Timezone field not affecting results

Dear Paul,I’m working with some NSRDB and WindToolkit data from India, which has a timezone of UTC +5.5. I included this number in the .csv and .srw files, but PV still peaks on UTC time. I experimented by changing this value around, and it didn’t seem to have any impact on the timing of the output daily time series. Not sure if you were already aware of this bug, but here’s a heads-up! For now I’ll manually shift the input resource files by 5.5 hours, but please let me know if you address this so I can shift them back.All the Best,Marty Schwarz

Hi Marty,

I'm not seeing that in my tests. Here are results for the Detailed PV model with weather data as I downloaded it using SAM's NSRDB download feature for "Delhi, India".



If you download data from the NSRDB website to use with SAM, be sure to check the Convert UTC to local time check box to ensure the resource data matches the time stamps for local time.

Best regards,
Paul.

Hi Paul,

Thanks for the quick response. I have a script that pulls NSRDB data from Eagle, so I am not using SAM's download feature. I think my confusion stems from a misunderstanding of when in the pipeline SAM adjusts for time zone. From what you mentioned about the Convert UTC to local time check box, it seems like SAM shifts the time index in the resource file within the NSRDB download function. I was operating under the assumption that SAM adjusts for time zone when it converts resource profile to power output profile. 

In other words, because I am not using the download feature to pull resource data, I should manually shift the time index before importing it to SAM. 

Does this sound correct?

Thanks for helping me clear this up!
Marty

Hi Paul,

As for wind resource data: the standard .srw format does not include a time index. So is it safe to assume that SAM matches the input timezone field to the time axes for the wind plots? I'm not sure where else the wind time index would be defined...

Thanks again!
Marty

Hi Marty,

That is correct. SAM expects both wind and the solar resource data time stamps to be in local time. It assumes that the first row in the file is for the hour that ends at 1 am on Monday, January 1.

Best regards,
Paul.

Hi Paul,

That being the case, I'd like to implement the "Convert UTC to local time check box" function manually. So how does it deal with half timezones? I tried changing the minute column in the solar resource files from 0 -> 30, but that didn't have an effect.

More broadly, if SAM always expects the first row to correspond to the first hour of the year, what is the purpose of the Year, Month, Day, and Minute columns in the solar resource files?

Best,
Marty