Hubless Flywheel with Null-E Magnetic Bearings

For space-born energy storage systems, the energy to weight ratio is extremely important. From this perspective, a hubless flywheel energy storage design is very advantageous since most of the flywheel energy is stored in its outer circumference, while the core significantly adds to the system weight. One of the problems with this design is that conventional active magnetic bearings are difficult to integrate into the overall system. We propose to utilize recently developed Null-E Magnetic Bearings instead, which appear to be better suited for the hubless topology. Their major advantages over active magnetic bearings include inherent stability at high rotational speeds, simplicity, low cost and lack of laminated components. At the same time, Null-E bearings deliver the desired combination of high load capacity, stiffness and low rotational losses. They can be designed to operate as entirely passive systems with no electronics or external power supplies, or as partially active systems, with some supplementary electronics. A combination of different modes is also possible, e.g. an active system at low speeds and passive at high. The proposed study includes electromagnetic design and analysis of Null-E bearings as well as research of composite material technologies suitable for the proposed design.