High speed flywheel

A flywheel, comprising:

• a composite annular rotor having a central axis of rotation perpendicular to the rotor, wherein:
• the composite comprises a matrix material in which fibers are embedded at a concentration of about 50% to 80% by volume, the fibers being helically wound at an initial angle of about 50° to about 80° relative to the axis of rotation, the winding angle increasing to about 90° in a continuous or a stepwise manner;
• wherein the fibers comprise:
• a single chemical composition within a first chemical class of fiber;
• or
• variable chemical compositions within a first chemical class of fiber;
• or
• a first chemical class of fiber, which may comprise a single chemical composition or variable chemical compositions, wound to a predetermined rotor dimension whereupon a second chemical class of fiber, which may comprise a single chemical composition or variable chemical compositions, is introduced either gradually or all at once.