the energy current that we currently use is goes into cooling things. Yeah, it's around that. And I guess, specifically, it's electricity, I think, maybe not energy in total. But globally, yeah, it's about that. And I think what's, what's kind of scary about it is that our energy use for cooling is expected to grow about six fold by the year 2050, which is which is only about 30, 32 years away. So it's not that far away. And most of this growth right now is not coming from, you know, Western industrialized countries, but it's really coming from Asia and then many African countries as well. You know, a lot of them, a lot of equatorial countries and countries in East Asia, get very warm in the summer, folks want to have the benefits of air conditioning and certainly refrigeration for, you know, their food system. So it's completely understandable that this kind of this is like one of the first technologies that someone arriving in the middle class wants to purchase. Now, the problem from a kind of system level, however, is that right now these systems contribute to about 10% of global greenhouse gas emissions. And if this trend goes, that's a that's a big increase in greenhouse gases. And some people have pointed out that if our planet gets warmer, which is widely expected to get and has been getting, you know, the warmer it gets, the more we're going to run those air conditioners and the more they're going to put greenhouse gases at the atmosphere. So there's this nasty feedback loop that we might initiate and perhaps we've already initiated it. Right, you can just sort of see it gets hotter, you need more air conditioning, you're running more air conditioning, you're dumping more, you're using more fuel, you're dumping more greenhouse gases out and you're on a on a vicious cycle right away. And so this technology that you have developed has the capacity to cut into that one, sort of several different ways, right? Yeah, I think there's there's a lot of different potential ways we can we can tackle the problem. We realized that one of the most important things that we needed to do first was figure out how we could couple this to today's air conditioning refrigeration systems. In the long run, there may be ways of designing buildings to really take advantage of these kinds of materials that we're making. However, in the short run, you know, we have a large amount of cooling systems that exist already. And, and it's not likely that there's going to be a dramatic shift in how we use these systems within the next 10 or 15 years. So we wanted to be able to tackle the problem that exists today and right away. The strategy we went about is to actually build what we call fluid cooling panels using our materials. And if you go to the next slide, you'll actually see some pictures of these panels in operation at a field field trial in Davis, California. So these panels, essentially, you should think of them as being analogous to solar water heaters, flat plate kind of solar water heaters, not the evacuated tube variety, if you're familiar with the different kinds. However, we use our specialized films to cool the water instead of heat it up. So that's what you're actually seeing in the picture. Exactly. So you, so you essentially have a sky water cooler, if you want to think about it that way. I mean, just to emphasize, we're not using the sun at all, where the sun is actually a bad thing. We're typically, actually, we're typically tilting our panels slightly to the north away from the sun. The, so the really remarkable thing about this that, you know, we, there, that we realized was that we could actually scale the film pretty quickly using existing processes, manufacturing processes. And that we were able to kind of rapidly go from something that was very lap scale to the prototype products you see right there with our startup sky cool systems. And the the panels you see there, for example, about three by six feet in size, so they're fairly large. And that means they can actually reject a meaningful amount of heat. Right. So then now you've got this cool water, which you can then use in any sort of a cooling system, right? Right. So you've now got essentially, you know, a closed loop way of rejecting heat and keeping something colder than the air temperatures. And that makes it entirely unique in the space of existing cooling technologies. So it's been, it's a very kind of compelling ability that technology has. We think the most direct way to use it is as an add on to today's HVAC and refrigeration systems. So the main way to I think, think about this is that that every cooling system has, which is called a condenser. Right. And if you if you the basic idea in a cooling system is that you're actually taking away heat from somewhere else, heat flows from hot to cold. Right. So in a cooling system, there's an inside part, which is called an evaporator, which draws the heat in. The heat is then and there's a refrigerant, which is then compressed, and then taken up to a higher pressure, which then allows us to reject that heat outside. Now typically this condenser, to be able to reject its heat to its ambient environment, needs to sit at, you know, 10, 20, even 30 degrees Fahrenheit above the air temperature to be able to efficiently get that heat out. Our panels connect in on that side to keep that condenser at a lower temperature. And what that means is then that that compressor has to do less work. It uses less electricity to deliver the same amount of cooling for the person who's sitting inside. Okay. Okay. I see. So you've got sort of an assistive device then for existing air conditioning systems. Right? Yeah. And I think the it's perhaps one way to think about it is this is probably the way to immediately get this idea into its most widely applicable use case and to really tackle the largest variety of systems that exist today. So