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Question about module-specific partial shading and power optimizer efficiency


Borlingmax
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Hey,

I encountered some things I didn't understand in the energy balance section of the PVSOL report, see attached figure.

In the figure I have pasted the energy balance from two almost identical simulations. The only difference between the two is that the one to the right has power optimizers from tigo and the one to the left has no power optimizers. Why does the module-specific partial shading differ between the two (underscored in green in the figure) ?

Another question the popped up is about the Power Optimizer (DC conversion/down-regulation). Is that due to losses in the power optimizer, meaning that it has an efficiency of 2 %?

Thanks!

Max

power optimizer question.png

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Hello Borlingmax,

nice question :) The results can be difficult to read and interpret, especially with power optimizer. Basically, the losses have changed category, which can lead to confusion.
With the PV system without Power Optimizer you have losses due to shading.

  • Module-specific partial shading
  • Diodes  (losses caused by the bypass diode of a totally shaded pv module))
  • Mismatch (Configuration/Shading)


By using power optimizer you can avoid losses due to mismatching, but you now get new losses due to DC conversion from the power optimizer (DC Conversion/Down control). In your case, the power optimizers have an efficiency of 98% because you have 2% conversion losses.

In addition, the power optimizers managed on your PV system to avoid total shading by controlling the i-v curve of the PV module. As a result, the losses from total shading (diodes) are now partial shading losses.

I hope that makes the results more understandable.

Kind regards,

Marcel

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Hi Marcel,

Thanks a lot for you answer, it makes sense.

Was surprised about the efficiency of the optimizer though, Tigo says on their website that the maximum efficiency of their optimizer are 99,5 %? I suppose that the efficiency of the optimizers depends on the whole system configuration but is it normally around 98 %? 

Max

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Hello Max,

yes, the efficiency always depends on the general conditions, because only under optimum conditions will you achieve maximum efficiency.

Whether the 98% is normally the case or not, I can't say for sure, because as you yourself said, it depends on the whole system.

Kind regards,

Marcel

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