Identification of BRDF parameters with spectral measurements in the visible light spectrum towards solar irradiation evaluation in urban environment for photovoltaïc technologies

In order to incorporate real construction material reflectance properties in a Monte-Carlo ray tracing algorithm, a representative cladding material is characterised with a spectrophotometer to obtain reflectance angular distribution. These measurements are used to design a BRDF model with a reduced number of parameters that are further identified, along with their confidence intervals. Obtained results are compared to reflectance coefficients measured with an integrating sphere. The prospects of such a model is to allow for a more accurate modelling of the optical properties of materials in reflection. This knowledge can then allow a better integration of photovoltaic technologies, both in terms of energy and visual acceptance. For the particular HPL cladding material tested and despite a highly specular behavior at grazing incidence angles, we found that the specular term only amounts to 4% of reflection.