P50 - P90 Evaluations

[sramadan]

If I use the 'Meteonorm 7.1 (1980-2009)' Data in PVsyst's database to run my simulation, is it a P50 data simulation?

Also, which data sets can I use for a P90 simulation?

[André Mermoud]

Meteonorm provides average data over more than 10 years. Therefore the result of simulations will be P50.

Now defining P90 results will use the same input meteo data set (it is an interpreataion of the same simulation).

You have to specify the annual variability from an external source (not provided by Meteonorm).

Please carefully read the help "Project design > P50 - P90 evaluations"

NB: Very few meteo data providers propose TMY data corresponding to P90. I don't know how they construct such data.

[unilhexio]

You have to specify the annual variability from an external source (not provided by Meteonorm).

 

I think they do... In the final output in Meteonorm software, it is specified "Variability of GH/ year".

Evenmore, they give a value for the uncertainty.

[hgoenka]

I think they do... In the final output in Meteonorm software, it is specified "Variability of GH/ year".

Evenmore, they give a value for the uncertainty.

 

However Meteonorm does not provide any information on how they arrive at these values. Since the data outputs from Meteonorm software are combination of multiple datasets (satellite-derived and ground measured) from vicinity of selected site it is not clear how they estimate yearly variability in situation where yearly variability of one dataset may differ from the other.

Also, the method used by Meteonorm for estimating uncertainty appears quite simplistic and does not give realistic results always.

http://www.meteonorm.com/images/uploads/downloads/Accuracy_of_Meteonorm_7.pdf

http://www.meteonorm.com/images/uploads/downloads/PVSEC_11_mn7_p.pdf

For example, in some case when calculating final uncertainty, they are even considering uncertainty of ground measurements to be 1%. This is never the case (not even for research-grade BSRN stations). In reality the best achievable uncertainty for ground measurements is 2% for GHI (and in most cases uncertainty will be higher because of poor maintenance of ground sensors).

[André Mermoud]

When I talked about the data provided by Meteonorm, I meant the Meteonorm DLL implemented in PVsyst.

Yes of course the Meteonorm program provides much more information than the basic meteo data available as standard in PVsyst or other PV simulation programs.

[Muthuraj]

PVsyst's P50-P90 evaluation tool provides option to include inter-annual variability.

But, how can I include uncertainty of radiation itself?