Comparison of Different Motor-Generator Sets for Long Term Storage Flywheels

Flywheels feature relatively low size, long lifetime and robustness and are, therefore, very attractive as energy storage devices. In case of long term energy storage, low idle losses are essential to keep the stored energy in the system. The motor generator set for mechanical energy storage systems are most likely permanent magnet, synchronous and switched reluctance machines. In this article, the different motor topologies, suitable for long term energy storage, are analyzed regarding the trade-off between efficiency and material utilization, including permanent magnet synchronous and synchronous reluctance machines. The used evolutionary optimization procedure considers iron losses as well as material saturation effects for certain points of operation. Finally, an overall comparison shows the performance of the different drive topologies.