 Hi, I'm Kate Young and you're listening to This is Purdue, the official podcast for Purdue University. As a Purdue alum and Indiana native, I know firsthand about the family of students and professors who are in it together, persistently pursuing and relentlessly rethinking. Who are the next game changers, difference makers, ceiling breakers, innovators? Who are these boiler makers? Join me as we feature students, faculty and alumni taking small steps toward their giant leaps and inspiring others to do the same. We did some analysis on using our paints on the hot climates in Reno, Nevada or Phoenix, Arizona. Those are like hot and dry climates and will be sort of ideal location for using our paints. Our analysis shows that during the summer months, using the paints can save up to 70% of the air conditioning cost. You may have heard about this latest guest on This is Purdue through national media outlets like CNN, BBC, Fast Company, Yahoo, and oh yeah, The Tonight Show with Jimmy Fallon. Shulan Ruan is a professor of mechanical engineering at Purdue University. His giant leap as a boiler maker, inventing the whitest paint on record in an effort to curb global warming. We'll get more into the paints effect on climate, but one of the most interesting things Shulan shared with me, when the team first started this project, they didn't actually set out to create the whitest white paint. When we started the project about seven years ago, we had the energy savings and fighting climate change in mind. That's right, this invention is seven years in the making. Shulan explains. We started working on this in 2014. We tested many different materials, concentrations, and the different particle sizes, and so on. It does take a lot of effort, and many students who graduated and then new students continued the effort to really make it happen. Using radar cooling in paints really started in the 1960s. At that time, people were trying to create white paint that can reflect the sunlight as much as they can. At the same time, we know any surfaces when you put on the roof, they're going to emit their own heat to the surrounding as well. The problem was that at that time, the whitest paint people created can reflect 80 to 90 percent of sunlight, which means they absorb 10 to 20 percent of the sunlight. That's still too much heat absorbed from the sunlight, and that's more than the heat they lose. Although they are cooler than the other colored paints, they cannot be cooled below the ambient temperature. A few years back, we started on this first inspired by a group at the Stanford University, which created multi-layered nanostructures that can do below ambient cooling, but was very expensive, not viable for buildings. We went ahead and think about whether we can create the paints to be below the ambient temperature, because we had much better nanotechnology than half a century ago. We eventually came up with this new paint formula with a few innovations compared to the commercial white paints. This new whitest white acrylic paint reflects 98.1 percent of sunlight, compared with the 95.5 percent of sunlight reflected by the team's previous ultra white paint. It deflects infrared heat, allowing buildings to cool below the surrounding air temperature. In fact, the team's tests have shown that the paint is able to keep a surface around eight degrees cooler than its ambient temperature in the afternoon, and up to 19 degrees cooler at night. But what makes this paint the coolest? A very high concentration of a chemical compound called barium sulfate. It's also used to make photopaper and cosmetics white. Barium sulfate was used in the paint in pigment particles of various sizes, which allows the paint to scatter more of the light spectrum from the sun. But the barium sulfate used had to be just the right amount. If they used a higher concentration of this, it would likely cause the paint to break or peel off, according to the research team. Shulin walks us through how this new paint differs from commercial paint. You can go buy at a local hardware store. Tell us about what's in the paint. How is this different from if you go to the store and buy a regular can of paint? It has a few key innovations compared to the commercial white paints you can buy. I mean, that took us a long time to figure out actually each aspect, each innovation, over the years. Now, first, the commercial white paints are based on titanium dioxide. So titanium dioxide reflects very well in the visible portion and near infrared portion of the sunlight but it absorbs the UV. So we first went out to look for materials that would not absorb UV at all. Those included oxides, carbonates, and sulfates. So those were our candidates. But that's not sufficient. We came to realize that we need a much higher concentration in the commercial paints. So commercial paints, they usually have less than 10% of the particle loading and that's not sufficient to reflect sunlight for the energy purpose. So we tested different particle loading and eventually landed at 60% and is an appropriate number to sufficiently reflect on the scattered sunlight. At the same time, it still behaves like the paints. So a third key innovation that really pushed our paint to the performance we see today is not using a uniform size. That's kind of a little bit counterintuitive at the beginning, but our predictions