Evaluation of the energy yield prediction error depending on the methodology to estimate global tilted irradiance from measured global horizontal irradiance

The evaluation of the energy yield (EY) in Photovoltaic (PV) systems depends strongly on the quality of the onsite irradiance measurement. Prior to system installation, normally only the horizontal plane irradiance is available and therefore various mathematical models are used to translate the measured values into the plane of the PV array. This paper evaluates the influence of irradiance models, and specifically diffuse tilted irradiance models, on the accuracy of the EY calculation. For this purpose several PV installations were evaluated by comparing measured global tilted irradiance values and measured DC energy with modeled values.