Methodology for the calculation of the shadow factor on roofs and facades of buildings in urban areas

Abstract

[EN] The present paper presents a systematic methodology to obtain the shadow factor on roofs and facades of buildings. The approach is based on the use of Geographic Information Systems (GIS), and helps to obtain, accurately and on urban scale, the incident solar irradiance on each surface of any building. Given the characteristics of the entire urban area, the solar gain of the buildings can consequently be calculated more accurately than with a stand-alone building model. A good quantification of the solar gain is essential, for instance, to better evaluate the consumption of Air-Conditioning systems. This approach can also be useful to size and simulate the introduction of PV panels in facades or roofs of urban regions, or to carry out a climate-sensitive urban design and planning. This approach is based on a vector-based 3D model of the buildings or trees of the urban region. Open data of cadastral cartography and LiDAR altimetric data are used as inputs. Using the previous 3D model and solar geometry data, analytical models are applied to calculate the shadow of each tree or building on any desired surface. The mentioned methodology has been implemented in R and has been applied to buildings of Valencia (Spain). The results have been validated with SketchUp, both for horizontal and vertical surfaces, and the error has been calculated for different hours of the day.