Optimal Design Method for Surface Shape of Exterior Material to Improve Thermal Environment in Streets

Abstract

Retro-reflective materials have garnered attention as a countermeasure against heat island phenomena. However, the existing materials are inadequate for improving the thermal environment of outdoor spaces because these have been developed for traffic signs. Hence, in this study, an optimal design method for near-infrared rays retro-reflective materials to be installed on the exterior surfaces of buildings is proposed. It consists of a multi-objective genetic algorithm (MOGA) coupled with numerical analysis based on a ray tracing method. First, the outline of the method is shown. Next, the investigation of optimized surface shapes is presented. The results show that in individuals with high summer reflective performance, most of solar radiation hits a surface element only once and reflects upward in summer. In the investigation, the elevation angles of surface elements were approximately 70° and 60° for the installations in the south and west, respectively. It is predicted that the normal of the surface element where solar radiation reaches first is one of the determinants of the summer reflective performance. In addition, the effect of installation city or direction on the optimal design is analyzed. The results show that the direction does not significantly affect, the city suggests to affect the optimal design.