About the shortwave multiple reflections in an urban street canyon building related to three different European climates

Abstract

Energy exchanges between buildings is affected by urban fabric. As a matter of fact, heat exchange between adjacent buildings is due to convective and radiative heat flows. The main parameters which influence these heat exchange mechanisms are due to climate conditions such as air temperatures/humidity, wind speed/direction and solar irradiance. Most building energy simulations are done on an independent single building with typical meteorological year (TMY). These TMY meteorological data cannot represent the state of the urban microclimate and rather ignores the microclimate influence on buildings adjacent to street canyons. However, solar radiation shading and reflection of the environment within the street canyons are important factors affecting the energy consumption of buildings. In this work, a building energy simulation tool is used to study the impact of multiple shortwave inter-reflections in an urban environment. A street canyon model validated in a previous work was modeled in TRNSYS in order to simulate the effects of the urban radiative trapping. An urban canyon with aspect ratio H/W=1 was chosen, with South-North orientation, with transparent/opaque surfaces ratio Atr/Aop=0.5 and 4 values (0.2, 0.4, 0.6, 0.8) of reflectance factor of the envelope surfaces. The goal is to characterize how solar absorption influence the urban energy requirements. The analysis was conducted for 3 cities in different climatic zones: Rome, Palermo and Krakow.