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Hourly discontinuities in calculation


Bert
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I am new to PV*SOL and testing my private project successfully so far but I am puzzled about the results after a 1 minute timestep simulation. The phenomenon is best visible in a Carpet Plot (Diagram Editor) of e.g. "PV energy (DC)", "Mismatch (Configuration/Shading)" or “MPP Voltage” that shows a discontinuity at the full hour values. This shows as horizontal stripes in the plot.

I tried to analyse the cause of this phenomena but the only assumption that I have is that the somewhere in the calculation hourly values are not interpolated correctly into minute values. I tested this also in the 3D Bay example (with 1 minute demand data) with the same effect.

I tried to include a screenshot but I do not understand how to “insert an image from URL”.

This URL points to “Hourly discontinuities in calculation MPP 4 Voltage.JPG” on my Onedrive:

https://1drv.ms/u/s!AnJoS9oSoABOmPQeIqS6vG3TpJB_LQ?e=Rokcqm

Is this indeed an error in the program or is there another explanation?

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HI Bert,

thanks for the project files. What you see there as "hourly discontinuities" is the effect of hourly calculated shadows from the 3D environment. That is, they are calculated on a 10 min basis, but then averaged to 1h values prior to handing them over to the main PV*SOL application for performance reasons.

One can see that the phenomenon is not visible until the module specific shading (and low light behaviour, which is of course dependent) come into play:

grafik.png

And then:

grafik.png

So, no error here, just hourly shading values. In future we want to be able to use 1min values of the shading as well, but this requires much more performance (factor 60), so unfortunately this is not so easy to accomplish.

Hope that helps, kind regards,

Martin

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Hi Martin,

Thank you for taking the trouble to explain. I am happy with this because a more accurate 1 minute simulation of 3D schadows probably wouldn't effect the hourly, dayly, monthly, yearly or lifetime results much. However allow me to suggest an alternative future improvement to get rid of these "hourly discontinuities": instead of using hourly shade values you could first fit a curve through the hourly values to generate "continuous minute values" during the main calculation.

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