Operating principle

RARE Cooling Paint

Reduces surface temperature by 10–40°C

to approximately the temperature of the shade. Reduces room temperature and saves at least 30% on cooling energy.

The cooling mechanism of RARE Cooling Paint is based on Skyactive nano microparticles.

Heat reduction through thermal reflection

Outdoor surfaces heat up due to solar energy absorption. RARE Cooling Paint reflects 95% of solar energy from the visible spectrum of 0.3µm to the thermal infrared spectrum of 3µm across the entire solar spectrum.

Other heat-reflective paint products on the market currently focus mainly on reflecting infrared radiation near around 1µm, resulting in less effective heat reduction. Moreover, the use of less selective materials leads to these paints achieving thermal reflectivity of less than 90%.

Cooling through thermal radiation

The Earth’s atmosphere is transparent in the 8–14µm range. Radiation within this wavelength range is not absorbed and travels straight into outer space. The material in RARE Cooling Paint radiates 98% in the 8–14µm range, thereby directly exchanging heat with space and cooling itself. This mechanism helps RARE paint to cool to approximately the air temperature.

No other product on the market uses this cooling mechanism. Therefore, no other product cools as effectively as RARE paint without external energy.

THE SOLAR SPECTRUM AND THE SPECTRUM OF RARE COOLING PAINT

Solar radiation spectrum (blue): At a temperature of 5000°C, the sun radiates strongly in the visible range of 0.3 – 0.7µm and the infrared range of 0.7 – 3µm, as shown by the blue line in the image. During summer, this heat can reach up to 1000W. To avoid absorbing this heat, surfaces need to reflect over 90% in the 0.3 – 3µm range.

Atmospheric transmission spectrum (yellow): Atmospheric gas molecules absorb strongly, especially in the 5 – 8µm range. However, the 8 – 14µm range is completely transparent. If a surface radiates strongly in this 8 – 14µm range, it will have a radiative imbalance compared to most surrounding surfaces. Cooling through radiation based on this imbalance can potentially reduce heat by 100W/m².

Radiation spectrum of RARE Cooling Paint (red): RARE Cooling Paint exhibits multiple peaks in the 8 – 14µm range, demonstrating strong thermal radiation in this range. This radiation is not absorbed but instead passes directly out into space, causing a radiative imbalance. To cool down to air temperature, RARE Cooling Paint also possesses the ability to reflect solar thermal radiation.

The prototype steel house, 2×2 square meters

always maintains a temperature equal to or lower than the surrounding environment. During nighttime when there is no sunlight, the prototype house is cooler than the air by up to 5°C. On hot sunny days, the prototype house consistently stays at or below the air temperature, with a temperature difference of up to 40°C compared to a steel house without RARE Cooling Paint.

In the temperature graph:

  • Red: Represents the temperature of steel house without RARE cooling paint.
  • Gray: Represents the temperature of air in the shade.
  • Green: Represents the temperature of air around a steel house coated with RARE Cooling Paint.
  • Blue: Represents the temperature of the roof of a steel house coated with RARE Cooling Paint.

The temperature of the steel house with RARE (green) paint compared to the air temperature (red) over several consecutive days.

In 2023