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Luis Fernandes avatar image
Luis Fernandes asked

60kW Off Grid system with Quattro and Fronius +85 kW Storage

Hi Everyone,

I'm currently planning to build a off-grid solar system to be used in an agriculture farm. The system will be mostly used to power the water irrigation system and to will have to provide a mini-grid as we are several Kms away from the grid.

The system will be composed of the following components:

1-60kW Solar array with 450W mono panels

2-3x Fronius Eco 27 3 Phase Inverters

3-4x Quatro 15000VA (2xPh1, 1xPh2, 1xPh3)

4-85kW Battery Storage


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The main load of the system are the water pumps that source water from a borehole well and the distribution pumps that adds boost pressure. The majority of load will be exclusively operated during sunlit hours and the energy produced should be consumed directly from the output of the Fronius inverters while the remaining output will be used to slowly charge the batteries. The are a few small loads such as lights, a weather station and an alarm system that will be using the battery during the night as well as the residual consumption of the Quattros and Inverters.

When the main loads are not active the frequency shifter functionality should adapt the inverters output.

The reason for the post is to ask for comments on the setup, if anyone thinks there something I missed or any foreseen problems. Also I would like simplify the setup and use a single 3 Phase inverter, does Victron provide a compatibility matrix of brands and models that enable off-grid functionality with the Quattro.

Thanks a lot

MultiPlus Quattro Inverter Chargeroffgrid3 phase
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2 Answers
basil katakuzinos avatar image
basil katakuzinos answered ·

Look, i could be very wrong but i am yet to see an installation with a different amount of quattros on one phase. It is normally balanced (1 quattro on each phase or 2 quattro on each phase etc...).

I will list a few things to keep in mind when designing your system.

1) DC system needs to be identical to each quattro, make sure wiring is not longer or shorter to any inverter.

2) Your system only has AC Coupled solar (through the Fronius inverters) this means if your batteries die, you will need to connect a generator to start up the system again (As an AC Coupled system can not black start) . Maybe consider adding some DC solar using a Victron MPPT and a panel or two just to start up the system if it ever goes down or flat.

3) Make sure you follow the Factor 1 rule, Your AC Coupled solar (Fronius) can not exceed the max VA rating of your Victron inverters (This is not a problem with your current configuration but will be if you only have 3 Quattros and not 4).

Could you provide us with a list of all your loads and what their power requirements are so we can help size your system out?

Maybe give these a read

AC-coupled PV with Fronius PV Inverters [Victron Energy]

AC-coupling and the Factor 1.0 rule [Victron Energy]

Parallel, split- and three phase VE.Bus systems [Victron Energy]


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basil katakuzinos avatar image basil katakuzinos commented ·
Compatible Fronius inverters are listed in first link I attached.
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Luis Fernandes avatar image Luis Fernandes basil katakuzinos commented ·

Hi There,


Thanks for taking the time to reply, yes I'm aware of the Factor 1 rule hence the 4x quattro, as for the asymmetric number per phase, the question as been asked directly to Victron that confirm as long as they are the same models there is not a problem.

The scenario you described where the batteries completely run down, I did not consider but I was thinking to add a small backup generator for emergencies so thanks for the advice I think that will be essential now. Regarding the distance of the distribution and other pumps location we deliberately placed all the equipment in order not to exceed 200m from the furthest equipment.

In regards to size I have already done a detailed analysis and expect not to have a peak load of no more than 30kW and according to the estimates from this calculator:

https://ec.europa.eu/jrc/en/pvgis

we will be able to produce between 28 kW/h to 44kW/h during the summer months that are when we will have the system in use.

What I was interested as well was to explore other brands other than Fronius so that I could find a model that would allow me to replace the 3 inverters for a single one.

Thanks again.

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michelg avatar image michelg Luis Fernandes commented ·
Hi Luis, my 2 cents... Replacing 3 Fronius with only 1 unit (any other model / brand) could be a weak link, if it fails. If 1 Fronius fails, you still 2 others providing power to the pumps... With only 1 unbit, if it fails, everything goes down.


We had such issue due to a very strong storm with a near lightning strike which destroyed one of the units. Fortunately we had a backup one which was not physically connected to the cabling, and could manage to switch them.

Michel

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Luis Fernandes avatar image Luis Fernandes michelg commented ·

Good point, I was just looking at options to simplify and reduce some costs. But I agree this way we have more redundancy. Does anyone has experience of working with Solis inverters?

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shaneyake avatar image shaneyake Luis Fernandes commented ·

My 2 cents would be to run 3x 15kva quattro
Install a 2x RS 450/200 MPPTs so you have DC-PV. 2x would do 24kw.
MPPTS can handle the battery charging and then running once battery is full.
Then install a 3x Fronius inverters or one big 3phase SolarEdge inverter if you want a single inverter.

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Luis Fernandes avatar image Luis Fernandes shaneyake commented ·

Hi there, thanks for the comment, the point is that battery usage is really very low priority as we will only use quite small loads out of battery during the night. The primary objective of the system is really to drive the water pumps and irrigation system straight out of the inverter. The more power and for longer we get it, the more water we can pump and feed into the reservoirs. I'm building an arduino controller that based on the available power will activate the pumps but ideally is that we have the max power for the pumps and whatever small amount to charge the battery. As someone mentioned the drawback is that if the battery fully drains it needs external power to bring the system back up, so we will add a small backup generator for emergencies.

We have an 85kW battery just so that there is a good sink in case to allow the frequency shift to do its work and also because we got hold of a Tesla battery for a very small price.

