工程师们已经发明了一种高性能的外部PDRC聚合物涂层，它具有纳米到微尺度的空隙，可作为自发的空气冷却器，并且可以被装配、染色，并且像油漆一样涂在屋顶、建筑物、水箱、车辆甚至航天器上——任何可以涂装的东西。他们使用基于溶液的相反转技术，使聚合物具有多孔泡沫状结构。

An alternative to these energy-intensive cooling methods is passive daytime radiative cooling (PDRC), a phenomenon where a surface spontaneously cools by reflecting sunlight and radiating heat to the colder atmosphere. PDRC is most effective if a surface has a high solar reflectance (R) that minimizes solar heat gain, and a high, thermal emittance (Ɛ) that maximizes radiative heat loss to the sky. If R and Ɛ are sufficiently high, a net heat loss can occur, even under sunlight.

Polymer coating cools down buildings

https://www.sciencedaily.com/releases/2018/09/180927145555.htm

1. J. Mandal, Y. Fu, A. Overvig, M. Jia, K. Sun, N. Shi, H. Zhou, X. Xiao, N. Yu, Y. Yang. Hierarchically porous polymer coatings for highly efficient passive daytime radiative cooling. Science, 2018; eaat9513 DOI: 10.1126/science.aat9513