Off-Grid Fuel Cell/Battery/PV model?

Hello!

I am trying to model a off-grid system that consists of PV, loads, a battery as the first backup and a DMFC fuel cell as a second backup.
In my system, the PV charges the battery whenever the production exceeds the loads for future use. Whenever there is no more energy in the battery, then the fuel cell turns on to supply for the system. 
I have issues modelling this, and I think the problem is in the Dispatch settings, I have the following: 
-Fuel Cell operation- Follow electric load
-BTM - Charge from system only when system output exceeds load
         -Discharge battery only when load exceeds system output
There are errors that appear and I dont know what I am doing wrong, I have tried several options and it doesn't work  
Is there a way I can prioritize first the battery operation then as a backup the fuel cell? 

Thank you in advanced!
Rita
 

Hi Rita,

Can you tell me what specific errors you are seeing? If you don't mind attaching your .sam file, I can try to help you troubleshoot.

Best regards,
Paul.

Hello,Thanks for the reply.The errors are: Simulation battery failed :precheck input: variable 'dispatch_manual_btm_discharge_to_grid' (Periods 1-6 behind the meter discharging to grid allowed?) required but not assignedbatt_annual_discharge_energy not assignedSimulation cashloan failed :batt_annual_discharge_energy not assigned

Please find attached the file BW1   

Hi Rita,

Thank you for describing the error and providing the file.

This is a bug. We will fix it for the Fall 2023 release:  github.com/NREL/SAM/issues/1406

In the meantime, as a workaround, please run this LK script to fix the problem:

1. Download the attached fuel-cell-battery-fix.zip file and extract it into a folder so that you have a folder that contains the .lk files and three .json files.
2. Start SAM, and click Open script from the Welcome page. (If SAM is already open, close it first.)
3. Go to the folder containing the fuel-cell-battery-fix.lk file and open it.
4. Click Run at the top of the script editor window.
5. When the script finishes, close the script editor and close SAM.
6. Start SAM and open your Fuel Cell file and confirm that the simulation runs without generating a message.

Please let me know if you have trouble with the script, or if you find any other problems with the manual dispatch option.

Best regards,
Paul.