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retrotransposition model
https://forum.pvsyst.com/viewtopic.php?f=22&t=2238
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Author:  innovart [ Tue Dec 01, 2015 1:23 pm ]
Post subject:  retrotransposition model

Hi,
I would like to figure out how PVsyst performs when POA data values are used as input. Because I found the same POA output values both using Perez and Hay's model, is it a expected result? or should I experience some displacements?

Thank you

Author:  AndrĂ© Mermoud [ Thu Dec 03, 2015 5:12 pm ]
Post subject:  Re: retrotransposition model

In principle, in recent versions, when you have meteo data created by original POA data, PVsyst doesn't allow to use the Perez model for the next transpositions.
Using the Perez model should obviously give different results (not matching your input POA values).

Author:  innovart [ Thu Dec 03, 2015 5:25 pm ]
Post subject:  Re: retrotransposition model

Thank you.
I need a detail, thus the retrotransposition and the next transposition are performed according to the Hay's model, in according to the following scheme?

1) POA measured ---> GHI and DHI (retrotransposition by Hay's)
2) GHI and DHI -> POA modeled (transposition by Hay's)
3) POA measured is not perfect equal to POA modeled

Is it correct?

Thank you.

Author:  AndrĂ© Mermoud [ Sat Dec 12, 2015 11:58 pm ]
Post subject:  Re: retrotransposition model

Yes the sequence is correct.
But at the point 3, the POA modeled should be equal to the input measured POA (within some few permille).
If you observe discrepancies (in the morning or evening), this means that you have not imported your data correctly, or the data themselves are not correct.
Please check your file in "Databases > Meteo Tables and Graphs > Check Meteo data", and here press F1 for explanations in the help (especially about the Timeshift).

Author:  lennert_oostvogels [ Thu Mar 05, 2020 5:58 pm ]
Post subject:  Re: retrotransposition model

Hi,

I have a question regarding this remark:
Quote:
In principle, in recent versions, when you have meteo data created by original POA data, PVsyst doesn't allow to use the Perez model for the next transpositions.
Using the Perez model should obviously give different results (not matching your input POA values).
I'm importing hourly POA and ambient temperature values of the site. I'd like to know if the Perez-model can be used for retro-transposition in V6.86. I've manually selected to use the Perez-Ineichen model for the project and on the simulation report it says it used Perez for Transposition and Perez, Meteonorm for Diffuse. However, it says nothing about the model used for the intermediate step of retro-transposition.

Looking forward to your reply.

Lennert

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