showed us eventually if you use a single size, it only reflects one wavelength of the sunlight really well, not the other wavelengths. So once you have different particle size in your paint, each size will be responsible to reflect one wavelength in the sunlight. So eventually the whole spectrum of sunlight can be reflected effectively. So these are the three key differences from the commercial paints. I can summarize again. First is a material that does not absorb UV. Second, high particle concentration. Third, not uniform particle sizes. Throughout Shu Lin's journey with creating this paint and pushing the limits on their previous white paint, of course came with challenges and roadblocks. The team had considered over 100 different materials, narrowed them down to 10 and tested about 50 different formulations for each material. To be honest, seven years ago, we didn't know that we would achieve such great reflectance today. So we did run into a lot of roadblocks and then but we're really happy that working with our students postdocs, we were able to overcome these challenges and that led us to arrive where we are today. So each innovation actually came out of the challenges we were facing. For example, at the beginning, we were trying to push the titanium dioxide that is used in commercial paints to perform very well. So we made many different trials based on titanium dioxide, different particle loading, different substrate. At that time, we didn't believe we were able to achieve this in a single layer. So we tried putting these materials into like a two-layer structure and so on. So after many trials, we were not able to get pulling below the ambient temperature and we came to realize it's the materials problem. So that's how we set out to look for other materials like bermsulfate, calcite and so on. But even with that, we tested many materials, maybe as many as 100 materials. Some materials, we kind of expected them to work, but it didn't work eventually. We also had a hard time on the matrix material like polymer to use. Some of the particle fillers, they don't really like the polymer. I mean, we're not able to disperse them so well in the polymer matrix or binders. So we kind of explored that to find the good pair of the filler as well as the polymer to have a good dispersion. We came to realize the particle concentration was not high enough. So we tested many particle concentrations. And the last maybe challenge I want to highlight is that after we've done all these, we were trying to explain the performance why it is 98.1%. So using previous models, we're not able to match the prediction with our experiment data to be more specific. The theory says that reflectance should be lower than experimental measurements. And we spend time on that and eventually find out that that's because we have different particle size in it. Previously, people just neglect the nine uniformity in the size that we found that it plays a very important role in increasing your reflectance from just above 90 to 98.1%. So I have to say that the innovations were pushed by the challenges we were facing. And that's how the science and engineering works. I love that quote. The innovations were pushed by the challenges we were facing. And that's how science and engineering works. As Boilermakers, Shulin and his team continued in their persistent pursuit of making this paint a reality. Let's dig further into how this whitest white paint can help our planet. Shulin's team calculated that if one half to 1% of the Earth's surface was covered in this paint, it would reverse the total effects of global warming to date. When applied to the roof and walls of a building, the paint can reduce the need for air conditioning and the associated carbon emissions. First of all, if you compare our paints with commercial white paints, we can see that it reflects 8% more of the sunlight back to the deep space. And it provides cooling by its own emission. So that will translate to about 10 kilowatts more cooling power from our paint compared to commercial paints if you have a 1,000 square feet one-story house. Okay. So what does that mean to the energy sort of a sector and the global warming? Now, on one hand, if again using that house as an example, you can save about 10 kilowatts hour power every day, right? That power usually comes from burning fossil fuels which involves carbon emissions. So without using any power, our paints cause carbon emissions in that aspect. The other very important aspect for the conventional air conditioners, they just move the heat from inside of your house to the outside ambient. But the heat still stays in the city, it still stays on the earth. So that really contributes to the urban heat island effect in cities that create many issues in large cities, even pose some theory of kind of a threats to health. On the other hand, the heat is on the earth and contributes to warming the earth. So totally different from that, our paints on the roof, it kind of sends off all the heat from the sun and from its own emission directly through the atmosphere and the loss to the deep space. So the heat totally goes off the earth. To put it in perspective, 10 kilowatts is more powerful than the central air conditioners used by most houses. New York recently coated more than 10 million square feet of rooftops white and California has updated