A PAINT that helps keep cars cool in hot weather is being tested by Nissan.

Developed in partnership with Radi-Cool, a specialist in radiative cooling products, the paint incorporates metamaterial, synthetic composite materials with structures that exhibit properties not usually found in nature.

The project is part of Nissan's pursuit of differentiated innovations to help create a cleaner more sustainable society.

The paint has been part of a feasibility study taking place at Tokyo's Haneda airport where it has been applied to a Nissan NV100 service vehicle operated by All Nippon Airways airport services.

With its large, open tarmac, the airport provided the perfect environment to conduct real-world evaluation of the paint's performance under an exposed high-temperature environment.

Nissan says that although still in a testing phase, when parked side-by-side under the sun, a vehicle treated in the cool paint has shown yields of up to a 12-degree Celsius reduction in exterior surface temperatures and up to five-degree Celsius cooler interior, compared to a vehicle featuring traditional automotive paint.

A cooler cabin is not only more pleasant to enter, but also requires less air-conditioning run-time to cool the cabin to a comfortable temperature. This helps reduce load to the engine, or in the case of an electric vehicle, draw on the battery. In both powertrains, an improvement in efficiency is expected, as well as occupant comfort.

The metamaterial embedded within Nissan's cool paint features two microstructure particles that react to light.

One particle reflects near-infrared rays in the sunlight that would typically cause molecular level vibrations within the resin of traditional paint to produce heat.

The second particle enables the real breakthrough. It creates electromagnetic waves, that counteract the sun's rays, redirecting the energy away from the vehicle into the atmosphere.

Combined, the particles in Nissan's cool paint reduce the transfer of heat into surfaces such as the roof, bonnet, doors and panels.

While the testing and development continues, Nissan hopes that it can one day be offered for special orders and in a variety of colours.