Open-hardware platform for synchronous performance testing of multiple passive radiative cooling materials

<h2>Summary</h2> The growing interest in passive radiative cooling (PRC) poses a pressing need for standardized and accessible methods to compare the performance of different material. Here, we report on the development of FRESCO-board, a low-cost, open-hardware platform providing continuous monitoring of temperature drop (T_Drop) and net cooling power (P_Cool) for multiple PRC materials at the same time. The proposed platform is further equipped with multiple sensors monitoring ambient temperature, humidity, solar irradiation, and sky temperature, an important and yet rarely measured quantity that is strongly correlated with the instantaneous radiative cooling performance. An integrated display and Wi-Fi module allow streaming real-time data to a web application or a Grafana dashboard linked to the InfluxDB database. The availability of a portable and affordable testing platform can streamline access to this multidisciplinary research field, enabling research groups to develop and compare new materials, gaining insights into their performance under different in-field conditions.