Subarray Module Efficiency Calculation

Dear SAM team, 

I'm trying to find the formula which calculates the subarray module efficiency (subarray1_modeff) but I can't find it on SAM documentation. Could someone shed a light on this? I can see there is a variation on module efficiency when albedo and POA rear side irradiation are at very high values, but I'm trying to understand why this variation is happening. Appreciate your feedback on this topic.

Best Regards,

Gustavo Rocha 

Hi Gustavo,

SAM calculates the module efficiency after calculating the power output to report as a model output. The efficiency is not used to calculate the power output. For more detail about SAM's PV models, see the PV technical manual referenced here: sam.nrel.gov/photovoltaic/pv-publications.html .

For the CEC Module model, the module efficiency is calculated using the equation

eff = P / ( A * G )

Where:

eff = module efficiency
P = array DC output in W
A = array area in m2
G = array POA irradiance in W/m2

See the attached Excel file for an example.

The source code for this calculation is here: github.com/NREL/ssc/blob/4cbf27085c17d39140ea444c514431907d072a15/shared/lib_cec6par.cpp#L199

Best regards,
Paul.