grid, generator and solar battery backup

[Zee]

How would you hook up a generator and PV with ESS so that both gen and PV with ESS can back up house?
Is there even a solution currently?

Solaredge says:
Unfortunately the only way to backup a home when the power goes out is with battery backup. Generators are not compatible at this time with our product.

Details:
I sold a 12 kW grid-tie-only system on a residence. SE11400US INV.
When i went to install.... they had a 22 kW GENERAC gen all installed. It feeds thru a 200A Generac ATS to back up whole house (200A).
That was an unwelcome surprise, given I planned a load side connection with the PV. (No supply side possible unless I replace MSP)
I finally worked around the gen thanks to amazing and patient expertise from a forum member here.
(A contactor disconnects INV output circuit when ATS switches to gen. e.g. in an outage)

Homeowner thinks it a shame no PV when grid out.
Is there manual way to switch to PV with ESS if ....say .....gen runs out of gas?

 

[tortuga]

You have to pay to play, but anything can be done if the customer can write a big enough check.
We use Sunny island inverters its a pretty out of the box solution, you do need some batteries.

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[winnie]

We've had long threads on this topic, which you can search out and use to educate your customer.

The basic issue is that grid tie inverter systems are designed to supply as much energy as possible to the grid, but generators are not capable of acting like a grid and absorbing energy. If the solar power system produces more energy than the home is consuming then something has to go.

If the system is designed well, then the excess energy production will cause a small overvoltage, and the equipment will shut itself down to prevent damage. If the system is designed poorly then something will break, leaving the customer with no power at all.

There are solutions to this issue, in theory a solar inverter could be generator aware and reduce production to match loading, or could be designed to engage optional loads during excess production. As tortuga describes: pay to play, probably not worth it in most residential situations.

Jon

 

[jaggedben]

Option 1: use an ESS that supports a generator. Sonnen does. Enphase will soon. Even older technology like the Conext XW will do it although it's the opposite of user friendly. Also Sunny Island as mentioned, but like the Conext that's becoming somewhat obsolete in my opinion. There are others.

Option 2: put an ATS between the ESS and the backup loads panel. But this precludes reharging the ESS with the generator, and may have other difficulties with ATS operation (depending on ESS off-grid switchover time) and pass through amperage.

 

[Zee]

Option 2: put an ATS between the ESS and the backup loads panel. But this precludes reharging the ESS with the generator, and may have other difficulties with ATS operation (depending on ESS off-grid switchover time) and pass through amperage.

I need to wrap my head around this solution....
Interesting though.

In this case, the Generac ATS is between the main breaker and the main bus bar
( fed by the main 200 amp breaker
and ahead of the 200A bus bar)
The 60A solar brkr is currently opposite feed on that 200A bus bar (at the very bottom).

So I guess my next question would be..... does Generac support the solar tie-in upstream of the ATS .....perhaps in the ATS itself?

Sent from my SM-G950U1 using Tapatalk

 

[jaggedben]

I need to wrap my head around this solution....
Interesting though.

In this case, the Generac ATS is between the main breaker and the main bus bar
( fed by the main 200 amp breaker
and ahead of the 200A bus bar)
The 60A solar brkr is currently opposite feed on that 200A bus bar (at the very bottom).

So I guess my next question would be..... does Generac support the solar tie-in upstream of the ATS .....perhaps in the ATS itself?

Sent from my SM-G950U1 using Tapatalk

So you could (presumably) put a micro-grid interconnect device upstream of the Generac ATS, and connect solar and ESS between MID and ATS. The MID would need a pass-through amps rating of 200A. If the grid goes out, the solar&ESS kick into off-grid mode, but the Generac ATS doesn't flip because it still sees 'grid' voltage from the solar/ESS. Transfer times have to be coordinated. If the battery runs out and the solar/ESS no longer provide power, then the Generac ATS flips and generator starts like it would have before.

I'm not sure if Solaredge has released a solution that would do this yet. Haven't been paying attention. They were working on a separate MID type transfer switch. Tesla supports the solution I describe above. Sonnen is different, you'd ditch the Generac ATS and have the Sonnen call the generator when it wants, which is a bit more of an integrated and elegant solution.

 

[pv_n00b]

Off-grid residential systems have been doing this for decades, there's nothing really new. The inverter monitors the ESS SOC and when it drops below a set point it starts the generator, disconnects the PV array, and the generator supplies both the load and the battery charger to recharge the ESS. When the ESS reaches a set SOC the generator is shut down and the PV array reconnected. Wash, rinse, and repeat as long as the PV array can't keep up with the load demand. The only difference with grid tied backup systems is to make sure your multi-mode system supports generator integration. Then it just acts as an off-grid residential system of old when the grid is down.

 

[winnie]

Agreed, this is known and understood for off grid solar. But in off grid solar, batteries are a necessity, and that battery is a buffer that makes it easy for the different parts of the system to play nice.

How many grid tie inverter systems without batteries will work with backup generators ?

Jon

 

[JoeNorm]

Just install a battery/inverter(ESS) that supports a generator, like Sonnen. Simple.

