Inertial energy accumulating device

A device for accumulating inertial energy, comprising a housing defining a rotor chamber, a rotor having a first end face and a substantially opposite second end face, the rotor being mounted in the rotor chamber, so that it can be displaced relative to the housing and so that it can rotate relative to the housing about an axis of rotation leaving free a gap between the outer rotor perimeter and the inner perimeter of the rotor chamber, wherein a seal is provided in said gap separating a first section of the rotor chamber and a second section of the rotor chamber, a pump for exposing at least the first end face of the rotor in the first section to a gas pressure, which, by comparison with the pressure exerted upon the substantially opposite second end face in the second section, generates a differential pressure force that at least partially compensates for the weight of the rotor, wherein the device further comprises stabilizing means for counteracting vibration of the rotor.