Translation of Outdoor Tandem PV Module I-V Measurements to a STC Power Rating

The procedures for the power rating of tandem-cell-based concentrator photovoltaic (CPV) modules defined in the international standard IEC 62670-3 are adapted to the requirements of tandem-cell-based flat plate PV modules. The adjusted procedure describes how to translate outdoor measured PV current-voltage characteristics to standard test conditions (STC): 1000 W/m, 25°C cell temperature, AM1.5g spectral conditions. In this work, we describe how to obtain all required input parameters: thermal transient measurements to determine the module temperature coefficients, categorizing and filtering the prevailing spectral irradiance conditions using spectral matching ratios, and determining the 25°C module open-circuit voltage from dark curren-voltage curves. Three specimen PV modules (triple-junction, III-V on Silicon and III-V on Germanium) have been measured for several months outdoors on a dual axis tracking unit at Fraunhofer ISE in Freiburg. In this work, we demonstrate that the CPV module power rating procedures in IEC 62670-3 are also - in a modified form - to be recommended for the outdoor rating of tandem-cell-based flat plate PV modules.