Radiative cooling performance and life-cycle assessment of a scalable MgO paint for building applications

Passive daytime radiative cooling reduces building cooling load by simultaneously radiating infrared to the outer space (∼3 K) and reflecting solar irradiation without energy input. Developing a paint-format radiative cooling material and improving evaluation methods are critical for commercialization. Taking the advantage of high bandgap (7.6 eV) for low solar absorption, a facile, scalable, and high-performance MgO paint was developed in this work. Model Building cooling experiment and the corresponding thermodynamic modeling were carried out to investigate the cooling potential of the proposed paint in building applications. In addition, for the first time, a life-cycle assessment has been conducted for the developed MgO radiative cooling paint. Results show that the MgO paint exhibits a broadband infrared emissivity of ∼0.93 over the mid-IR region (2.5–25 μm) via phonon polariton resonances, simultaneously delivering a high solar reflectivity of ∼0.95 by particle scattering. A sub-ambient temperature reduction of ∼3.5 °C and a net cooling power of ∼61.2 W/m2 were experimentally demonstrated even on a humid and cloudy day with a peak solar irradiation of 868 W/m2. Furthermore, the MgO paint-coated building can achieve an indoor temperature reduction of ∼9.2 °C and a maximum cooling energy saving of ∼10 kWh/(m2⋅yr). The total environmental impact can be reduced by 7.92–24.75% with the developed MgO paint compared to the commercial one in the non-severe cold areas of China. This work provided a potentially scalable radiative cooling material and opened a new pathway for comprehensively evaluating radiative cooling materials.