This was planned and deliberate. This system is called a Micro grid because of how it works. The Fronius is a Grid tie string inverter and exceptionally good at converting Solar to AC, highly efficient at that. All Grid tie inverters must always terminate the generation process when the grid fails, no exceptions.
So now we have a problem in that when a blackout happens, we lose the Solar just when we could use it the most, well daytime anyhow.
Building a Micro grid solves this issue. So the battery inverter charger, Quattro in my case, builds a grid from the battery, UPS function really, and creates the AC grid from internal clock at 50Hz.
Connecting the Fronius output to the Quattro AC1 output, yes to the Quattro output, provides the grid to allow the Fronius to operate even when the Utility grid is down, a Micro grid is formed. So now we have Solar with high efficiency providing energy even during blackouts and carrying the AC loads directly. The Quattro only adds from battery whatever the Solar and Fronius are not able to provide.
For my system, most days from around 8 to 5 in the afternoon, all my loads and most of my battery charging is done by the Fronius. And this is true on cloudy days as well, with few exceptions.
In actual fact, The Fronius on the Quattro output does not count. Only The Quattro input is considered , and it has no dual redundant contactors, therefore the Ziehl is required.
Now I wonder if CoCT would sign such off, as they have not that I’m aware, stand to be corrected for it opens a hell of a lot of doors!
Problem is, they are not as “free to do as they wish” with NERSA and Gov watching them like hawks, bloody politics.
If CoCT can do what they want, we would all be paying the <R200 connection fee, have a bi-directional meter for free, with a deal to sell power back to them that makes sense so that they can shave off another LS level daytime, if the weather holds, dams are full and Koeberg is sorted, to attract more investments as a City.
And I would bet, if that was so, that they would encourage people to have more battery banks too, to smooth over weather and such, shave off the peak loads some more … making it worthwhile for thousands of homeowners and businesses, to do what you did.
But the Constitution currently prevents that from happening.
Good question. Always remember, energy sales are the main income stream for any council. All they are doing, and will be doing, is to protect that. When you start to not buy from them, they will add a tax in the form of fixed fee to make up what you don’t buy.
I’m quite sure it is fine to put a Fronius on the output of the Quattro, but I’m not actually sure the Quattro is on the list!
I’ve also been debating getting a Fronius on my MPII instead of another MPPT when I upgrade to additional PV (somewhere in the future). I think it is probably a good idea for the energy you intend to use during the day, and effectively charging batteries off the MPPTs during the day and using them at night then.
The Quattro’s are not on the list, for sure. But with the Ziehl that is on the list it does not matter. Put the Ziehl in front of the Quattro.
Also, the Victron’s are bi-directional energy devices. So with the Fronius on the output of a Victron, that will charge the batteries, and the Victron can assist with Utility mains at the same time as well to allow faster charging, for magic….
One thing that @Sarel.Wagner implies, but doesn’t say outright: the Fronius (any grid-tied inverter really) is much better (more efficient) at generating AC than any Quattro / Multiplus + MPPT system could ever be.
I assume he uses most of the power in the day, i.e. immediately once generated, so he actually wanted a Fronius and then needed something to keep it going during load-shedding. The Victron-Fronius integration is top-notch so it’s a no-brainer.
If you used most of your generated power later, i.e. into a battery and then out again, the Victron DC MPPTs are much more efficient at that, and using a Fronius would waste a lot of power. If Time-of-Use (TOU) tariffs become more common I think a lot of people would time-shift their daytime generation into batteries to use during the evening peak. DC-coupled MPPTs would be best at that, assuming you have low daytime load otherwise.
So yes, people can want a not-Victron and then happily add a Victron for another reason
Correct indeed, I did describe that, but still, right you are. My system is effectively off grid, but still Utility grid connected. As I am typing this, my Main breaker is switched off and has been for some time now.
I have described, at great length, on another forum, the principles of my system, and the time warping I am doing. Pffhttttt to ToU tariffs…. as I wont be partaking in that no more.
