Impact of radiative cooling on the energy performance of courtyards in Mediterranean climate

Abstract

Radiative cooling has proven to be a useful tool to address the problems of lack of comfort and excessive energy consumption in situations of high temperatures, overheating and heat waves. Likewise, incorporating courtyards in warm climate zones has been found to be highly beneficial in addressing similar challenges. Hence, there is interest in analyzing the combined effects of both: radiative cooling and courtyards. This paper presents an analysis of the impact of the application of radiative cooling on a courtyard using a comprehensive simulation approach that includes a CFD model for the thermodynamic airflow in the adjacent roofs and inside the courtyard, equations for the transient heat conduction through roofs, walls and courtyard slabs, and a hybrid raytracing-radiosity model for the evaluation of the solar radiation reaching the building surfaces and its reflections, both of specular and diffuse origin, and for the calculation of the thermal radiation exchange, especially with the sky. The results show that in the hot season, the courtyard with radiative cooling always provides lower temperatures than the initial courtyard does, with a temperature range of 18.33 °C to 33.78 °C, compared to a range of 19.32 °C to 38.00 °C in the initial courtyard, and producing a greater difference with outdoor temperatures that can reach 12 °C versus 8 °C for the reference case. In addition, it was found that the courtyard with radiative cooling is able to significantly reduce the observed nighttime overheating by providing lower temperatures than the outdoor temperatures in the 50% of the nights studied. It was also found that the thermal loads to achieve indoor thermal comfort in the spaces adjacent to the courtyard were reduced by 63.46% to 69.85%.