How to 'trick' PV into staying on during a grid outage

[notJEA]

Let's look at their claim.

"So, to address this limitation we have invented a microinverter technology that is completely grid agnostic. This means that even if the grid fails and there is sufficient sunlight, the Enphase system will continue to produce energy and meet the demands of the home or business."

Nope. A grid tie inverter that does not care what the grid is doing will not meet UL1741. What he probably means is that the inverter has a way to power a SEPARATE output that is not connected to the grid, similar to what the SMA inverters do. For example, a system with a transfer switch at the grid connection point that selects either grid or essentials panel can work. This, of course, will need a lot of installation work that will include installing a subpanel.

They also note that it "can" be integrated with their AC battery, but I suspect that for any realistic system it will effectively be a requirement. Their 1.2kwhr battery isn't much (only 280 watts AC output max) but it will be able to supply a little starting surge for motor-based appliances and let you run a night light at night - and of course you can parallel them. At that point you have to compare that sort of system against a conventional battery based system.

Hey guys,

This thread is a little older and i was curious if there has been any technological advances over the years.
The company i work for is starting to install solar.

I am the sales manager and learning as much as i can about solar. I am far from an expert at this point.
One of the biggest objections our guys are hearing is that a grid tied system does not operate during a power outtage due to UL1741.
We would love to tell our customers that they can use the system during daytime during an outtage - Without a battery package.

I have done research on SMA inverters sunny boy etc. and it seems like the systems wouldnt be cost effective.
Are there any good tutorials on the installation of a transfer switch? Is this the most feasible way to handle this?

Looking forward to learning and hopefully contributing on this forum moving forward.


Thanks so much
JBD

[SunEagle]

Hey guys,

This thread is a little older and i was curious if there has been any technological advances over the years.
The company i work for is starting to install solar.

I am the sales manager and learning as much as i can about solar. I am far from an expert at this point.
One of our biggest objections our guys hear is that a grid tied system does not operate during a power outtage due to UL1741.
We would love to tell our customers they can be use the system during the day with light during an outtage.

I have done research on SMA inverters sunny boy etc. and it seems like the systems wouldnt be cost effective.
Are there any good tutorials on the installation of a transfer switch? Is this the most feasible way to handle this?

Looking forward to learning and hopefully contributing on this forum moving forward.


Thanks so much
JBD

The only safe and legal grid tie inverters that will partially work when the grid goes down would be something like the SMA that has the Secure power option.

[Ampster]

The only safe and legal grid tie inverters that will partially work when the grid goes down would be something like the SMA that has the Secure power option.

Otherwise, one would have to use a hybrid inverter with batteries to modulate and control the grid tie inverter. Examples are the Tesla Powerwall, Outback Radian and Skybox, Solaredge Storedge with additional batteries and others that I am not as familiar with such as some Schneider products and others. If you are in design stage this is the time to decide how much you want to pay for the option to keep some or all of your loads powered during an outage.
And you will have to weigh the cost of doing that witha hybrid inverter or just using a transfer switch and a generator which ma be more cost effective.

[SunEagle]

Otherwise, one would have to use a hybrid inverter with batteries to modulate and control the grid tie inverter. Examples are the Tesla Powerwall, Outback Radian and Skybox, Solaredge Storedge with additional batteries and others that I am not as familiar with such as some Schneider products and others. If you are in design stage this is the time to decide how much you want to pay for the option to keep some or all of your loads powered during an outage.
And you will have to weigh the cost of doing that witha hybrid inverter or just using a transfer switch and a generator which ma be more cost effective.

All true but the original post was looking for solar grid tie equipment that would still work even if the grid went down.

[jflorey2]

I am the sales manager and learning as much as i can about solar. I am far from an expert at this point.
One of the biggest objections our guys are hearing is that a grid tied system does not operate during a power outtage due to UL1741.
We would love to tell our customers that they can use the system during daytime during an outtage - Without a battery package.

Short answer - they can't.

Slightly longer answer - if they have an SMA inverter with secure power they can, but they're not common. Pretty soon Enphase IQ8+'s will be able to operate off-grid but they are not available yet. The Skybox is a grid tie inverter that can operate without a battery for grid tie; you can add a battery later for backup power when the grid goes down.

You can also use a standard grid tie system with a hybrid inverter and AC couple it, but that's not something that's cheap or easy.

[Ampster]

All true but the original post was looking for solar grid tie equipment that would still work even if the grid went down.

I guess it depends on how you look at it. All the hybrid inverters that I mentioned can be grid tied. The Tesla Powerwall is a different animal altogether. In rereading his post I see he also asked if it was feasible to do it without batteries, and other than the SMA it is not feasible.

[notJEA]

All true but the original post was looking for solar grid tie equipment that would still work even if the grid went down.

This is accurate.
I just don't understand why we can't use some kind of physical transfer switch to allow our on grid system to operate off grid during a power outtage?
Similar to the way a generator works. As long as we pass the UL1741 compliance in our system somewhere is there not an easy way to achieve this?

Are inverters engineered to prevent this or is it something with there being nowhere for the excess power to go?
Wouldn't this be an issue even with batteries if this was the case?

For example something like this: Solar Module - MicroInverter (without UL compliance) - Charge Controller/Main panel to a physical switch then a UL Compliant inverter(or some kind of controller) that prevents backflow to the grid. The physical transfer switch cuts off the circuit prior to reaching our UL complaint inverter(controller?) and protects the grid. This would allow us to meet UL compliance while giving the customer a way to manually turn their system on during an outtage. I apologize if this verbiage is off hopefully this makes sense.

