The goals have been set: energy revolution until 2050 which in turn means primarily use of renewable sources such as wind and hydroelectric power, solar energy, geothermal energy or renewable raw materials. Another important factor is the economical and efficient use of energy. As the supply of renewable energy fluctuates, storage systems are important in order to retrieve energy with a time lag.
Desirable characteristics of a battery-storage include high efficiency, high reliability and easy maintenance, ideally combined with low resource consumption and low cost. A DBU-funded project has a good chance of fulfilling this "wish list": the modular multilevel battery (M2B) developed by Smart Power GmbH, Feldkirchen and the University of the Bundeswehr München, Neubiberg as well as Osnabrück University of Applied Sciences.
As batteries usually store DC power, but the power grids work with AC voltage, an inverter is required between the storage and the grid. "Conventional battery storage systems deliver a high voltage from a large high-voltage battery, which is "chopped" by the inverter, so that it is similar to an AC voltage after appropriate filtering," explains project manager Johanna Jungbauer from Smart Power. To obtain this high voltage in conventional batteries, many single cells are connected in series in a conventional battery; thereby the weakest cell determines the strength of the entire battery. If one cell fails, the entire battery has to be replaced. This does not apply to the M2B. "In our system, many small battery modules are interconnected with their own power electronics modules," says Jungbauer. "A parallel connection results in a high degree of reliability, because defective modules can be bridged and easily replaced."
Also, different state of modules e.g. cells of different voltage, chemistry and aging can be used for the battery. Thus, the use of so-called second-life cells is possible (e.g. from electro-mobility). Furthermore, the system can be extended by modules of any technology or renewed piece by piece or module by module.
"Without the support of the DBU, the universities involved would not have been able to finance the project, and for us as a company the risk would have been too high. In addition, the responsible DBU-specialist was very helpful and supported us with the application and even responded obliging to changes in the project process", said Jungbauer. In the meantime, M-BEE GmbH, Neubiberg, became a spin-off company to bring the product to the market.
With projects such as the M2B project, the DBU supports the expansion of renewable energies and is committed to increasing energy efficiency and implementing energy-saving measures. Other central aspects are the optimization of the overall energy system and the consideration of the environmental and social compatibility as well as aspects of participation and acceptance. The DBU as a funding institution with a broad portfolio awards money to all projects regarding environmentally friendly, exemplary innovations.
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