Utility Scale PV + Battery Modeling

I am trying to do a case study of utility scale system considering 3 scenarios:

1. Standalone PV
2. Standalone Battery
3. Solar + Battery

For standalone battery system, electricity to grid from the battery(kW) is 0, but both electricity to/from battery(kW) and electricity to/from grid(kW) are non-zero. I have attached result file with this question.

For Solar + Battery system, NPV of the system is increasing indefinitely with the increasing size of the battery( tried 1000000 kWh battery). I am unable to understand this. I am charging my battery by just using solar. NPV should go down after a certain point.

I will appreciate if you can answer my questions soon. I am working on a tight deadline research project.

Thank You!
Nitish

Dear Nitish,

It is hard to tell what is going on without seeing your file.

I think your table is from the Statistics tab on SAM's result page, which means that the fourth column is the sum of hourly (or subhourly) values over the lifetime of the project. Electricity to grid from battery means that the battery is not being dispatched to sell power to the grid. On the Battery Storage page, under Manual Dispatch Model, did you allow the battery to discharge for at least one of the periods you defined in the weekday/weekend schedules?

As for the NPV increasing with battery size -- be sure to choose the "Specify PPA price" option on the Financial Parameters page before you run those simulations. Otherwise, SAM adjusts the PPA price for each battery size to achieve the target IRR.

Best regards,
Paul.