Modelling and Validation of Spatial Irradiance Characteristics for Localised Irradiance Fluctuations and Enhancements

Irradiation peaks were identified during the analysis of high temporal resolution measurement data of several locations demonstrating that the effects of irradiance enhancements (IE) on photovoltaic (PV) systems cannot be simulated by the use of hourly measured irradiation data. For systems of significant spatial expanse data of a single sensor is also not sufficient as parts of the systems will operate under IE while others will be clouded. This paper focuses on spatial aspects of this, i.e. IE effects across the expanse of the PV system. The method of deriving the cloud velocity vector from irradiation measurement data sets by tracking the movement of irradiation minima across the sensor plane is presented. This cloud velocity vector is used generating an accurate irradiation map of sufficient resolution from a few sensors. The resolution of the generated irradiance map is sufficient to generate irradiances on each module in large grid connected PV-systems and the mismatching losses can be investigated. Same applies to distribution networks, in which the transformer power on a connection point of several small PV systems can accurately be simulated.