Module loss

Hi,

I am trying to gain a better understanding of "Module" loss in the loss diagram for PV systems. I was wondering what are the exact list of things that are taken into account in the module. If I were to compare "Module" to PVsyst losses, would they be IAM losses, PV loss due to temperature, and PV loss due to irradiance? It isn't very clear to me, and a list of what is taken into account for "Module" would be very helpful.

Thank you!

Hello,

The losses that SAM reports in the "module loss" category that you see in the loss diagram and in the "single value" category on the Data tab and elsewhere on the Results page includes all power losses between the irradiance incident on the plane of array (POA irradiance) and the module DC electrical output. The details of that loss value depend on which module model you use. For example, the CEC module model and Sandia module model use different methods for calculating the module output and model those loss mechanisms differently.

In general, the module loss category includes the following:

• Incidence-angle-related losses (IAM) losses.
• Spectral-related losses.
• Losses associated with converting light to electricity.
• Temperature-related losses.

Because of the way those losses are accounted for in the model calculations, there is not a straightforward way to report each loss as a reduction in the module's electricity output in kW. There are some ways to estimate the kW impact of each loss mechanism, but we have chosen not to report those estimated loss values because of the uncertainty associated with the estimates, and because there is not a way to report those losses for the different module models in a consistent way.

For example, for the CEC module model, the cell temperature is part of the equation that determines the value of the light current parameter of the single diode representative model (See Equations 9.26 and 9.11 in the SAM PV reference manual available on the Performance Documentation page ). As you can see from the equations, there is not a simple relationship between the values of cell temperature, the light current parameter, and the module DC output. For the Sandia model, which is an empirical model rather than single-diode model, the cell temperature is part of several of the empirically-deterimined equations (See Equations 9.4 through 9.8 in the reference manual).

Best regards,
Paul.

Dear Paul,

according to the information provided here and in the SAM manual, the CEC module model considers spectral losses based on modelling coefficients derived for Si modules. However, the CEC database contains the module type as a parameter type, and the user-specified CEC module input page in the SAM GUI also explicitly asks to specify the module type (Si, CdTe, etc.).
How is that module type information used within SAM?

Thank you and best regards,
Timo

Dear Paul,

I only now found the part in the manual that comments on this as it was only explicitly mentioned in the section about the user-defined CEC module. In case anyone else stumbles upon this issue: "This parameter is used to guide the solution of normalized module coefficients, but is not directly used for power calculations once the coefficients are determined."

Best regards,
Timo

Thanks for that clarification, Timo.