Comparative performance analysis of grid-connected photovoltaic system by use of existing performance models

Performance analysis of real world efficiency of photovoltaic installations is proven to be a challenging task, as demonstrated by the processing of data from monitoring operation of a photovoltaic park for a period of 3 years. It is important to establish a procedure which evaluates the photovoltaic plant performance based on real world system monitoring data. The role of air mass and clearness index variations in this context is well established and the analysis is conducted with the aid of these factors. The analysis has three main objectives: (i) the evaluation of three existing models, (ii) performance ratio calculation and (iii) the formulation of an evaluation procedure based on normalization to Standard Reporting Conditions. Processing of the monitoring data reveals significant scatter in normalized efficiency. A 10% fluctuation in yearly energy production is observed in the period 2013-2015. It is important to analyze this fluctuation in order to shed light to the reasons behind this fact. Performance ratio analysis, normalization procedure and models comparison, point to a decrease in PV panel's efficiency from the first year of operation. However, this is a small decrease covered by the terms of the manufacturer's warranty. Application of the proposed procedure to the analysis of data from older installations is expected to improve understanding and assessment of aging effects in the PV panels.