Most of my heavy consumption was moved to daytime use, family trained, well except for me…. Heavy loads are scheduled, automatically in the case of battery charging and water heating, to Solar times only. All other uses are manually taken care of during Solar times. In case of low Solar yield, the battery is used, and there are normally enough Solar to slowly recharge batteries.
You can say that I love blackouts so much, I create my own by tripping the Main breaker manually, all the time
One think to keep top of mind with a Victron Fronius Micro grid tho, and that is black start ability, or rather the lack thereof….
Doesn’t matter that it is on the list. NRS097-2-1 requires at least one active anti-islanding measure, and the Ziehl only does passive. The Quattro does have active anti-islanding, but the combination of the two was not tested for NRS097-2-1 (it was tested for VDE-AR-N-4105 though, Germany, so there is no reason it shouldn’t pass with flying colours). For that reason I suspect CoCT will reject such a setup.
But also, the Fronius is the conversion interface between the embedded generator (the PV modules) and the grid, so in Cape Town that’s where you’d put the focus. The Quattro is just a UPS.
Edit: Just to clarify, @Sarel.Wagner, you are perfectly correct that the input of the Quattro is what really matters, and in a perfect world, that’s what you’d sign off… but there was one guy on the old forum (actually also lives not far from me, older gentlemen into aviation) who managed to sign things off by installing approved PV-inverters on the output of his Quattro.
Unless you have the black-start capability mentioned, then the Quattro could do the same via ESS.
I suppose if the Quattro is truly running as a UPS only, i.e. not using ESS, then the extra DC-coupled MPPT wouldn’t matter. And then you don’t even need the Ziehl.
Does PowerAssist also require anti-islanding or only ESS?
Only ESS. In fact, the way it works can be gleaned from the documentation, when you consider there is a minimum amperage below which PowerAssist cannot work. They make sure energy feed-in is disabled high up…
But what if you have an MPPT as well? Then it isn’t different from an MPII system with an MPPT and there the MPII has to be on the list because it is the conversion device?
Yeah, but the MPPTs are still more efficient at charging batteries, so the balance for me is to size the Fronius compared to my daytime consumption and the MPPTs compared to my nighttime consumption.
The last bit of PV I added was also AC-coupled. Same reason. I have so many day-time loads that I’m using only the top 1kWh in the battery, while 15kWh-20kWh (depending on season) goes directly to loads during the day. Doing this with a DC-coupled setup is very inefficient.
How did I end up here? Easy enough. I moved house, took all the old equipment along with the move, and the new place has a swiming pool, with an extra 4kWh per day required for that pump…
So the solution was to put up MORE PV pointing west, put that on a PV-inverter, and move the pool pump to the afternoon (so the water heating panels on the roof can also work better).
The Fronius, or even the ABB/Fimer that I’ve got, are quite excellent in efficiency, and the MPPT often tracks a little faster too.
Just for completeness, the reason the MPPT tracks faster isn’t because anything is wrong with the solar chargers. It’s merely a condition that happens when the batteries are full and your solar chargers go into voltage-controlled mode (rather than MPP mode). When a large load starts, it takes time for the inverter to spool up, then the battery voltage drops, then the solar charger wakes up and starts scanning… etc etc. With the PV-inverter, it’s immediate.
For the Fronius, you can over dimension the array by quite some margin. Their calculator will guide you. Even with the better DC-DC efficiency, the cost of more MPPTs and panels compared to just more panels and lesser efficiency of battery charging from AC side, it should work out less expensive to just add panels to the Fronius and not worry about the efficiency.
Just have one black start DC coupled MPPT with a few panels, I used 6 panels, to have black start and break the deadlock. If you have a generator or Utility grid, that can be used for black start as well.
In my case, I wanted automated recovery under any conditions, hence my setup. Completely hands off recovery, not dependent on either Utility or genset.
th Ziehl is on the CoCT approved list, so the answer should be, it will pass.
Then both of them needs paperwork (Multi and PV-inverter).