Devices and methods for increasing energy and/or power density in composite flywheel energy storage systems

Abstract

A flywheel formed of a composite material having fibers, oriented substantially in a circumferential direction around the flywheel, embedded in a matrix material. The flywheel having an inner surface, an outer surface, and a thickness therebetween and defining an axis of rotation. A plurality of load masses are distributed circumferentially on the inner surface at a longitudinal segment along the axis. A rotation of the flywheel about the axis with a rotational velocity generating hoop stress in the fibers in the circumferential direction and through-thickness stress is generated in the matrix material in a radial direction. Each load mass produces a force on the inner surface operative to reduce the maximum through-thickness stress in the matrix material as the flywheel rotates about the axis. The rotational velocity otherwise sufficient to produce structural failure of the matrix material produces structural failure of the fibers and not the matrix material.