Nothing freshens up a home like a new coat
of paint. But what if that paint could do more than
just change your home’s appearance — what if it could actually make your home much cooler…. Literally? Well, that’s just the idea behind a new
type of Ultra White Paint developed by researchers at Purdue University. The paint is officially the whitest substance
in the world — so white that it can actually create a cooling effect on the objects it
covers. So… could the solution to climate change
really be as simple… as a fresh coat of paint? How exactly does it work? And… are there any potential downsides? We thought these questions deserved a deeper
dive today on Two Bit Da Vinci So
when we think of paint… we might think of those old classic Bob Ross videos. But can paint really go from making happy
little clouds and trees to… literally saving the planet? To start, let’s talk about visible light,
and what gives colors their color. First of all visible light is only a tiny
little part of the entire electromagnetic radiation spectrum. Wavelengths here on this spectrum determine
the amount of energy the waves carry. Things like Radio waves, microwaves, and infrared
light, have less energy than visible light, and things like ultraviolet, x-rays, and gamma
rays have more. In the visible light spectrum, each color
perceived by the eye is based on the wavelengths of light reflected by a surface. For example, if you look at a red t-shirt,
you’re seeing a fabric that reflects more red light, while absorbing other wavelengths. A material that absorbs all wavelengths of
light is seen as black, because very little light bounces off and hits your eye. White then, is the opposite, as a white material,
is prone to reflect most of the visible light spectrum, and all those colors mix to be perceived
as white. This is why a white car stays cooler in the
sun, because it reflects more of the sun’s energy than a black car, which absorbs more. This then is where we start our journey. Clearly, white paint isn’t new, so what
makes this stuff so much more “white” and does it actually make that much of a difference? Well, researcher and professor of mechanical
engineering at Purdue University Xiulin Ruan seems to think so. The paint developed by him and his team has
come as the result of over six years of research — chasing a question that dates back to
the 1970s. Can you use paint to replace air conditioning? And after all these years of research — the
team finally stumbled on a substance that has officially been deemed the whitest on
earth according to the Guinness Book of World Records. Looks like Vladimir Putin’s shirtless chest
has been dethroned. But the team’s goal was never to create
the whitest substance. Instead, they were trying to develop a paint
that could generate a cooling effect on objects — in particular, rooftops and buildings. It just so happens that in order to achieve
that, they also inadvertently created an ultra white substance — since the color is actually
achromatic, and reflects and scatters all the visible wavelengths of light. Because white objects don’t absorb any light,
they are inherently much cooler than other objects. The trick was to find a material that could
reflect the most light. After testing over 100 different materials,
the team finally landed on a chemical compound called Barium Sulfate — commonly used to
make photo paper and cosmetics appear white. It turns out, Barium Sulfate has a high electron
band gap for low solar absorptance — that’s the ratio of the radiant energy absorbed by
a body to that incident upon it — and phonon resonance at around 9 μm — which makes
it an incredibly suitable material for a phenomenon called radiative cooling. We covered this topic in a previous video
about SkyCool systems which you should definitely check out if this kind of stuff interests
you. Basically, as radiation from the Sun hits
the Earth, some of it reflects back out into space through tiny “sky windows.” This is why your car might have a layer of
frost on it in the morning. Infrared radiation can pass through clear,
dry air in a wavelength range somewhere between 8–13 µm. This helps this radiation in particular to
cut through the water vapor and CO2 in our atmosphere. Materials with the right reflective capabilities
can bounce that radiation right back out into space and generate a cooling effect even in
direct sunlight. And it turns out, Barium Sulfate possesses
those reflective properties. But it’s not just a high concentration of
particles that give Ruan’s paint, it’s whiteness. The size of the particles also plays a crucial
role. By adding particles of varying sizes, the
paint’s reflective property increases, as it scatters even more of
the light spectrum from the sun — similar to a shiny, expertly cut gem. With particles of the right shape and size,
the paint can reach a solar reflectance of over 98%. Using white paint to reflect heat is nothing
new. It's been a common practice in places like
Greece for years. And in densely populated urban areas like
New York, initiatives to paint rooftops white have been implemented to combat what’s known
