Combined Cases - Wind Power Subhourly Simulations Unsupported Error

I am attempting to combine relatively large wind generation profiles (>500 MW capacity) with solar generation profiles with the use of the generic system model combine cases module. The "Calculate generation profiles and nameplate capacity from open cases" function works as intended until the wind generation capacity exceeds ~400 MW. Once this power capacity is exceeded, the "Calculate generation profiles and nameplate capacity from open cases" function returns the error "The subhourly simulation for case Wind Power is not supported". This is strange because the function works correctly for lower wind generation capacity (all other inputs are the same), and both the wind and solar individual cases are only setup to run hourly (60 min) simulations. Furthermore, these individual cases simulate without any errors or warnings. Therefore, I do not understand why the combined cases module cannot simulate.

There seems to be a something else going on under the hood of the interface that could possibly be triggering this issue. Please let me know if there's a workaround to avoid/prevent this.

Thanks,
Don

Hi Don,

Please attach a copy of the .sam file and also the solar resource and wind resource files you are using if you would like help troubleshooting.

Best regards,
Paul.

Hi Paul,

I am attaching the .sam file which contains the three cases of interest: solar resource file, wind resource file and a generic resource file (used to combine the solar and wind cases in a combined system).

 

Thanks,
Don

Hi Don,

Thank you for sharing your file.

That looks like a bug as you suggest. We will fix that for the Fall 2023 release: github.com/NREL/SAM/issues/1633

As a workaround, you can export the "System power generated" output variable for each of the PVWatts and Wind Power cases, and use a spreadsheet program to add the hourly values to use with the "Import hourly or subhourly generation profile from file" option on the Generic System Power Plant page.

The Fall 2023 version of SAM will introduce hybrid system configurations, including PVWatts / Wind configurations. We hope to release that version in a couple of weeks.

Best regards,
Paul.

Hi Paul,

I'm using the Combined Cases feature to simulate the production at plant level from open cases which are modelling different subarrays of the PV system.
I'm using 15 minute weather file, which seems to work for the cases individually. 
However, when I run the combined cases case, even when changing the time step to 15 min at "edit array" > "change time step" the simulation finishes around the beginning of April, and doesn't display production for the rest of the year - it looks like it's running only 8760 time steps and not the full 35040 expected for 15 min resolution weather data.

Thanks in advance and all the best,
 

Hi Carolina,

The Combine Cases feature does not support subhourly data. You should see an error message about that:

 

One solution to that problem is to manually run a simulation for each case, export the data to Excel to calculate the sums, and then manually import the resulting data on the Generic System Power Plant page.

You could also write an LK script to automate the process: sam.nrel.gov/lk-script.html

Best regards,
Paul.