3 phase grid tied for the win or a lost cause?

brandnewb

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I am in the process of storing power that I generate myself
TL;DR I will settle on 48 volts max, I intend to run my household, whichi is a 3 phase household located in Europe.

I'd like to keep feeding my appliances through my breaker panel

eventually being able to simply disconnect the mains grid connection when I have had a year or 2 track record of not needing it any longer.

I think I need a 3 phase grid tie inverter somewhere in between my panel and the battery pack refered to above

Is this the way to go indeed? Please ask for more details so I can help you guys help. I am far too inexperienced to think of a better way of explaining myself at this point in time.
 
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MichaelK

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I'm fully aware of three-phase motors, but how is a three-phase household supposed to work? What household appliances out there use three-phase power?

My own system is split-phase 120/240VAC. Why will that not work for you?
 

brandnewb

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I am in Europe.

In the 3 phase category I have an EV charger, eheater and a wind turbine alternator (under construction)

My whole household is 3 x 25 amp mains connected, just like most of the modern households in my area if not the whole of Europe, Please see the threads I referred to for more details. specifically;

At the risk of offending the USA, which is not my intend, why does it seem that assumptions are quickly made based on imperial units and US customs? This is the second time I have ran into a misunderstanding like this since my beginning on this forum which was like 2 days ago ;)
No ill intend meant by this remark but just an observation.

My most important remark would be; thank you for participating in this thread
 
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MichaelK

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At the risk of offending the USA, which is not my intend, why does it seem that assumptions are quickly made based on imperial units and US customs? This is the second time I have ran into a misunderstanding like this since my beginning on this forum which was like 2 days ago ;)
No ill intend meant by this remark but just an observation.
This site is run by an American, located in America, and published in English, with about 95% of the posters here located in the US, so why would you assume that anyone here would automatically know you are European? Just an observation!
 

stienman

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You're kind of in a hard spot.

3 phase solar inverters are readily available - but they are generally grid tie, not hybrid or battery. Further, they are often HF inverters, and will not handle loads with huge startup currents or have a power factor very far from 1.


...how is a three-phase household supposed to work?

A 3 phase system has 3 wires and no neutral, L1, L2, L3, or 4 wires, which adds the neutral. Phase to phase will be one voltage, phase to neutral will be another voltage. This is why you have appliances that may accept 208-277VAC - it covers quite a few different standards for hooking up to three phase.

In a three phase breaker box you'd have three bus bars for the mains. If you attach a single breaker, then you're connecting to one phase, and neutral. If you use a double breaker then you're connecting to one phase and another phase. If you connect a triple breaker, then you get all three, and are most likely running a motor of some sort.

See https://ctlsys.com/support/electrical_service_types_and_voltages/ for the Three phase Four Wire Wye system.

Note that powerlines do not use a neutral. The neutral is created by the transformer outside the house.
 

brandnewb

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This site is run by an American, located in America, and published in English, with about 95% of the posters here located in the US, so why would you assume that anyone here would automatically know you are European?
because it is stated in the other threads. Where I referred to for details.

I will admit though that this
I intend to run a 3 phase household.
statement was poorly constructed and I will change it directly after posting this reply,

Still, no ill intend meant and still looking very much forward to suggestions.
 
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time2roll

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Since you are planning to go off grid.....just do it now. Run the house off the solar, battery, and inverter.
Since you are still in the proof of concept phase.... connect the utility power to a charger to supplement the battery only when needed.

Otherwise you may need different equipment to be grid tied and then switch to off grid.

going off grid also allows separate equipment such as stand alone solar controller and separate single function inverter.
 

brandnewb

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Since you are planning to go off grid.....just do it now. Run the house off the solar, battery, and inverter.
Since you are still in the proof of concept phase.... connect the utility power to a charger to supplement the battery only when needed.

Otherwise you may need different equipment to be grid tied and then switch to off grid.

going off grid also allows separate equipment such as stand alone solar controller and separate single function inverter.
YEs, this is an interesting and possibly a very valuable suggestion. Although I am not qualified to asses the merrets of it it naturally feels the right way to go. I just have an instant connection with it.
 

wattmatters

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It's not actually clear from the various threads (which are quite confusing) what your actual objective is.

What is your primary motivation? Is it:
- to save money?
- to reduce carbon emissions?
- to stick your middle finger up at the energy utility?
- to have fun building stuff, but don't care about the costs?
- Other?

You can of course have multiple motivations but your primary motivation will dictate a different solution path.

For instance, adding storage may or may not be a financially viable option if saving money is #1 on your list. It will depend in large part on the specifics of your particular home energy production and consumption patterns and the tariff regime you operate under. If the grid is already available then in many cases that is usually more cost effective than adding storage. But every case is different.

Also not all solutions are suitable for DIY. As a rule of thumb, grid tied systems usually require a level of system approval and oversight from energy supply authorities which can quickly rule out DIY. Where I am, grid tied and DIY are verboten, unless you just happened to be an accredited and licensed solar system electrician, in which case you would not be asking the sort of questions you are. Even off-grid systems have variable levels of regulatory oversight and standards and these are not to be trifled with since it can have impacts on things like insurance coverage.

