Flywheel energy storage device with a hubless ring-shaped rotor

A flywheel based energy storage apparatus, comprising:

• a housing;
• a hub-less, ring-shaped flywheel mounted within the housing and rotatable about a horizontal axis, wherein the flywheel comprises a plurality of magnets aligned to form a rotor;
• a flywheel support system;
• and
• a plurality of coils, the plurality of coils and the rotor being aligned to form a motor/generator.

A method for energy storage, comprising;

• rotating a hub-less flywheel about a horizontal axis within a housing, the flywheel comprising an outer axially extending annular surface, an inner axially extending surface, and two radially extending side surfaces, wherein one of the inner or outer axially extending surfaces comprises a plurality of magnets aligned to form a rotor;
• supporting at least one coil on the housing, the at least one coil and the rotor being aligned to form a motor/generator;
• and
• controlling electrical power transfer to and from the motor/generator.