time zone in met data file and site file

[rickholz12]

I'm working on a simulation in Chile. Chile Std time is officially UT -4 and my site's latitude is -70. Based on latitude, the time zone would be UT -5. PVsyst is "reading" the met data file time zone as UT-5. PVsyst will not allow me to change the time zone to UT -4 in the SITE file. How does PVsyst determine the time zone from the met data? Is there a problem if I use UT-5 for this site in Chile?

[André Mermoud]

This depends on which kind of data you are importing.

If you import Monthly values, you have to choose the time zone in the "Site" definition, and this will be used for the generation of synthetic hourly data.

If you import hourly values:

- either you import them from a "known" source referenced by PVsyst, and the Time Zone is usually mentioned in the header of the file read by PVsyst. You don't have to define it by yourself (exception: the helioclim hourly data don't mention it if I remember well).

- or you import them from another kind of ASCII file, and you have to define the Time Zone in the associated Site file which defines the geographical coordinates. In this case be carteful: the chosen time zone should be closely related to the time steps of the ASCII source file. In the format protocol, you can choose whether le time stamps of the data source represent the beginning or the end of the interval.

After such import of data, please carefully check the time of you data by respect to the internal time of PVsyst (i.e. the clear day model), using "Meteo tables and Graphs" / "Data quality check".

NB: As with most of the meteo data, PVsyst doesn't take the DST (Daylight Saving Time) into account, and people usually choose the Winter time as reference.

You have a map of the Time Zones over the world at http://www.worldtimezone.com/

as well as a summary of DST situations and dates on the same site http://www.worldtimezone.com/daylight.html

Now PVsyst fixes limits to the differences between Legal Time and Solar Time, for avoiding rough errors. It accepts differences from -1 to +2 hours. If in some special cases these limits should be overcome you can modify them in the "Hidden Parameters", topic "Miscellanaeous".