fill factor vs annual energy

I recently ran a python batch process that put every crystalline module in the current CEC database through the simulator. I noticed that panels with low fill factor were often the best annual producers. Can you explain this?

This module in particular had 2% better production than the others (with .63 FF):
Hengdian Group DMEGC Magnetics DM245-P156-60
It is not in the default SAM library (it is in the current CEC database). I also see a somewhat jagged IV curve shown on the module characteristics page.

The next best is in the SAM library (.71 FF):
Grape Solar GS-P-200-OR

Are low fill factor PV modules not modelled well, or does this represent real performance?

Best,
Kelley Dagley

SAM does not calculate the module fill factor. By 2% better production, do you mean that the system's annual output is 2% higher?

Does your Python script run SAM in the "Specify desired array size mode?" If so, it may that the voltage ratings of the modules that you identify as having lower fill factors are causing the array sizing calculator to choose smaller array sizes.

As for the jagged IV curve for the module you specified, please be sure you have correctly specified the temperature coefficient as described in this post .

Best regards,
Paul.

I calculated fill factor myself. Vmp x Imp / (Voc x Isc)

Yes, 2% higher annual output. Strange, since the module's most striking characteristic is poor fill factor which I would generally expect to cause poorer performance.

My script actually sets precise string sizes for each inverter in the array to optimize utilization. (And it checks for over-volatge too.)

The jagged IV plot for the DMEGC DM245-P156-60 shows in the CEC PV database in the current beta SAM. It's probably just an artifact but you can really see how low the fill factor is just by looking at the plot.

This really leaves me doubting the accuracy of the simulation for low fill factor modules. I wish I could understand why this result comes out.

Just compare the DMEGC module to any other, like a 245W mono SunPower. The DMEGC will "blow it out of the water."

Kelley