Solar Edge grid tie to ac couple

[Jim1033]

So I have 10k worth of 315watt solar world panels with a 10k solar edge inverter (SE10000A-US) with enhancers. It is not a HD one. I live in Florida and have lost power for weeks several times with hurricanes. I really want to get some system to keep running if I lose power. My goal it to have a system with a reasonably small battery backup to buffer the existing system. I am fine with primarily grid tie. But if we lose power to have the backup system able to work. I have a 100 ah 48v system on the way. I need a reasonably good inverter to keep the solar edge working. I would be ok to put a voltage sensing automatic transfer switch to protect the grid. I am not worried about everything working all the time. Just to help during the day when I have good production. My daily production is anywhere from 15 kw on a bad day to average over 45kw as high as 65kw on cold day in March. My normal usage is about 60kw. But could easily be under 40kw in an emergency. My peak loads are a well and 2 2.5 kw ac units. I have powered one ac compressor and both fans with a 5kw regular generator. That with the fridge and lights. I see lots of things about needing major battery banks and inverters as big as my current solar edge.?. I do not want to get a new solar edge HD to shed voltage. Is there anything that might work? I was hoping to stay in the $1500 range but at this point ready to go to $2500 or maybe more. I do want to upgrade batteries as I go but for now needs to stay with the 100 ah pack. MPP solar seems to have some good things but none specifically say ac coupling? It has to be at least 220vac and be able to get rid of excess at the peak of the day. My peaks is typically at or below 7 kw with the PV. Please help!

 

[Hedges]

I use Sunny Island to form a grid for AC coupled inverters.
Probably two are required, both for 120/240V split phase and to handle 10,000W of AC coupled PV.
This would likely make the price twice your upper limit (many units being liquidated on eBay.)

AC coupling works best if the PV inverter ramps down its power output with increasing frequency, called "Frequency/Watts" under California Rule 21. Find out if your Solar Edge does that. If not, batteries have to cycle as the GT inverter toggles between full power and off line.

Sunny Island should have a compatible BMS (e.g. REC) for use with a lithium battery.

 

[Jim1033]

Thanks for the information. So the sunny Island kills the voltage once the batteries are full and no power is being used?

 

[Hedges]

SMA Sunny Island is probably the first battery inverter that uses increased frequency to signal GT PV inverters are to reduce power output. Some other brands support that as well.

Sunny Island isn't killing voltage - it is producing a stable "island" grid for your house, either as an off-grid system or during grid power failures. It uses a 48V battery and works like an off-grid inverter to generate 120VAC, 60 Hz for household loads including starting motors. If GT PV inverters are present, it can draw down power from them to charge batteries. As batteries get full and charge current tapers off (or if power from PV inverters exceeds all loads), it maintains stable 120VAC but raises frequency as high as 62 Hz, and compatible GT PV inverters reduce their power output. If a motor turns on, Sunny Island delivers the current start it, and adjusts frequency until PV again supplies all loads plus battery charging.

My system works this way, with about 10 kW of AC coming from PV. The system powers my A/C during power failures along with the rest of the house loads, and at night I avoid large loads because my battery is small. My original Sunny Boy PV inverters were an older model that weren't supported, so I picked up new models.

It looks like your Solar Edge model does support "Rule 21"
There are multiple options for Rule 21.
One is to simply remain on-line up to 61 Hz for 299 seconds, delivering full power. That doesn't help for Sunny Island.
The other option is "Frequency/Watt", where the inverter decreases power output as frequency increases. It appears Solar Edge implements this, in which case it should work nicely (you need to enable the feature).

https://www.solaredge.com/sites/default/files/se-single-phase-us-inverter-datasheet.pdf

https://www.solaredge.com/sites/default/files/se_instruction_california_electric_rule_21_upgrade_instructions.pdf

 

[Jim1033]

I called solar edge about another issue it turns out they have some newer stuff. The backup interface seems like a pretty good 200amp auto transfer switch with generator contacts and I think remote start for that generator. I think the generator slot could be used for the battery and maybe inverter. I am going to get some more info on it. I need the transfer switch either way... will give an update when I get it.

 

[bhoth]

I called solar edge about another issue it turns out they have some newer stuff. The backup interface seems like a pretty good 200amp auto transfer switch with generator contacts and I think remote start for that generator. I think the generator slot could be used for the battery and maybe inverter. I am going to get some more info on it. I need the transfer switch either way... will give an update when I get it.

Yes I am interested in what you find out. Thank you

 

[XO4001]

SMA Sunny Island is probably the first battery inverter that uses increased frequency to signal GT PV inverters are to reduce power output. Some other brands support that as well.

Sunny Island isn't killing voltage - it is producing a stable "island" grid for your house, either as an off-grid system or during grid power failures. It uses a 48V battery and works like an off-grid inverter to generate 120VAC, 60 Hz for household loads including starting motors. If GT PV inverters are present, it can draw down power from them to charge batteries. As batteries get full and charge current tapers off (or if power from PV inverters exceeds all loads), it maintains stable 120VAC but raises frequency as high as 62 Hz, and compatible GT PV inverters reduce their power output. If a motor turns on, Sunny Island delivers the current start it, and adjusts frequency until PV again supplies all loads plus battery charging.

My system works this way, with about 10 kW of AC coming from PV. The system powers my A/C during power failures along with the rest of the house loads, and at night I avoid large loads because my battery is small. My original Sunny Boy PV inverters were an older model that weren't supported, so I picked up new models.

It looks like your Solar Edge model does support "Rule 21"
There are multiple options for Rule 21.
One is to simply remain on-line up to 61 Hz for 299 seconds, delivering full power. That doesn't help for Sunny Island.
The other option is "Frequency/Watt", where the inverter decreases power output as frequency increases. It appears Solar Edge implements this, in which case it should work nicely (you need to enable the feature).

https://www.solaredge.com/sites/default/files/se-single-phase-us-inverter-datasheet.pdf

https://www.solaredge.com/sites/default/files/se_instruction_california_electric_rule_21_upgrade_instructions.pdf

This is a very interesting idea do you mind to draw a simple drawing how this is all connected

 

[Hedges]

This is a very interesting idea do you mind to draw a simple drawing how this is all connected

https://files.sma.de/downloads/SI6048US-DS-en-27.pdf

 

[XO4001]

https://files.sma.de/downloads/SI6048US-DS-en-27.pdf

Thanks.

 

[fafrd]

https://files.sma.de/downloads/SI6048US-DS-en-27.pdf

So your Sunny Islands sit between the grid and your main panel?

If the Sunny Island fails, grid power is not available to the house/loads?

 

[Hedges]

So your Sunny Islands sit between the grid and your main panel?

If the Sunny Island fails, grid power is not available to the house/loads?

Yes. Or actually between garage panel and house panel. I can flip interlocked breakers to power the garage.
Correct.

I have four SI wired 2s2p. If the master fails, everything downstream shuts down. I could reassign one of the three slaves as master. Probably only a particular one which is wired to the same phase!

If one slave fails, I think system keeps running. But pass-thru current on that phase would be limited to 56A.

I do have a manual transfer switch to bypass Sunny Island, so a flip of the switch restores power. But that is not automatic, so if not at home all refrigeration would go off.

The inverters should not get snapped from one AC source to another (e.g. grid to generator), because not in phase would fight the inverter, shoot-through current in the FETs. Needs 5 seconds off.

The house loads could be set up to auto-transfer direct to grid with a suitable transfer switch. Having a motor land out of phase is probably less stress than starting from a complete stop. (big generators don't like to be connected to grid out of phase; stories of them ripping out their mounting bolts.)