Comparative Study of Topographical Effects on Simulated Solar Irradiation between DEM-based Terrain Reproduction and Manipulated TMY Input Data
Abstract
Alpine and pre-Alpine regions are more affected by climate change than other parts of Europe. Their complex topography and dispersed urban structure present both challenges and opportunities for solar design strategies. Dynamic building energy simulations typically rely on high-resolution weather data from reference stations that are unable to capture local topographic shading effects in the weather representative area. More accurate solar irradiation data for micro-locations can help reduce the Energy Performance Gap (EPG). Shaded areas with high solar deficits could mitigate overheating and reduce the cooling demands of buildings. This study applies a radiation-based, terrain-aware simulation framework to quantify the influence of orography on solar availability of micro-locations. A computational workflow was developed in the Grasshopper environment using sky matrices derived from EPW weather files. Solar radiation distributions were visualized as radiation roses. Two approaches were compared: a DEM-based geometrical orographic model and a numerical method manipulating TMY data by excluding radiation when the sun angle falls below the terrain horizon. Results show significant irradiation reductions due to topographic shading. The geometrical method enables detailed site-specific analysis, while the numerical approach supports broader regional assessments with minimal input, improving Building Energy Modelling (BEM) with topographic effects absent in typical workflow.