Error in using customised weather files - cannot determine time step

Dear Paul and fellow users

I managed to run SAM PV model beautifully with a single year of weather data for Melbourne Australia with SAM CSV format. I used 30 min data, so I had 2 rows of metadata, one row for headings and 17,520 rows of weather data. When I tried other years of data the same format I got the error message "exec fail(pvsamv1): could not determine timestep in CSV weather file Simulation pvsamv1 failed" . Iy should work as there are the correct number of rows

This is strange because it worked the first time and when I created a new csv file using the previous one by overwriting the data it gave the error message. I think the 2 files are identical except for the values.

Note I have avoided leap years, the number format is "general" and there are some gaps in the data record which come up as #value in excel. However these records were i the cdvv file that worked the first time too.

Any thoughts on what is going wrong?

Have attached the unsuccessful file (2009) here

regards, Michael

Dear Michael,

The weather file you attached to your post has a total of 17520 rows, but only 17517 rows of weather data.

Also, SAM does not know how to interpret data that appears in Excel as blank or with "#VALUE". You can replace those values with a value like -9999 to avoid problems with SAM's weather file reader.

Best regards,
Paul.

Dear Paul

Thanks for your rapid and helpful response. I looked at the txt file appended to my message and yes it is three rows short. However the original file saved as csv in Excel has a total of 17.523 rows of which 17,520 are weather data. I wonder why the data was truncated as I uploaded this file to my post and if this is related to the time step error. I have double checked all my input csv files and they have 17,523 rows.

I have experimented some more by replacing the #values! cells with -9999 as per your suggestion and saving with different file names but unfortunately the time step error comes back. Any suggestion what to try next?


kind regards

Dear Michael,
It turns out that the names in Row 1 can be in any order, but they have to be exactly the same as the ones shown in the SAM CSV format description in Help. For your file, they should be:

Location ID,City,State,Country,Latitude,Longitude,Time Zone,Elevation,Source

 

In your file, what should have been "Location ID" was "Location," and what should have been "State" was "Region."

 

In the file you attached to your original post, I changed the Row 1 heading, and was able to run a detailed photovoltaic simulation (after adding three rows at the end to give it 17,520 data rows), even with the missing data and "#VALUE" in some of the cells.

 

One other note: I assume you are modeling a photovoltaic system because the file only has data for GHI, DNI, Tdry, and Wspd. SAM's detailed photovoltaic model will run with a weather file that does not have all three solar radiation components, but the PVWatts will not. To use your file, you'll have to tell SAM to use GHI and DNI instead of the default DNI and DHI: On the Location and Resource page under PV Albedo and Radiation (click the plus button to expand that part of the page), choose Total and Beam for the irradiance components.

 

Best regards,

Paul.