Investigating crystalline silicon photovoltaic module degradation in the Maltese climate

Abstract

Photovoltaic (PV) modules may experience degradation as soon as they are exposed to outdoor weathering conditions. This occurs from the early stages of installation up to the decommissioning stage. PV degradation exists in many forms, some of which occur during the first few months of exposure while others depend on the materials’ susceptibility to continuous weathering. The Maltese climate is characterised by high levels of sunshine, humidity and temperatures. These three factors together with coastal region conditions may have a detrimental effect on the maximum power over the PV module’s lifetime. The aim of this research was to gain an understanding of the visual degradation modes together with the rate of loss in maximum power over a number of years of operation. PV modules operating over a range of one to twenty-eight years were analysed. This would provide a clear picture to the installers of such systems and investors with the expected degradation in power per year for warranty and energy yield purposes. The electrical analysis was carried out by extracting the individual PV module I-V curve. This curve was normalised to standard test conditions (STC) using IEC standards, obtaining values of interest such as the open circuit voltage, short circuit current and maximum power. Hence, the maximum power loss could be eventually calculated for different PV modules. The introduction presents the motivation and scope of this research. A description of the Maltese climate is included for an understanding of the conditions PV modules are exposed to. A description of the PV module I-V characteristic in order to highlight the importance of this curve in degradation analysis is presented.