Are microinverters with battery supply a thing?

[jholovacs]

I'm not clear on how a microinverter system can supply off-hour power and storage.

I have a sizeable acreage in southern New Mexico and I want grid independence, but I also use a lot of electricity. Between HVAC and my EV, plus all cooking, water heating, and laundry, I'm easily into low-to-mid 2000's of KWh/ month. I want to fully support my 200A service with something that could give me grid independence as efficiently and reliably as possible.

I thought I could do this with 4 separate EG4 18kPV, each wired up to a 5x rack of 48VDC LiFePO4 battery arrays, each getting several strands of high-voltage solar input from dual-axis arrays (I'm thinking the ECO-WORTHY) type. Seems like this would work, but it also seems... pretty expensive, and takes up a lot of space. Plus, if one of those inverter/ chargers fails, it's really expensive to replace and I'm down to 75% capacity immediately.

Then there's the microinverters. In principle I understand how they work, and they seem to be a little more tolerant and long-lived, but as far as I can tell:

1. They feed back into the grid, which I really don't want to deal with (my grid electric is not especially embracing of the concept)
2. They seem to support a certain amount of wattage, and I don't understand how they would be wired up in parallel to circumvent the wire gauge they use
3. I don't understand how they would be used to store energy, i.e. if I want grid independence, I'd only be able to get there during daylight hours.

Is there something I'm missing? Can microinverters support battery storage and retrieval somehow, or do I still need string inverter/ chargers if I'm going to use battery storage? If so, I don't understand why I hear so many people singing the praises of microinverters... seems like you're still grid dependent.

 

[BentleyJ]

Microinverters do not store energy they produce AC and send it out, either to the grid or batteries or both. For example Enphase makes a proprietary battery system that works with their microinverters.

However, microinverters can be AC Coupled to a hybrid inverter that supports AC coupling.
Most hybrid inverters can be programmed for 0 grid export so power will only go to the loads and/or battery charging.

 

[BentleyJ]

Regarding question 2: The installation manual will specify how many microinverters of that specific model number are allowed on a single branch circuit of X amps. There is no circumventing wire gauge.

EDIT: If its a large array requiring multiple microinverter strings then a combiner box will be used.

 

[SparkyJJO]

I'm not clear on how a microinverter system can supply off-hour power and storage.

Short answer - they can't.

Is there something I'm missing? Can microinverters support battery storage and retrieval somehow, or do I still need string inverter/ chargers if I'm going to use battery storage? If so, I don't understand why I hear so many people singing the praises of microinverters... seems like you're still grid dependent.

If you're not looking for backup power, but to offset your power usage - especially if you have favorable net metering agreements with your PoCo (I have 1:1) - they are super easy to implement because they take care of a lot of shading issues, rapid shutdown issues, and have no high voltage DC running anywhere so less expensive circuit protection required, etc. A regular old electrician can understand them and hook them up for the most part.

To get backup power out of them, you need a hybrid inverter that can "grid form" and control them via frequency-watts or something like that. I have an Outback Radian, which is what my microinverter manufacturer recommends. It can pass through their power to the grid, when grid is up, and when grid goes down, it can provide a "grid" by means of battery and control the microinverter output to charge the batteries and manage their power production by using frequency-watts control (basically if there is little/no power needed from from, it steps up the frequency from 60hz to say 60.5hz, 60.6hz, and they see that and curtail their output instead of pumping 100%).

 

[jholovacs]

OK, so what I'm hearing is that my suspicions are correct: microinverters are good for offsetting electric costs, but pretty much worthless for grid independence. Thanks.

 

[wpns]

OK, so what I'm hearing is that my suspicions are correct: microinverters are good for offsetting electric costs, but pretty much worthless for grid independence. Thanks.

While they _can_ be made to work, there's a lot of specialized jumping through hoops involved, and adding batteries later, or rewiring for All-In-One thing inverters with batteries is going to be a major undertaking, so I'd definitely go with AIO-string. In fact, I did. 8*)

 

[Quattrohead]

How often are you pulling the full 200A from your grid supply ? Never !!!
Grab yourself an Emporia or 2 and monitor your use for a while.
Knowledge is power

 

[Quattrohead]

As to your current guestimated use, 1 or 2 18k that can be grid interactive and 2+ 6000XP for the heavy stuff would cover your suspected 200A consumption.

 

[zanydroid]

I don't understand why I hear so many people singing the praises of microinverters... seems like you're still grid dependent.

You need to qualify the feedback by the use case of the people talking about it. It's engineering, not religious tenets.

If you have good design skills and knowledge of how to install, DC coupled hybrids have a lot of advantages over microinverters for a typical home-sized system

If you're running a very massive system (IE utility scale) AC coupling has a lot of scalability advantages (and there are even utility scale installations of microinverters, presumably 277/480V WYE).

For grid-tie with cost offset, microinverters are good modulo costs.

For small roof facings, microinverters cannot be beat.

For moderate shading, microinverters mitigate the design work / risks from using strings.

For shading, microinverters are more cross-vendor and mature than optimizers. In exchange for the costs, bypassing shade is done via power conversion rather than dissipating through bypass diodes.

If you're running a very massive system (IE utility scale) AC coupling has a lot of scalability advantages (and there are even utility scale installations of microinverters, presumably 277/480V).