AC COUPLED SYSTEMS

One of the greatest benefits of AC coupling is that it allows virtually any type of power generating device to be connected to the system, i.e. solar, wind, water, even gas or diesel powered generators. This provides
system designers the opportunity to take advantage of all the resources available to them at a given location.It also allows for easy system expansion by providing a simple solution for integrating future power sources.
The Sunny Island itself has also been designed for easy expansion. The power provided by the Sunny Island can be increased simply be adding an additional Sunny Island inverter in parallel. AC coupling provides
easy system expansion and ensures that over the long term, the system will continue to serve the needs of its users safely and reliably. 

AC Coupling
The AC coupling of off-grid PV systems is becoming more and more popular the world over. AC coupling greatly simplifies system expansion, extends the life of the batteries by reducing the cycling of the battery bank and increases the overall efficiency of daytime power usage. SMA’s Sunny Island series of inverters was specifically designed for AC coupled applications and can be easily connected in parallel to increase the overall capacity of an off-grid system.

Why AC Coupling?
One of the important factors in off-grid PV system design is making sure that the system can be added onto in the future. In other words, how easily can the system be expanded to accommodate increases in demand for power? AC coupling provides an elegant solution to this issue by allowing all of the power generating devices to be connected to the system via a common AC bus. As the demand for power increases, new sources of power can be installed and connected to the AC bus instantly increasing the overall capacity of the system.

The Concept
In remote off-grid power scenarios, a Sunny Island connected to a bank of batteries acts as the source of AC power, or the “AC grid” for that location. All power generation devices as well as AC loads are connected together on the AC side of the inverter. During the day, when sun production is high and load use is low, the Sunny Island uses the sun power to charge the batteries. Once the batteries are full, any daytime loads are powered directly from the power generating devices on the AC bus. This eliminates the need for the power for the loads to be run through the batteries, which reduces the number of charge cycles and extends the overall life of the batteries. At night, when power production is low and load use is high, the Sunny Island provides power from the battery bank. In the morning, the batteries are recharged and the cycle begins anew.