Understanding Losses in PV-Battery Model

Hi Paul and NREL Team,

Thanks so much for always quick and helpful responses.

I am currently working on a PV-Battery model. I have an AC connected, BTM battery using the Self-consumption dispatch option. I would like to tie back the values to understand where the losses are in general.

I would expect the following to be true:
yr 1 system generated kWAC > (yr 1 electricity to grid from systemv+ yr 1 electricity to load from system + yr 1 electricity to battery from system).

With any shortfall being considered system loss. However, there is no shortfall. Instead, yr 1 system generated kWAC is smaller than the aggregated outflows.

I am also looking at the inverter AC output power, which is greater than the system generated value. I would like to see the flow from DC to AC output to grid, load, and battery.

Could you please provide some guidance with this? I would like to understand the flow, so I can see where to largest losses are and account for them. I have attached my SAM file and spreadsheet. Thanks so much for your help!

Kind regards, 
Ondrea

Hi Ondrea,

Analyzing the flow of losses should make more sense if you look at individual hours instead of annual totals.

For the AC-connected battery, in any given time step:

Inverter AC output power = Electricity to grid from system AC + Electricity to load from system AC + Electricity to battery from system AC

This is true except when the system is not generating power at night, and the inverter AC output power is negative for inverter night-time consumption.

Keep in mind that the system power generated variable many include power from both the PV array and battery, so for some time steps System Power Generated = 90,000 kW and Electricity to Load from System AC = 90,000 kW while Electricity to Battery from System > 0.

Best regards,
Paul.