What Is Ac Coupled Battery Storage?
The connection of a battery energy storage system to a solar system via AC (alternating current) electricity is known as AC coupled storage.
AC Coupled Battery Storage System
The components that make up a AC Coupled Battery Storage System are:
- Solar panels
- Solar Inverter
- Payback meter
- Battery inverter/controller
- Off-grid cut-off switch
- The national grid
The direct current (DC) travels into the solar inverter as normal. Wind generators, for example, may be utilized in addition to solar energy.
The solar inverter is a key component as it changes the DC into AC electricity, making it compatible with batteries and the national grid. The electricity can now flow in both directions.
There are two meters installed as part of an AC coupled system: a normal production meter and what’s known as a ‘payback meter’.
The payback meter monitors any extra electricity that’s produced, for example on a sunny day, and stores it in the batteries.
So instead of this power being exported back to the grid, you can use it later on.
The battery inverter/controller regulates the charging and discharging of the batteries, and also manages any excess power that’s being sent back to the grid.
The batteries store the extra electricity for later use. You can choose between lead-acid, lithium-ion or nickel-cadmium batteries.
Related: What is a gel battery?
Off-grid cut-off switch
The off-grid cut-off switch is a safety measure that’s installed as part of an AC coupled system.
It ensures that, in the event of a power cut, your home is completely disconnected from the grid.
This prevents your solar panels from feeding electricity back into the grid, which could be dangerous for maintenance workers.
The national grid
The stored electricity can be used to power your home or business when there’s a power cut, or you can sell it back to the grid.
If the grid goes down, on certain systems, an automatic switch kicks in and switches to off-grid mode, allowing your solar panels to keep charging your batteries while also fully disconnecting from the grid.
Advantages Of AC Coupling A Solar Battery
- Easy to Retrofit
- Extremely Reliable
- Extremely Flexible
- Versatile Charging
AC coupled batteries are easy to retrofit as they don’t require any changes to be made to your existing solar system.
You simply need to install the necessary components (solar inverter, payback meter, battery inverter/controller, and batteries) and connect them to your existing solar panels and the national grid.
AC coupled systems are extremely reliable as they use tried-and-tested technology. The solar inverter, for example, is a key component that’s been used in solar systems for many years.
AC coupled systems are extremely flexible as they can be easily expanded or upgraded.
For example, if you want to add more batteries to your system, you simply need to purchase and install them.
AC coupled systems are versatile when it comes to charging, as they can be charged from the grid, solar panels, or wind generators.
This makes them ideal for homes and businesses that want to make the most of renewable energy.
Disadvantages Of AC Coupling A Solar Battery
- Power Supply
The fact that you need separate inverters for your solar panels and batteries (as well as a payback meter) can make AC coupled systems more expensive than other types of solar battery systems.
AC coupled systems are not as efficient as DC-coupled systems, as they lose some electricity during the conversion from DC to AC.
AC batteries are unsuitable as backup sources of power because they are not intended for off-grid use.
Since AC batteries lack transformers, they are unable to withstand the surge demands of many appliances.
Tesla AC Coupled Battery Storage
Tesla is fast becoming the go-to name when it comes to solar battery storage, and their AC coupled system is one of the most popular on the market.
The Tesla Powerwall is a home energy storage system that is completely integrated with an AC battery pack.
Its rechargeable lithium-ion battery pack stores electricity for solar self-consumption, time-based control, and backup.
The electrical connection between the Powerwall and your house or business is simple to set up.