Japan's summers are getting hotter, and the insulated glass is becoming less effective, leaving cars parked in the scorching sun like giant ovens. In August, Nissan announced the results of its trials for a new coating called "cool paint," claiming it can reduce car temperatures by 5-12°C, improving comfort while also reducing air conditioning energy consumption.
New developments have moved from the laboratory to feasibility testing. Beginning in November 2023, Nissan will conduct outdoor testing at Tokyo's Haneda Airport, applying the cold paint to an airport service vehicle used by partner All Nippon Airways (ANA). These Nissan NV100 vehicles frequently operate on the tarmac, a treeless area ideal for high-temperature exposure.
Nissan said the outdoor test results were satisfactory, with the vehicle surface temperature dropping by up to 12°C and the interior temperature dropping by 5°C.
Nissan points out that the cool paint is particularly effective for vehicles parked in the sun for long periods of time. Entering the vehicle will make it feel cooler, eliminating the need to turn the air conditioner to high cooling, which can reduce the load on the engine and the consumption of the electric vehicle battery.
Developing metamaterials while taking vehicle characteristics into consideration
The new cold paint uses "metamaterials" (also known as "supermaterials"), which are artificially designed structures with properties that natural materials do not have.
Nissan explains that the cool paint contains two special microstructured particles: one reflects near-infrared (NIR) sunlight, reducing heat, while the other, the key breakthrough technology, generates electromagnetic waves that offset sunlight and direct heat away from the vehicle and into the atmosphere.
The new technology was developed in collaboration between Nissan and Radi-Cool. According to the Associated Press, Radi-Cool is a Chinese company that develops cooling films and fabrics. It collaborates with several Japanese companies on cool hats and parasols, but only with Nissan on the development of cool paint for cars.
The development was led by Susumu Miura, Senior Manager of the Advanced Materials and Processing Laboratory at the Nissan R&D Center. Radiative cooling materials are also widely used in architectural coatings. This research focused not only on adapting them to vehicle painting methods but also on reducing coating thickness. Current cold paint samples are six times thicker than typical automotive paints, and further reduction is needed to meet commercial standards. The team hopes to apply the cold paint to commercial vehicles, such as trucks and ambulances, that are subject to prolonged operation under the scorching sun.
References：
Nissan (August 6, 2024),Nissan trialing cool paint technology
♦ Nikkei (August 6, 2024),日産自、自動車用自己放射冷却塗装の実証実験を公開
♦ Associated Press (August 6, 2024),Japan’s Nissan is developing ‘cool paint’ for cars to keep drivers cooler
Sources: Environmental Information Center
