Relating Short-Therm Measurements With Long-Therm data

[Rafael Santos]

Hi, I am a new PVsyst user as I used to only design wind energy projects.

I have 1 year worth of data (global horizontal irradiation, temperature, wind speed and direction) measured on site.

Which is the best source of meteo data? The long therm ones that come in PVsyst (NASA, Meteonorm) or my own measurements?

Also, is it possible to correlate my short therm measurements with the satellite data? If I do this, would there result in a significant reduction in uncertainty?

Lastly, are there any open source of hourly radiation data, (like MERA and reanalysis in wind)?

Best regards,

Rafael

[André Mermoud]

This depends on where you are.

Reliable meteo data ara available in some regions (Europe, USA), but very scarce in other ones.

See the help of PVsyst "Meteorological data > Meteorological data sources".

When using your own data, be aware that the annual variation may be of the order of 4-5% RMS from year to year, dending on the climate (less with very sunny climates).

And also that own measurements are subject to high unaccuracies when not registered with very high care (namely careful calibration and alignment of the instruments).

Now at least in Europe, the climate has changed since the beginning of this century: the irradiance is higher by as much as 5% (or more). See the PVGIS database.

I don't know for other regions of the world.

You can get reliable recent data for anywhere (for example SolarGIS provide excellent data), but this is for pay.