1 00:00:01,920 --> 00:00:06,440 Speaker 1: Welcome to brain Stuff, a production of iHeart Radio, Hey 2 00:00:06,480 --> 00:00:10,480 Speaker 1: brain Stuff Lauren Vogel bomb Here at noon on a 3 00:00:10,560 --> 00:00:14,240 Speaker 1: sunny summer day, the temperature of a conventional dark colored 4 00:00:14,240 --> 00:00:17,599 Speaker 1: flat roof can reach a hundred and fifty degrees fahrenheit 5 00:00:17,720 --> 00:00:20,479 Speaker 1: that's sixty five degrees celsius, according to the U. S 6 00:00:20,520 --> 00:00:24,279 Speaker 1: Department of Energy, and that heat will warm the inside 7 00:00:24,280 --> 00:00:26,960 Speaker 1: of the building or home as well, making it more 8 00:00:27,000 --> 00:00:29,960 Speaker 1: likely that the occupants will turn to air conditioning, an 9 00:00:30,080 --> 00:00:33,919 Speaker 1: energy expenditure that often requires burning fossil fuels at electrical 10 00:00:33,920 --> 00:00:38,280 Speaker 1: power plants, whose emissions contribute to the progression of climate change. 11 00:00:39,000 --> 00:00:43,240 Speaker 1: It's a bedeviling problem that might easily be solved if 12 00:00:43,320 --> 00:00:46,800 Speaker 1: we only had roofs that reflected solar energy back into 13 00:00:46,800 --> 00:00:51,280 Speaker 1: the sky instead of absorbing it. It's a deviling problem 14 00:00:51,440 --> 00:00:54,280 Speaker 1: that might be easily solved if we could only have 15 00:00:54,520 --> 00:00:58,200 Speaker 1: roofs that reflected solar energy back into the sky instead 16 00:00:58,240 --> 00:01:02,800 Speaker 1: of absorbing it. That's why researchers development of the whitest 17 00:01:02,880 --> 00:01:06,560 Speaker 1: paint ever created an ultra white formulation that reflects up 18 00:01:06,560 --> 00:01:09,720 Speaker 1: to nine point one percent of sunlight could turn out 19 00:01:09,760 --> 00:01:11,600 Speaker 1: to be a really big deal in the effort to 20 00:01:11,640 --> 00:01:14,800 Speaker 1: reduce energy consumption and combat the warming of our planet. 21 00:01:15,880 --> 00:01:19,720 Speaker 1: The breakthrough is detailed in April issue of Applied Materials 22 00:01:19,760 --> 00:01:24,520 Speaker 1: and Interfaces, an American Chemical Society journal, and not only 23 00:01:24,600 --> 00:01:27,840 Speaker 1: does the paint absorb very little energy from sunlight, but 24 00:01:27,920 --> 00:01:31,119 Speaker 1: it also emits thermal energy in the infrared range back 25 00:01:31,160 --> 00:01:34,040 Speaker 1: into the atmosphere so that it travels out and away 26 00:01:34,080 --> 00:01:37,960 Speaker 1: from Earth before the article. This episode is based on 27 00:01:38,120 --> 00:01:40,680 Speaker 1: how Stuff Works. Spoke by email with Zen You Lee, 28 00:01:41,080 --> 00:01:44,480 Speaker 1: the paper's first author. He's a postdoctoral researcher at the 29 00:01:44,560 --> 00:01:47,960 Speaker 1: Massachusetts Institute of Technology who worked on the project while 30 00:01:47,960 --> 00:01:52,080 Speaker 1: in graduate school at Purdue. He said this paint not 31 00:01:52,160 --> 00:01:55,280 Speaker 1: only reflects the majority of the sunlight to avoid overheating, 32 00:01:55,600 --> 00:01:59,000 Speaker 1: but also cools itself down colder than the air surrounding 33 00:01:59,040 --> 00:02:03,120 Speaker 1: it even under direct sunlight. In some way, it's effectively 34 00:02:03,200 --> 00:02:09,040 Speaker 1: an air conditioner without consuming any electricity. Researchers have been 35 00:02:09,040 --> 00:02:11,600 Speaker 1: trying to make paints that could be used in passive 36 00:02:11,600 --> 00:02:14,680 Speaker 1: cooling since the nineteen seventies, but most of them have 37 00:02:14,760 --> 00:02:18,160 Speaker 1: absorbed too much sunlight, so they don't provide any cooling 38 00:02:18,160 --> 00:02:22,520 Speaker 1: effect in the daytime. Lee explained, in recent years, scientists 39 00:02:22,520 --> 00:02:27,080 Speaker 1: have also been exploring exotic technologies for creating light reflecting surfaces, 40 00:02:27,120 --> 00:02:31,400 Speaker 1: such as multi layered nanostructured films, but those solutions tend 41 00:02:31,400 --> 00:02:36,120 Speaker 1: to be expensive and not easily scalable to buildings. That 42 00:02:36,200 --> 00:02:38,760 Speaker 1: brought this team of researchers back to thinking that the 43 00:02:38,800 --> 00:02:42,520 Speaker 1: best approach might be a particle polymer composite similar to 44 00:02:42,600 --> 00:02:47,520 Speaker 1: commercial paint. Ordinary white paint isn't quite white enough to 45 00:02:47,720 --> 00:02:51,480 Speaker 1: help much with passive cooling. It only reflects eight of 46 00:02:51,520 --> 00:02:55,840 Speaker 1: sunlight and actually gets warmer from absorbing ultraviolet light, and 47 00:02:55,960 --> 00:02:58,760 Speaker 1: so the task became finding a way to make white 48 00:02:58,760 --> 00:03:02,840 Speaker 1: paint even whiter, and that turned out to be a challenge. 