Summer may have just passed in the Northern Hemisphere, but we're sure that you can easily recall some of those blazing hot days. Not that we're complaining—overall, summer is a ton of fun. But all of us had those days where all we wanted to do was stay inside with the air conditioning blasting.
And that's a problem.
Because while A/C makes things frosty inside, it creates big problems outside. It uses tons of energy. It also often requires coolants—substances that lower the temperature of the machine as it operates—that are themselves greenhouse gases. And, above all, the air conditioner itself releases heat into the atmosphere.
In short, too much A/C creates a vicious cycle where things outside get even hotter and the solution is even more A/C! You see where that is going. It's unsustainable.
That's why scientists are so interested in something called passive daytime radiative cooling, or PDRC. Don't let the phrase fool you—it's actually a simple idea. And thanks to a new invention, using it could be a coat of polymer paint away.
An affection for reflection
PDRC is basically all about reflection. Specifically, reflecting light and heat.
You see, too many surfaces in our cities absorb heat. Think of all of that pavement and metal, all those dark surfaces. They hold on to the heat, warming cities overall and the buildings themselves.
PDRC technology instead reflects this heat away, sending it back into outer space. The city and buildings become noticeably cooler, A/C usage can go down, and the cycle is broken. Yay!
Except ... most PDRC tech is expensive and often prefabricated (or pre-made in a certain shape and style). These issues make it difficult to use on a large scale. After all, even if you can afford PDRC tech, buildings come in lots of odd sizes. Who wants to deal with installing custom panels and tiles? It would be way easier if we could just paint the roof instead.
Paint away the heat
Now it appears that you can! This polymer paint has been designed by researchers at Columbia University in New York (a city that knows a thing or two about unbearably hot summers). It's not actually a paint at all, but a coating that goes on like a paint. And it starts off going on clear.
But as it dries, it turns white to the eye. White is a great reflecting colour already. But this coating takes things one step further. It dries in a way that leaves lots of tiny air voids, or holes, in the surface. These all reflect tons of sunlight and heat into the sky.
In fact, an amazing 96% of heat is reflected away by this handy dandy 'polymer paint'. This video from Columbia does a good job of explaining how this stuff works. Plus, it looks super-cool (pun intended) as it dries! Check it out.