It is essential that an energy grid must remain stable at all times. The amount of electricity fed into the network from power plants must be more-or-less equal to the amount of energy consumed at power points by customers. Currently, grid stability is provided automatically by coal-fired power plants, which provide instantaneous reserve (electrical power that is available at short notice) and absorb frequency fluctuations in the large rotating masses in the generators of the plants. Germany’s transition to fluctuating, renewable energies such as wind and solar presents an enormous challenge in this regard.

In the ReserveBatt project, which is led by the Energy Storage Technologies Research Centre at the Clausthal University of Technology (IEE) in Goslar, a team of experts has designed a special battery to provide instantaneous reserve, which can be coupled to the grid via a frequency converter (in this case, a powerful bidirectional inverter). The reserve power of the battery system was found to be equivalent to a one-megawatt power plant.

"In the future, power electronic equipment, such as inverters, will have to compensate for the elimination of rotating masses in large power plant generators in combination with short-term energy storage devices in order to maintain grid stability" explains the project leader Professor Hans-Peter Beck, head of the Institute of Electrical Power Engineering and Energy Systems at IEE, in an article on the forum Energiesystem-Forschung.

The market for providing instantaneous reserve is as yet undeveloped. The team, which includes the Fraunhofer Institute for Telecommunications, Heinrich Hertz Institute (HHI) and Infineon Technologies GmbH, believe that grid operators are the most likely candidates to provide a battery reserve service, but they will need to adapt their business models and a legal framework for provision needs to be created.