Hello folks.
I am looking at setting up solar pv system with off grid capability in extended downtime at our home in New Zealand that is grid tied. We have 2 phases at home but 95% of the load is on single phase currently and I am hoping I can keep the setup on single phase for solar PV as well. I don't care about the remaining 5% load on 2nd phase, and it using grid power when needed. We are currently consuming on average 40kWh per day.
Gear I am looking at purchasing
- 1 x 8kW Fronius Single Phase inverter
- 1 x 5kW Fronius Single Phase inverter
- 15kW of 38 x Trina 390W Vertex S All Black modules/panel
- 1 x Victron Multiplus II 48/10000/ 140-100
- 1 x Victron Cerbo GX
- 1 x 25kWH 48V LifePo4 battery system ( 5 x 5kWH batteries stacked together)
The plan is to put between 10kW to 11kW of panels on North West to capture afternoon and evening sun as this will generate the most amount of solar energy and put between 4kW to 5kW of panels on South East to capture early morning to late morning sun.
What I want to achieve
- Ability to power home during extended grid downtime capability where if grid is down for a week for e.g and when the battery storage runs out eventually, the sun continues to provide AC power to home while it's there in the sky or charge the battery and battery continues to provide AC power to running load at same time.
- Ability to run our 14kW peak power ducted aircon overnight on battery and in event of a grid outage. Aircon usually uses between 5kWh to 7kWH. I will be gradually adding more battery storage every year so I understand that for now 25kWH of battery storage will not last me days or even hours.
- Ability to export power back to grid while grid is online. I understand power cannot be sent back to grid when it's down for safety reasons.
- I don't want to setup anything like critical load circuit? I am happy to manually switch off things around the house that we do not need running in the event of grid outage and to conserve battery power.
Is the above hardware I am looking at purchasing through an electrician/pv installer, correct? Is there $ that can be saved? For e.g, Is purchasing 2 x Multiplus II 5VA 48/5000/70-50 better than a single Multiplus II 48/10000/ 140-100 if it can work in my single phase environment and be parallel connected together? Multiplus II 5VA 48/5000/70-50 is $3k each in NZ so $6k total while Multiplus II 48/10000/ 140-100 is $7k for 1 unit. Is Quattro the better solution here? I will never plug a diesel generator as we live in suburbia so due to noise it is out of the equation.
Is it also possible to use the same 15kW PV array that will be connected between the 2 x Fronius AC inverters to bunch of solar chargers/mppt at same time which then connect to the 48V battery directly so I have best of both AC coupled and DC coupled world?
Thanks