Anti islanding

[Techno]

Hi all, I'm just ordering a solar panel/battery system which will be linked to the grid and have become aware of a safety feature called "anti-islanding". As I understand it if the grid goes down then the solar panel/battery system are shut down to prevent electrical current going back into the grid and endangering personnel working on the grid.

The consequence is that should the grid go down you also have no access to your battery or solar panel power.

I'm guessing this is a feature of the inverter and was wondering if there are any available that would isolate you from the grid but not turn off your in house power.

[oregon_phil]

When you say just ordered, do you mean you are committed to the purchase?

What brand and components did you order? This might help steer potential solutions for you.

In a few words, what do you want your system to do when the power goes out?

So many questions...

[organic farmer]

In my state, that is strictly illegal.

The power company engineers must approve your design and inspect installation [and you agree to pay their wages, as they do so]. then you must hire a state-approved installer, who will discard every component that you have purchased, and insist that they can only install components that they have provided [at a 3X mark-up].

[Srrndhound]

I'm guessing this is a feature of the inverter and was wondering if there are any available that would isolate you from the grid but not turn off your in house power.

Yes. I'm using an inverter from Solar Edge that disconnects from the grid when it fails, so it can run the house off of the PV panels and batteries.

[peakbagger]

UL 1741 SA is the specification for anti islanding required by utilities. Manufacturers can elect to build and sell grid tied inverters that disconnect from grid and homeowners can buy them. The grid is very reliable in most areas so it fits 99% of the demand at lower cost. If the homeowner actually needs or is convinced by the media and companies that make a profit on selling equipment to run without the gird, they can buy equipment at a higher cost and complexity to run isolated from the grid. The vast majority of these systems are sold to folks who suffer from Fear Of Missing Out.

The alternative many folks including myself is buy a generator on sale, park it in the garage and rarely if ever use it. I live in rural area and have gone 22 years without mine being used for a power outage. Sure the power on rare occasions does go out but its minor inconvenience.

The trade off with going with a system that can be run isolated off the grid is complexity and potential long term maintenance costs. IMO, the big switch to electric cars is going to introduce a new wrinkle in home power usage with inverters that can both run without the gird using the EV battery and export power to the grid for compestation when its needed. In order to have this capability, the PV system will most likely need new electronics and configuration so why not wait for the new technology?, The panels will still work, its just the electronics that will need replacing.

[Mike 134]

The alternative many folks including myself is buy a generator on sale, park it in the garage and rarely if ever use it. I live in rural area and have gone 22 years without mine being used for a power outage. Sure the power on rare occasions does go out but its minor inconvenience.

X2!!!

I'm in Illinois and my utility does not allow me to participate in Time of day metering because of my solar panels being grid tied (and currently one for one net metering) so ZERO advantage to having batteries.

I also have a 6KW generator collecting dust in the garage.

[Srrndhound]

The trade off with going with a system that can be run isolated off the grid is complexity and potential long term maintenance costs. IMO, the big switch to electric cars is going to introduce a new wrinkle in home power usage with inverters that can both run without the gird using the EV battery and export power to the grid for compensation when its needed.

Is this what you really meant -- export your EV's power into the grid? Or did you mean use the EV's power to run the house?

[peakbagger]

I meant that having an EV battery in the mix allows a couple of options that are currently not supported by technology. One option is on the rare occasion that the grid is down, use the EV to power the house without needing to maintain a separate battery bank. In a few states, the homeowner can elect to participate in demand reduction program where the utility can "borrow" power from a home battery battery during high demand periods. The owner gets a paid a capacity fee for just being hooked up and usually a fee if the capacity is used. This same option is being discussed to use the EV battery. The problem is currently is the vehicle to grid tech is still a work in progress. Far better waiting a bit until the tech settles out.

[albert436]

Could anyone clarify something very basic for me?

Is there a typical setup for an area like mine, which is in California, (I happen to be on SDGE)? Eg. using typical equipment such as SunnyBoy string inverters or Enphase microinverters.

OK so do these setups typically disconnect from feeding power back to the grid when there is an outage?

Are you typically able to then use your solar panels to tide you over during a daytime blackout?

I know, there are many different systems out there but I bet there is at least a majority that are set up in very similar ways.

I don't remember where you guys are all located and I understand that different regulations etc apply in different places.

So what's the normal deal out here.

Is there one setup when there is a battery vs no battery? I mean in terms of isolating from the grid etc.

Thanks everyone, just trying to get a grasp on the overall subject, which is one that would never have occurred to me.

[Srrndhound]

OK so do these setups typically disconnect from feeding power back to the grid when there is an outage?

Any system that can feed the grid must automatically disconnect from the grid during an outage. It's a safety thing for grid repairs.

Are you typically able to then use your solar panels to tide you over during a daytime blackout?

It may seem odd, but PV systems must have a battery in order to enable the system to supply your house during an outage, even though the PV panels may be capable of significant power by themselves. Perhaps the reason for that is the batteries act as a local buffer to stabilize operation.

[Techno]

It may seem odd, but PV systems must have a battery in order to enable the system to supply your house during an outage, even though the PV panels may be capable of significant power by themselves. Perhaps the reason for that is the batteries act as a local buffer to stabilize operation.

Ah perhaps it was my misunderstanding.....so a grid tied PV panel/system with a battery will still operate to supply the owners home in a power outage regardless of the inverter used?. Is that correct?

[Srrndhound]

Ah perhaps it was my misunderstanding.....so a grid tied PV panel/system with a battery will still operate to supply the owners home in a power outage regardless of the inverter used?. Is that correct?

Allow me to rephrase. The system has to be specifically designed for backup operation. This capability may be provided by a separate component, as in the Solar Edge Backup Interface, or that could be part of the inverter unit.

[albert436]

Any system that can feed the grid must automatically disconnect from the grid during an outage. It's a safety thing for grid repairs.

It may seem odd, but PV systems must have a battery in order to enable the system to supply your house during an outage, even though the PV panels may be capable of significant power by themselves. Perhaps the reason for that is the batteries act as a local buffer to stabilize operation.

Yes does seem unexpected but interesting to learn what the real deal is.

But the reason is a perhaps, I'm going to ask around a bit and see if I can understand why this would be. what is the battery buffering from what ?

Another question, maybe already answered -- if you do NOT have a battery, then can your solar panels power you in a blackout? I mean during the daytime of course

[solardreamer]

Not regardless of the inverter. The inverter has to be specifically designed for backup operation.

Not just a battery. You need a hybrid battery inverter system that can isolate your grid-tied solar system via a transfer switch from the grid and also generate grid quality AC power to form an island grid in order to activate your grid-tied solar inverters.

[Srrndhound]

But the reason is a perhaps, I'm going to ask around a bit and see if I can understand why this would be. what is the battery buffering from what ?

From fluctuations in solar generation. But this is just my guess -- I have not heard a full explanation why a battery must be present in order for the system's inverter output to made suitable for local consumption.

Another question, maybe already answered -- if you do NOT have a battery, then can your solar panels power you in a blackout? I mean during the daytime of course

That appears to be the rule -- no battery, no backup. I hope someone will provide the background for this.