The heat mitigation potential and climatic impact of super-cool broadband radiative coolers on a city scale

Extreme urban heat causes serious climatic, environmental, and economic problems. Daytime radiative cooling technologies are the most promising cooling technology in recent years. Here, we report experimental and numerical analysis to assess the cooling performance of scalable broadband radiative coolers, evaluate their heat mitigation potential in cities, and investigate their impact on local climate and the atmospheric dynamics. We show that, when air temperature reached its peak, the sub-ambient surface temperature of 8.2°C was achievable for samples with a wind cover. The maximum reductions of peak ambient temperature, average daytime ambient temperature, and highest urban canopy temperature are 5.3°C, 3.6°C, and 13°C, respectively. Collectively, we show that broadband coolers can significantly mitigate urban heat, but the cooling island effect they generate would increase side effects such as a decrease in the mixing layer of the atmosphere and an increase in pollutant concentration.