as the “urban island effect.” Basically — a “heat island” is when
a structure — like a building, road, or some other form of infrastructure — absorbs
and re-emits the sun’s heat at a much higher rate than the natural landscape, even after
the sun goes down. Obviously, because urban areas have significantly
more infrastructure, they are the biggest culprits of heat islands. According to the EPA, in the United States,
the heat island effect can result in daytime temperatures in urban areas about 1–7°F
higher than temperatures in outlying areas and nighttime temperatures about 2–5°F
higher. The problem with most commercially available
paints, even white reflective paints, only reflects between 80 ad 90% of sunlight. And what’s worse, they still absorb a significant
amount of heat. What makes this new ultra white paint so unique
is that not only does it reflect over 98% of the sunlight — it also creates a cooling
effect. Purdue researchers were able to show that
their paint can keep surfaces up to 8 degrees F below their surroundings under direct sunlight
during the day, and up to 18 degrees F cooler at night. That’s a pretty big temperature gap considering
it’s literally nothing more than a coat of paint! Not heat pumps. No working fluids. No grid energy to power complex machines. All things that residential and commercial
AC units require, and all of which can have detrimental impacts on the environment. And again, all AC units do is transfer heat
from inside your house to outside, whereas this ultra white paint literally sends that
radiation back out into space! Sounds pretty… cool… to us! When field-testing their paint, Ruan and his
team covered a 1,000 square meter roof in their reflective paint. The result, according to their data, was a
cooling power equalling roughly ‘10 kWhs of electricity or about 34000 BTUs — more
powerful than most residential central AC units which can vary but tend to average about
24,000 BTUs. Ruan and his team estimate that this could
reduce your electricity bill by about $1 per day, or possibly more just by painting the
roof. By painting both walls and roofs, retails
stores could see up to an 11% reduction in annual energy costs, while single-family homes
could see up to an 8% reduction. But Ruan sees an even greater potential for
his paint — actually reducing global temperatures. According to Purdue researchers, if just 1%
of the planet’s surface were covered in the world’s whitest paint, worldwide temperatures
could drop about 1-degree Celsius — which is about how much the global temp has increased
since 1880 according to NASA. Of course, as with all scientific breakthroughs,
there are some who are skeptical about this new ultra white paint. Researchers from both the South Coast Air
Quality Management District and the Heat Island Group at Lawrence Berkeley National Laboratory
have suggested that ultra-white paint may actually contribute to the very problems it’s
designed to alleviate. Some of the research indicated that while
white paint does indeed cool urban surfaces, it can actually prevent moisture and energy
from traveling upward to form clouds. Fewer clouds mean that more sunlight ends
up hitting the exposed area which could offset the cooling effect. Another potential flaw in reflective paint
came via observations from air quality scientist Scott Epstein who observed that winter-time
air pollution in rural Utah was worse than in the summertime due in part because the
white snow actually reflects that UV light back into the atmosphere. This then triggers a chemical reaction that
forms smog and pollutants such as black carbon — which of course contributes to heating
the atmosphere. Then there’s the more practical drawback
that conflicts with the very problem this tech aims to solve. In Winter, any stray sunlight that might have
warmed your home, well... now is reflected away. In turn, this could potentially lead to higher
heating costs, especially on cold days, with good sunshine. My Mum was right, you really can’t have
it all. So clearly, this is a technology for cooling
in climates where hot summers are worse than cold winters. Places like the American Southwest immediately
come to mind. As of right now, the research team is looking
for a commercial partner to scale up the production of the paint and hopes to have it available
in the market within the next two years. The team also intends to investigate creating
colors other than white, which will still maintain some reflective properties though
obviously not as much. This could help the product become more commercially
viable cause… you know… we don’t want all our houses to look the same like some
dystopian sci-fi novel. Imagine a future where your home could be
coated in reflective paint and outfitted with reflective solar panels, creating a cooling
effect 24 hours a day while consuming virtually no electricity! That sounds pretty chill to us! But what do you think? Is white paint the way to go for passive cooling? Do you think the rewards outweigh some of
the potential risks? Sound off in the comments section below!
