Tunable daytime passive radiative cooling based on a broadband angle selective low-pass filter
Passive daytime cooling could contribute to a reduction of our global energy consumption. It is capable of cooling materials down to below ambient temperatures without the necessity of any additional input energy. Yet, current devices and concepts all lack the possibility to switch the cooling properties on and off. Here, we introduce a dynamic control for passive radiative cooling during daytime. Using an angle-selective solar filter on top of a nocturnal passive radiator, allows tuning the surface temperature of the later in a wide range by just tilting the filter from normal incidence up to around 23 °. This angle-selective filter is based on optically engineered, one-dimensional photonic crystal structures. We use numerical simulations to investigate the feasibility of a switchable low-pass filter/emitter device.