diy solar

diy solar

All grid tied inverters in UK/EU/US/AUS limited to 5.5kW?

faringdon

New Member
Joined
Oct 2, 2021
Messages
8
Hi,
Are all grid tied inverters for use in UK/EU/US/AUS all limited to 5.5kW?
If so , do you know why?
Also, is there a limit on the amount of electrical energy you are allowed to export to the grid each day?

If so, then what happens when your battery is full, and your house load is low, and your panels are generating, and your already above the maximum amount of export allowable?

That is the grid tied inverters going from solar panels to mains, and from battery to mains.
 
Are all grid tied inverters for use in UK/EU/US/AUS all limited to 5.5kW?
If so , do you know why?
I am not aware of any such universal restrictions. However, I have heard of individual localities or utilities limiting system size.

Why? The main technical reason comes down to: Can the grid take more? I know of at least one case that a person was limited because the transformer feeding the house was too small...at least that what they were told. The cynical part of me says they limit it because they don't want you selling power.
Also, is there a limit on the amount of electrical energy you are allowed to export to the grid each day?
Again, I do not know of any nation wide limit, but some utilities do limit the system size in order to limit what can go onto the grid. However, I have not heard of any type of 'per day' limit.

The closest thing to a per-day limit that I know of is that many net-metering programs will only let your bill go to zero dollars. Any power you put on the grid above what it takes to get to zero cost is given to them for free. (They will never pay you).



 
I have seen listings for 6k and announcements for upcoming 8k and 12k units.

Plus many of the MPP and Growatts let you sync up 9 of their units for MOAR POWAH!!!
 
Hi,
Are all grid tied inverters for use in UK/EU/US/AUS all limited to 5.5kW?
If so , do you know why?
Also, is there a limit on the amount of electrical energy you are allowed to export to the grid each day?

If so, then what happens when your battery is full, and your house load is low, and your panels are generating, and your already above the maximum amount of export allowable?

That is the grid tied inverters going from solar panels to mains, and from battery to mains.

Here in the EU in some countries you can put up to 30-50kW solar system into a roof.
And you export as much as you can. No limitation.
Of course first you have to get the permit from utility (transformer in your street can handle it).
The EU loves grid-tie (a bit too much)


I have seen listings for 6k and announcements for upcoming 8k and 12k units.

Plus many of the MPP and Growatts let you sync up 9 of their units for MOAR POWAH!!!
Deye (Sol-Ark too?) allows 16 unit to be paralleled :)
 
Thanks
The following...

....seems to say that "solar export" to grid is limited to 5kw.

But it makes you wonder what a battery inverter is limited to.....for example, presumably you can top a 20kwh battery up with a 5kw solar inerter..and then use the battery inverter to feed 10kwh to the grid over a day?

So are "household battery inverters" limited in power? It seems that "solar inverters" are indeed limited to 5kw
 
I see a problem with grid-tied solar and that is voltage regulation when there is a lot of power coming in and a cloud comes over you lose that power and the power company's generators cannot react fast enough to keep the voltage up. Large generators need time to adjust to the power needed they cannot react in seconds like solar can.
 
In the U.S., some years ago we were limited to 10kW export for most residential installations. Larger commercial systems could be installed, with more expensive review.
We had to document consumption to justify system size, but could do 5kW without because it was decided that would supply a typical home's average power.

The limit many people run into is "120% rule". You aren't allowed to run more current through a breaker panel busbar (or wire) than its ampacity rating. Breaker and fuse ratings can't be higher than conductor ampacity. Maximum continuous current through breaker or fuse is 80% of rating (to avoid tripping.) Most breaker panels have main breaker rating equal to busbar rating, which wouldn't allow any PV amperage at all, if they added together. But, we are allowed main breaker plus PV breaker to be 20% higher than busbar rating - and, PV breaker must be at far end of busbar, so current doesn't add but rather subtracts.

A 200A busbar breaker panel, with 200A main breaker is allowed 40A PV breaker. At 80% of 40A, 32A is allowed. 32A x 240V = 7680W. So there are a lot of 7680W (or 7700W) inverters. Half that for 100A panel with 20A PV breaker, 3800W.

