PV + Battery Parametrics Error

Hi Alex,

We found a bug with the transformer loss calculation that is causing these results. We will fix this bug for the next version of SAM: github.com/NREL/ssc/issues/847 .

Note that this only affects the value of the "electricity from battery to grid" outputs that SAM reports for reference. It does not affect the battery dispatch or other outputs. You can calculate the time series values of "electricity from battery to grid" by subtracting "electricity from system to grid" from "system power generated."

For now, any of the following options avoid this issue:

• Set the transformer losses on the Losses input page to zero.
• Model the battery as AC connected instead of DC connected.
• Set the inverter night-time loss to zero.

None of these is ideal. The most sure workaround is to use SAM 2020.11.29, but that would require manually recreating your file because it is not possible to use an older version of SAM to open a file saved by a newer version. (You can install multiple versions of SAM on your computer and run them simultaneously.) You can download legacy versions of SAM from the Downloads page: sam.nrel.gov/download.

Thank you for your patience while we sorted this out.

Best regards,
Paul.