被动辐射冷却技术的发射率和反射率测量

Abstract Due to their optical properties, passive radiative cooling (PRC) materials can effectively reflect solar radiation while simultaneously dissipating heat through the infrared transparency windows using outer space as a cold and renewable heat sink. This makes it possible to achieve sub-ambient temperatures even in direct sunlight without using any electricity for cooling or air-conditioning. However, the accurate determination of these peculiar optical properties is challenging and subject to high uncertainty levels when using commercial instruments available to industrial end users and research laboratories. Within the EU project PaRaMetriC, aiming at establishing a metrological framework for the comparable performance evaluation of PRC technologies, the Physikalisch-Technische Bundesanstalt is leading a work package dedicated to the development of accurate and traceable methods to determine the infrared optical and thermophysical properties of PRC materials. These include reflectivity and emissivity in the broad spectral range from 250 nm to 50 µm, encompassing both, the solar spectrum (250 nm–2500 nm) and the infrared transparency window of the atmosphere (7.1 μm–13 μm) with a target absolute uncertainty of less than 0.03. For this purpose, several candidate benchmark passive cooling materials have been characterized by PTB in the wavelength range between 1.4 µm and …