Losses for PV-battery systems

The following questions and answers are about how losses are applied for PV-battery systems. You can use the attached .sam file to display the Electricity to grid from battery AC and Electricity to grid from system AC time series outputs to verify these answers.



In case of AC Coupling, when PV is charging the BESS, the “AC to DC conversion efficiency” parameter need to also consider efficiency of PV Inverter & AC cables (originating from output of PV inverter till input of AC to DC Converter) ?? I ask this because when I choose “AC Connected” BESS then the “PV inverter nominal efficiency” parameter becomes deactivated.

Yes. For AC-connected batteries, the PV inverter with parameters specified on the Inverter page only converts DC power from the PV array, not power from the battery.

In case of AC Coupling, when BESS is discharging to grid, the “DC to AC Conversion efficiency” should consider efficiency of DC cables, BESS inverter (including Transformer), correct ??

Yes. SAM applies the DC losses to the PV array DC output, not the battery output. You can account for equivalent losses for the battery in either the DC to AC conversion efficiency, or with more detail using the Battery Losses inputs on the Battery Cell and System page (you may need to scroll down the page to see the expandable panel for those inputs).

In case of AC/DC coupling, is the AC wiring losses are applied on energy out of PV/BESS inverter ??

SAM applies the AC wiring loss to the inverter output, so for DC-connected batteries the AC wiring loss affects the battery output power, but for AC-connected batteries it only affects the PV array output power.

For the case of “Transmission Losses”, where is it applied exactly in the calculations ?? Is it applied on system output to Grid ???

SAM applies the transmission loss to the AC output of the PV inverter, so it only affects the output of the PV array.

Best regards,
Paul.