Reflective and transparent cellulose-based passive radiative coolers
Sampath Gamage, Debashree Banerjee, Md. Mehebub Alam, Tomas Hallberg, Christina Åkerlind, Ayesha Sultana, Ravi Shanker, Magnus Berggren, Xavier Crispin, Hans Kariis, Dan Zhao, Magnus P. Jonsson
Abstract
Abstract Radiative cooling passively removes heat from objects via emission of thermal radiation to cold space. Suitable radiative cooling materials absorb infrared light while they avoid solar heating by either reflecting or transmitting solar radiation, depending on the application. Here, we demonstrate a reflective radiative cooler and a transparent radiative cooler solely based on cellulose derivatives manufactured via electrospinning and casting, respectively. By modifying the microstructure of cellulose materials, we control the solar light interaction from highly reflective (> 90%, porous structure) to highly transparent (≈ 90%, homogenous structure). Both cellulose materials show high thermal emissivity and minimal solar absorption, making them suitable for daytime radiative cooling. Used as coatings on silicon samples exposed to sun light at daytime, the reflective and transparent cellulose coolers could passively reduce sample temperatures by up to 15 °C and 5 °C, respectively.