Bidirectional charging means that an electric vehicle not only draws power from the grid to charge the vehicle battery, but also feeds power from the vehicle battery into the grid. Such vehicle-to-grid applications enable electric vehicles to provide system services. These system services are of particular interest to the transmission system operator TransnetBW.
But there are still a few hurdles to take before e-car batteries can make reliable contributions in this regard: Communication between electric vehicles and charging points, the controllability of charging and discharging operations, and the associated data exchange must be developed and implemented too. Bundling of power is also important: Grid-relevant scales will only be achieved if many small units, e. g. mobile e-car batteries, can be tapped together. This means high requirements for standardization and automation in the tapping process as well as for its documentation. Therefore, TransnetBW is testing defined use cases and the associated communication technology at two locations as a network partner in the BDL project. For implementation, TransnetBW uses special Kostal wall boxes in connection with three refitted BMW i3 cars. Fraunhofer ISE is developing special optimization software and assists the setting up of a data infrastructure for the targeted control of the vehicles.