Fraunhofer UMSICHT

Key to energy transition: Powerful redox flow batteries

Since wind and solar energy fluctuate, one big challenge of the energy transition is the stabilization of the flow of power. Electrical energy storage systems are able to do so. At the ENERGY STORAGE in Düsseldorf from March 13 to 15 Fraunhofer UMSICHT presents especially long-lasting redox flow stacks and highly flexible bipolar plates with which individual cells can be assembled to large-scale stacks.

Electrical energy storage systems are a key component in the success of the energy transition in order to stabilize the unsteady flow of power from wind power plants and solar cells commensurate with demand. Especially in case of high outputs (megawatts) and high capacities (megawatt hours), redox flow batteries provide clear economic ad-vantages over other energy storage systems. “In addition to the independent scalability of output and capacity, a high system efficiency and especially a long service life are advantages of this chemical energy storage system,” says Jan Girschik of Fraunhofer UMSICHT.

At the ENERGY STORAGE 2018 in Düsseldorf Fraunhofer UMSICHT will present a fully welded and therefore completely tight redox flow stack with an output of approx. 450 watt and internal pressure losses of less than 200 mbar. This stack consists of 5 battery cells with an active area of 1100 cm² per cell. Unlike lithium batteries, redox flow bat-teries can also be realised with very large cells. Therefore, Fraunhofer UMSICHT has set for itself the goal of increasing the active cell area successive in the square meter sector.

Conductive bipolar plate as a coil

Most of the battery components needed are already available or can already be pro-duced at sufficiently large scale. A challenge is the production of large-scale thin and at the same time mechanic stable bipolar plates. Research regarding this issue is being carried out worldwide at high financial expenditure. It is only with bipolar plates that the necessary stacks can be assembled from individual cells in order to subsequently config-ure them into a battery with technical usable voltage and performance parameters.

In order to bridge this technology gap, Fraunhofer UMSICHT developed a totally new thermoplast based material for the bipolar plate. By means of this new material and a special production process conductive and highly flexible bipolar plates can be produced within a continuous process. Fraunhofer UMSICHT produced a 3.2 m²-sized bipolar plate jointly with SAUERESSIG GmbH + Co. KG in a project funded by the Federal Ministry for Economic Affairs and Energy (BMWi).

”The bipolar plate has several decisive advantages: a low minimum thickness (400-500 µm), the corresponding good conductivity, their flexibility, and the cost-efficient, continuous roll-to-roll production method,” explains Lukas Kopietz from Fraunhofer UMSICHT. Bipolar plates cannot only be produced for redox flow batteries but also for PEM (proton exchange membrane) fuel cells.

ENERGY STORAGE 2018, booth B39, hall 8b

From March 13-15, the ENERGY STORAGE EUROPE 2018 trade fair takes place in Düs-seldorf, Germany. You can meet the experts of Fraunhofer UMSICHT on all days of the trade fair at booth B39, hall 8B. We are looking forward to your visit

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