PV and SAM

Hello all

I just have a question, I am trying to model a PV-Battery system for a low energy building in Sweden since the current trend is to increase the self consumption and self sufficency for residential PV systems instead of Selling electrcity to the grid.

My questions are:

1- Is there a built-in function or macro to calculate the self consumption and self sufficency?
2- Can I find some files describing the alogorithem behind Peak demand shaving for a PV system? or do I need to try and access the code and see where it could get me

Dear Usama,
1. You define the self-consumption by providing data for the Electricity Load. You can then choose dispatch options on the Battery Storage page to determine how SAM operates the system, and an electricity rate structure on the Electricity Rates page that determines how SAM calculates the monthly electricity bill.
2. We do not yet have a detailed description of the peak shaving algorithms, but in general, for the "1-day look behind" option, SAM considers the solar resource and electric load for the previous day, and operates the system on the current day based on yesterday's data. For example, if there was a load peak yesterday at 3 pm, at the same time that the solar resource was low (perhaps because of a cloud passing over the array), then today at 3 pm, SAM would use battery power to meet the load to avoid using grid power for that hour.
Best regards, Paul.

Dear Paul.

Thanks for the reply, I will keep get in touch in case I was able to script a macro for Self Consumption and Self Sufficency.

Hi Usama,

Just to elaborate a bit more on your questions:

1.) There is not an explicit function or macro, but we do provide outputs that should make it possible for you to determine the self-consumption of the system. If you are running with Lifetime set to "PV simulation over one year", the outputs appear in the "Data Tables" under "Single Values". The values are:

- Battery annual energy charged (kWh)
- Battery annual energy charged from PV (kWh)
- Battery annual energy charged from grid (kWh)
- Battery annual energy discharged (kWh)
- Battery annual energy loss (kWh)

Note, if you are running with "Lifetime" set to "PV simulation over analysis period", then these values will be present under the "Data Table" results under "Annual Data", and will have values for every year. So, if for example, you have:

"Battery annual energy charged": 16189 kWh
"Battery annual energy charged from PV": 3017 kWh
"Battery annual energy charged from Grid": 13172 kWh

You could calculate that you charge your battery 18.6% from PV and 81.4% from the grid, i.e, it's not very self sufficient.

2. Paul gave a nice description of the look-behind controller. The same concept applies for the look-ahead controller, except the algorithm has a perfect forecast of the next 24 hours electric load and PV production, so it can more accurately compute the peak grid power and when to schedule the battery to charge and discharge to reduce that peak. Every 24 hours, the controller tries to reduce the grid power as much as possible, but doesn't reduce the peak any lower that the current monthly peak, since that is the peak that will be used to compute demand charges.

I hope that helps, I will eventually publish more documentation on the automatic dispatch algorithm, please don't hesitate to ask if you have additional questions.

Best,
Nick DiOrio