Time reference

[cvernay]

Dear M. Mermoud,

I am working on the PVsyst output file which is hourly-based. I can read in an old topic that the labeling convention is always the beginning of a time step.

http://forum.pvsyst.com/viewtopic.php?f=18&t=123

To close the subject, what is the time reference? UT, TST, Legal time?

In case of Legal time, does PVsyst consider winter/summer shift? Is it really UT + time zone + winter/summer?

Best Regards

Christophe Vernay

[André Mermoud]

The time reference in PVsyst is indeed the Legal time, i.e. UT + Timezone, and the time label is the beginning of the hour.

But as with most solar software and meteo data, it doesn't take the DST (winter/summer time) into account. For most Meteo data, the Time Zone is fixed according to the Winter time.

NB: If sometimes meteo data are not recorded exactly during a Legal hour - may be for example accumulated from 8:15 to 9:15 - then when importing these data into PVsyst you have to specify a "Time shift", which indicates that the solar geometry will not be computed at 8:30, but at 8:45 in this example (middle of the measurment recording interval).

NB: for being compliant with some old research meteo data, PVsyst can also work in "Solar time", i.e. the time defined by the passage of the sun at south at Midday. This time definition is really not practical, and should never be used except for very special reasons.