Abstract :
For simulation-based prediction of buildings’ energy use or expected gains from building-integrated solar energy systems, information
on both direct and diffuse component of solar radiation is necessary. Available measured data are, however, typically restricted to global
horizontal irradiance. There have been thus many efforts in the past to develop algorithms for the derivation of the diffuse fraction of
solar irradiance. In this context, the present paper compares eight models for estimating diffuse fraction of irradiance based on a database
of measured irradiance from Vienna, Austria. These models generally involve mathematical formulations with multiple coefficients
whose values are typically valid for a specific location. Subsequent to a first comparison of these eight models, three better performing
models were selected for a more detailed analysis. Thereby, the coefficients of the models were modified to account for Vienna data. The
results suggest that some models can provide relatively reliable estimations of the diffuse fractions of the global irradiance. The calibration
procedure could only slightly improve the models’ performance.
2012 Elsevier Ltd. All rights reserved
