Saving the measured data points in custom weather data format

[Mike99]

Hello PVsyst Team,

I am trying to import a 7-day site weather measurement dataset into PVsyst.

My measured weather data starts from 00:00 AM at the midnight of each day and  runs all the way to 11:59 PM.

I'm taking the average of the 60 data points for each hour and saving it as a middle point of that hour.

For instance, for the average of 00:00AM to 00:59 AM data points I'm entering the average of it as 1:30 and for the next hour average I enter it as 2:30 and so on as per the snip below.

Saving the measured data points in custom weather data format:

00:00 AM - 00:59 AM --> average of this goes into custom weather data as 1:30;

01:00 AM - 01:59 AM --> average of this interval goes into custom weather data as 2:30

...

11:00 PM - 11:59 PM --> average of this interval goes into custom weather data as 24:30

I'm just wondering if this is the right way of mapping site measurement to create a custom weather data, since the time seems 1 hour off to me.

Thanks,

[Linda Thoren]

Hello,

The denomination of a given time interval in PVsyst is always defined as the beginning of this interval. This is valid for hourly, daily or monthly values. For weather data, the time stamp is the time interval over which the irradiance measurement (or any other value) is averaged. For example, the time stamp 11:00 corresponds to measurements averaged between 11:00 and 12:00.

The time stamp is not defined in this way for all external weather data. Some of them use the end of the interval, some are measurement between 11:30 and 12:30, or any shift within the hour. Therefore when importing weather data, PVsyst has to adapt its internal time interpretation, in order to always calculate the Solar Geometry in the middle of this interval.

In general, when importing a custom file, you can import minute data and PVsyst will adapt the format to run hourly simulations. In the databases window, click Custom file, choose your datafile, define your site, click New and define all the relevant parameters (time step, date format, variables etc.).

You can read more about the Time Definition in PVsyst in the following link:
https://www.pvsyst.com/help/physical-models-used/time-definition-in-pvsyst.html?h=time+stamp#basic-time-dst