building codes to promote cool roofs and painted on top of your average 1000 square foot ranch house. The team estimated that a coat of this super white paint alone could save an estimated $1 per day on your electric bill during the summer months. I'll let the expert break it all down for us. Now we can use that 1000 square feet single story house as an example. Our paint compared to the commercial white paint can provide 10 kilowatt additional cooling power. If we use a typical air conditioner efficiency numbers, so that translates to save about 10 kilowatt hour electricity per day for this house. If we use that 10 cents per kilowatt hour, you know, price that that's about one hour per day saving for the house. So I can give you another example. We did some analysis on using our paints on the hot climates in Reno, Nevada or Phoenix, Arizona. Now those are like hot and dry climates and will be sort of ideal location for using our paints. Our analysis shows that during the summer months using the paints can save up to 70% of the air conditioning cost. In other words, in certain days when it's not too hot, you do not need to turn on your air conditioners at all. The paints will just provide enough cooling for the temperature indoor to be more to be comfortable for human beings. Now if the outside becomes very, very hot, you need to turn on your air conditioners still, but the paints can offset a lot of heating and can reduce the demand for the air conditioner. So overall it saves up to 70% of the power considering the typical weather over, you know, a few months in the summer. So what if people don't necessarily want a white roof? Do you have plans for the future of taking this formula and creating different colors with it? Sure. Yeah, that's a great question. First of all, I want to sort of, you know, highlight that, you know, some many locations people do like white color. For example, we got a lot of inquiries from the Middle East, Africa, Central America, South America, or even the thousand part of the United States. It's good to know that, you know, many locations like Greece, they were painting their house already in white. They were asking us whether they can get our white, which is whiter than the commercial white available these days. Like in New York, they were painting like a million square feet of roof area to mitigate the urban heat and the effect. So people were already using white. But yeah, of course, other people may not like white, you know, they want other colors. So that's definitely our mind. Our white paint provides a great platform actually to develop color paints that are cooler than the other commercial color paints, because, you know, our white, the farm sulfate base can be a base pigment, just like the other colored commercial paints, they are based on TiO2 or titanium dioxide. So we can modify the paints to be based on farm sulfate. And we are optimistic that the color paints created this way should be cooler than the color paints on the commercial market. It may not necessarily to cool below the ambient temperature anymore, because color paints means you've got to absorb some portion of the sunlight to show the color. Yeah, that's something we're working on right now. And then we hope to report some results in the future that we have cooler color paints than the color paints you can get on the market today. If you're ready to run out to the store and grab a can of this paint, it's not on the shelves just yet. The good news though, this paint isn't going to be crazy expensive. It'll be comparable to a normal can of paint. Our lab can only produce like a small amounts for painting samples or like a cardboard or so, but we are working with a large corporation towards commercializing our technology. So we need to do more testing and optimization of the paints to make sure it has a long-term reliability. It can untie dust, can last for many years. Yeah, we are working hard on that. And hopefully we will see this eventually on the market if we do everything quick in a year or two or so. Yeah, I mean, we do get a lot of inquiries from people from the hot, especially from the hot climate. A large customer would be India, very hot. If you use too many air conditioners, the heat and the effect is very serious there. So yeah, pushing this into the market will really help a lot of people that really have the cooling needs. The cost is comparable to the commercial paints. So the Barham Salfi pigments is actually slightly less expensive or maybe at most comparable to titanium dioxide. And beyond that, the manufacturing process of our paint is compatible with the industry practice right now. So we expect that the final cost of our paint should be comparable or even slightly cheaper than the commercial paints on the market. Shulin realized this paint would make waves in the science and engineering industry. But what he didn't know was that artists and even art museums have reached out to the team about the ultra-white paint. Why? Artists have expressed interest in your work, as well as obviously all of the attention you're getting from the scientific and engineering world. But how does it feel to know that there may be art created with this paint someday? Yeah, that's a pleasant surprise. Again, as we published our work, we didn't really emphasize the color aspect. But it's great to know that the artists