PVsyst Aging _ Clarification on Degradation Calculation in PVsyst

[Kanagavel K]

Dear PVsyst Team,

 

I am working with an N-type Module that has 0% LID (as technology says) loss and would like clarification on how to properly apply the degradation values for simulation. The module datasheet specifies the following:

• 1st Year Degradation: 1%
• Annual Degradation (2nd year to 30 years): 0.4%

However, I noticed that PVsyst assumes half of the annual degradation applies in the first year. This leads to some confusion regarding how to properly simulate the degradation over the 30-year period.

To clarify, I am trying to split the LID and annual degradation using the following methods:

 

1. Case 1 (as per PVsyst):

• LID = (1st Year Degradation) - (Annual Degradation / 2)
• i.e., LID = 1% - (0.4% / 2) = 0.8%
• As per case 1, I can set the Input in PVsyst like, LID - 0.8% and annual degradation - 0.4%
• As per these results, PVsyst considers: 1^st year - 1.0% (0.8% + (0.4 / 2)%), 2^nd Year - 1.4% (1.0% + 0.4%),  3^rd Year - 1.8% (1.4% + 0.4%) ,..........

 

2. Case 2 (General Practice Approach):

• LID = (1st Year Degradation) - (Annual Degradation)
• i.e., LID = 1% - 0.4% = 0.6%
• As per case 2, I can set the Input in PVsyst like, LID - 0.6% and annual degradation - 0.4%
• As per these results, PVsyst considers: 1^st year - 0.8% (0.6% + (0.4 / 2)%), 2^nd Year - 1.2% (0.8% + 0.4%),  3^rd Year - 1.6% (1.2% + 0.4%) ,..........

 

When using Case 2, the total first-year degradation will be 0.8%, which is lower than the module datasheet value of 1%. On the other hand, if I want to match the datasheet values accurately, I would need to use Case 1, which results in the actual degradation values throughout the 30years of entire simulation (both for the first year and for the following years).

 

Also, Kindly clarify why PVsyst considers only half of the annual degradation for the first year? If the PV module vendor provides the LID value, how can we adjust the degradation losses in PVsyst to align with the datasheet values for the first year?

 

Could you please provide clarification on how to simulate the full 30-year degradation, taking into account these considerations? I want to ensure the simulation should aligns with both the datasheet values and PVsyst’s recommended degradation approach.

 

Thank you for your assistance.

[André Mermoud]

Please observe that the degradation specification of the PV module manufacturers is not the degradation factor. It is a warranty on the power of each PV module individually.
The long-term degradation of the whole PV system is an average of the real degradations of all PV modules, which is indeed less than the warranty limit.

Moreover, the LID is an initial degradation which has nothing to do with the long-term degradation. The initial value of this warranty curve (usually -2 or -3%) may represent sometimes the LID degradation, but also the uncertainty of the Power measurement (at factory) of each PV module.
In PVsyst, the LID loss is specified independently in the "Detailed losses". It acts over the whole simulations (i.e. the whole life of the PV plant) as a permanent diminution of the real PV module efficiency. 

This is explained in detail in the help  https://www.pvsyst.com/help/project-design/array-and-system-losses/ageing-pv-modules-degradation/index.html?h=degradation

Now for the long-term degradation of a given year, the PVsyst simulation result represents the average degradation along this year, i.e. the average of the degradation value  between the  beginning and the end of the year.  This is the reason why the degradation of the first year uses half the annual coefficient  (and the next years use 1.5, 2.5, 3.5, etc).

 

 

[Kanagavel K]

Thanks for response

For the further Clarification, If average of real degradation means then why only for first year is taking average and next will be actual.

             My recommendation is that the annual module degradation value can be set to 100% (or customizable) for the first year as well. This way, I can generate yield analysis based on the module warranty data.

Thanks,

Kanagavel 

[LauraH]

Could you confirm that the only inputs to the degradation calculations are the values circled in green here?  I'm assuming that the red values are calculated and the warranty info is only for plotting.  Thanks.

[André Mermoud]

Yes, the red behaviour indicates the global degradation to be applied for each year, taking the mismatch evolution into account.

The black line is the warranty of the PV modules manufacturer, that you may define as you like. It is indicative.

[André Mermoud]

Answer to Kanagavel above.

No, the ageing represents an ageing from year to year. There is no reason for being different during the first year.

The first year differences should be accounted in other loss kinds like LID or Module quality loss.