SAM - Detailed PV - Battery Inquiry

Hello Paul,
I hope you are doing well.

May I inquire how to make the solar system feed the battery first and then feed the load if any extra electricity is generated? Please let me know. I have tried all the dispatch algorithms, and I believe that the closest one is the manual dispatch, but still, it doesn’t feed the battery 100% first. The only way I figured to feed the battery 100% is through the grid, although I believe that the system can feed it completely without using electricity from the grid.In the attached picture, the blue represents the battery, and the red represents the system. I have designed the battery to shave the peak at 17 and 18 but it seems that it didn’t get fully charged from the system.
Please let me know what I should do? Thank you.

Hi Eslam,

In general, SAM prioritizes meeting the load with system generated power over charging the battery to minimize losses. In some cases, that approach may not be the most cost-effective.

Please see this discussion for more -- we will revisit this for a future version of SAM: sam.nrel.gov/forum/forum-general/3492

Best regards,
Paul.

Hello Paul, Thank you for your reply. I think it's very important to have this option due to the fact that in Canada, we have financial incentives that would be utilized from such an approach. 
I have also tried to model the detailed PV + battery option twice. The first is without charging the battery from the grid (NPV= 1.9million). The second is charging the battery from the grid (NPV= 1.3million). I made sure that the only variable was the battery charging source. The question is that I am confused why there is a huge difference in the NPV, although the electricity rate is the same. For example, using 300KW to charge the battery at the cost of 0.1$/kW and then discharging to the load should be equal to directly feeding the load. Even if there is some power loss, I don't think it would cause such a big difference in the net present value. Please let me know if that makes sense. Thank you!

Hi Eslam,

The losses are a partial explanation.

The other factor that would affect the NPV when you switch between turning "Battery can charge from grid" on and off on the Battery Dispatch page is the dispatch option, electricity rate structure, and load.

You can investigate this by exploring the outputs in the Data Tables tab of the Results page. Under "Monthly Data," outputs like Energy to battery from grid/system, Energy charge with system, and Demand charge will system will show how the charge-from-grid option affects the monthly electricity bill, which in turn determines the value of electricity generated by the system for the NPV calculation.

Best regards,
Paul.