Module and system degradation methodology

Dear Paul,

I am trying to study the module degradation and its effect on inverter clipping losses and power output over the life of the project. I guess the simulation over an analysis period has only been recently included hence I could not find the details of module degradation methodology used in SAM in the PV model technical reference.
I would like to know how does SAM has calculated the impact of module degradation in current and voltage. Is it equivalent decrease of Impp (50%) and Vmpp (50%) ? I was not able to find any experimental justification for the same.

Any help related to the topic will be highly appreciable.

Best Regards
Radhesh

Dear Radhesh,

In SAM's detailed Photovoltaic model, module degradation is an input that you provide on the Lifetime inputs page.

In the "PV simulation over one year" mode, SAM applies the degradation rate to the system's AC output, so it only roughly approximates the effect of module degradation, and cannot model its effect on inverter clipping over the life of the project.

In the "PV simulation over analysis period" mode, SAM applies the degradation rate to the array's DC output power in kW, so you can see how inverter power clipping is affected by degradation, but not how it affects the operating voltage and MPPT clipping.

SAM only reports clipping losses for the Year 1 simulation. You can see the annual energy value ("Energy" on the Cash Flow tab or under "Annual Data" on the Data Tables tab), and compare the array DC power to the system power generated under "Lifetime Hourly Data" on the Data Tables tab.

Best regards,
Paul.