GT PV has to limit current to what is allowed. If fed through a separate battery inverter with relay, must be within relay limits.
Typically inverter will have maximum current capability (or programmed limit) which complies with export to grid limit.
Some markets set the limit to zero, like Hawaii once excessive PV installations were there, so zero-export systems were made that measure power feed at utility connection, adjust inverter output to prevent export while supplying household loads.
Same can be used to limit to say 5kW export from 10kW of inverters, allowing fully PV output if household consume the balance but limiting when necessary.

With my Sunny Island (battery inverter), it has 56A max current through its relay, so I have to limit PV on the circuit to 6.7 kW per Sunny Island (I have four, 2s2p). If it was only off-grid, never backfeeding, I could have 12kW of PV managed by the battery inverter. But on-grid, it has no way to curtail production, because frequency-shift can only be performed off-grid not on-grid. A separate system commanding power from PV inverter would be needed.
 
I have a Solar edge 7600 watt system but have seen some much larger systems going up recently based on the size of their array. Pennsylvania allows net metering and the PUC dropped the 200% metering cap in 2016.
 
I see a problem with grid-tied solar and that is voltage regulation when there is a lot of power coming in and a cloud comes over you lose that power and the power company's generators cannot react fast enough to keep the voltage up. Large generators need time to adjust to the power needed they cannot react in seconds like solar can.

Real problem. When there was an eclipse in Germany they prepared a lot of extra turbines to make the lost power.
Here in Hungary one time we had to throttle down the nuclear power plant (and that hates it) because there was too much solar production.
Grid-tie can not make stable power ... the grid to function correctly it needs a lot of big_batteries/gigapacks to balance out the grid-tie production and load alterations.
 
Grid-tie can not make stable power ... the grid to function correctly it needs a lot of big_batteries/gigapacks to balance out the grid-tie production and load alterations.
This is an excellent point.
If we are to have lots of grid tied solar/batteries, we are going to need thousands of mega big battery stations first.
And i cant see the electricity companys swinging for that.
 
This is an excellent point.
If we are to have lots of grid tied solar/batteries, we are going to need thousands of mega big battery stations first.
And i cant see the electricity companys swinging for that.
There are grid batteries being built, some of them amazingly large. However, everything built along with everything planned isn't even a drop in the bucket compared to what is needed.

I suspect this is going to remain true for the foreseeable future. I even suspect that it won't happen till there are new chemistries other than lithium-based chemistries are commercialized at a large scale. There are a few things like flow batteries that look promising....but they have a long way to go to get to the scale needed.
 
This is an excellent point.
If we are to have lots of grid tied solar/batteries, we are going to need thousands of mega big battery stations first.
And i cant see the electricity companys swinging for that.

There are some really big big batteries under development nowadays. Even GWh battery size.
But I think the real solution is to make a lot of smaller batteries.
Locally generated and locally stored power is the best. Nothing beats it.

So I think it is better if every substation has a 50-100 MWh battery with 20-40 MW inverter.
First it is not centralized. A centralized big battery is a SPoF (Single Point of Failure).
Second it can work as a local UPS. Here is a town part where a substation has a 2 MWh battery with an 500kW inverter (in a container). And it can separate the substation from grid, make a microgrid to the homes and give power even it does not get from the main line.
It is exactly what we do, only bigger. And frankly, it is the utility company's job to do it.
 
There are some really big big batteries under development nowadays. Even GWh battery size.
But I think the real solution is to make a lot of smaller batteries.
Locally generated and locally stored power is the best. Nothing beats it.

So I think it is better if every substation has a 50-100 MWh battery with 20-40 MW inverter.
First it is not centralized. A centralized big battery is a SPoF (Single Point of Failure).
Second it can work as a local UPS. Here is a town part where a substation has a 2 MWh battery with an 500kW inverter (in a container). And it can separate the substation from grid, make a microgrid to the homes and give power even it does not get from the main line.
It is exactly what we do, only bigger. And frankly, it is the utility company's job to do it.
It is interesting. Others argue that we need more inter-state grid capability so a drop in renewable energy in one region can be compensated for by another region.

