The invention herein relates to a flywheel capable of high speed rotational operation in excess of 15,000 rpm, the flywheel comprising a composite rotor having a polymeric matrix in which are embedded fibers helically wound at an initial angle with respect to the axis of rotation of the rotor of from about 50° to about 80° and increasing in a stepwise or continuous manner to about 90°.

The flywheel energy storage device (3) comprises a rotor (2) with at least two hubs (11, 12) and a drive (33) for the rotor (2), whereby the rotary element (23) is mounted at least via the first hub (11) with the first journal (21) in a first bearing (31) of the flywheel energy storage device (3), and at least via the second hub (12) with the second journal (22) in a second bearing (32) of the flywheel energy storage device (3), and the rotor (2) can be made to rotate by means of the drive (33) via the first and/or second journals (21, 22), whereby the journals (21, 22) in the rotor (2) are connected to each other exclusively via the hubs (11, 12) and via the rotary element (23).

This invention relates to a flywheel and method of manufacture thereof wherein the flywheel is capable of operation at very high rotational speed without precise balancing.