Energy Loss Due to Irradiance Enhancement

The analysis of high resolution measurement data from Munich showed significant and repeated irradiance peaks. For irradiance enhancement (IE), the observed irradiance is above the theoretically-calculated global irradiance of a clear-sky day (i.e. for the given time with a clear-sky and atmosphere). The increased irradiance is caused mainly by reflections from cumulus clouds. Concurrent with the elevated global irradiance, low ambient and module temperatures were observed, due to cloud coverage between irradiance enhancement peaks. This analysis investigates the essential meteorological observations from these data records. It also depicts the technological effects on a PV system. To illustrate this, the irradiance peaks are classified by their specific characteristics such as magnitude, duration, distribution or slope. Data sets from several Baseline Surface Radiation Network (BSRN) sites, representing various climatic zones are examined to evaluate the magnitude of this effect across Europe and its dependence on general meteorological conditions. It is crucial to understand the PV system response to the monitored IE-effects. The employment of the simulation environment INSEL (for various PV cell types and panels) enables simulations incorporating high resolution measurement data and (commercially available) PV module simulation data. The output power of the modules investigated can be up to 30 % higher than under STC conditions. The system response was also explored by using a solar generator simulator and by evaluating data sets of operating MW PV plants.