There's a wide range of system solutions for photovoltaics plus energy storage available on the market. They're often referred to as photovoltaic storage systems, which primarily consist of photovoltaic panels, inverters, energy storage batteries, and loads. Currently, there are several ways to establish photovoltaic storage systems. However, in all cases, energy needs to converge on a certain point. Mainly, there are two types of systems in place: Direct Current ('DC') Coupling and Alternating Current ('AC') Coupling.

What is AC coupled ?

 In AC-coupled systems, there are two inverters at work: the photovoltaic inverter and the energy storage inverter. Photovoltaic inverter connects the photovoltaic components, converting their produced energy into an AC output, whereas the energy storage inverter connects to the batteries, releasing their stored energy into the system for use.

AC couple inverter principle

AC Coupling Inverter introduction

In simple terms, the input of the device is AC power, and the output can be either AC or DC.

Applicable place:

AC Coupled Inverter primarily used in various regions with power shortages such as islands, mines, farms, and remote areas.

work mode:

 AC coupled inverter can switch work states, operating in both grid-tied and off-grid modes.

safety protection:

AC coupled inverter effectively prevent the risk of high Direct Current voltage at the battery and photovoltaic side, thereby ensuring the safety of the entire electrical system.

increase of efficiency:

If the user has more load during the day and less at night, The photovoltaic modules directly supply power to the load through the grid-connected inverter, and the efficiency can reach more than 96%. These inverters can also boost the inversion efficiency of low-voltage batteries by up to 96.5%.

Extendibility:

Compared to Direct Current (DC) coupling methods, these systems can be easily combined with various types of energy and are simpler to expand in the future.support parallel connections, enabling easy capacity expansion and enhancing the flexibility of system configurations and installations.

What is DC coupled

In the DC coupling system, photovoltaic modules and energy storage batteries connect directly to a hybrid inverter. This type of system employers an MPPT (Maximum Power Point Tracker) controller, which stores the energy created by the photovoltaic panels into the batteries. The energy in such systems is stored on the DC side, hence, the system is named DC-coupled.

DC coupled inverter principle

Dc coupled vs Ac coupled

Generally, AC coupling inverter is mainly used in existing installations, like homes that already have a photovoltaic system and want to add an energy storage system. DC-coupled systems are mainly used for new installations, such as setting up a whole new photovoltaic storage system from scratch.

Energy Utilization Efficiency: DC coupling surpasses AC coupling.

In an AC coupled system, photovoltaic energy is stored in the battery after going through two changes - DC-AC, AC-DC, and another DC-AC transformation is needed when the battery releases energy. The three-step conversion results in significant system energy loss, with overall efficiency around 90%.

In contrast, DC coupling charges the battery through MPPT, leading to extremely low energy loss during the DC-DC change. When energy is released, it only requires one DC-AC conversion through a mixed inverter, achieving an overall efficiency of above 97%.

Cost: DC coupling is also superior to AC coupling in terms of cost.

Intuitively, AC coupling requires two inverters, while DC coupling only needs one. Additionally, DC coupling offers the option of an integrated energy storage device, providing advantages in both equipment and installation costs.

System Flexibility:AC coupling systems have an upper hand.

In AC coupling systems, the modules are in a parallel state, making it very convenient to add or remove modules, such as adding a new set of photovoltaic systems or energy storage systems. These can be directly incorporated without the need for additional system design adjustments. On the other hand, DC coupling modules are in a serial state, connected closely to each other, making adding or removing modules more complex.

Scenarios for AC Coupled Inverter Use

10kwh installation site

1.Homes Without Solar Energy Backup Battery Systems:

For regions with significant discrepancy in peak electricity prices, Need to install the backup power supply, although whole house battery backup without solar, use AC-coupled inverter can also let you have a perfect home backup power supply, this device can optimize consumption. The strategy of using a battery backup to shift load allows for substantial savings on electricity bills.

2. a Full Solar Power Generation System is Already in Place:

You can add more PV plants to the existing PV plants. Battery storage systems using AC-coupled inverters support more energy input, or generator input. The ac coupling inverter supports parallel operation and has very good flexibility.

the benefits of whole home battery backup without solar

Although solar panels and home battery backup systems often go hand in hand, even without solar power, a home battery system can be very effective. We've listed some of the most crucial advantages below:

Load shifting/Peak shaving: 

This refers to charging the battery to store energy during off-peak hours when utility rates are low, later using this stored energy during peak hours when rates are high. Implementing this strategy can help manage and reduce your electricity bills.

Emergency backup:

 One of the main reasons people invest in home battery backup systems is to provide power during outages. With increasingly frequent power cuts due to aging infrastructure and severe weather conditions, this feature has become crucial.

Reducing reliance on the grid: 

Pairing solar panels and batteries can decrease dependence on the power grid and fossil fuels. Solar power systems provide a buffer against fluctuating electricity prices and a reliable power source when the aging power grid fails.

With the 10kW storage battery, you can buy power at the lowest price to fully meet the home load needs. Therefore, whenever you enjoy the lowest electricity price, even if the peak electricity price in your area is extremely high.

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