Measurement and analysis of annual solar spectra at different installation angles in central Europe

Real world solar spectra are rarely equal to those under standard test conditions, which points to the importance of measuring, analyzing and understanding the implications of solar spectra variations in photovoltaic performance. This work presents and analyzes one year of solar spectra measured with installed spectrometers at optimum and vertical (building-integrated-photovoltaics relevant) angles in central Europe, reporting for the first time experimental datasets measured simultaneously over such timespan. In addition, we quantify the differences between these datasets with known key performance indicators and discuss the implications of spectral changes on the maximum current density of ideal single-junction and tandem devices for both installation angles.