Impact of module temperature coefficient of max. power point

Hello,
I was curious about the impact of the temperature coefficient of max. power point under the "CEC Performance Model with User Entered Specifications" module setting. I have done some research into the CEC 5 parameter model, but I was unable to find any mention of this coefficient. I have however seen some other documentation referring to this coefficient as gamma, but have not been able to determine how this affects the output open-circuit voltage Voc. 
I can see that changing the value does affect the output Voc but would like some clarification as to how and why this is. How is the temperature coefficient of max. power point used to calculate the string open circuit voltage? And how, if at all, does this temperature coefficient relate to the temperature coefficients for Voc and Isc?

Hi Gabriel,

SAM's single diode module model does not use the temperature coefficient of maximum power. It uses the temperature coefficient of open circuit voltage and short circuit current.

For references to publications describing SAM's PV models, see sam.nlr.gov/photovoltaic/pv-publications.html .

Best regards,
Paul.

Thanks for your response, Paul. I'm a bit confused since when I do a parametric run to determine the open circuit DC voltage, I get different results when I modify the temp. coefficient of max power point while keeping all other module inputs the same. Is there some other input being modified whenever I change the value for the temp. coefficient of max power point?

Hi Gabriel,

Sorry that my previous response was a little misleading.

For the "CEC Performance Model with User Entered Specifications" the temperature coefficient of max power does affect the shape of the I-V curve because the temperature coefficient of power is an input to the mathematical solver that calculates model coefficients from the datasheet parameters.

The source code for this solver is here:  github.com/NatLabRockies/ssc/blob/develop/shared/6par_solve.h

Best regards,
Paul.