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DC-coupled LIONICsolar® ESS storage system

Store energy efficiently and maximise self-generated power consumption.

By the year 2022, an 800km-long power line between Schleswig-Holstein and Bavaria is expected to be constructed to transport wind energy from the north-German coastal regions to the south. The planned power highway has attracted much criticism. Local residents and associations fear serious environmental consequences, among other things. Furthermore, the state of Bavaria is increasingly developing its own renewable energy sources, such as wind turbines or photovoltaic systems, which then calls the necessity of this so-called ‘south link’ connection into question.

DC-coupled LIONICsolar® ESS storage system
DC-coupled LIONICsolar® ESS storage system

The growing use of energy storage means an increase in the usage of self-generated power, which could soon start to ease the strain on the public grid. Since energy storage systems reduce the supply of renewable electricity into the public grid, consumption of stored energy can be deferred. It offers operators the flexibility to maximise their self-generated electricity, since the stored energy can be used at any time of the day or night, regardless of the weather.

To get the most from the yield of self-generated energy, BENNING has developed the electrochemical LIONICsolar® ESS energy storage system. It detects excess electricity and stores it in ultramodern lithium-ion-batteries. This allows for effective energy conversion and storage, with an energy conversion efficiency of over 90%. But how is this possible?

DC coupling is the magic word

If an energy storage system has a conventional AC coupling, several conversion processes need to take place in order to store the PV energy in the battery. The reason for this is that the DC output produced by the PV generators first has to be converted into an AC output via an installed PV inverter. In order to reach the battery, it has to be converted again into a DC output via a charging rectifier. Even if all the individual components are energy efficient, the different conversion processes use considerable energy when added together. The upshot is that the overall efficiency of an AC coupling system is no more than 80%.

By connecting the PV module directly to the storage system (the so-called DC coupling), two of the conversion stages are omitted. The energy to be generated is adjusted only in the voltage level, and can be stored directly, resulting in an increase in the overall efficiency of the LIONICsolar® ESS. Thus, efficiency ratings of over 90% are realistic.

Each power electronic plug-in module is provided with a maximum charging power of 3000 W.
Each power electronic plug-in module is provided with a maximum charging power of 3000 W.

Operators of DC-coupled systems therefore have the major advantage of efficiently increasing their self-generated power consumption. They do not need to draw as much power from the public grid, and their energy and operating costs are significantly lower in comparison with costs generated by an AC-coupled system.


Lower investment costs and simpler installation

The BENNING LIONICsolar® ESS offers other advantages. Customers who choose this storage system incur fewer investment costs because an additional PV inverter is not required. With its high-performance electronics, this system comes equipped with an inverter so that it can draw from the stored DC energy when AC current is required.

Moreover, with less equipment and fewer cables to install, the start-up process is quicker and commissioning can commence sooner.

DC-coupled LIONICsolar® ESS storage system

High-performance charger

On days when the weather is changeable, any excess solar energy must be quickly stored, so that the power generated can then be used on cloudy days. In this way, the energy throughput increases further, which automatically results in a reduction of the total costs of the energy storage system.
LIONICsolar® ESS achieves this by using a charge controller with a high charging capacity. Together with its cutting-edge lithium-ion- batteries, a fast charge and short interim charges are possible. Within just one hour, the batteries can be charged so that the system can operate at full capacity numerous times throughout the day.

ESS Cabinet-System with EPM 7.3-PV / ESS Cabinet-System with two EPM 8.3-PV
ESS Cabinet-System with EPM 7.3-PV / ESS Cabinet-System with two EPM 8.3-PV

Independent supply

Energy storage systems offer additional reliability during a general power cut because you can switch to emergency power. However, AC-coupled storage systems are only able to produce power until the battery has discharged. Recharging does not take place, since the normal PV inverters automatically switch off when there is a power cut. Only with DC coupling is it possible to use energy storage during a power failure. With the PV modules’ direct connection to the storage system, the load can be supplied primarily by the PV energy and the excess is charged. In this way, it is possible to ensure a significantly larger, independent supply.

Furthermore, a storage system like the LIONICsolar® ESS is able to implement a conventional AC connection in addition to the DC coupling. This means that other energy sources, such as a small wind turbine, can be easily connected, thus further increasing the operator’s self sufficiency.

Economic benefits

To conclude, it is clear that DC-coupled energy storage systems, with their lower investment and running costs, are more economically viable than AC-coupled systems.
Moreover, they offer functional advantages, such as the possibility of using the system independently of the public grid.


The LIONICsolar® ESS is the ideal choice for many areas of application. On the one hand, it helps operators to minimise costs and on the other, it helps to maximise self-generated power consumption. In the face of rising energy costs, the LIONICsolar ESS presents itself as a secure, sustainable investment for the future, which additionally reduces CO2 emissions and thus preserves the environment.

Further information

contact: Peter Höptner
telephone: +49 (0) 2871 / 93 233

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