Abstract: The present disclosure relates to a flywheel system (1), comprising a ring-shaped flywheel rotor (3), arranged on a rotation axis (7); and a substantially cylindrical casing (2), enveloping the flywheel rotor (3) at least in a radial direction to contain the flywheel (3) in case of a calamity. The flywheel system (1) further exhibits the feature that the casing (2) comprises and having at least one inward protruding bumper (8) defining a variation from the circular shape in cross section of the casing wall (5) surrounding the flywheel rotor (3). The casing wall (5) may itself be circular and the bumper (8) can define a deviation relative to the circular shape thereof, to enhance deceleration of the flywheel rotor (3), if, in case of an accident or calamity, the flywheel rotor (3) comes loose.

Abstract: The present disclosure relates to a flywheel system (1), comprising a ring-shaped flywheel rotor (3), arranged on a rotation axis (7); and a substantially cylindrical casing (2), enveloping the flywheel rotor (3) at least in a radial direction to contain the flywheel (3) in case of a calamity. The flywheel system (1) further exhibits the feature that the casing (2) comprises and having at least one inward protruding bumper (8) defining a variation from the circular shape in cross section of the casing wall (5) surrounding the flywheel rotor (3). The casing wall (5) may itself be circular and the bumper (8) can define a deviation relative to the circular shape thereof, to enhance deceleration of the flywheel rotor (3), if, in case of an accident or calamity, the flywheel rotor (3) comes loose.