Experimental Investigation of Parameters Influencing Test Box and Material Behavior in Daytime Radiative Cooling Measurements

ABSTRACT Nowadays, renewable energies are employed to reduce fossil fuel consumption in buildings and industrial applications. Radiative cooling (RC) technology uses the Earth's natural heat radiation to cool surfaces without any electricity supply by emitting thermal radiation to outer space through the transparent atmospheric window. RC technology can produce a cooling effect both during the night and during the day. However, daytime RC is a challenge, and special materials are to be used. Materials highly reflective in the solar spectrum , and highly emissive in the atmospheric IR transparency window are required for daytime RC technology. This study explores the influence of several parameters in the design of the daytime RC materials testing set‐up (test box), aiming ultimately at an effective measurement and evaluation of RC materials during daylight hours using a test box. The approach utilizes a test box setup to assess the materials' ability to emit thermal radiation while under the influence of direct sunlight. By employing precise measurement techniques within this controlled environment, this study contributes to the identification of key parameters affecting daytime RC materials measurements. The outcomes of this investigation contribute to the ongoing efforts in the field of daytime RC, offering practical guidance for researchers, engineers, and designers involved in developing a test box for daytime RC materials testing.