Deutsche Version  ACT
Electrical Storage
Redox flow battery 1.8.2016

Frontal view of the local storage system in Tussenhausen.

Liquid storage simplifies network expansion

Scientists of the project SmartPowerFlow integrated a large redox-flow

battery into the power grid of a German operator. They wanted to find

out to what extent energy storages increase the capacity of the grid and

so reduce the cost of grid expansion.

Project status Project completed
Typical system size 0,4 MWh
Typical system size Output 0,2 MW
Volumetric energy density ca. 50 Wh/l
Gravimetric energy density ca. 30 Wh/kg
Volumetric power density < 10 W/l
Gravimetric power density 166 W/kg
Efficiency AC/AC ca. 70 %
Storage loss Cold Standby 2,4 kWh/d
Cycle durability (80% discharge level) ca.13.000
Typical discharge time 1 to 10 hours
Response time when preparing the energy < 60 ms
Examples SmartRegion Pellworm (Deutschland), Photonenbauer (Niederlande), King Island (Australien)
Project duration August 2013 until July 2016

German network operators are facing great challenges nowadays due to the rapid increment of renewable energie penetration into the electrical grid. To ensure network stability important decisions are to be taken concerning the restructuration of the electrical grid. An open issue is, whether the integration of big stationary battieries may be an essential step to enhance the integration capability of an increasing share of renewable energie sources. The objective of the project SmartPowerFlow is to demonstrade for the first time the grid parallel operation of redox flow batteries in the distriburion grid by using a especially desigened inverter. The partners of the project are the Reiner Lemoine Institut, SMA Technology, LEW Verteilnetz and Younicios.

  • The local storage system in Tussenhausen consists of an inverter (left) and a so called Cellcube FB 200 – 400 (right). &copy; LEW
  • The foundation of the storage system is being erected. &copy; LEW
  • This picture shows the installation of the inverter. &copy; LEW
  • The company SMA AG deveolps a new battery inverter based on the design of the Sunny Central 500 CP. &copy; SMA Solar Technology
  • The implementation is completed. &copy; a + f GmbH
  • The 200 kW redox flow battery CellCube FB 200-400 of the company Gildemeister energy solutions has a capacity of 400 kWh. &copy; a + f GmbH
  • Battery cross section &copy; a + f GmbH
  • The operation priciple of the battery. In contrast to other batteries the redow flow battery uses tanks to storage the energy. &copy; a + f GmbH
  • The system circuit diagram shows the electrical connection to the distribution grid as well as the energy and the battery management system. &copy; a + f GmbH
  • Frontal view of the local storage system in Tussenhausen. &copy; LEW

Relieve the distribution network

In this project for the first time a large scale stationary redox-flow battery (CellCube FB200-400 DC) of the company Gildemeister energy solutions has been integrated into a distribution grid in order to reinforce an electrical network with a high share of renewable energies. The main aim is to quantify which and in what amount network expansion measures can be avoided through the usage of battery storage systems. In addition it is examined to what extend the balancing act between economic and grid-supportive operation is manageable. The storage device is installed in the market town of Tussenhausen in the district of Unterallgäu.

Analysis and optimization

The main objectives of the project are the technical and economic analysis and optimization of network expansions and usage of local energy storage systems. As part of the project a redox-flow storage of the company Gildemeister energy solutions will be integrated into the distribution network and adapted to a new demand profile, due to the rapid increase in the use of renewal energies. The most important intermediate steps are: Identification of network characteristics for achieving an effective optimization of network expansion versus the implementation of decentralized energy storage systems; Development of battery inverters for 200 kW DC / 630 kVA redox-flow batteries; Demonstration and confirmation of the analytically identified network optimization measures.

The scientists developed a simulation-model to determine the optimal placement of big stationary batteries within distribution grids with high shares of reneable energies. The aim of the model is to facilitate a wide scale mentation of stationary batteries into the German electrical grid. Currently the memory is deployed in a way that, by using smart voltage control at the site of installation, not only the local grid expansion is reduced but at the same time primary control reserve is provided, which is the most lucrative application area for large-scale batteries under the current conditions.

Result in three steps

Phase 1: Optimization of the location of a redox flow battery in the grid of the DSO LVN (LEW Verteilnetz GmbH) by using simulation tools; development of a battery inverter (first year)
Phase 2: Integration of the battery into the grid of LVN and validation of the simulation modells using measured data (second year)
Phase 3: Development of a concept for the integration of large batterie storage systems into distribution grids; technical and economical evaluation of grid extension versus integration of battery systems into the distribution grid (third year).


At first the actual and the future penetration with renewable energies of the LVN grid is analyzed and the impact of the battery implementation on the distribution grid is simulated. The goal of the simulation is to determine the optimal storage size from an economical point of view and to evaluate the technical specifications of a redox flow battery for the implementation in distribution grids, especially the dynamic behaviour.
In parallel to the tasks mentioned above an inverter in the power range of 200 kW/ 500 kVA suitable for redox flow batteries and able to provide ancillary services will be developed by SMA AG. The Younicos AG develops the definition and the realization of the interfaces between the distribution grid operator, the inverter and the battery.

Based on the simulation results a battery storage of the company Gildemeister energy solutions according to the determined specifications will be planned and integrated into the local distribution grid on an optimal grid node.
Finally, an economic and technical overall concept for the integration of redox flow batteries into the grid as well as a concept for their operation will be developed. The results of the projects will show, whether redox flow batteries are suitable to play an signigicant role in a turnaround in the energy policy toward a energy system based on renewable energies, or not.

Supported by: The Federal Government on the basis of a decision by the German Bundestag


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Research funding

The information system EnArgus provides information on research funding, including on this project (German only).