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# PR Calculation

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report

Hello,

I get lost with the PR calculation in the report.

E_grid = 261.1 MWh

Pnom = 250 kWp

GlobEff = 1137.5 kWh/m²

PR = 261.1/(250 x 1137.5) x 1000 = 91.8%

Report shows 85.6%

Please help?

Best regards,

Bart Van Vooren

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The performance ratio is referenced to the GlobInc (irradiance in the collector plane without optical losses), not GlobEff which includes the shading, IAM and soiling losses.

indeed.

Thanks!

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• 2 years later...

Frequently I need to know what is the "Perfomance Ratio P90", as well the P90 of Global Incident irradiation over the collector plane.

Does the PVsyst evaluate these values automatically in any version?

What formula/equation could be used in the case of "Perfomance Ratio P90"?

Anything like PR_P90 = E_Grid_P90 / (Glob_Inc_P90 * Pnom) ???

Regards,

Erick Castro.

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This requires that you avail of data about the yearly variability of the meteo data for your site.

You have a complete explanation about the P50-P90 concept in the Help "Project design > P50 - P90 evaluations"

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• 6 years later...

There are two formulas mentioned in PVsyst .

1) PR = E_Grid / (GlobInc * Pnom)

2) PR (corr) = E_Grid / ( PNomPV * Σ hours ( GlobInc / GRef * (1 + muPmpp * (Tarray - TArrayAver) ) )

I can see in the report PR is calculated based on the first formula and in the report losses due to temperature are already taken into account . > My question is why the second formula is there , Is it used while calculating PR ( If not then can it be used and  based on it PR be seen on PVSYST report)

> In the PVsyst forum it's mentioned " In PVsyst the weather-corrected result variable is named PRTemp. You can get it on the report by using "Settings > Report preferences" in the Report editing menu." Could you please explain in steps where i can find report editing menu .

Thanks

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Please carefully read the help   "Performance Ratio"     https://www.pvsyst.com/help/performance_ratio.htm

The PR corrected for the temperature is a very special evaluation, to help for the evaluation of the global annual PR from a little period data for in-site production assessments.

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