Error running battery-only system

This is my first time trying to run a battery-only system. There doesn't appear to be a no-power-plant option. I'm using 15-minute timesteps for load and for generic 0 kW PV system, with output for PV set to 0 in all intervals. Here's the error message:

fail(system_capacity, positive): 0
Simulation cashloan failed.

Any idea what's going wrong and how to fix it?

Thanks

Hello,

Are you using the battery model with the Generic System model?

You can model a battery-only system, either with the Detailed Photovoltaic model by setting the DC constant loss to 100% (on the Losses input page), or with the Generic System model by using the import generation profile option to specify an hourly or subhourly generation profile of zero for all time steps.

In either approach, use the manual dispatch option on the Battery Storage page, and be sure to define dispatch periods so the battery is both charged and discharged.

Would you mind attaching a .sam file to your original post above (edit the post to add an attachment) so I can see how you set things up?

Also, please be sure you are using the latest version of SAM (2018.11.11 r3). The latest update includes some fixes for the Generic System model with subhourly simulations.

Best regards,
Paul.

Hello,

I've uploaded a version of your file as an attachment to your original post above. It that compares using the Generic System model to the Detailed PV model, both configured as battery-only systems.

The Detailed PV model case shows a reduction in the monthly demand charge, and the Generic System model case does not.

The Generic System model requires a non-zero nameplate capacity value even with the generation profile of all zeros. I arbitrarily set it to 50 kW. Note that you could just set plant loss to 100% instead of using a generation pofile of zeros.

The peak shaving dispatch seems to work better with the Detailed PV model approach, so I would recommend using it instead of the Generic System. I'll let the battery model developer know about this to investigate further.

Results from Detailed PV Model:

 
Results from Generic System model:

 
Best regards,
Paul.

Hi,

We're investigating the issue with the Generic System model. Will the "Detailed PV" case in the file I attached work for you?

I haven't tried the BLAST model yet, but I don't think it has as detailed a cost and financial model as SAM. If you do try it, please let us know how it compares to SAM for your analysis purposes.

Best regards,
Paul.

To follow up, I've identified a few issues with the Generic System + Battery model that result in this behavior. We will soon release a beta and patch to fix the issue. In the meantime, for standalone battery systems, please use the "Detailed PV" case, curtailing the DC production from the PV array on the losses page.

Best,
Nick