Preliminary Design and Analysis of an Energy Storage Flywheel

Energy storage is becoming increasingly important with the rising need to accommodate a greater population. Flywheel energy storage systems store kinetic energy by constantly spinning a compact rotor in a low-friction environment. When short-term back-up power is required as a result of utility power loss or fluctuations, the rotor's inertia allows it to continue spinning and the resulting kinetic energy is converted to electricity. Unlike the fossil-fuel power plants and batteries, the Flywheel based energy storage systems does not emit any harmful byproducts during their operation and have gained a lot of interest recently. A typical flywheel system is comprised of an energy storage rotor, a motor-generator system, bearings, power electronics, controls and housing. Conventional flywheel designs have a large diameter energy storage rotor attached to a smaller diameter section which is used as a motor/generator. The cost to build and maintain such a system can be substantial.

The goal of this thesis is to successfully design a 1KW-hr inside-out integrated ROMAC flywheel energy storage system using a single uniform composite rotor to perform the functions of energy storage, motor and generator. Active Magnetic bearings (2 radial and thrust) will be designed to support the flywheel. The weight savings from this type of design can be substantial, and additional advantages include lower component count, reduced material costs, lower mechanical complexity, and reduced manufacturing costs. The first part of the thesis deals with preliminary calculations, design and finite element analysis of the flywheel components. The subsequent parts of the thesis involve system level analyses to ensure the structural and functional integrity of the ROMAC flywheel.