How to solve "Weather file has no snow data. Simulation will fail."

Hello,

I used the SAM tool's built-in downloader to get data for my location. It ended up coming from Station ID 891492, I guess. The data source appears to be NSRDB. I thought that this source included snow data, but when I go in the Shading and Layout page and check, "Estimate losses from snow coverage," I get the error message, "Weather file has no snow data. Simulation will fail."

Is there a way to overcome this for my location in the Chicago suburbs and include the snow losses?

Thank you!
Shaun

Dear Shaun,

The only NSRDB files that have snow data are the old 1960-1991 TMY2 files. To get that data, you can go to the NSRDB Archives and download them in a 530 MB zip file:

nsrdb.nrel.gov/data-sets/archives

Note that this data is very out of date, so is only suitable to see how the snow model works in SAM.

This data is also available in files in the SAM CSV format on the SAM Weather Data website page, listed with the NSRDB Archives in the table of free data sources.

1. Unzip the file and go to 1961 - 1990/ tmy2/ where you will find another zip file. Unzip tmy2_data.zip file and find the file for the location you want to model. You can find a list of stations in the TMY2 Users Manual available here: www.nrel.gov/docs/legosti/old/7668.pdf
   
2. Move the .tm2 file to your weather file folder, for example [user]/SAM Downloaded Weather Files. You can also rename it to something more recognizable than the station number, for example rename 26451.tm2 to anchorage.tm2
   
3. In SAM, on the Location and Resource page, choose the file from the Solar Resource library. If it does not appear in the library, try clicking Refresh Library, or Add/Remove Weather File Folders to add the folder containing the file so SAM can find it.
   
4. Look under "Weather Data Information" in the "Optional Data" section. If the file contains snow data, Minimum Snow Depth will be a number. If it does not contain snow data, it will be "NaN" for "not a number."
   
5. On the Shading and Layout page, under "Snow Losses" at the bottom of the page, click Estimate Losses from Snow Coverage.

Best regards,
Paul.

Looks like I am about 18 months late to this post - reference website is down.  Any new workarounds you can recommend?

Hi Tom,

I just updated my reply to Shaun's original message above. Let me know if any of that doesn't work.

Best regards,
Paul.

Hi Paul,

I selected the weather data file for my area of interest, and I want to keep all the data that it has on that location. However, under maximum snow data it says NaN. The location is in AK so this is definitely incorrect. The field is blue and will not let me change it. Is there anyway that I can manually edit the maximum snow depth value? 



Thanks,
Andrew 

Hi Andrew,

Please see my post above. Weather files from the NSRDB do not have snow depth data, so they can not be used with SAM's snow model.

If you have hourly snow depth data in centimeters, you could add a column to your weather file with the heading "Snow Depth."

Another option is to model the effect of snow using a fixed DC loss factor, which you can look up for some locations in Alaska in the table in Appendix A of the following publication:

Ryberg, D.; Freeman, J. (2017).  Integration, Validation and Application of a PV Snow Coverage Model in SAM. National Renewable Energy Laboratory. 33 pp. TP-6A20-68705. ( PDF 3.1 MB )

Best regards,
Paul.