about ageing Vmp and Imp RMS disperion values

[Chen]

Dear PVsyst team：

    For the distribution choice is limited to 2 sigmas (95% of the hits) of ageing parameters setting.

    if there is a clear warranty statement for the annual  degradation rate of photovoltaic modules,  such as maximum degradation rate 0.35%/ year，maximum 1% for the first year. 

    The slope of the warranty is 0.35%.  Can the Im or Vm RMS dispersion be set to 0.35/2 = 0.175 %?  thanks！

 

 

 

[Chen]

The 2 sigmas is approximately 65.26% of the hits？

[Michele Oliosi]

The degradation in PVsyst compounds the average degradation rate, and the fact that there is an RMSD in this degradation rate. The worse possible degradation rate is therefore AVG + 2*RMSD.

A warranty is in principle below the worst case (because manufacturers need to play safe with these numbers). Therefore, you could estimate an upper limit for the degradation model by saying: WARRANTY > AVG + 2*RMSD (PMPP degradation). Note that given the first year degrading differently, this is not entirely correct. I also note that this warranty seems too good.

But in this case, I do not think you should set "Vm RMS dispersion be set to 0.35/2 = 0.175 %".

[Chen]

OK，we assume that the degradation given to the user is achievable, that is, in the first year, each solar panel power degradation will not exceed 1%, and starting from the second year, the maximum degradation per year will be 0.35%（the minimum degradation is 0%）. 

According to the upper limit of warranty.

 "maximum average degradation factor"="1/2 of  yearly warranty"="0.175%",  right？ 

So at the end of the first year, the minimum power of the module is still 99% of the initial level, and at least 98.65% at the end of the second year, can the average degradation rate from the second year be equal to 0.35%? The worse possible annual degradation rate we assumed in the  warranty is 0.35%.

 

 "Average degradation factor"+2*"Imp/Vmp RMS dispersion" ＜ "The worse possible annual degradation rate (the upper limit of warranty is 0.35%) " ；

so that "Imp/Vmp RMS dispersion"="0.0875%" ，( 0.35% - 0.175%)/2= 0.0875%

 

Thanks for your time!

[Chen]

The Average degradation value obtained from the the module warranty interface is 0.38%/ year. Is 0.38% used in the PV module ageing parameters input settings interface？should we change 0.35% to 0.38%？thanks!