Cost-effective pearlescent pigments with high near-infrared reflectance and outstanding energy-saving ability for mitigating urban heat island effect

Abstract

Cooling down the surface temperature of buildings and saving energy consumption are tasks of top priority in mitigating the urban heat island (UHI) effect. The bright and colorful pearlescent pigmented cool coatings with high near-infrared (NIR) reflectance possess promise in enhancing the reflective effect of solar light and the visual aspect, which is still an undeveloped domain. Herein, these novel solar reflective coatings containing mediums and pearlescent pigments with high NIR reflectance of 85% embodied obvious energy-saving effects on building materials. EnergyPlus software was used to simulate the energy-saving effect of four applied climate zones, including New York, Nanchang, Lima, and Brasilia. Compared to commercial pigments (Fe2O3, γ-Ce2S3) with similar colors, the RK 402 and RK 301 pearlescent pigments demonstrate superior energy-saving capabilities in Nanchang climate zone, and can save 1.00 kW h m−2 and 1.60 kW h m−2 annually, respectively. In the warmer climate zone of Brasilia, the highest energy-saving efficiency is 2.06 kW h m−2 over one year by RK 301 pearlescent pigment. After irradiated by an NIR lamp, the surface temperature of the RK 301 coating can be reduced by 34.8 °C compared with that of the Fe2O3 commercial coating, and that of RK 402 coating is 5.2 °C compared with the γ-Ce2S3 commercial coating. Furthermore, the 7-day field test also has consistent effect of cooling down the surface temperature. This work demonstrated that pearlescent coatings with brilliant colors have great potential for application as cold materials in building areas to mitigate the UHI effect.