Energy storage is a vital part of the modern world and billions of dollars are invested each year to develop more efficient solutions. Chemical batteries are widely utilized but their drawbacks are prevalent particularly in applications such as electric cars.
Flywheel Energy Storage (FES) systems have many advantages over chemical batteries, including a higher energy density, freedom from capacity degradation, and extremely fast recharge. They accomplish this through storing energy as rotational kinetic energy. These benefits make FES systems ideal for applications that demand large reservoirs of power, such as electric cars. However, FES systems can be subject to issues such as energy loss through friction and mechanical instability.
This research highlights the construction and testing of an innovative hybrid magnetic bearing and a unique modular FES system designed for mobile use.
Hybrid Magnetic Bearing System
The hybrid bearings effectively minimize friction losses and maintains flywheel stability through the use of two permanent magnetic bearings, two electromagnetic bearings, and two thrust bearings. The permanent magnetic bearings provide most of the levitation while the electromagnetic bearings stabilize the system.
PID Control System
A PID control algorithm is used to control the electromagnetic bearings. The PID is programmed in the C in the Arduino controller.
A series of backup bearings safeguard the rotor from damage in case the active electromagnetic bearings fail. In addition to the thrust bearings, two radial roller bearings are installed on the ends of the shaft.
The whole FES system is modular which makes it easy for maintenance and expansion. Various magnetic bearing modules can be used for different applications. The standard size components with different capabilities allow for easy upgrades and customizability.
A magnetic coupler links the motor/generator with the flywheel. This enables flexibility for energy input/output, reduces the load on the flywheel when coasting, and enables the flywheel to be completely enclosed and have a permanent vacuum.
Tests comparing an identical flywheel system with the novel hybrid bearings against conventional ball bearings demonstrated the advantages of the hybrid bearing system.