The M5BAT modular battery storage system is put into operation

  The M5BAT put into operation Copyright: © Joint Press Release Prof. Ernst Schmachtenberg, RWTH Aachen Volker Wachenfeld, SMA Solar Technologies Dr. Rainer Bußar, Exide Technologies Prof. Dirk Uwe Sauer, RWTH Aachen Eckhardt Rümmler, Uniper SE Prof. Rik W. De Doncker, RWTH Aachen (from left)

An Important Step for the German Energy Transformation: The M5BAT modular battery storage system is put into operation in Aachen

  • “M5BAT” (Modular Multi-Megawatt Multi-Technology Medium-Voltage Battery Storage System)
  • Technical suitability and commercial use tests on the storage batteries provide valuable findings for the energy system
  • Innovative technology to store energy promotes system stability during the ongoing energy transformation

After a full year of construction, the M5BAT modular large-scale battery storage system was put into operation in Aachen today. Prof. Dirk Uwe Sauer of the Institute for Power Generation and Storage Systems (PGS) at RWTH Aachen University, director of the project and M5BAT operations, said regarding the significance of the project for energy research: “From day one, we have intensely and individually monitored more than 25,000 battery cells in six strings of different lithium-ion battery technologies and four strings of different lead batteries. This will allow us to gather valuable information on aging, reliability, and service life. At the same time, we want to use intelligent battery management to show how overall operations can be optimized with a hybrid system using different technologies.”

The energy storage system is located next to a transformer and RWTH Aachen University research centers. The fully-automated operations will be monitored and operated via a remote control system from Uniper SE for the purposes of energy trading, and the battery storage system will be used in various markets for research purposes, for example to provide primary control power. Eckhardt Rümmler, who is Uniper’s Chief Operating Officer and, among other things, responsible for new technologies, emphasized the role of storage systems in the future: “M5BAT will allow us to test the possibility of using a combination of different battery technologies in a real network and on the market. This storage system has already been incorporated into Uniper‘s trading business, and will soon deliver important findings regarding the development of business models based on decentralized storage systems. Energy storage systems are important if energy transformation is to be a success. They contribute greater flexibility and stability to energy systems. They are thus essential for a low-carbon energy supply based on renewable energies.”

The unique feature of M5BAT is the five different battery technologies it uses. Prof. Dr. Rik W. De Doncker, Director of the Sustainable Energy Cluster at RWTH Aachen University said regarding the opportunities M5BAT offers: “The commissioning of the M5BAT battery storage system is a milestone in RWTH Aachen University’s energy storage research. Now that operation has started, we expect interesting new findings regarding the economic and technical characteristics of battery storage systems. We plan to use these research results to improve economic feasibility and, so, effectively promote the introduction of battery storage systems onto the market.”

Several partners are implementing this project. Uniper is responsible for modifying the building and fitting it with the technical equipment, as well as for trading with the battery storage system on the energy market. Exide Technologies is responsible for the lead-acid battery strings, and SMA will install its special, newly developed inverters. In addition, various types of lithium-ion batteries will be employed. The PGS and the Institute of Power Systems and Power Economics (IAEW) at RWTH Aachen University are responsible for the scientific research, operation, and tests.

Dr. Rainer Bußar, Director of Industrial Batteries / R&D Europe at Exide Technologies, commented on the potential of lead batteries in large-scale storage networks: “In stationary applications, where size and weight matter less than they do in mobile applications, lead batteries represent an interesting technological alternative to finite lithium resources. Two of the five M5BAT lead battery strings will undergo direct technology comparison tests in the field.”

Volker Wachenfeld, Executive Vice President / Head of Business Unit Off-Grid and Storage at SMA Solar Technology AG, whose company will connect 10 of its inverters to the grid, stated the following: “The intelligent and dynamic integration of larger-scale storage systems into the grid is of fundamental importance for a 100% renewable energy supply. SMA Solar Technology AG’s flexible, modular, and efficient battery inverter system technology meets the requirements to do this and offers solutions that will allow operators to use energy storage systems in innovative business models in the future.”

