Possible to Island a Grid Tied Solar Array ?

Status
Not open for further replies.
I'm interested in the answers. If you can do this, do you need some kind of battery storage for when you are in off grid mode?

It just doesn't make sense to have a solar system and not be able to use it if the grid goes down.
 
SG-1 said:
Considering adding a solar array & would like to be able to island during service outages. Is this an option ?
Click to expand...
No. Hence the “anti islanding” requirement

you do have the option with battery backup to power certain circuits from the battery back up and have the solar charge the batteries.
there’s also the non export mode on something like the generac control.

islanding is a condition in which the overhead lines (or underground) are powered from the solar when a breaker or fuse opens. There is a possibility to have voltage and frequency runaway without the grid to regulate the output.
 
Last edited:
oldsparky52 said:
It just doesn't make sense to have a solar system and not be able to use it if the grid goes down.
Click to expand...

It does make sense to not have this capability if doing so expensive and outages are rare.

Line interactive PV systems are designed to operate in parallel with the grid supply, exporting power to the grid when there is excess production, but never energizing the grid when the utility supply is down.

Inverters can certainly take PV output and create AC without the grid and without energy storage....but this path is fraught with difficulty. Maintaining your system voltage stability would be virtually impossible unless you have a large excess of PV capacity and a system smart enough to dial back excess production.

There are heat pump systems designed to be directly connected to solar panels. These systems are designed to use PV production when available, to dump excess production, and to only draw power from the grid if needed and available. These systems will work without grid power...but can never export power to the grid.

Jon
 
Someone said: It just doesn't make sense to have a solar system and not be able to use it if the grid goes down.

But of course it does. The purpose of the vast majority of residential PV systems isn't to provide power when the grid goes down, it's to produce energy from sunlight to offset payments to the utility for electricity. Most residential PV is installed in urban areas with dependable grid power for economic reasons.
 
ggunn said:
Someone said: It just doesn't make sense to have a solar system and not be able to use it if the grid goes down.

But of course it does. The purpose of the vast majority of residential PV systems isn't to provide power when the grid goes down, it's to produce energy from sunlight to offset payments to the utility for electricity. Most residential PV is installed in urban areas with dependable grid power for economic reasons.
Click to expand...
Very true.
We have several PV with battery backup systems tied to our system.
I’m amazed at the new PV owners that actually believe their solar/battery will carry them through a major outage event.
mince I explain to them it will only power the refrigerator and a couple of lights for about 8 hours they are in disbelieve.
One family bought a $40,000 system. The salesman told them they will not need the power company once the system is up and running. They are still upset they have to make payments on the system and still pay the utility.

For a major outage like an ice storm, hurricane, or the like, the PV/battery owners will still need a backup generator...
 
The primary purpose of this system is to offset the power bill & ROI.

Additional equipment will be needed in the winter to heat & store water for heating at night. Wonder how hot an IBC tote can get before it looses it molecular integrity ?

Could add some inverter heat pumps later.

I can say I'm saving the planet too !
 
SG-1 said:
Considering adding a solar array & would like to be able to island during service outages. Is this an option ?
Click to expand...

Conventional grid-tied inverters can't produce power by themselves without a grid forming power source due to anti-islanding requirements. However, some inverters (SMA Sunny Boy with Secure Power Supply option, Delta M5, hybrid inverters like Sol-Ark) can automatically switch between grid-tied and off-grid modes and produce power on their own based on the available solar power without batteries. However, the power from these inverters while off-grid can be very unstable if solar power changes (e.g. passing clouds, bird flocks, planes, etc.) so they are only practical in limited situations. Some other inverters (e.g. SolarEdge inverters using the Alternative Power Source feature) now offer the ability to produce power without batteries when off-grid but also support integration with generators so they can provide stable power. So, there are definitely options.
 
ggunn said:
Someone said: It just doesn't make sense to have a solar system and not be able to use it if the grid goes down.
Click to expand...
Well some of us have to be simple minded so the rest of us can .....

Curious, my electric bills average go between $85 and $140 a month. Could I have a solar system installed that would pay me back before I die? (I'll be 69 this year)
 
oldsparky52 said:
Well some of us have to be simple minded so the rest of us can .....

Curious, my electric bills average go between $85 and $140 a month. Could I have a solar system installed that would pay me back before I die? (I'll be 69 this year)
Click to expand...

What is your electric rate?

Can you do the install yourself?

-Jon
 
Adding some details:

In my case I use 10-30 kWh per day at $0.24 per kWh. I get on the order of 4-4.5 peak sun hours per day, so that means that 1 kW of installed capacity makes about 4 kWh per day. It looks like panels, inverter, and racking can be had for about $1500 per kW, installed perhaps $3000 per kW. Then there are incentives that take this down. So 1 kW of installed capacity generates about $360 worth of electricity per year, for a great ROI if I do the install myself even without incentives.

Wilmington, NC appears to average 6 peak sun hours per day, so you will get 50% more kWh per kW of installed capacity than me, making your payoff better.

But if your electric rate is only $0.10 per kWh then the lower value of the kW you produce will make the payoff worse.

I think it is a pretty good bet that solar would pay off for you in your lifetime.

-Jon
 
winnie said:
What is your electric rate?

Can you do the install yourself?

-Jon
Click to expand...
My rate works out to somewhere between $0.11 and $0.12 per kwh.

I can probably figure out how to install it myself, but I doubt I have the physical capability to finish it in a reasonable amount of time. I have a difficult time cutting about 10,000 square feet of lawn with a 21" push lawn mower :( , I get pretty winded and tired. So, in reality, probably not.

The other issue is my roof flat area faces more east/west so I would be much better off if I had a southern direction so to max out solar generation I think I would have to install some kind of mounting to orient the panels perpendicular to the roof vs flat on the roof (maybe not, IDK).
 
There are others here who install PV professionally, I've just been looking at it as a potential customer.

Yes, ideally you want a south facing panel for maximum production from your panels, however just like the value of generating power during an outage, what really matters is production per $ of investment.

Panels are getting cheap compared to the 'balance of system', so positioning panels to have less production but paying for more panels may actually be worth it.

With your lower electric rate but better sun means that each kW of installed system will produce about $240 of electricity per year. (Note that seeing that value really depends upon your utility tariffs. If your loads are matched to solar production such that you simply lower your utilization then you see the full value...but if you are sending electricity to the grid then the value produced depends hugely on how that gets accounted for.)


For me: I have a nice south facing roof, but it is steep, has lots of protrusions that will create shadows, and has a nice tree in front which also provides shade. I am instead considering putting a 'solar pergola' at the north end of my property. It would not be shaded, it could be at the ideal tilt for my latitude, and it would add a great shaded patio to my back yard. You might consider such a structure for solar.

Jon
 
oldsparky52 said:
My rate works out to somewhere between $0.11 and $0.12 per kwh.

I can probably figure out how to install it myself, but I doubt I have the physical capability to finish it in a reasonable amount of time. I have a difficult time cutting about 10,000 square feet of lawn with a 21" push lawn mower :( , I get pretty winded and tired. So, in reality, probably not.

The other issue is my roof flat area faces more east/west so I would be much better off if I had a southern direction so to max out solar generation I think I would have to install some kind of mounting to orient the panels perpendicular to the roof vs flat on the roof (maybe not, IDK).
Click to expand...
Turn some of that 10,000 sq. ft. lawn into ground mount solar? Easier install, get the orientation you want, and less lawn to mow.
 
Status
Not open for further replies.
Top