An issue that has been discussed among the photovoltaic professionals is that of the battery voltage in the residential storage systems.
Is there a better configuration than others?
Basically there are three type of systems:
» those in low Voltage, about 48V;
» those said in “high Voltage”, 400V approximately;
» high voltage modular systems (from 250 to more than 500V). The latter are realized by composing several battery packs, like in Lego® bricks, until the wanted capacity is reached.
In addition to assessing the type of battery, we need to consider the complete system, including the electronic power that performs the coupling with the network or with the build system: you can think that the greater economy and efficiency is obtained by connecting the battery to the DC side of a standard photovoltaic inverter and using the DC/DC converter input stage.
With this configuration, the most suitable battery voltage would be starting from 1/3 – 1/4 of the inverter DC bus voltage and the system would see an economy as regards installation costs (cables of reduced sections and switches).
The advantageous battery
The producers of residential storage systems consider advantageous the use of that kind of cells that are spreading also for other use, especially in the car industry, that makes the price competitive in terms of €/kWh.
This leads to the use of cells with a capacity in the range from 40-60Ah and voltages of about 48V.
High voltage systems contain lower voltage batteries (around 100V) and a DC/DC converter that raises the voltage up to the rated voltage.
Compared to this type of configuration, high voltage modular systems do not need an additional converter and potentially have a higher efficiency.
Battery standard configuration and conversion system
It should be pointed out that today the standard configuration battery and conversion system has not yet been consolidated: 48V batteries have economic advantages, those in high voltage have potentially higher return.
ABB: REACT 2
“All-in-one” storage solution, inverter with integrated high-voltage (200V) lithium-ion battery for long life.
- Ideal for new installations and retrofits
- Power ratings 3.6 and 5.0 kW
- Storage capacity ranging from 4 to 12 kWh
- Flexible design with the possibility of integration at any time
Fronius, Fronius, Inverters, Storage
Fronius Symo Hybrid
Fronius has extended its range of three-phase inverter MPPT replacing an entrance with a battery charger so you can put a lithium iron phosphate with a capacity ranging from 3.6 to 9.6 kWh can also be used in case of blackuot.
Remain unchanged all the control functions and standard monitoring Snapinverter Fronius.
The result: the sun by day, the sun at night and the sun during the blackout.SKU: n/a
Inverters, Kostal, Kostal, Storage
Kostal PLENTICORE plus: 4.2/5.5/7.0/8.5/10 kW
PLENTICORE plus the new hybrid inverter from Kostal, designed for photovoltaic storage ideal for both new and existing installations.
- 3 MPPT to configure almost all types of roof
- compatible with different high voltage battery
- easy configuration
- EEBus and Sunspec for the Smart Home connection
- available in 5 power classes
AC side storage system, Inverters SMA, SMA, SMA, Storage
SMA Sunny Boy Storage
Inverter designed for high-voltage batteries for domestic use. Sunny Boy Storage allows economic integration, simple and flexible storage solutions for photovoltaic systems both new and existing.
- 97% efficiency
- WLAN and intuitive web interface
- Compatible with high-voltage lithium-ion batteries
- For new and existing systems
Inverter residential systems, Inverters SMA, SMA, SMA, Storage
SMA Sunny Boy Storage 3.7/5.0/6.0
The first battery inverter with a multistring battery connection. Ideal for grid-connected systems.
- Connect up to three high-voltage batteries
- 10-year warranty
- The integrated service package SMA Smart Connected for automated monitoring of battery inverters
- Fully automatic backup function for supplying electricity to the complete home (optional)
SolarEdge: energy meter with Modbus Connection
The SolarEdge counter is used for battery integration and production/consumption reading for limiting input.
- High accuracy meter readings for production/consumption monitoring
- Small and easy to install – fits in standard electrical panel
- Available: SE-WND-3Y400-MB-K2
SolarEdge: StorEdge AC Coupled HD-Wave SE3680H-SE5000H
StorEdge AC Coupled Single Phase Inverter with HD-Wave Technology
The main features are:SKU: n/a
DC side storage system, SolarEdge, Storage
SolarEdge: StorEdge system DC coupled solution
The SolarEdge StorEdge DC coupled solution allows to optimize the efficiency of the accumulation system.
The solution involves the use of a single inverter both for photovoltaic and storage systems, of a special interface and of an high-voltage battery compatible with LG Chem.
1] Power from 2.2 to 6 kW
2] StorEdge can be integrated into existing SolarEdge systems
3] Compatible Batteries LG Chem RESU7H SEG and RESU10H SEGSKU: n/a