49 00:03:03,240 --> 00:03:07,040 Speaker 1: Alice said. We first tried multiple materials with high electron 50 00:03:07,120 --> 00:03:11,440 Speaker 1: band gap to avoid solar absorption. However, the paints often 51 00:03:11,440 --> 00:03:14,919 Speaker 1: appeared semi transparent at low thickness due to the lack 52 00:03:14,960 --> 00:03:18,920 Speaker 1: of ability to reflect sunlight. During our previous studies on 53 00:03:18,960 --> 00:03:23,120 Speaker 1: commercial paints and theoretical modeling, we identified that both high 54 00:03:23,120 --> 00:03:28,120 Speaker 1: concentration and broad particle size distribution were beneficial. As we 55 00:03:28,160 --> 00:03:31,640 Speaker 1: implemented these two approaches, we saw the paint solution appere 56 00:03:31,680 --> 00:03:36,800 Speaker 1: wider compared to previous attempts, they landed on burying sulfate 57 00:03:36,880 --> 00:03:39,440 Speaker 1: as a way to make the paint very reflective and 58 00:03:39,680 --> 00:03:43,400 Speaker 1: thus very white. You may have heard of burying sulfate before. 59 00:03:43,720 --> 00:03:45,920 Speaker 1: It's the stuff that medical patients take in drink or 60 00:03:45,960 --> 00:03:49,560 Speaker 1: tablet form to code the esophagus, stomach, and intestines when 61 00:03:49,600 --> 00:03:52,480 Speaker 1: they're getting an X ray exam or CT scan, so 62 00:03:52,560 --> 00:03:55,800 Speaker 1: the doctors can see diseased or damaged areas more clearly. 63 00:03:56,520 --> 00:04:00,400 Speaker 1: As a paint ingrediently notes it's already widely available safe 64 00:04:00,440 --> 00:04:05,200 Speaker 1: for humans and the environment. The researchers used a variety 65 00:04:05,280 --> 00:04:08,040 Speaker 1: of sizes of barry and sulfate particles in the paint, 66 00:04:08,320 --> 00:04:12,320 Speaker 1: which enabled the paint to scatter more of the spectrum. 67 00:04:12,480 --> 00:04:14,280 Speaker 1: They also had to make sure that the paint would 68 00:04:14,320 --> 00:04:17,440 Speaker 1: last long enough outside to be suitable for painting rooftops. 69 00:04:18,040 --> 00:04:22,279 Speaker 1: Lee explained, we tested the abrasion resistance, three week outdoor weathering, 70 00:04:22,440 --> 00:04:26,040 Speaker 1: and a water rinse test. All three showed promising results 71 00:04:26,080 --> 00:04:29,880 Speaker 1: as initial durability tests. We also tested the viscosity and 72 00:04:29,960 --> 00:04:32,599 Speaker 1: the paints can be brushed and dried very similar to 73 00:04:32,720 --> 00:04:36,880 Speaker 1: commercial paint. It can also be fabricated in a similar way. 74 00:04:37,040 --> 00:04:39,360 Speaker 1: In this work, we not only achieved a paint that's 75 00:04:39,360 --> 00:04:42,599 Speaker 1: superior to the commercial paint, but also do not need 76 00:04:42,680 --> 00:04:46,799 Speaker 1: specialized equipment or materials to fabricate, transport, or apply the paint. 77 00:04:48,839 --> 00:04:51,839 Speaker 1: The ultra white paint looks pretty similar to regular white 78 00:04:51,839 --> 00:04:56,039 Speaker 1: paint because the difference in reflectivity, while significant in terms 79 00:04:56,040 --> 00:05:00,880 Speaker 1: of cooling, is imperceptible to humanize. The next step in 80 00:05:00,920 --> 00:05:03,400 Speaker 1: the research is to optimize the paint for long term 81 00:05:03,480 --> 00:05:07,000 Speaker 1: durability under different sorts of weather conditions, but there isn't 82 00:05:07,080 --> 00:05:08,919 Speaker 1: yet a target date for it to be market ready, 83 00:05:09,080 --> 00:05:11,159 Speaker 1: so don't search for it at your local hardware store 84 00:05:11,279 --> 00:05:19,080 Speaker 1: just yet. Today's episode is based on the article the 85 00:05:19,080 --> 00:05:22,839 Speaker 1: whitest paint Ever produced could save energy climate change on 86 00:05:22,880 --> 00:05:25,440 Speaker 1: how stuff works dot com, written by Patrick J. Keiger. 87 00:05:25,880 --> 00:05:28,200 Speaker 1: Brain Stuff is production of I Heart Radio in partnership 88 00:05:28,200 --> 00:05:29,960 Speaker 1: with how stuff works dot com, and it is produced 89 00:05:30,000 --> 00:05:33,200 Speaker 1: by Tyler clang. Or more podcasts my heart Radio, visit 90 00:05:33,240 --> 00:05:36,040 Speaker 1: the iHeart Radio app, Apple Podcasts, or wherever you listen 91 00:05:36,120 --> 00:05:37,080 Speaker 1: to your favorite shows.