An energy storage module for the reversible storage of electric energy is provided that comprises several flywheel energy storage units that are electrically connected in parallel via a shared DC link. A first regulation system is connected to the DC link and that, during normal operation (NO), connects the DC link to one or more external power networks in order to absorb (En) energy from or release (Ep) energy into the external power network(s). A second regulation system includes an input side and an output side, whereby the input side is connected to at least the DC link while the output side is connected to an internal supply network for purposes of supplying one or more electrically powered operating aggregates that are needed to operate the flywheel energy storage units.