DIAGNOSTICS OF DEGRADATION OF THIN FILMS PV MODULES DURING 3.85 YEARS OF OUTDOOR EXPOSURE

摘要

The lifetime energy production of photovoltaic modules depends on their aging behaviour. Aim of the subproject 5 of the EU-PERFORMANCE project is the identification and modelling of long term aging mechanisms. For this purpose, eight different PV module technologies are exposed outdoors at the Solar Outdoor Measurement Platform in Cadarache (South of France) since August 2008. This paper shows the power variations of four PV technologies over 3.85 years (p-Si: -1.1%, CIGS: - 7.5%, a-Si: -9.6% and CdTe: -10%) and describes how to link the observed power variations and the ones of the equivalent circuit parameters determined with the Variable Illumination Measurements (VIM). VIM is a simple tool revealing rich information about PV modules. This allowed for a clear separation of the aging of technological key issues determining the performance of the modules: the rectifying capacity, the second diode, the contact resistance, and ohmic leakage currents. The CdTe module shows a degradation of the junction diode parameters indicating an ageing of the active material itself, and a heavy increase of leakage currents. The a-Si module has a problem with the contacts resulting in a high and unstable series resistance. This module and the CIGS module present an initial degradation of the second diode meaning an increase of the leakage currents. The parameters of the p-Si module are almost stable.