Nissan has demonstrated a new automotive paint that can drastically cool a vehicle parked in direct sunshine. Tests have shown that treated cars stay up to 21.6 °F (12 °C) cooler than untreated cars parked side by side.
We’ve all felt that blast of heat getting into a car that’s been parked in the Sun on a hot day. It’s not just unpleasant, it can also put a strain on your health – and your car when you crank the AC to cool it down.
One possible solution is passive cooling paints and coatings. Engineers at Nissan Research Center have now developed one that contains metamaterials that help reflect the Sun’s rays more efficiently.
Two types of particles are embedded in the coating. One efficiently reflects near-infrared wavelengths of light, reducing the amount of heat generated in the resin of regular paint. The second particle creates “electromagnetic waves,” Nissan says, which redirect more energy away from the vehicle and vent it directly into space, as seen in other radiative cooling technologies.
Nissan has been testing the coating since last November on a Nissan NV100 service vehicle at Haneda International Airport in Tokyo. The treated vehicle has been found to have temperatures up to 21.6 °F (12 °C) cooler on the external surfaces, and up to 9 °F (5 °C) cooler inside the cabin, compared to a vehicle with regular paint parked right next to it in direct sunlight.
The basic idea of these sunlight-reflecting coatings has been around for a while, painted onto rooftops to cool buildings. To do so, they’re usually ultra white and can contain ceramic, glass, or titanium dioxide particles, with promising results so far.
It seems like a logical next step to start coating cars and other vehicles with them, but there are a few hurdles in the way. For one, at 400 microns these coatings are much thicker than vehicle paint, which is roughly 20 microns per layer on average. It also can’t have a topcoat, which reduces durability and leaves a chalky residue when you touch it.
The Nissan researchers have managed to shrink their coating down to 120 microns – much thinner than other cooling coats, but still much thicker than existing automotive paint. Further work is underway to make thinner versions with the same cooling performance. Thankfully, the current version shows resistance to chipping, peeling, scratching, chemical reactions and other types of damage. They can also maintain color consistency and are repairable.
Ultimately, the goal is to develop a version that can not only cool vehicles but can have a clear topcoat, be applied from a spray gun, and ideally even be available in other colors besides white.
The team describes the coating in the video below.
Source: Nissan
