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

Mattia Manni,Emanuele Bonamente,Gabriele Lobaccaro,Francesco Goia,Andrea Nicolini,Emmanuel Bozonnet,Federico Rossi

doi:10.1016/j.buildenv.2019.106638

Abstract

Highly- 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-buildings 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/m2 respectively.

Highlights

Rising urban densification and global warming actively contribute to raising urban temperatures and increasing building energy demand for cooling [1,2,3]
The workflow followed in this research study was carried out in three steps, which focus on assessing the accuracy of the proposed numerical model developed in Matlab for the simulation of short-wave solar reflection events (Fig. 6)
The proposed numerical model was validated by comparing the Irrpyr amounts estimated by the numerical model to the quantities measured in La Rochelle’s experimental facility

Summary

Introduction

Rising urban densification and global warming actively contribute to raising urban temperatures and increasing building energy demand for cooling [1,2,3]. Densified and altered urban patterns along with increased solar reflectance of building surfaces have the consequence of worsening the effect of inter-buildings solar reflections. This phenome non, which concentrates a high amount of solar irradiance within the street environment [5,6,7,8] can lead to several issues amongst which the most documented one being the so-called Urban Heat Island (UHI) effect [9,10]. The main drivers of the UHI effect are anthropogenic heat, properties of the surface of the materials used in the built environment, the lack of permeable and vegetated surfaces in cities, and (higher) pollutant concentrations in the atmosphere [3,11,12,13]. Akbari et al [6]

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Conclusion