How best to set-up solar system switching from Grid-tied to Off-grid for emergency use.

[1holaguy]

While there are similar posts they do not seem to directly apply so I am re-asking the question. Here is the current situation:
My son lives in a suburb of Tampa Fl and like many in Florida is without power due to Hurricane Milton. As a result he is trying to maintain basics using a gasoline powered generator. What is frustrating is he has on the house an 8Kw solar solar array that is grid tied. The two inverters tied to the system do not work if the grid has no power so here he has this big investment to generate clean energy and can not use it because of the system design.

I am thinking there must be a way (in the future) for him to modify his system with switching and the addition of storage so the system could be easily switched to off-grid should the grid go down. Any recommendations would be greatly appreciated.

 

[MakeMePower]

While there are similar posts they do not seem to directly apply so I am re-asking the question. Here is the current situation:
My son lives in a suburb of Tampa Fl and like many in Florida is without power due to Hurricane Milton. As a result he is trying to maintain basics using a gasoline powered generator. What is frustrating is he has on the house an 8Kw solar solar array that is grid tied. The two inverters tied to the system do not work if the grid has no power so here he has this big investment to generate clean energy and can not use it because of the system design.

I am thinking there must be a way (in the future) for him to modify his system with switching and the addition of storage so the system could be easily switched to off-grid should the grid go down. Any recommendations would be greatly appreciated.

people will need to know what model inverters he currently has.

 

[timselectric]

While there are similar posts they do not seem to directly apply so I am re-asking the question. Here is the current situation:
My son lives in a suburb of Tampa Fl and like many in Florida is without power due to Hurricane Milton. As a result he is trying to maintain basics using a gasoline powered generator. What is frustrating is he has on the house an 8Kw solar solar array that is grid tied. The two inverters tied to the system do not work if the grid has no power so here he has this big investment to generate clean energy and can not use it because of the system design.

I am thinking there must be a way (in the future) for him to modify his system with switching and the addition of storage so the system could be easily switched to off-grid should the grid go down. Any recommendations would be greatly appreciated.

A hybrid AIO, capable of AC coupling is what is needed.
This gives you backup and can utilize the existing grid-tied system.

 

[sumpower]

My opinion on this is to have your critical loads on an off-grid system all the time.

I have installed multiple systems this way and when the power went out, the customers were impressed that they were ready by default.

 

[glandpuck]

While there are similar posts they do not seem to directly apply so I am re-asking the question. Here is the current situation:
My son lives in a suburb of Tampa Fl and like many in Florida is without power due to Hurricane Milton. As a result he is trying to maintain basics using a gasoline powered generator. What is frustrating is he has on the house an 8Kw solar solar array that is grid tied. The two inverters tied to the system do not work if the grid has no power so here he has this big investment to generate clean energy and can not use it because of the system design.

I am thinking there must be a way (in the future) for him to modify his system with switching and the addition of storage so the system could be easily switched to off-grid should the grid go down. Any recommendations would be greatly appreciated.

Okay, I can tell you what to do. I have a dual SMA grid tied system. If the grid goes out, and there is daylight, the inverters have a local (attached to them) 120V 15 amp outlet. No sun though, no power. And they do not accept batteries.

Now if the system is using grid tied string inverters, then you could keep them in place and install a hybrid inverter that AC couples from the grid tied inverters and then when the grid goes out, the hybrid inverter supplies power to the backup loads via batteries and a generator connected to it. This option number one. I don't favor it because AC couple systems are not as efficient as DC coupled systems.

Option number 2 is to remove the grid tied inverters and install a hybrid inverter in its place. Examples are Sol-Ark, Luxpower (EG4) and Mid Nite Solar. The panels will be wired into the MPPT controllers built into the hybrid inverter as well as a generator and batteries. when the grid goes out, power is automatically switched to batteries so fast you will never notice. the generator can be 2 wire autostart also so that when the grid goes out and parameters are set, the generator starts up and can supply loads AND recharge the batteries.

In Florida, I would avoid use of micro inverters. If roof damage, panels can get damaged, but inverters in a garage or outdoor wall may survive while microinverters can be easily damaged.

 

[Hedges]

SMA's Secure Power (PV-only batteryless backup) mentioned by glandpuck is inexpensive, and if your son has a recent model Sunny Boy he should do that first.

Option number 3 is AC coupling the existing PV inverters to a battery inverter, which is what I do with Sunny Island.

As MakeMePower says, we need model number to give specific advice.

 

[DIYrich]

Option number 3 is AC coupling the existing PV inverters to a battery inverter, which is what I do with Sunny Island.

I would look at option 3 before option 2. Might be easier(don't have to go on the roof), and have a system with higher output. Although there are some operational advantages when grid down of having some dc pv on the inverter with the battery.

 

[wpns]

Yeah, as others have said, need to know what he has now, but there are a bunch of options.

I'd(*) rip out the grid-tie stuff and go with an 18Kpv or two with PowerPro WallMount batteries, an appropriate number of ChargeVerters, and a small generator or two for emergency use when the grid is down and there are too many Dark Days.

(*) contraction of "I Did". AC coupling is conceptually possible, but there are so many moving parts that I opted for simplicity.

 

[glandpuck]

All great comments. The new SMA Hybrid inverters are available I believe up to 7.7 kW each that can be paralleled. Easy to install, What I don't like is current limitation to only BYD high voltage batteries. This limits the battery capacity because the high voltage stacks can't go over like 500 volts and they are not able to install parallel stacks of in series batteries. But worth a look.

 

[Hedges]

SBSE 11.5kW should be coming this quarter.

SBSE can't be paralleled offgrid. One is all you get, and surge is only to 120% of continuous wattage.

I expect SMA to support additional HV batteries, as they do for SBS.

As you say, no paralleling of batteries. SBS did support 2 or 3 batteries. SolarEdge supported paralleled LG RESU batteries.

There is a project and code on Github which interfaces complete EV battery+BMS with HV inverters. One guy has Leaf working with SBS now, emulating BYD. It should work with Tesla since the project supported that too. I would expect it to work for SBSE as well.

 

[1holaguy]

Thanks all. I shared your comments with him and invited him t join DIYsolarforum so he can provide additional info about his system and ask follow up questions.