A tailored indoor setup for reproducible passive daytime cooling characterization

Passive daytime cooling materials can lower global energy consumption owing to their autonomous cooling capability. Although a significant number of passive cooling materials have been developed recently, their performance characterization is still challenging. Field tests experience high variability due to uncontrollable changes in environmental conditions. Here, we design an indoor setup to characterize the performance of passive cooling materials reproducibly and independently of weather and season. Outdoor measurement conditions are approximated using a liquid-nitrogen-cooled aluminum dome, a solar simulator, and a wavelength-selective inverse sky-window filter. In contrast to outdoor measurements, the results of various reference materials show remarkable precision and repeatability. Additionally, the impact of solar light intensity and temperature on the passive cooling performance can be experimentally investigated. Our setup is a first step in the development of a standardized test method to bring accuracy, reproducibility, and comparability to the emerging field of passive cooling materials. [Display omitted] •Powerful indoor setup for daytime passive cooling characterization•High stability and reproducibility•Control of solar intensity and ambient temperature•Robust, cost-effective, and easy to build Standardized test methods are urgently required to characterize the performance of passive daytime cooling materials in a reliable and reproducible way worldwide. Song et al. introduce a robust test setup that unites cool space, solar radiance, and ambient environmental conditions in a compact indoor test setup with superior characterization performance.