PV Aging Model Applied to Several Meteorological Conditions

Photovoltaic installations are usually guaranteed to operate for 25 to 30 years, with a warranty of 80% of initial performance remaining after this time. However, in order to determine the profitability of a project, it is important to estimate the performance of the photovoltaic modules over their lifetime, depending on their environment. In this study, a first version of an ageing model for photovoltaic systems is considered, taking into account the influence of the environmental stress factors, which are the temperature, the relative humidity, and the exposure to UV radiation. Another stress factor also needs to be taken into account: the module’s voltage potential versus ground (Potential Induced Degradation). The impact of cell cracks on the modules is also included in the model, their impact over the years depending on the temperature, but mainly to thermal cycles, due to the differences in temperature between day and night (thermal dilatation). Accelerated Damp Heat tests, thermal cycling tests, PID tests and UV tests are interpreted and used for calibrating the model, in addition to other degradation studies taken from relevant literature. A simple model is first built for the corrosion, with the temperature and humidity as stress factors, considering only the maximum power degradation. A more advanced model is then built, considering the degradation of the two-diode model parameters. A model has been built for each degradation, that is to say corrosion (temperature and humidity), AR coating and EVA discoloration (UV exposure), PID causes (temperature, humidity and voltage), and cell cracks (Thermal cycling). First simulations have been done, with weather data from the south of France (Mediterranean climate), Miami (hot and humid), and Dubai (hot and dry) showing that the power output after 30 years is still above the warranty limit of 80%.