Enhancement Request: Grid Power Connection Limit

Following. We are based in New Zealand and have a similar scenario here. However, given that we focus on smaller systems, the limitations imposed by the lines companies are considerably simpler. In our case, a simple "limit grid export to X kW/MW" or "limit grid export to X%" would do the job.
Regards,
Alex

Hi Alex,

We've implemented this for the next version. You can try it out in the Beta version if you like:

sam.nrel.gov/download

We'd be interested in any feedback you might have on the Beta in case there are improvements we can make before the release at the end of February.

Best regards,
Paul.

Hi Paul,
Many thanks. Downloaded the beta version and tested the Grid Interconnection Limit and the Grid Curtailment options.
Both do their job perfectly fine for our needs. Much appreciated!

Regards,
Alex

Hi, 

I've set a grid interconnection limit for a PV+battery system and notice that it is being respected only in the year 1 hourly data, not in the lifetime hourly data. I am using the generic commercial model in SAM 2020.2.29. I've tried it with the detailed PV model and get the same issue. 

To illustrate the point, I'm attaching a case where I've added the output of a very large PV system (compared to the load) and set a comparatively small grid limit (50 kW). In the hourly data, the electricity to grid in year 1 never exceeds 50 kWh. However, in the lifetime data in kW, the electricity to grid exceeds it by a lot. Is there something I'm missing that is causing the grid exports to exceed the limit? I would like to use lifetime data and not only the year 1 outputs because of how the battery performance will change over the years. 

Also, I cannot find anywhere the exact definitions of the following lifetime hourly outputs: system power before grid interconnect, system power before grid curtailment and system power generated. In my simulation, the first of these is roughly equal to the power plant generation I gave SAM as input (times the years in the lifetime), although it did not apply the annual degradation. The last 2 are equal to each other and are about 20% greater than the electricity from the system to the load, so I am struggling to guess how SAM determines these hourly values. I would expect that 20% difference to be curtailment, but the grid export limit is not being respected. The battery is essentially unused, so that energy is not going there, either. Could you offer any ideas or sources for more detailed definitions?