Solar Battery Storage Solutions
A battery storage system may be used to enhance the self-consumption of a PV system, provide backup in the case of a grid failure, or both. Segen has systems for either application, with various sizes, using either lead-acid or lithium-ion batteries.
The main benefits of choosing solar storage include:
Increase your self-consumption. Promoting the benefits such as lowering their electricity bills and being more self-sufficient.
Save money. Promoting the benefits of self-consumption to protect against rising energy prices.
Protect against power cuts. Promoting that some products can function and provide energy during a power cut.
Have total visibility of your electricity use. Promoting the use of monitoring and overseeing consumption to see how much they save/could save.
Types of Storage systems
Operating totally “off the grid” requires a large capacity battery array capable of powering the property during periods of low irradiance in winter and an inverter capable of supplying the maximum load ever required at one time. This requires a significant investment in PV modules, inverters and especially batteries which cannot normally be justified if there is a good quality grid connection available at the property.
Typically a residential system will generate the most power during the day when household consumption is low. Without the ability to export surplus power the only options are to a) reduce the size of the PV system so that excess energy is minimised (this also reduces the usable energy) or b) store the energy until needed.
Reducing the size of the PV system by 50% would all but eliminate the surplus but would reduce the useful energy generated by 30%. In the same example there is about 8kWh of surplus energy which could be used to recharge a battery for use in the evenings. The use of a time switch on a washing machine and/or dishwasher can help to maximise the use of generated energy during the sunshine hours.
In properties where the grid reliability is low or ensuring maximum power availability is essential, then it may be appropriate to have a grid-backup system that can operate with no grid for a period of time. Adding a battery inverter, or a hybrid inverter, along with a battery makes it possible to combine the energy from the PV system with that from the stored battery to power at least the essential loads in the property. The size of the battery required depends on the rating of the essential loads to be driven from it at times when no solar power is available.
Shown to the right is a typical system layout for a grid-backup system, using a Solar PV inverter and a Battery Inverter, which gives maximum flexibility in the system design and can be retrofitted to an existing Solar PV system.
An AC coupled system provides the most flexibility in the design in terms of different battery and inverter sizes and backup capabilities and can be easily retrofitted to an existing solar PV system.
DC String Connected
The simplest type of self-consumption system is to add a DC battery controller into one of the strings of the PV system. This manages the charging and discharging of the battery in line with the solar PV energy available and the demands of the property.
Typically these types of system, like that available from Growatt, only support one value of current (single MPPT ), so for systems with strings on different roof faces, the most productive string should be utilised.’
Solar Edge DC Connected
A string connected system is not suitable for use with an SolarEdge system but SolarEdge and Tesla provide a combined solution that interfaces directly to the DC side of the SolarEdge inverter using a special interface box.
These types of systems monitor the energy exported to the grid and use any surplus energy to re-charge the battery during the day and control the amount of energy extracted from the battery during periods of lower generation than demand. This allows for PV and battery monitoring on one easy platform.
DC String Connected
Segen offer two AC coupled self-consumption systems. The SolarEdge AC Coupled System, and the SMA AC Coupled System, both partnered with Tesla.
This system is a great retrofit option as it is independent from an existing array on the AC side.
With thousands of PV arrays installed in the UK, there is a large potential retrofit market available for installers to target.