Bill Marion's algorithm for snow losses

I would like to know what kind of POA SAM refers to calculate the string coverage, is it nominal POA or POA after shading?

What's more I would like to know if the software takes into account the bybass diodes of the module in addition to the string diodes. I was wondering about that because I used a CEC Performance Model with User Entered Specifications and there is no space to specify the presence of three bypass diodes.

Thank you for your help.

Dear Maria,

SAM's PV snow model uses the POA irradiance after shading and soiling as input.

The snow model determines the number of strings in each subarray that are either completely or partially covered in snow, and removes the DC output of those strings from the subarray's total output. It does not model partial output of individual modules.

Best regards,
Paul.

Hi Paul,

Following this post, I would like to know if it makes more sense to use POA irradiance after shading but before soiling instead? assuming the snow has a side effect of cleaning the panels.

Best regards
Brandon

Dear Brandon,

SAM's snow model does not account for any cleaning action the snow might have. The soiling losses are a monthly input, so you could reduce the soiling loss value for winter months to account for that effect.

Best regards,
Paul.