Losses Values PV Watts and PV Detailed

Hi, my name is Gita.

Currently using SAM on my research. And now, I am Studying losses in PV System

I would like to ask about the default losses values on SAM. When opening the Losses tab on PV Detailed, it already has value for every loss parameter (soiling 5%, module mismatch 2%, and so on).PV Watts model also has a value for every loss parameter. But for some parameters, it's different, for example for soiling 2%.
I have some questions about this, I wish you could help me
1. What is the consideration of picking that value as default in SAM? Is there any document or paper that I can look up to?
2. Why the soiling default value for PV Detailed and PV Watts model is different?
3. I read some literature, and it said that the range of soiling is 2% - 25% for SAM, in what term we can define the percentage of soiling?

Best Regards,
Gita Heatubun

Hi Gita,

The default losses are reasonable values to use if you do not have more information about losses for your system.

PVWatts and the Detailed Photovoltaic models use a different method to model soiling losses:

PVWatts models it as part of the total system losses, which is applied to the total AC electric output of the system.

The Detailed PV model applies the soiling loss to the plane-of-array beam irradiance value in each time step, so the soiling loss decreases the solar energy available to the array.

The PVWatts default loss values are based on the values used for NREL's online PVWatts Calculator at pvwatts.nrel.gov . The Detailed PV model default loss values are adapted from those values.

Best regards,
Paul.