PV technology differences and discrepancies in modelling between simulation programs and measurements

Side by side comparisons of kWh/kWp from individual dc modules are usually <; ±5% when correctly measured. Some PV simulation programs give biases towards certain technologies mainly due to the limitations in the 1-diode model [1] which predicts incorrect Pmax - temperature and low light efficiency coefficients [2]. The distribution of plane of array insolation vs. irradiance is affected by averaging by time [3]. PV low light efficiency often differs between clear dawn/dusk and diffuse conditions which is not modelled. The spectral response and angle of incidence dependence between the PV technology and the irradiance sensor (particularly with pyranometers) differ. Some thin film devices are also susceptible to seasonal annealing (improving after hot weather periods i.e. better in autumn than spring). These discrepancies are discussed further and a new PV model (LFM-B) is introduced which was developed with Oerlikon Solar to lessen these limitations and errors[4].