Question about equation of Simple Efficiency Module Model

 I am using  Simple Efficiency Module model for my own PV generation model. I am a bit confused with the eq (9.32) (pasted with the question) of  "SAM Photovoltaic ModelTechnical Reference" (Gilman et. al, 2015).  

Base on the temperature, one can sometimes have negative DC power output from the equation, which is not possible. I think the equation is mathematically incorrect and the temperature terms should be inside a bracket,  subtracted from 1. 

Can anybody comment on this and let me know if I am making any mistakes here? 

Hi Siddarth,

The latest version of the technical reference for SAM's detailed photovoltaic model was published in 2018, so you may want to use that as your reference instead of the older 2015 version. It is available on the SAM website at:

sam.nrel.gov/photovoltaic/pv-sub-page-2.html

The equation you mention in the 2018 version of the manual is Equation 10.33. According to the code in the lib_pvmodel.cpp source code, when the power output value resulting from that equation is negative, the model sets the value to zero:

 

You can find the source code on the GitHub.com repository for SSC:

github.com/NREL/ssc/blob/develop/shared/lib_pvmodel.cpp

Best regards,
Paul.