I need to build a system which will power up small company.
I have to move to a new building were I can get only 16kW from the grid (around 23A/phase) for now. (80kW in 14-16 months). Our constan consumption (from 6 to 15 - working hours) is around 15kW but we have a lot of energy consumption peaks up to 30-35kW. I is from 90-120 kWh daily.
I was thinking about:
3x Multiplus 48/8000, 32kWh battery, 10kW PV instaltion with Fronius or …? something that works perfectly with freqency shifting - to reduce PV production when there is no consumption and battery if full. (I am not allowed grid feed-in)
I dont know which solution will be better. In first solution I have AC directly from inverter, but I don’t know if frequency shifting is working “on-grid” and what is the respons time when it works. What happens with this extra power before inverter will lower down the production. It goes to battery, what if the battery is full allredy? or the second option will work better, but there Multiplus will have to constantly convert 48v to 230v.
In cloudy days (winter) I want to charge the battery during the night from the grid to have energy to cover consumption above 23A/phase.
How cerbo is controlling production on fronius? What do you mean by small injection? Is there a way to avoid this small injection? Redirect to battery?
I think two elements (3xMultiplus and Fronius) in the system will be enough. Are there any benefits of using DC MPPT charger?
I want to oversize the AC inverter. I want to take Fronius 20kW and connect 10kW of panels. Later when I will be able to export to grid I will add 10kW more.
I hope this is a good idea.
Cerbo typically would control the Fronius by a network data connection, In your case, with High AC peaks on the load, AC coupled (using the Fronius grid tie inverters on AC out) would be the best way to go.
Any ‘small injection’ to the grid can be avoided by setting the grid setpoint at ~500W input, but this would depend to an extent on the largest load that would switch off suddenly.
Do not AC-couple PV inverters unless export is allowed.
Install three Victron MultiPlus-II 48/8000 inverters in power assist mode with the loads on AC out.
To handle 30–35 kW peaks within your 16 kW grid limit, increase battery capacity to 48–52 kWh. The system will use grid power for your typical 15 kW load and seamlessly supply the extra 14–19 kW from the battery during peaks.
This capacity provides around 90 minutes of sustained 35 kW demand or multiple shorter surges with recovery time, ensuring uninterrupted operation. Night grid charging keeps the battery full for the next day. The setup prevents grid trips, supports full production, and scales easily to your planned 80 kW grid upgrade—requiring only configuration changes, not hardware swaps.
When adding solar, you can grid-connect a 3-phase Fronius inverter and use Victron ESS to charge the battery from excess solar. MPPT DC-DC charging is ideal for storing energy for night use, while AC-coupled systems are best for covering daytime loads.
If installing solar immediately, consider a grid tied 3-phase Fronius with zero-export settings, using the Victron inverters in power assist for peak coverage.
When you turn off a load the PV inverters need some time to adjust (seconds usually, depending on the load). Current takes the path of least resistance so probably some will go to the grid.
Yes, more efficiency when charging the battery and less grid injection when adjusting power.
[quote=“Owen, post:5, topic:42910, username:owenb79”]
If installing solar immediately, consider a grid tied 3-phase Fronius with zero-export settings, using the Victron inverters in power assist for peak coverage.
[/quote] - This is exactly what I want to do.
In this case Fornius goes between “grid” and Multiplus (+fromius Smart Meter on grid side so PV inverter will know when the grid feed-in starts)
or
it goest between Multiplus and “loads”, and the Victron system (Multiplus+cerbo+victron smart meter) tells the Fronius inverter to lower down the production to avoid grid feed-in