The end result will probably be some combination of both local and nationwide planning.... but that is little better than a guess on my part....Particularly since it will end up being the (*^&^ politicians making many of the critical decisions..

Whether the installs are lots of smaller battery systems or fewer huge installations.... the magnitude of what is needed is huge.
 
Rotating mass like hydro generators should be a big help in stabilizing grid. Pumped hydro makes that a battery.
Even if efficiency isn't great, very useful if it lets us reach 100% and higher PV (and wind).

There was talk of compressed air storage in salt caverns, but air heating/cooling was said to impact it (the guy promoting it wanted to sell natural gas to heat it back up.)
 
It is interesting. Others argue that we need more inter-state grid capability so a drop in renewable energy in one region can be compensated for by another region.
That is a good thing also.
If you remember I did a post about the incident when the European grid separated in two half and both parts almost collapsed (because a transfer station overloaded in the middle ... north imported a lot from south and that stopped suddenly)
So it is good and bad in the same time :) Here it was a SPoF that failed and hit hard.


The end result will probably be some combination of both local and nationwide planning.... but that is little better than a guess on my part....Particularly since it will end up being the (*^&^ politicians making many of the critical decisions..

Whether the installs are lots of smaller battery systems or fewer huge installations.... the magnitude of what is needed is huge.

The joke is that it can be done in small steps. A little battery plant here, an another there ...
They do not need to make a gigapack.

And I forgot the third big point: centralized command. The utility can control the function of these battery packs and inverters.
Huge cloud above half the country? No problem, automatic system sets nearby inverters to produce to the grid.
Full sunny day with cold wind making huge solar peak production? No problem, automatic system sets nearby inverters to store excess power into the battery pack.

This is the main problem with the grid-tie inverters.
Utility does not have any control over them.
There is too much power and PV systems overproduce? They can not do anything to prevent it.
Need to stop gas turbines, coal, and nuclear at last.
 
Rotating mass like hydro generators should be a big help in stabilizing grid. Pumped hydro makes that a battery.
Even if efficiency isn't great, very useful if it lets us reach 100% and higher PV (and wind).

There was talk of compressed air storage in salt caverns, but air heating/cooling was said to impact it (the guy promoting it wanted to sell natural gas to heat it back up.)

Rotating mass is good to overcome the inrush.
But it is bad also because slow to respond. An inverter + battery can correct in ms.
More the mass, slower the response. So it is good for base power plants. But fast reaction power plants need fast response.
 
This is the main problem with the grid-tie inverters.
Utility does not have any control over them.
There is too much power and PV systems overproduce? They can not do anything to prevent it.
Need to stop gas turbines, coal, and nuclear at last.
A while back I saw an article that talked about requiring the utility to control personal solar production but have heard nothing since.... (but me not hearing means very little).

The biggest technical hurdle with allowing utility control would be coming up with the standard to do it. Getting all of the cats herded into the same standard will not be easy.....Then add to that the probability that each country will end up with a different standard makes it even more difficult.

If they ever do start doing something, it should be targeted at what is going onto the grid, not what is produced.
 
A while back I saw an article that talked about requiring the utility to control personal solar production but have heard nothing since.... (but me not hearing means very little).

The biggest technical hurdle with allowing utility control would be coming up with the standard to do it. Getting all of the cats herded into the same standard will not be easy.....Then add to that the probability that each country will end up with a different standard makes it even more difficult.

If they ever do start doing something, it should be targeted at what is going onto the grid, not what is produced.

Yep, there was a thread about an Australian system I think.
The other big problem with that was: power is lost (when grid-tie inverters shut down or hold back production).
With big batteries power is stored (and used).
 
The other big problem with that was: power is lost (when grid-tie inverters shut down or hold back production).
With big batteries power is stored (and used).
That is why I said the control should be focused on what goes on the grid, not what is produced. If the personal system has storage capacity, it can move from supplying the grid to charging the storage.
 
Back
Top