Fully Organic and Flexible Biodegradable Emitter for Global Energy-Free Cooling Applications
Chanil Park, Choyeon Park, Xiao Nie, Jaeho Lee, Yong Seok Kim, Youngjae Yoo
Abstract
In recent years, many researchers believe that global energy consumption can be significantly reduced by passive daytime radiative cooling (PDRC) without any electricity input. Over a decade, PDRC has been developed to enhance solar reflectivity and emissivity in the long-wavelength infrared (LWIR) region; however, sustainable materials for radiative cooling have not been sufficiently investigated. In the present study, the preparation of an eco-friendly polymer structure for effective radiative cooling via thermally induced phase separation is described. The as-fabricated radiative cooler exhibits reasonable durability for application to buildings, and furthermore, biodegradable polylactic acid (PLA) is environmentally benign with respect to end-of-life disposal. Moreover, the hierarchically porous PLA exhibits a solar reflectivity of 0.91 and an LWIR emissivity of 0.92, thus realizing high-performance passive radiative cooling without a silver coating for solar reflection. In addition, a radiative cooling power of 117 W m–2 is achieved under direct sunlight, and the porous PLA cooled as much as 9 °C below the ambient temperature. This cooling effect is the highest among all organic-based passive radiation cooling emitters reported so far. The present work provides an ideal passive radiative cooling strategy for creating environmentally friendly buildings with reduced energy consumption.