[notJEA]

I guess it depends on how you look at it. All the hybrid inverters that I mentioned can be grid tied. The Tesla Powerwall is a different animal altogether. In rereading his post I see he also asked if it was feasible to do it without batteries, and other than the SMA it is not feasible.

How is the Tesla Power Wall a "different animal"?
My understanding is that it was similar to some of the other battery options.
If there's a good resource i can use to start understanding everything better please let me know.
I'm considering taking the following class - https://www.everbluetraining.com/solar-pv-mastery

I really appreciate everyones help!

[notJEA]

Short answer - they can't.

Slightly longer answer - if they have an SMA inverter with secure power they can, but they're not common. Pretty soon Enphase IQ8+'s will be able to operate off-grid but they are not available yet. The Skybox is a grid tie inverter that can operate without a battery for grid tie; you can add a battery later for backup power when the grid goes down.

You can also use a standard grid tie system with a hybrid inverter and AC couple it, but that's not something that's cheap or easy.

I've been doing research on AC Coupling.
Best document i found is from Outback power here: http://outbackpower.com/downloads/do...te_acc_new.pdf

Is this just not a cost effective solution?

[SunEagle]

This is accurate.
I just don't understand why we can't use some kind of physical transfer switch to allow our on grid system to operate off grid during a power outtage?
Similar to the way a generator works. As long as we pass the UL1741 compliance in our system somewhere is there not an easy way to achieve this?

Are inverters engineered to prevent this or is it something with there being nowhere for the excess power to go?
Wouldn't this be an issue even with batteries if this was the case?

For example something like this: Solar Module - MicroInverter (without UL compliance) - Charge Controller/Main panel to a physical switch then a UL Compliant inverter(or some kind of controller) that prevents backflow to the grid. The physical transfer switch cuts off the circuit prior to reaching our UL complaint inverter(controller?) and protects the grid. This would allow us to meet UL compliance while giving the customer a way to manually turn their system on during an outtage. I apologize if this verbiage is off hopefully this makes sense.

If the inverter is "grid tie" then it has to comply with UL1741 by the National Electric Code. The UL1741 rule is there to keep anyone working on a "dead" grid safe. It has nothing to do with any excess power.

SMA has found a way to get a small % of the full inverter output to work without the grid but it still complies with the NEC rules. It uses a transfer/disconnect technology to isolate it from the grid but will not allow the inverter to produce the full output.

There are other ways to use your solar panels without a working, grid such as a hybrid inverter with batteries. But even a generator is not allowed to "backfeed" onto the grid so it must be isolated with a transfer switch.

Until the rules change the require a full disconnect between a solar pv system and the grid to be installed by all, there will not be any grid tie inverter that works fully without the grid.

[jflorey2]

I've been doing research on AC Coupling.
Best document i found is from Outback power here: http://outbackpower.com/downloads/do...te_acc_new.pdf
Is this just not a cost effective solution?

Let's put it this way.

A Radian based AC coupled solution plus battery is going to run you around $10,000. A Home Depot LPG generator plus transfer panel is $400. The generator will be more reliable overall. (And in fact if you are planning to be without power for any length of time, you need the generator PLUS the Radian/battery system.)

If someone is a prepper, or they need 100% clean uninterrupted power, then the Radian system (which you linked to) might be acceptable to a customer. But most customers are going to be far happier with a generator and a transfer panel.

[SunEagle]

Let's put it this way.

A Radian based AC coupled solution plus battery is going to run you around $10,000. A Home Depot LPG generator plus transfer panel is $400. The generator will be more reliable overall. (And in fact if you are planning to be without power for any length of time, you need the generator PLUS the Radian/battery system.)

If someone is a prepper, or they need 100% clean uninterrupted power, then the Radian system (which you linked to) might be acceptable to a customer. But most customers are going to be far happier with a generator and a transfer panel.

All good info. A generator is still the best emergency backup power solution in my book.

I think the OP was looking for a way to utilize their expensive solar pv array when the grid is down. Not being able to use any of it or just a little of it seems to get people pretty hot under the collar.

[jflorey2]

Not being able to use any of it or just a little of it seems to get people pretty hot under the collar.

Yep. And during Hurricane Sandy I saw several people with solar lamenting that they could not pump out their basements/charge their cellphones/run a fan even though they had an expensive solar installation. Which makes me think:

1) Solar installers have to be better about explaining what the system can and can't do and
2) If that sort of backup is important to them, be willing to install a system with backup (SMA, Enphase IQ8 or even Skybox with a battery option later)

[SunEagle]

Yep. And during Hurricane Sandy I saw several people with solar lamenting that they could not pump out their basements/charge their cellphones/run a fan even though they had an expensive solar installation. Which makes me think:

1) Solar installers have to be better about explaining what the system can and can't do and
2) If that sort of backup is important to them, be willing to install a system with backup (SMA, Enphase IQ8 or even Skybox with a battery option later)

I agree. Solar pv system sales people need to provide more and better information concerning the technology. But then again they get rated on the number of sales and not all have to be happy customers.

[notJEA]

I agree. Solar pv system sales people need to provide more and better information concerning the technology. But then again they get rated on the number of sales and not all have to be happy customers.

There is definitely a problem with misinformation coming from salesmen. Our company did research on competitive solar companies prior to working on this program and the vast majority of negative reviews were due to sales people not giving correct detail. We obviously want to avoid that.