Types of Off-Grid Solar Energy Storage System: DC-Coupled and AC-Coupled

Rooftop off-grid solar energy storage systems have had high-speed development all over the world as going off the grid represents no more expensive utility bills and a sudden power outage when the grid goes down.

But choosing the best off-grid solar system is a complicated job. Off-grid systems are built using either AC-coupling or DC-Coupling. Whether a system is AC or DC-coupled depends on the size of the system and the customer's requirements.

In this article, we will give further introduction on two types of off-grid solar system: AC-coupled systems and DC-coupled systems. 

AC or DC-coupling refers to the way how do solar panels connected to energy storage systems.

What are AC-coupled Off-grid Systems

AC-coupled off-grid solar system. Source: High Seasons Energy

In AC-coupled systems, solar inverter converts the DC power from solar panels to AC, which can directly fed into the load or the power grid.

The solar panels and batteries are controlled individually by separate inverters. These two modules, solar panel module and battery module, can operate independently without interference with each other.

What are DC-coupled Off-grid Systems

DC-coupled off-grid solar system. Source: High Seasons Energy

In DC-coupled off-grid systems, the DC power from solar panels need to be charged to the batteries by charge controller at first. Then the electricity flow is converted by inverter/charger to AC. The solar panels and batteries use the same inverter. 

Comparison between DC-coupled and AC-coupled systems

• Costs. DC-coupled systems are cheaper than AC-coupled systems. 

• Efficiency. The efficiency of DC system is higher than AC systems as the current only convert once. However, whether AC-coupled or DC-coupled is chose for PV system should be project specific. If the peak demand for electricity is in the daytime, AC-coupled systems are more suitable. Otherwise, the peak demand is in the evening,  the systems in AC-coupled generation sources are more recommended.

• Applicability & Flexiblity. DC-coupled systems are less flexible than AC-coupled systems. Installers have less flexibility than with an AC system, as the inverter needs to be located close to the battery.

           Please find more solar energy storage energy system here: 

           SVC solar inverter  

           SVC Lithium Battery Pack