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Determination of Degradation Rates for PV Modules and PV Generators Applying Various Methods
D. Stellbogen, P. Lechner
Degradation, Performance, Reliability, Field Testing
Performance, Reliability and Sustainability of Photovoltaic Modules and Balance of System Components
Subtopic: PV Module Performance and Reliability
Event: 33rd European Photovoltaic Solar Energy Conference and Exhibition
Session: 5DV.3.25
1805 - 1808
ISBN: 3-936338-47-7
Paper DOI: 10.4229/EUPVSEC20172017-5DV.3.25
0,00 EUR
Document(s): paper, poster


The proper determination of degradation rates is a key issue in the technical and economic performance assessment of PV installations. Due to the considerable variations in the meteorological operating conditions of fielded PV devices over time, sophisticated analysis methods are required to derive meaningful degradation figures which are usually in the order of several per mill per year. The study evaluated different procedures for the determination of performance change rates by applying them to multi-annual highly time resolved monitoring data of PV modules and PV generators from the ZSW test field Widderstall. A variation analysis has been conducted determining the linear trends of various sets of PR data derived with different irradiance filtering bands and of the respective medians over various intervals. Thereby, not only the change rates but also their uncertainty budgets have been computed. The results show that regression analysis of high resolution performance data filtered to an irradiance band close to 1000 W/m² determines degradation rates with sufficiently low uncertainty levels and is much more reliable than trend analysis of aggregated median values.