got interested in this and they have the need to push the whitest white to create unique artwork. Actually, I have quite a few museums who contacted me asking for samples donated to their collection, the whitest that they can have. So I already agreed to send them samples, including the U.S. as well as from overseas, such as Singapore. Some of those museums, they have the blackest black, the venta black, if you know that. Yeah, they want to put the white as a counterpart in their collection. So that's really interesting. Other artists already kind of emailed me asking about where they can get the paint or their interest in creating these paints. Definitely something interesting we're thinking about and it's good to know there is a market on the art side, you know, aside from the energy and the climate aspects. I didn't expect people who are interested in so white because the white is, to me, before all these, like a boring color, right? You like blue or red or so. I mean, it's kind of quite educational to me to see there are so much interest just into white and the black. And what about all of the attention Chulin and his team has received in the past few months? It's not every day you get mentioned on an Emmy winning late night show. At this point, you've been featured in hundreds of articles, you know, you've been on CNN, you know, you've been on the BBC, Fast Company, and Jimmy Fallon even mentioned this paint on the Tonight Show. That's crazy. So what's your reaction to all of this response to this white paint? Yeah, well, yes, it's definitely much excited what I expected. You know, every time we saw like, you know, a big news outside of our expectation, we say, wow, you know, particularly the Tonight Show and so on, the Jimmy Fallon. So it's great to get this level of publicity for paints. But we are really glad that our work together with, you know, the work in the field now has kind of contributed to raise the awareness of the among the public about how important it is to save energy to help our environment and combat climate change. I think that that's the point that, you know, with all these media, you know, it reaches out to the corners over over the globe. Now, we kind of contributed to that aspect. I mean, how the paints can help, you know, something as simple as paints can really help, you know, extremely important issue of the climate change. Right. And you guys are certainly contributing to that conversation. So were you surprised by all of this media attention to? Yeah, well, we were expecting coverage by a lot of the media, but we were surprised by a certain coverage like the talk show, right? Definitely. Yeah, then we got people from weather stations. They came to Purdue and shoot videos in our lab too. So that kind of really amazed us on the climate, on a climate site. Yeah, but you know, these talk shows, they definitely helped spread the work and, you know, help on the also maybe they didn't really focus on the energy climate site, but when people get more into either the news articles or even our paper, you realize that, you know, the paints can help. So, you know, using white paints to help our climate has been there for some time by the people who are kind of resistant to that if they don't like the white color. So I hope this artwork can contribute a little bit to the people's willingness to think about using paints to help our environment and our the Earth's sort of sustainability. Yeah, I think really, I think that would be great if our work made a tiny bit contribution towards that. As for the Purdue University community, Shulin shares this invention would not have happened without the resources and talent Purdue has at its fingertips. Purdue definitely played a critical role for all these that we have achieved. Just a few aspects, you know, Purdue has very strong academic reputation that helped our lab and others lab to attract the best students and postdoc fellows and the researchers all over the world. So I would say that without, you know, the high quality of our students and scholars, this work wouldn't have been possible. A lot of my students who worked on this project, they came up with solutions to the challenges we were facing. So that's really, really important. I feel the support from students, from colleagues, from the administration and from industry members. So Purdue really provided in the right and all the necessary resources, including human resources and the facilities. In the meantime, what's Shulin thinking about next? Well, naturally, he's already contemplating what he and his team can achieve in the future. Thank you for the great questions that really inspired me to think about our journey over the many years and how the students contributed and then many graduated or completed their postdoc experience and have their own successful either academic journey or even or in the industry. It's a great moment to also to reflect all those and look forward what we are going to achieve in the future. If you'd like to learn more about Shulin and his team's research on this ultra-white paint, please visit purdue.university slash white paint. Thanks for listening to This Is Purdue. For more information on this episode, visit our website at purdue.edu slash podcast. There you can head over to your favorite podcast app to subscribe and leave us a review. And as always, Boiler Up!