When solar power is absorbed into your panels, it is in the form of a Direct Current (DC). In a standard (i.e. DC coupled) battery-based PV system, the DC energy is sent through a charge controller to the battery, where it’s stored as DC. It’s then drawn from the battery through a battery-based inverter as AC (Alternating Current) energy.
However, in an AC coupled system, the DC power is converted to AC by a batteryless inverter – with energy then going to your power requirements (as AC), the grid as AC (if it’s attached to the grid/the grid is online), or to the battery-based inverter to convert it to DC for storage.
If you have a system which is attached to the grid, (grid-tie system), it will shut down when the grid goes down (i.e. a blackout). It’s a common misconception that a ‘normal’ solar power system will protect you from blackouts. However, if you utilise micro-grid AC Coupling your grid-tie system will work with a battery backup system, and it can even be charged if the grid is down. As such, it’s a great option for those who are looking to add battery backup to a grid-tied PV solar system.
Apart from the above, another of the main benefits of AC coupled solar systems is that you’re able to retroactively implement battery backup to an on-grid solar system without having to change any wiring. They’re also more efficient than a battery based inverter. Downsides are that they are more expensive, and more complicated to design and program.
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