[11.02.2019] The batteries for electric cars are also suitable as energy storage, which also the power grid can be stabilized.
Transmission system operator TenneT and Daimler AG, with their wholly owned subsidiary Mercedes-Benz Energy GmbH, have researched and tested the feasibility of innovative system services in the transmission network in a joint development partnership.
The result shows that the battery storage systems – as they are also used in electric cars – can take over tasks of large power plants and contribute significantly to grid stabilization and system rebuilding.
The joint study was carried out as part of the Enera project as part of the program "Schaufenster intelligent Energie – Digital Agenda for the Energy Transition" (SINTEG) of the Federal Ministry of Economics. With her, the project partners have demonstrated that lithium-ion-based automotive battery storage systems can be used for highly dynamic system support as well as for system rebuilding – specifically in the black start of power plants and to support inertia. In the end, the elimination of conventional power generation can be compensated.
Mercedes-Benz Energy Test Lab in Kamenz
For the development partnership, the prototype of a battery storage system consisting of automotive batteries with a total connected load of approx. 1 megawatt (MW) and a storage capacity of 750 kilowatt hours (kWh) has been installed in the test center in Kamenz. These are 2nd-life and spare parts batteries.
The challenge of the energy transition for transmission system operators
Due to the increasing proportion of weather-dependent regenerative energies, power generation is becoming much more volatile. In the power grid, generation and consumption must be balanced to maintain the frequency of 50 hertz. If this is not the case, frequency deviations occur. The masses of large power plants that rotate synchronously with the grid frequency of 50 Hertz, ensure that such fluctuations are damped and thus the system carrier reacts to such deviations. This is important because frequency deviations can only be compensated for delayed by primary control power. Without the sluggish masses in the network, the frequency would change so fast that it could no longer be compensated by control power. The result would be ever greater frequency fluctuations, which could lead to power outages in the worst case. In the test lab Mercedes-Benz Energy in Kamenz, the project partners have now proven that automotive battery storage reacts to a changing frequency in less than 100 milliseconds. This allows them to replace the inert masses of large power plants.
Energy storage as "starter battery of energy supply"
Furthermore, the project partners have demonstrated that battery storage systems are able to approach energy resources and even entire power plants after, for example, a large-scale power failure. For this purpose, today diesel units are used, which put the turbines of power plants (rotating masses) back into motion and supply auxiliary equipment. The development study shows that this can be done almost loss-free and significantly more environmentally friendly even by battery storage. The energy storage acts as a kind of "starter battery of energy supply" and pushes back the sluggish rotating masses of a power plant. The required energy, about two to four percent of the rated output of a power plant, is retrieved from the energy store if necessary. To prove this, the project partners in Kamenz set up a test network and rebuilt it after a simulated power failure with the help of the battery storage system.
In the next step of the development partnership, the project partners will jointly define the requirements that will allow TenneT to tender the future system services.