Mobile Flywheel Energy Storage Systems: Determining Rolling Element Bearing Loads to Expand Possibilities

Efficient energy storage is the key to modern hybrid or zero emission vehicles and low carbon mobility in general. Compared to conventional storage technologies like batteries, flywheel energy storage systems (FESSs) offer various theoretical advantages, such as high cycle life, no capacity fade over time, temperature independence, easy determination of state of charge, and complete recyclability. However, the special operating conditions of FESSs-such as vacuum, high rotational speeds, and high gyroscopic reactions, etc.-make bearing design a complex and crucial endeavor. This article describes methods of determining loads for rolling element bearings in automotive FESSs. An overview of FESS technology is given, followed by the discussion of an analytic, numeric, and empiric approach, including a detailed comparison of the different methods. Furthermore, the concept of a test bench investigating flywheel behavior in a resilient mount is described, and its results regarding the design of an FESS-tovehicle mount are discussed in depth.