From what I understand:
- you already have a grid-tied solar PV system which generates ~11MWh/year
- you import ~9MWh/year from the grid
- it is not clear if the existing solar PV system is a single or a 3-phase inverter (you can have either on a 3-phase home, and a modern utility meter will manage the net billing across all phases in either case)
- your actual household electrical energy consumption (or grid feed in) is unknown. Perhaps you mentioned it since there are threads all over the place.
- you have not done an energy audit beyond those annual numbers mentioned and listed a few higher power draw appliances (EV charger, cooktop and possibly the hot water storage)
- you only seem focussed on the energy supply side of the equation, when assessing options on the demand side may well be more productive.

It's hard to help with suggestions when we don't know why you are doing this.

It might be the best thing is to make far better use of existing system via better management of discretionary loads.

Or finding a better retail tariff.

Or you are better to engage a professional installer of solar PV and battery systems.

Things like a decision between being grid-tied or going off-grid result in quite profoundly different solutions, even if you draw very little energy from the grid. It's not a simple case of flipping from one to the other as the technical solution and scope of system required is quite different.

The grid is a pretty decent "battery", and depending on your tariff regime it might just operate like a battery with lower round trip efficiency but one with zero capital expenditure required, and that might be far more sensible.

Grid tied systems are designed to work in parallel with the grid, and they also require the grid frequency signal to operate. Off-grid systems can use grid to provide power at times but they work in series with the grid and so your power supply is more constricted unless you spend a lot more money on inverter capacity, often with two or more inverters operating in parallel. Personally, I think if you have the grid already available then going completely off-grid makes little sense.

There are quality 3-phase hybrid grid tied inverters (e.g. Fronius Gen24) which will work very well but these are not really DIY set ups and you'll need to use a commercially supplied compatible battery with such an inverter. That may or may not make financial sense, again it's hard to make sensible suggestions since we really do not know what your primary objective is.
 

brandnewb

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It's not actually clear from the various threads (which are quite confusing) what your actual objective is.

What is your primary motivation? Is it:
- to save money?
- to reduce carbon emissions?
- to stick your middle finger up at the energy utility?
- to have fun building stuff, but don't care about the costs?
- Other?
All of the above while caring about costs, hence the DIY aspect and to be prepared for when a mains power outage lasts longer than a couple of hours.
I really felt bad for what happened to the people in Texax last winter.
As @time2roll suggested since I plan to go off grid anyway in the future, or at least be able to, is to configure my system to do so from the start as to avoid having to replace components later down the line. I think that makes a lot of sense and I am going that route as long as I do not change my mind again based on possible future suggestions.
It might be the best thing is to make far better use of existing system via better management of discretionary loads.
I am not sure what that means ;(

Or you are better to engage a professional installer of solar PV and battery systems
I prefer learning how to do it my self so that things so that things like the current state my breaker panel is in do not happen again. Also it would be hard to find a professional to come by when in dire straights during a pandemic lock down. I never would have guessed I'd witness that one day.
There are quality 3-phase hybrid grid tied inverters (e.g. Fronius Gen24) which will work very well but these are not really DIY set ups and you'll need to use a commercially supplied compatible battery with such an inverter.
I strongly believe I should prevent vendor locking at al costs. Companies can go out of business and/or specialist components can become no longer available. I am not sure if going with LifePO4 cells is also a kind of component type locking but I guess it is not as one could always build a new battery bank with the then available components.
 

Hedges

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SMA has both single-phase and 3-phase grid-tie inverters. The single phase can be used on 2 lines or one line and one neutral of 3-phase.
They also have Sunny Island, which in Europe makes 220V 50 Hz and three can be configured for 220/380Y.
Larger battery inverters too, but Sunny Island + Sunny Boy could do this as grid-backup or off-grid.

These systems use frequency-shift to control output of GT inverters, so are compatible with others which also respond to that.
 

wattmatters

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I strongly believe I should prevent vendor locking at al costs.
Well unless you are planning to manufacture your own inverter, you'll be buying into one brand or another. That's hardly lock in.

I am not sure what that means ;(
It means you already have a large solar PV system and there's an opportunity to make better use of the energy it produces. You are already exporting a lot of it. Discretionary load is a load over which you have discretion on when you choose it to operate. Examples are hot water storage systems, space cooling and heating systems.

All of the above while caring about costs, hence the DIY aspect and to be prepared for when a mains power outage lasts longer than a couple of hours.
I really felt bad for what happened to the people in Texax last winter.
As @time2roll suggested since I plan to go off grid anyway in the future, or at least be able to, is to configure my system to do so from the start as to avoid having to replace components later down the line.
I dunno. You can be significantly self sufficient as well as have a system able to provide long term backup in the event of a grid outage.

The cost to get to 90+% self sufficiency as well as have good backup for grid outages is about half or less of that to get to 100% off-grid. The grid is really good for dealing with the peak surges in demand, while you can usually manage quite well without such peak demand loads during grid outage periods.

Going off grid without also dealing with the demand side is very costly.
 

brandnewb

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for all the ones nearby enough of me please see
 
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