Creating an Eco‐Friendly Building Coating with Smart Subambient Radiative Cooling

Abstract

may cause power blackouts. [1] Moreover, the refrigerant gases used in air conditioners are one of the largest contributors to greenhouse gas emissions. [2] Passive cooling, e.g., cooling with no power input and without greenhouse gas emission, provides an attractive solution to alleviate the power demands as well as negative environmental impact of building cooling. Recent theoretical and experimental demonstrations of subambient daytime radiative cooling (SDRC) represent a breakthrough in realizing passive daytime cooling. [3-21] These radiative cooling materials exploit the infrared transparency window of the atmosphere, in the wavelength range of 8-13 µm, to directly transmit heat from an object at ambient temperature, through blackbody radiation, to the cold outer space which has a temperature of 3 K (−270 °C). This radiation effect, in fact, is what causes one to feel chilly when staying outside in summer nights. However, to generate subambient daytime cooling under direct sunlight using the same effect, the materials must overcome the heating generated by the direct sunshine. In

A structural polymer for highly efficient all-day passive radiative cooling

“…The introduction of polymer-based radiative cooling materials can greatly improve the scalability and applicability of PDRC systems in practical applications 18 , 30 – 33 . Very recently, instead of using a reflective metallic mirror, state-of-the-art PDRC designs, such as porous polymer coatings 17 , 34 , 35 , polymeric aerogels 36 , white structural wood 37 and cooling paints 38 , 39 , have attracted considerable attention because of their high cooling performance, simplicity, applicability and economical efficiency. For example, Yu et al 17 made remarkable progress in the design of PDRC poly(vinylidene fluoride-co-hexafluoropropene) coatings with random micro-/nano-pores through a phase inversion-based method, demonstrating high solar reflectance (0.96 ± 0.03), as well as high longwave infrared emittance (0.97 ± 0.02) that enabled cooling up to ~6 °C and ~3 °C below ambient temperature under direct sunlight in dry southwestern USA and south Asia, respectively.…”

Colorful surfaces for radiative cooling

“…Therefore, this type of colored radiative cooling materials requires an even more stringent spectral selectivity than white cooling materials. [80][81][82][83][84][85][86][87][88][89][90] On the other hand, due to this inevitable optical absorption, the cooling power of these colored absorbing surfaces is generally lower than that obtained by white materials. Next, we will discuss another strategy to enable colorful radiative cooling surfaces with structural colors.…”

Reconfigurable and Renewable Nano‐Micro‐Structured Plastics for Radiative Cooling

“…In the past few years, a variety of materials have been investigated for intrinsic thermal emission properties. For example, multi-layer inorganic coatings, [1][2][3] microporous polymer films, [4][5][6][7] plastic textiles, [8,9] and artificial woods, [10,11] achieve high infrared emissivity via physically engineering the nano-and micro-structures. Besides, chemical functionalized polymers with the design of appropriate chemical bonds can also emit thermal energy through the atmospheric transmission window at mid-infrared wavelengths.…”