Hi.
I’m Amy Beaudet from the altE Store.
Thank you for watching our video series.
This video is called “AC Coupling”, or “AHHH!
The grid’s out, where’s my solar power?!?”
We’re going to discuss how a regular grid tied solar power system works, when the grid
is up, and when it’s down, and what some of your options are when it does go down.
With a home grid-tied solar system, when the sun is up, the panels generate DC electricity,
which is sent to the grid tied inverter, which converts it to the AC electricity your appliances
use.
The inverter sends the power through your breaker box, and out to the outlets in your
house, providing power for your appliances.
If you are making more power than you are using, the extra power gets sent out to the
grid, spinning the numbers in your power meter backwards, creating a credit that you can
use later.
During the day, if you need more power than you are generating, you just buy the extra
power from the grid, again, same as you do now.
Your meter will spin forward, but slower than usual, because you are making some of your
power yourself.
You need to buy less!
At night, or when there is no sun shining, the grid sends you all the power you need,
same as usual, so your meter spins forward just as it does now.
So, what happens when the grid suddenly goes out during the day?
The inverter will immediately detect that the grid is down, and will shut off.
Even if the sun is shining brightly, you will have no power at the house, and are lighting
the house with candles, the same as your neighbors without solar.
Why is that, you may ask.
Because most often when the grid goes down, it is because something happened to the power
lines in your neighborhood.
Therefore, the electric company is going to send their lineworkers out there to do the
repair.
If they think that the grid is down, and therefore there is no power on the line, they can be
injured or killed if it turns out you are sending power out to the line.
So it is required that the inverter automatically shuts off to protect them.
Meanwhile your other neighbor with the noisy stinky generator is making frozen margaritas
and relaxing in his hot tub.
So what can you do?!?!
Here’s an increasingly popular option to get energy storage.
You can add battery backup with AC Coupling.
AC Coupling allows you to add a battery backup to your grid tied solar system, without having
to change out your existing equipment.
As we discussed, your existing grid tied system consists of the solar panels and grid tied
inverter, which feeds right into your main breaker box, which powers your house and connects
to the grid.
To add a battery backup through AC Coupling, instead of the grid tied inverter going to
your main breaker box it will now go to a new “critical loads breaker box”.
Now that critical loads box is a busy box.
It is connected to the appliances you consider critical during a power outage, like your
fridge, some lights, and your well pump if you don’t have city water.
Also connected in that box, is the battery bank, and a new battery based hybrid inverter
which is now connected to your main breaker box.
You can see that no changes are needed out at the panels, or into the grid tied inverter.
The only changes are after the inverter.
Instead of going directly to the main breaker box and the grid, it now goes through the
hybrid inverter to get there.
When both the sun and the grid are up, everything works together seamlessly.
The power from the solar panels get converted to AC power through the grid tied inverter.
That power gets passed through the new hybrid inverter and the new critical loads panel,
and powers your critical loads, as well as going back to the main breaker box to power
your house, and send any extra power back to the grid.
It’s also going to make sure that your battery bank is fully charged and ready to go at any
moment.
If you don’t have enough solar power to make sure the battery bank is full, the grid
will provide the charge.
This is all going on completely automatically.
So, NOW what happens when the grid suddenly goes out during the day?
Just as before, the inverter that is connected to the grid will detect that the grid is down
and will disconnect itself from the main breaker box and the grid.
So that means that anything that is not considered critical loads will turn off.
However, what is different now is that the hybrid inverter will now turn on, and power
your critical loads off the battery bank.
Because the hybrid inverter output is also connected to the output of the grid tied inverter,
that grid tied inverter will see the power coming from the hybrid inverter.
It just sees power, it doesn’t know where it is coming from.
So it is tricked into thinking that the grid is still up.
Therefore it will NOT turn off.
That solar power can be used to power your critical loads and recharge the battery bank.
Keep in mind that the grid tied inverter output was changed, and is no longer going straight
to the grid.
It’s going through the new hybrid inverter, which has disconnected itself from the grid.
So the lineworkers are safely repairing the grid, while you are inside enjoying your cold
beverages.
And finally, what happens when the grid suddenly goes out during the night or cloudy day?
Just as during the day, the new hybrid inverter will disconnect itself from the grid, every
NON-critical load will turn off, and the critical loads will be powered from the battery bank.
Since the sun is down, the solar panels cannot recharge the battery bank until the next time
the sun is up.
So good design work needs to be done to size the battery bank big enough to handle your
critical loads until the sun is able to charge it back up.
altE Store has made adding battery backup to your grid tied solar power system easy
by designing some AC Coupling kits for you to add backup to your grid tied system.
We can work with you to determine which kit is right for your needs, or if you need a
custom designed kit.
Check out our website to see pre-designed AC Coupling kits available.
Also watch more of our Video Series on our web site.
We’ve got a team of highly trained Technical Sales Reps available to help you plan your
system, give us a call.
And remember, here at altE, we are making Renewable do-able!