Battery storage systems will play an important role in energy systems as short-term compen­sation for fluctuations in renewable power input. For this reason, M5BAT received a total of EUR 6.7 million from the “Energy Storage Funding Initiative” of the German Federal Ministry for Economic Affairs and Energy. In June of this year, the KlimaExpo.NRW also recognized M5BAT as a project of special significance for climate protection.

Your contact for all questions:

Uniper SE

Sabine Meixner

+49 2 11-45 79-4 72

RWTH Aachen

Dr. Sabine Vogel

+49 241-80-49667

Portraits of the participating partners


Uniper is an international energy company that operates in Europe, Russia, and numerous other markets across the world. With its well-balanced portfolio of energy plants and its ability to combine technical and business skills with a broad range of trading activities, Uniper creates links between the world’s energy markets. It participates in research projects in the areas of energy storage, tomorrow’s power stations, and alternative mobility concepts. It operates “power-to-gas” pilot plants in Falkenhagen (Brandenburg) and in Hamburg-Reitbrook, and the first LNG fueling station for trucks in Germany.

E.ON Energy Research Center, RWTH Aachen University:

The Institute for Power Generation and Storage Systems (PGS), headed by Prof. De Doncker and Prof. Sauer, and the Institute for Energy Efficient Buildings and Indoor Climate (EBC), headed by Prof. Müller of RWTH Aachen University, bring their skills in the areas of battery systems technology and power electronics (PGS) and energy-efficient buildings (EBC) to the project. PGS has taken over overall project management, the development of an energy management system and the control technology, and the operation of the battery storage system. It is also conducting battery aging studies and analyzing the potential to optimize battery storage systems technically and economically. EBC is conducting thermal monitoring and simulations of the battery storage system.

IAEW, RWTH Aachen:

In cooperation with Uniper, the Institute of Power Systems and Power Economics (IAEW), headed by Prof. Moser, will investigate and test various marketing models for storage batteries.

Exide Technologies:

Exide Technologies operates in more than 80 countries, is one of the world’s largest manufacturers and recyclers of lead-acid batteries, and offers a broad range of electrical energy storage solutions tailored to its customers. With over 120 years of experience in developing innovative technologies, Exide Technologies is a valued partner for OEMs and serves the industry and automobile applications aftermarket. GNB Industrial Power, a division of Exide Technologies, offers an extensive range of storage products and services, including applications for telecommunications systems, rail transport, mining, photovoltaic (solar electricity) systems, uninterrupted power supply (UPS) systems, energy supply and distribution, and forklifts and electric vehicles.


The SMA Group generated sales of over EUR 800 million in 2014. It is the global market leader for solar inverters, a key component of all PV plants, and offers innovative key technologies for future power supply structures. It is headquartered in Niestetal, near Kassel, and is represented internationally in 21 countries. The Group employs more than 4,500 people worldwide. SMA’s broad product portfolio includes a compatible inverter for every type of module on the market and for all plant sizes. The product range includes both inverters for photovoltaic plants connected to the grid as well as inverters for off-grid and hybrid systems. Its technology is protected by over 550 patents, and its product catalogue is complemented by a wide range of services and the operational management of large-scale solar power plants. Since 2008, the Group’s parent company, SMA Solar Technology AG, has been listed on the Prime Standard of the Frankfurt Stock Exchange (S92) and also in the TecDAX index.

This press release may contain forward-looking statements based on current assumptions and forecasts made by the Uniper SE Management and other information currently available to Uniper. Various known and unknown risks, uncertainties and other factors could lead to material differences between the actual future results, financial situation, development or performance of the company and the estimates given here. Uniper SE does not intend, and does not assume any liability whatsoever, to update these forward-looking statements or to adjust them to future events or developments.