micro inverter off grid system buying guide

Rednecktek said:

I've never figured out how that works with AC coupling. I know in the regular world the SCC just draws less power when the batteries are full, but microinverters are full-bore-full-time? Is that like the wall outlet analogy?

(For the newbies here... yeah... asking.. uhhh.. for a friend... yeah..)

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Current codes ( UL1741-SA/-SB ) have specifications for maximum power output is a percentage of the operating line frequencies.

Here is a quick overview and here is where the concept evolved from and more on what frequency control is and even more technical artical on the subject.

Basically as the line frequency shifts from 60hz ( up or down ) the proportional outputs decline. From the IEEE 1547 is this image the is a good example of what this is:



Line Frequency is only one of dozens of parameters, what started out as UL1741 as a binary on/off on voltage window had become problematic as adoption grew it became a major concern that UL1741 was actually magnifying grid instability ( small blip, and megawatts of solar had to drop off line for 5 minutes ). Changes over the 20+ years have morphed into All GRIDTIE solar is now an extension of the utility which has become dependant on the energy in help improve stability.

Bluedog225 said:

I looked around at his videos. Great resource. But I don’t see a vid one off-grid micros. Could you link? Thanks

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This was his last one but I think he had a few more discussing the idea.

Solar Guppy said:

If the loads are lower than 300W ( or lower than the inverter is pushing to grid ) in your example, there would be issues, you need an AC coupling certified inverter ( frequency shift derating ) or things could go badly.

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I'm not talking about a code compliant system but it's quite simple. The GTI just needs to see a grid. I use a low frequency inverter which are bidirectional so the GTI power goes to loads or battery as required.

The GTI is plugged into a smart switch so I have control over it thru Home Assistant. I shut it down outside daylight hours and if the battery voltage reaches a specific value. Been working fine for months now. The key is obviously having a suitable inverter.

amit5674 said:

Hi,
I'm looking micro inverter off grid system buying guide or even some guidelines on what to look\check
thanks

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for off grid you need battery. there is no AC battery, there is no benefit to convert PV into AC at the panel when you need to store it as DC.

Full stop.

Ellcon123 said:

I'm not talking about a code compliant system but it's quite simple. The GTI just needs to see a grid. I use a low frequency inverter which are bidirectional so the GTI power goes to loads or battery as required.

The GTI is plugged into a smart switch so I have control over it thru Home Assistant. I shut it down outside daylight hours and if the battery voltage reaches a specific value. Been working fine for months now. The key is obviously having a suitable inverter.

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Which low frequency inverter are you using?

amit5674 said:

What does it means "AC Coupling" exactly and what solution are exits?
And why does Micro-Inverter forcing AC coupling?

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It seems you have created confusion. Please clarify if you just want a (very?) small/low power capacity inverter for off-grid use rather than "microinverter" which is a specific type of inverter that is mostly used on-grid.

schmism said:

for off grid you need battery. there is no AC battery, there is no benefit to convert PV into AC at the panel when you need to store it as DC.

Full stop.

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It depends.

See posts 10 and 11.

Also, there are the things you can dump AC power into. Examples would be a water heater, in floor heating/concrete slab, or timselectric’s monster sand battery.

cs1234 said:

Which low frequency inverter are you using?

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Doesn't need to be anythong special. I have 2kW and 3kW units but only using the 3. One from Aliexpress and one from Alibaba but freight is the big cost due to weight.

Ellcon123 said:

Doesn't need to be anythong special. I have 2kW and 3kW units but only using the 3. One from Aliexpress and one from Alibaba but freight is the big cost due to weight.

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Yeah, I'd probably just grab some cheap AIMS clone off Amazon or something with a warranty, and when it breaks just get another one.

If it breaks then just buy a new inverter board. Very cheap on Aliexpress. The hard bit can be getting a decent transformer but once you have one it will never break.

Ellcon123 said:

If it breaks then just buy a new inverter board. Very cheap on Aliexpress. The hard bit can be getting a decent transformer but once you have one it will never break.

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I meant get another one as a free replacement under extended Amazon warranty. 3+ years is longer than I expect an inexpensive low frequency AIMS style inverter to last..

I would be pleasantly surprised if it lasted longer though.

Not sure if this is the right Topic area, but here goes, if Im in the wrong place pls advise.
My beef is about panel mounted micro inverters. But here seems to be hung up on connecting to the grid - not my concern.
I am looking at the solar farm prospect where I have seen Flir aerial inspections - very illuminating.
It occurred to me that managing a large array of conventionally strung panels leaves you in the dark NPI as the Flir drone survey may show.
Think of the MIPs this way - Each panel has its own MPPT controller, 240Vac o/p, low current 1-2 A (instead of heavy dc currents) claimed to improve total array o/p by 25%. If one panel goes down it doesnt spoil the whole string. Gives domestic mains supply directly, extra energy can be diverted to storage heaters or ice plants (up to your needs) and ultimately diverted to batteries.
But a principle advantage is that the health of a panels can be sent to a hub for trend analysis, fault detection etc. Check performance against a reference photometer.

Does anyone have experience of collecting data and managing arrays by this method? It seems to me that the usual 48V strings paralleled together is a bit Mickey Mouse