Regarding PVSyst Aging parameters

[Mikhail123]

Good morning everyone, I would like to ask how can we determine the average degradation value and the Imp/Vmp RMS dispersion of the pv panel? I am using LongI LR8-66HGD 620Wp model. All reference are welcomed. Thank you for your time. 

[Luca Antognini]

Dear Mikhail,
The aging tool is a general tool to represent several situations.

Unfortunately, the literature is a bit scarce on aging (real aging tests need years of field testing and there are a variations among technologies and climates - new technologies still need to be monitored more extensively) and on our side we don't have at the moment a clear literature review on the topic to hand out on to give clear recommendation on our side.

However, here are a few additional clarifications:

First recommendation: if provided, input the aver. degradation factor from the data sheet of your module (/!\ this is not equivalent to the warranty!). Know that average degradation factor lies between 0.2-0.6%/year. So you can adapt it if you want to see a more or less optimistic/conservator impact.

The Imp / Vmp contribution is set by default to 80/20 %, to represent the fact that often the first impact on the long term are first of optical nature (=decrease the current), for example due to encapsulant yellowing. But this is to adapt with what you find in the literature about your technology or what you observe in the field.

The Imp and Vmp RMS dispersion are tuning parameters of the model. If you set them at 0, all the PV modules will have the exact same degradation rate and your system will follow the blue curve. Set to higher values, the PV modules will have mismatch among them and an additional loss occurs because of this (mainly driven by the PV module whose current degrades the fastest). There is not really literature to advise what parameters to input here, but you can use this parameters to visualize the extra impact of this mismatch or tune it to make it correspond to existing measurements of a PV system.