Question about Grid Tie vs Grid Connected/Hybrid

[cschill2020]

Hi,

I am planning on going Solar in 2 phases.

Phase 1: Add battery backup (48V, 44kWh LifePO4+Seplos BMS modules), Inverter/Charger and power a critical load subpanel.
Phase 2: Add solar (7-10kW) + MPPT controller(s).

Option 1/Phase 1: I would like the inverter to prioritize grid for powering the subpanel and keeping batteries charged/balanced. Then have the inverter auto-transfer to batteries+inverter during an outage. I am confused as to whether I can set this up in the US/California (PG&E). Does this setup require a grid code? I am not planning on Net Metering or feeding back to the grid.

Option 2/Phase 1: Run the critical loads off of battery and use the inverter to keep the batteries charged. I am not sure what the pros/cons are of the 2 solutions.

I was planning on buying 2 Victron 48V 5kW inverters. But they are not UL-certified and I am confused as to whether I can set them up to handle Option 1

If I do require a UL-certified to support Option 1, what are my options for inverter/charger? I assume that the main choice would be a Sol-Ark 12k?

Thanks for the help!

 

[zanydroid]

Option 1/Phase 1: I would like the inverter to prioritize grid for powering the subpanel and keeping batteries charged/balanced. Then have the inverter auto-transfer to batteries+inverter during an outage. I am confused as to whether I can set this up in the US/California (PG&E). Does this setup require a grid code? I am not planning on Net Metering or feeding back to the grid.

In California you need a UL9540 inverter/battery combination to get this permitted.

There are a couple different configurations. Parallel operation and fully isolated (among others like momentary parallel). I am not sure hybrid inverters set up in UPS mode guarantee fully isolated, they tend to be parallel. You can do fully isolated with external components. Within fully isolated there are a few possible topologies as well for setting it up.

In terms of hardware EG4 18kpv is the other one a lot of people have used for grid tie. There’s a crap ton of new ones UL9540 that got approved by CEC this year too, not that much forum experience yet with those.

Victron is never going to be grid tie eligible in California at the rate that company is complying with US grid tie regulations.

SolArk 15k is easier to use than 12k if you might eventually want full house backup since it has the 200A built in transfer switch. There are a few people on here that will say the 15k is nicer for resell because of its easier integration, dunno if that's true or even an important consideration.

Why not do Net Metering on stage 2? You might have some chance of breaking even on the interconnection application fee even with the reduced sell back credit on NEM3. Assuming you are already pulling permits (if you're skipping permits then you can save on some drawings and permiting fees, but as a DIY in a high density suburban area and really expensive house repair prices if you blow something up I'm not sure you want to combine skimping on permits with DIY). Also I believe you need to pay interconnection application fee for the non NEM parallel interconnect anyway.

Fully isolated I don’t think you need permission (even though they have an application form for it)

 

[Siamac]

That's an expensive battery system. Probably costing you over $10k.
I would do solar first and at least save some money. You can use a gas generator in case of outage if that's what you're worried about. Generator is much cheaper, around $500-1000. Then do the battery with the solar savings