Radiative sky cooling potential in Brazil

Abstract

Radiative sky cooling (RRC) occurs due to temperature differences between terrestrial surfaces and the sky. Its application in passive building cooling can be a sustainable way to remove heat from buildings without increasing the temperature of the immediate surrounding external environment. RRC is not a widely adopted bioclimatic strategy. This research aims to assess the potential for radiative cooling in Brazil based solely on Typical Meteorological Year (TMY) as a first step toward investigating its effects on the built environment. The study utilized 577 TMYx (2007-2021) climate files to calculate the Radiative Sky Cooling Potential (P_RRC) and selected eight climates corresponding to bioclimatic zones to evaluate the Sky Temperature Depression (DTC). The annual average P_RSC in Brazil was 53 W/m², with higher values in the semi-arid and dry regions of the Northeast and Central-West and lower values in humid areas. The DTC was highest in cities with a dry tropical climate, such as Brasília/DF and Goiânia/GO, reaching 20 °C during the dry season. In contrast, Belém/PA, with an equatorial climate, showed DTCs below 8 °C. The differences found are significant, even considering the limitations of the indices.

Keywords
Radiative sky cooling; Passive cooling; Downward longwave radiation