Because energy saved over a car journey means that range is increased, or the same distance is covered more economically, manufacturers are constantly looking for ways to improve energy efficiency.

Nissan’s new ‘cool paint’ uses heat-reflective technology which can, compared with standard paint, reduce the car’s surface temperature by 12˚C which in turn reduces internal temperature by 5˚C.

Given the impact of temperature on a car’s efficiency – for example, the reductive effect of air-con or climate control, this could have a significant impact on fuel economy in ICE cars and range in electric cars.

Given that manufacturers have long used infrared-reflecting (IR-reflective) windscreens to enhance the ability of glass to filter the sun’s UV rays, thus maximising cabin heat from direct sunlight, heat-reflective paint feels like a logical step.

In development since 2021, Nissan’s ‘cool paint’ consists of a synthetic composite of metamaterials configured in a specific two-particle microstructure of repeating patterns able to filter out unwanted near-infrared light wavelengths.

How the two microstructure particles react differently to light is key to the process. One creates electromagnetic waves that redirect energy from the sun back into the atmosphere away from the surface. The other reflects near-infrared light that would normally, by creating a molecular vibration in standard paint’s resin, generate heat.

Reflective paint has long been a low-tech solution for sustainable cooling in buildings thanks to radiative cooling – the emission of thermal radiation directly into the atmosphere without any power demand.

Recently, researchers have been investigating ways to exploit radiative cooling using dual layers of materials including metal, polymers and silica nanocomposites. However, these structures have usually been highly complex or require high thicknesses – creating a barrier to development and application in other sectors.

So in the motor industry, the challenge has been to produce satisfactorily motor-grade paint able to take a clear top coat and be applied as part of the standard car manufacturing spray process.

Extensive testing from Nissan has confirmed their ‘cool paint’ to be a capable defence against scratches, chips, chemicals and peeling while maintaining consistency of colour and repairability consistent with standard car paints.