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Performance Differences: Black Back Sheet vs White Back Sheet

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  • #16
    Originally posted by sensij View Post
    I'm not comfortable enough in these results to feel good about running the follow up simulation. For some reason SAM is showing a slight difference in the temperature coefficients of the 265 W modules that does not agree with the data sheets. If that difference is really true, then the black ones will *slightly* outperform the white ones as the temp gets hotter. 16 kWh is much less than the margin of error for this kind of thing, especially when you have a factor like panel color that is not accounted for in SAM (based on what is in the documentation, and based on other tests I've run).

    How many panels are being put up? If possible, my vote would be to install one string of black, and a string of silver / white, in way that will allow both strings to see the same amount of sun. If using microinverters, even easier. Publish the results here after a few months of running!
    I'm not sure the difference you are seeing is worth worrying about. Sometimes the CEC (CA Energy. Comm.) Performance model #'s (the common one I believe SAM defaults to) are different than the mfg. data sheet. Two of perhaps many possible sources for this might be: input error at the CEC input level or ongoing updates to the mfg. specs./sheets that don't get to the CEC list, making SAM's #'s somewhat outdated. Sunpower seems to do that more than others, but they sell more stuff too.

    To change the parameters in SAM you can change the Module Model Options - Top line on the Module input page, click the change button and follow the bouncing ball and change the inputs.

    At the end of the day, SAM does a pretty fair job but, like all other such tools, it's an estimate good to +/- some % and nowhere near as tight as those 16 kWh which, besides due to temp. coeff. diff., may very well also come from other behind the screen 2d level interactions with things like temp. coeff. induced changes in plate temps., etc.

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