Powerwall 2 Off grid clarification

[weewards]

No. In normal conditions when the system is totally grid interactive, the solar will simply be exported when it exceeds the home consumption and the batteries are full. The system can only change the frequency when off grid.

Solar will only be curtailed (reduced or shut off) in two conditions:

1. When the system is running off grid and there is nowhere for the solar production to go.
2. Your system is grid interconnected, but not allowed to export. This can be before you have Permission to Operate, or it can be part of the interconnection agreement. Automatic curtailment to prevent export can be accomplished with Tesla solar inverters or third party inverters that independently measure the grid flow and curtail their own output independently from the Powerwalls. When Powerwall batteries are charging from solar in this situation, it looks like household load to the solar controller.

Thank you that is exactly what i wanted to know & it is very clear now.
Thanks again.

 

[lodar]

Other replies here seem to indicate that when the "go off grid button" is pressed solar will charge the batteries until full but will then turn off the solar panels until needed

The solar panels should never be “turned off” by the Powerwalls. They will be allowed to power the house while the batteries are full.

The Powerwalls will signal the solar panels to generate less power, so they make just enough or a bit less than the house needs.

Only if the solar panels ignore the Powerwalls, or you actually turn everything off in the house, would the solar panels shut down.

 

[miimura]

The solar panels should never be “turned off” by the Powerwalls. They will be allowed to power the house while the batteries are full.

The Powerwalls will signal the solar panels to generate less power, so they make just enough or a bit less than the house needs.

Only if the solar panels ignore the Powerwalls, or you actually turn everything off in the house, would the solar panels shut down.

In an ideal world, what you way would be true. However, grid tied solar inverters have to follow the rules set by your local grid. Many utilities require solar inverters to support "ride through". What this means is that they should not modulate their output based on small changes in voltage and frequency. When you have a Powerwall system that has to operate in grid tied and off-grid modes, it is very difficult to have one set of settings that are optimal for both modes. I think you will find that in California, most solar inverters will shut down for 5 minutes when the Powerwall system first goes off grid in a real power outage. If the battery is at a high state of charge, the Powerwalls will keep the frequency between 62.5 and 65 Hz until the state of charge drops to some level between 90 and 97%. Then the frequency will drop somewhere in the range of 60 to 62 Hz and the solar can start up again. Most solar inverters that are configured for grid tied operation will not do proportional curtailment because the default California grid profile doesn't include it due to ride through.

The end result of all this is that most solar systems tends to turn on and off in a binary fashion, not modulating power output.

 

[lodar]

I think you will find that in California, most solar inverters will shut down for 5 minutes when the Powerwall system first goes off grid in a real power outage. If the battery is at a high state of charge, the Powerwalls will keep the frequency between 62.5 and 65 Hz until the state of charge drops to some level between 90 and 97%. Then the frequency will drop somewhere in the range of 60 to 62 Hz and the solar can start up again.

FWIW… I live in California and my Enphase IQ7 and IQ8 system curtails gradually. I ran a bunch of experiments during an all-day PG&E utility pole replacement. I was as off-grid as I possibly could be with the power lines disconnected on the ground.

Batteries filled up around Noon and Solar started curtailing without shutting down.

 

[jjrandorin]

FWIW… I live in California and my Enphase IQ7 and IQ8 system curtails gradually. I ran a bunch of experiments during an all-day PG&E utility pole replacement. I was as off-grid as I possibly could be with the power lines disconnected on the ground.

Batteries filled up around Noon and Solar started curtailing without shutting down.

View attachment 1048579View attachment 1048580

There are two separate discussions happening here. One is, lets not confuse this OP. The OP was under the impression that:

Can you settle an argument, my logic is that if I choose to go off grid from the App then ALL power for my house will come from the Powerwall and even if solar power were available from my solar panels it would NOT charge the powerwall while it is off grid.

Which is not true, as we know. Solar power can and does charge a powerwall when off grid, full stop. Under what condition that happens, and whether solar is curtailed or shut off, may be setup as individual systems, but all solar + powerwall systems can have the solar charge the powerwall when off grid.

Whether a system curtails or not, probably depends on hardware capability. curtailment (not shutoff) is relatively newer (my system shuts off, does not curtail, for example). It would be safer to "assume" (with all the caveats of that word) that a system would turn off, rather than curtail, since curtailment is newer.

 

[miimura]

FWIW… I live in California and my Enphase IQ7 and IQ8 system curtails gradually. I ran a bunch of experiments during an all-day PG&E utility pole replacement. I was as off-grid as I possibly could be with the power lines disconnected on the ground.

Batteries filled up around Noon and Solar started curtailing without shutting down.

In the case of Enphase systems, the curtailment depends on your "Grid Profile". My recently installed IQ8A based system has this indicated under Grid Profile Settings: "Grid Profile: CA Rule21 201902 VV VW FW"

What is your grid profile?