Abstract

Operators of photovoltaic (PV) systems, especially the small ones, monitor only the produced energy output, since they are not equipped with a meteorological station, or there is none in the neighbourhood. When evaluating a large number of PV systems across a region or country, access to the data due to privacy restrictions is usually very limited. To resolve both aspects, we report on a methodology to evaluate the performance of photovoltaic systems where only produced energy data and rated power of the PV system are available and all other data, including orientation and inclination angles, and the exact location are missing. We developed a novel algorithm for automatic detection of orientation/inclination angles and used the recently developed Typical Daily Profiles (TDP) methodology for a fast and accurate evaluation of PV systems. TDPs are representative hourly profiles of the observed parameter (e.g., power, irradiance and temperature) on a monthly basis. For the PV system degradation rate extraction, year-to-year TDPs are used. The case study of 957 PV systems in Slovenia in the period 2015-2019 reveals an average PV system performance ratio exceeding 85% and an average PV system rated power degradation rate of-0.7% per year.