 

[winnie]

Agreed, this is known and understood for off grid solar. But in off grid solar, batteries are a necessity, and that battery is a buffer that makes it easy for the different parts of the system to play nice.

How many grid tie inverter systems without batteries will work with backup generators ?

Jon

My error; I missed that the op is using an ESS. Agree with the others, you need a controller/inverter that will manage the generator.

Jon

 

[pv_n00b]

Agreed, this is known and understood for off grid solar. But in off grid solar, batteries are a necessity, and that battery is a buffer that makes it easy for the different parts of the system to play nice.

How many grid tie inverter systems without batteries will work with backup generators ?

Jon

None that I am aware of.

 

[BandGap1.1eV]

None that I am aware of.

SolarEdge now does. Their Energy Hub system uses a "smart" transfer switch. Their new line of inverters are equipped with Alternative Power Source Mode also supports parallel operation with a generator.

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There are other more obscure manufacturers like Sol-Ark that support generator hookups as well. https://www.sol-ark.com/

 

[gadfly56]

SolarEdge now does. Their Energy Hub system uses a "smart" transfer switch. Their new line of inverters are equipped with Alternative Power Source Mode also supports parallel operation with a generator.

Storage Estimator - SolarEdge Energy Bank | SolarEdge US

Use our Storage Estimator to calculate the amount of power you’ll need in an outage. More Power. More Savings. Learn more about it here.

www.solaredge.com

There are other more obscure manufacturers like Sol-Ark that support generator hookups as well. https://www.sol-ark.com/

It appears that the off-grid solution requires a battery. You can't tie the inverter to a generator without a battery, or so it seems. The Energy Hub with Prism Technology data sheet says, first sentence: "Optimized battery storage with HD-Wave Technology." Did I miss something?

 

[synchro]

How many grid tie inverter systems without batteries will work with backup generators ?

None that I am aware of.

SolarEdge now does. Their Energy Hub system uses a "smart" transfer switch. Their new line of inverters are equipped with Alternative Power Source Mode also supports parallel operation with a generator.

One limitation of using SolarEdge Alternative Power Source Mode in parallel with a generator is noted on pg. 3 of the document attached in post #12:

"CAUTION!
To protect the generator(s) and avoid damage, ensure that the maximum power produced by the PV system does not
exceed 35% of the maximum power produced by the generator(s)."

 

[pv_n00b]

This is describing the operation of a PV assist generator supply system to a large commercial load. These have been around for a while and do not apply to the standard residential load. They require that the generator be sized to supply 100% of the load when in backup mode and that the PV system is sized to no more than 35% of the load. The load cannot be allowed to drop below the level of the PV system output, which is why the PV output is limited. If it does the generator and PV system will be damaged. So the load needs to have a high minimum value during any time the PV system is in production. These can be made to work where the load has a constant high demand but that's not usually a residential system.

 

[Zee]

It appears that the off-grid solution requires a battery. You can't tie the inverter to a generator without a battery, or so it seems. The Energy Hub with Prism Technology data sheet says, first sentence: "Optimized battery storage with HD-Wave Technology." Did I miss something?

I don't know to be honest.
For offgrid pv backup w/o generator we definitely need a battery, yes.

BandGap:
The new SolarEdge (SE) "Energy Hub" inverter and system claims generator compatibility. Not true. At least not yet.
1. Even so, their literature indicates 15 kW generator max (present system has a 22 kW gen)
2. SE tech support has repeatedly confirmed to me that they do not support generators.
This is at odds with certain mentions in manuals and possibly website that indicate generator compatibility..
3. The Back Up Interface (BUI) component of the new SE system seems to be prepped to eventually handle a generator, in some way or maybe with updates eventually (?????). They are kinda mum on this point.

(Side note: as far as battery + pv systems go..... the new SE system is MUCH preferable to older SE Storedge.)

 

[sketchy]

Tesla's Powerwall's can be integrated with generators. Their transfer switch is upstream of the generator ATS. UL1741 inverters will not turn on from a generator, the sine wave is too dirty and inverters don't like it. Although I've never tested this myself...

 

[gadfly56]

Tesla's Powerwall's can be integrated with generators. Their transfer switch is upstream of the generator ATS. UL1741 inverters will not turn on from a generator, the sine wave is too dirty and inverters don't like it. Although I've never tested this myself...

Do you mean in this case to have the generator act as the frequency source for the solar panels and inverter? I'm not a PV guy, so pardon my ignorance. Wouldn't you still need the batteries to buffer the panel output?

 

[jaggedben]

Tesla's Powerwall's can be integrated with generators. ...

That's kind of an overstatement. They can only do the Option 2 that I described in Post #4. This is just two layers of backup systems that operate one at a time and don't interact with each other. Unlike Sonnen or the Sunny Island (for example), where the ESS can call the generator to recharge the batteries. It makes some sense to describe as 'integrated' only those systems which have these more advanced control features.

 

[jaggedben]

Do you mean in this case to have the generator act as the frequency source for the solar panels and inverter? ...

He is not saying that.