(Morlacchi Editore University Press, 2023) Chiatti, Chiara; Kousis, Ioannis; Fabiani, Claudia; Carlosena Remírez, Laura; Pisello, Anna Laura; Ingeniería; Ingeniaritza
Reflecting the radiation of the sun while emitting thermal radiation to cold outer
space has proven to be an effective solution against urban overheating. The latter severely
impact the energy consumption of buildings, outdoor pollution levels, and heat-related
morbidity and mortality, which is why recent research has focused on new advanced
mitigation technologies to be implemented in cities. Passive radiative cooling (PRC) has the
potential to provide a temperature lower than ambient without any energy consumption.
While conventional cooling prototypes reject heat to the air, PRCs reject heat to the outer
atmosphere emitting radiation mainly in the 8-13 ¿m range, i.e., the so-called atmospheric
window. This work investigates the thermal behavior of different radiative cooling
materials under various exposure conditions to examine their effective cooling potential.
The basic structure of the samples comprehends a highly reflective substrate (aluminum or
Vikuiti) and a silica-derived emissive layer. After a preliminary characterization under
controlled environmental settings, the samples were exposed outdoors, and their
superficial temperature was monitored during the central hours of the day. Comparisons
among samples and a benchmark aluminum reference layer were made, also considering
the weather data collected during the days of exposure. Although the samples did not reach
sub-ambient temperatures during the monitoring, the emissive layer significantly reduced
the surface temperature. Furthermore, the effect of a tunable intermediate layer placed
between the substrate and the emissive element was demonstrated to positively impact the thermal performance of the sample, thanks to its capability of changing the emissivity
spectrum with temperature.