this applies for everything from, you know, your late air conditioning unit at home, window air conditioning unit, potentially as well, though they're a little, you know, their compact systems are a little difficult to modify them sometimes. All the way up to the commercial and industrial scale. So the cooling systems that are used to data centers in supermarkets and cold storage warehouses, these industrial scale systems, they all work under essentially the same principle. So any of these systems can have an efficiency boost with our panels and interfacing with them as an add-on. So, you know, no, you don't have to completely change your system. We can just serve as this efficiency boost. And what's remarkable is that efficiency boost can be 10, even 20 percent. And for folks that work in this industry, that's a huge number. We often face a lot of skepticism when you say something like 10 or 20 percent because, you know, usually there's not any technologies, if any, that can deliver that kind of that boost. So there's, I think there's been a tremendous amount of interest we've seen from people across the whole kind of spectrum of use cases cooling systems. Right. And then the nice thing that is, that gets your technology out into a broader public. More people will come aware of it, right, and will understand that there is this sort of odd exception to the universal rule that everything that sits in the sun warms up, right? Everything that sits in the sun except for the sky cool systems warms up. And then you can really begin to play with that system in other ways, right? Potentially. Yeah, definitely. I think there's there's a lot of potential directions you can take it from there. You know, there there have been third party studies that have been done by national labs in the United States, which have showed that if you use panels like ours in conjunction with higher efficiency internal cooling systems inside a building, you can actually boost or better phrased, you can reduce the electricity used for air conditioning in particular in a commercial office building by two thirds. So that's that's a huge number on it on that space. And it's not only our system, but you also want to take advantage of a lot of other efficiency technologies that have come into the market in the last few decades. And, you know, this particular scenario, we would pair our panels with indoor radiant ceiling panels. So these are you can think of them as sort of the indoor version of what we're doing, where instead of radiating the heat to the sky, you're drawing the heat from the people and objects inside the room to a ceiling tile where there's essentially water flowing through it. And that water can then be pumped directly to our panels, which then cool it back down and recirculate it back into the system. So that's, you know, that's a it's actually a well understood technology. It's been around for decades. It doesn't have a huge amount of market penetration in the US yet, but it's increasingly finding its way into a lot of high efficiency buildings. So there's a really neat opportunity for us to pair with these kinds of panels to perhaps go entirely passive, so zero electricity. Right. This is the beauty of this whole thing is that ultimate sort of here it is zero zero power AC, basically. And suddenly you don't need to be burning fossil fuel contributing to greenhouse gases. You're getting air conditioning for free from the sun, right? From the sky, the sky, right? Sorry. Right. And so yeah, I mean, yeah, go ahead. I was just going to wrap this up here by saying what you've done is really taking you're taking advantage of this tremendous temperature difference between the warm surface of the earth and the utter cold in the depth of space. And you are channeling heat very efficiently away from the earth into that sort of infinite cold sink, right? Yeah, exactly. And I just wanted to mention if you go to that very last slide, you can actually see the full deployment we had in Davis last summer, where we actually hooked up our panels, both with commercial scale refrigeration systems, as well as air conditioners where we were that's where we were demonstrating the 10 to 15 percent efficiency improvements that I mentioned. So, you know, that's just a plug to say that this is just kind of a pie in this kind of idea. It's, you know, something we've managed to reduce to something that is pretty much a product and ready to test out in the market. And yes, the ultimate way this is enabled is that we're taking advantage of the fact that what's outside our atmosphere space and it's very cold. This is this is amazing. This is to me it's sort of mind-boggling that you've done been able to do this and that you've taken it here just a relatively few years ago from when I first spoke with you to now and scale this up gotten out into commercial format that's practical, that's being applied. I can graduate you for that. I'm I'm in awe of your of your capacities and your abilities to do that. And I look forward to getting back here maybe another two or three years and seeing what's what you've done with it after that. Thanks so much. I really appreciate it. And, you know, the thing that excites me the most is that as much as you know, weird technologies going out there now into the marketplace there's there's just a lot more science here as well. There's so little we understand at this point about how to really leverage this phenomenon, what its limits are and what if other use cases might be there might be opportunities for water conservation power generation that we don't quite understand. So I think there's on both fronts a lot of exciting things to come. Excellent. Well, thank you so much. Dr. Aswath Rahman from University of Pennsylvania and Sky Cola Systems was our guest today on Think Tech. And I hope you'll come back next week and join us again. Till then.