Development and validation of a Monte Carlo-based numerical model for solar analyses in urban canyon configurations

Abstract High and retro-reflective materials have recently been investigated and proposed as a new urban coating solution to reduce the so-called urban heat island effect. The present study aims at providing a numerical model for assessing inter-building solar reflections when these materials are applied to urban canyon’s surfaces. The proposed model includes a function that accounts for sunray angle dependency of the solar reflectance, which is specifically important with regard to retro-reflective behavior. The novelty of this numerical model based on a Monte Carlo simulation approach implemented in the Matlab simulation environment is to conduct full ray-tracing solar analyses which can reproduce the energy exchange phenomena and simulate optical material properties. Experimental validation and inter-software comparison are carried out with measured data collected in an experimental facility in La Rochelle, France, in addition to simulation results from the Radiance-based Diva for Rhino tool. The results of the numerical model developed are in line with the values measured in the physical model (daily percent variation of 1.3% in summer) and within the boundary conditions defined in the present work. The residues, which were calculated for the hourly values throughout the day, are found to be in the range of ± 10 W/m2, with the arithmetic average and standard deviation equal to – 2 W/m2 and 7 W/m, 2 respectively.