Outdoor efficiency of different photovoltaic systems installed in Cyprus and Germany

The energy produced by different photovoltaic (PV) systems depends to a great extent on the inverter and photovoltaic module outdoor efficiency which in turn vary according to the irradiance and temperature of the field conditions. The objective of this paper is to describe the investigations performed to evaluate the outdoor efficiencies of thirteen (13) different types of PV modules which have been exposed to real conditions in Stuttgart, Germany and Nicosia, Cyprus. The inverter and PV array efficiencies have been evaluated by using direct outdoor measurements and data analysis on the measured metereological and operational data collected by the installed sensors present at the two test sites. The measured efficiency of the PV modules has been further evaluated on a seasonal basis reflecting the obvious effects of the seasonal variations of incident irradiation, operating temperature and seasonal spectral shift on the outdoor operating efficiency. The average annual inverter efficiency measured in Stuttgart was 89.8 % while the corresponding inverter efficiency in Nicosia was 90.9 % for the same period and for identical inverters that are rated at a European Efficiency of 91.6 %.