Paint that can reduce heat in cars by up to 12C showcased in Japan

Nissan has launched a paint that reportedly keeps cars cooler by upto 12C as sweltering temperatures become the norm across the world.

The “cool paint” launched on Tuesday promises to reduce both external and internal car temperatures, offering a potential solution to the discomfort and energy consumption associated with overheated vehicles as summers get longer and hotter.

The paint is six times thicker than standard car paint, a characteristic that currently poses a challenge for mass production. However, the company says the benefits are substantial.

Traditional commercial white paint, typically made with titanium dioxide nanoparticles, reflect 80–90 per cent of sunlight but still absorb some heat, limiting their cooling effectiveness during the day. These paints are generally applied in a thickness of around 120µm (0.12mm or approximately 0.0047 inches).

Tested on vehicles at Tokyo’s Haneda airport – a location notorious for its unshaded expanses – the paint demonstrated it could turn the cars noticeably cooler.

The technology reduced the roof panel temperature by 12C (22F) and the interior temperature by 5C (9F).

Nissan’s new paint works by reflecting sunlight more effectively and generating electromagnetic waves that deflect the sun’s rays, redirecting energy away from the vehicle.

This approach can not only help in keeping the cars cooler but also potentially reduce the reliance on air-conditioning, thereby conserving energy.

Cooler vehicles can also alleviate the strain on engines and extend the life of electric vehicle batteries, a significant consideration in today’s automotive landscape.

Developed in collaboration with Radi-Cool, a Chinese company known for its cooling technologies, Nissan’s paint is part of a broader effort to integrate temperature-reducing materials into everyday products.

Radi-Cool has also developed cooling fabrics and coatings for various applications, including hats and sun parasols. Nissan is currently the only Japanese automaker partnering with Radi-Cool, marking a unique collaboration in the industry.

The announcement of the innovative technology comes at a crucial time as Japan experiences one of its hottest summers on record. In fact, worldwide, heat records are shattering every month and the last 13 months have been the hottest on record.

People who spend long hours outside driving in the peak heat have been finding it difficult to cope with the temperatures, resulting in increased use of air conditioning, hence more energy usage.

Car companies have been innovating ideas to reduce vehicle temperatures without relying on traditional energy-consuming methods, not just an environmental initiative but also a public health consideration.

Nissan’s Susumu Miura, a manager at the company’s Research Center, emphasised the safety of the electromagnetic waves emitted by the paint, reassuring that they have no adverse effects on health.

“My dream is to create cooler cars without consuming energy,” Mr Miura said.

Toyota Motor Corp has also been experimenting with paint that delivers lower cabin temperatures, mostly focusing on colours that refract the sun’s rays.

In 2021, researchers at Purdue University made a white cooling paint using barium sulfate nanoparticles that could reflect 98.1 per cent of the sun’s rays, radiating more infrared heat than it absorbs.

But the paint works best in a coat 400µm thick, equivalent to 0.4mm or approximately 0.016 inches, almost four times thicker than the typical 120µm coat on vehicles.

Associate researcher of the study, George Chiu, said at the time the paint “has the potential to cool the exteriors of aircraft, cars or trains”.

“An aircraft sitting on the tarmac on a hot summer day won’t have to run its air conditioning as hard to cool the inside, saving large amounts of energy,” he said.

People living in hot climates have for centuries painted buildings white to keep them cool. White or silver coatings reflect the sun’s heat-producing infrared rays.

In fact, cool roofs and housing paints have been growing in popularity in countries like India. These paints, also known as reflective roof coating or thermal insulation paint, have been succesfully bringing temperatures down inside the houses by 5C.

However, making these paints easier to use for cars and more widely available at competitive pricing is where the companies are struggling.

Another paint was developed by Vantablack, a formula developed by researchers in the UK and displayed on a BMW X6 SUV in 2019, which claimed to absorb up to 99 per cent of light that hits it.

“To achieve this level of radiative cooling below the ambient temperature, we had to apply a layer of paint at least 400 microns thick,” lead researcher of the Purdue study, Xiulin Ruan, said in a media statement in 2021.

“That’s fine if you’re painting a robust stationary structure like the roof of a building. But in applications that have precise size and weight requirements, the paint needs to be thinner and lighter.”