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shaneyake avatar image shaneyake Luis Fernandes commented ·

Yes, I understand that you want to run the pumps but you can use the Quattros to do that, they can take the DC power from the MPPTs and push out AC to run the pumps without pulling power from the batteries. This won't reduce the amount of AC you have.
I don't really understand why you don't want to use the battery? If your goal is to maximize your total pumped water, you should be bring the battery down to 20% every night.

You can also use NodeRed on the larage firmware to control your pumps.
https://www.victronenergy.com/live/venus-os:large
This would be easier and more reliable than an Arduino.
Do your pumps have VFD's on them? Because you could vary their speed as you have more or less PV available. Also allows a soft start which you probably want. You can control the VFDs via NodeRed using Modbus.

Make sure to have a BMS, like the SimpBMS or an Orion BMS that has CAN coms to the GX.


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Luis Fernandes avatar image Luis Fernandes shaneyake commented ·
Hi there, thanks for the reply.


Ideally I don't use the battery too much as its really there to power the control equipment and security equipment overnight and for low solar production days. If I'm diverting 24kW as you suggested from the main system than that will not be enough for all the pumps, I really need all the solar array in a single system that will be directly used from the output of the inverters.

As for the NodeRed, thanks for the suggestion but the system as a lot more variables including about 10 multiparametric soil sensors, the input from weather station, leaf sensors, ph meters, etc. The concept is to use the Arduino/Raspi as integrators of a lot data coming from several sources and they are plugged into a decision algorithm that will turn things on and off. Additionally to the water pumps, there are the irrigations pumps, the fertigation pumps, etc so its a lot more complex than just driving the water pumps but I left out the details as I thought was out of scope for the discussion here.

Yes I have a SimpBMS setup that will be connected to the GX, and yes the pumps all have VFDs for both reasons you highlighted, to reduce the starting current plus the hammer effect at on/off and to be able to run them based on the solar output.



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shaneyake avatar image shaneyake Luis Fernandes commented ·

Hi,


Can you please explain what you mean? If you have DC or AC coupled PV it will power the loads. I don't understand what you mean by if you attached the PV to the Quattros you won't have enough power to run the pumps? If you are saying that you need more inverter capacity to run your loads, then that makes more sense however grid-tie inverters don't respond really quickly so I would be concerned that you would just trip the Quattros in that condition or if a cloud blows over.

This application is exactly what NodeRed is designed for. Aggregating data from many sources and making decisions. I wouldn't run this size system on the Cerbo but I do a lot of this kind of automation and have found NodeRed to be incredibly useful and flexible. Currently working on a Microgrid that is controlled with NodeRed, Over 30 inverters with Battery, 17x 9kw hot water heaters, Generator control, Building management systems for AC control, lots of load management and balancing algorithms.



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Luis Fernandes avatar image Luis Fernandes shaneyake commented ·
Does anyway has a list of compatible SolarEdge inverters ?
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shaneyake avatar image shaneyake Luis Fernandes commented ·

As far as I am aware all SolarEdage HDwave Inverters are compatible.
https://www.victronenergy.com/live/venus-os:gx_solaredge

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Luis Fernandes avatar image Luis Fernandes shaneyake commented ·
Great, thanks for that I will take a look.
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petajoule avatar image petajoule Luis Fernandes commented ·
There is no such thing as kW/h for production.

There is no such thing as kW for battery (if you meant capacity).

Sorry for smartassing, but it helps also you if you use the right units.

If you got hold of a Tesla 85kWh battery (what - some powerwalls or rest of a Model S?) for a good price it's nice, but then please add some fire precautions.


If your AC loads drop/vanish (fuse), pray for your L2 and L3 Quattros as there is no 1:1 rule anymore (15kVA versus 27kW), so one fuse failure will wreak havoc.

As for the Fronius replacement considerations, I wouldn't do it. In general, I would keep redundancy and the cooperation between the Quattros and Fronius inverters works really well. 27kWh is top of the line ofc.

How big are your loads? You probably know that a 27kW Inverter can start some 9kW motor, so take that into account. Probably make sure you turn on the loads sequentially.

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shaneyake avatar image shaneyake petajoule commented ·

If you have a fuse or inverter failure on one phase it isn't a huge deal. Nothing is going to blow up or get damaged. It will see a phase is lost and trip off. The 15kVA quattro can also take 25kw for a few seconds to minutes and be fine.

The loads will most likely draw all starting power from the quattros and not that PV inverters, once the load is running they will take over. Still has to be taken into consideration as you mentioned.




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Luis Fernandes avatar image Luis Fernandes petajoule commented ·

Hi there, thank you for your comments.


The 85kW reference was to the model of the tesla battery not any of its characteristics while the kW/h was the output used by the modeling software:

https://re.jrc.ec.europa.eu/pvg_tools/en/#PVP

As for the fire considerations, we are running the system in a climate control room with direct air cooling to the batteries but based on my literature research and our loads/peak loads and time they reach peak I don't think we will experience any issues. All the loads will be controlled so yes they will be initiated sequential and all they will be load controlled via VRFs that will also reduce the initial current draw from the motors. The same system will also control the load reduction so that it occurs smoothly and allows the Quattros to modulate the frequency. Obviously there are failure scenarios that we will attempt to avoid by using contactors and fuses. I'm fully aware of the metrics suggested by Victron( 1,5 kWp installed AC PV power requires 4.8 kWh of battery storage) however I dont have the financial resources to adhere to that at the moment, however the I intend to double the battery capacity when I manage to source more Tesla modules.

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basil katakuzinos avatar image
basil katakuzinos answered ·

Another concern is that you mentioned distribution pumps, how far away are they from where you want to install the system. It is quite hard to run power for long distances +-500 meters without moving into the territory of transformers and HV distribution which are beyond the scope of my knowledge.

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