Design of flywheel energy storage device with high specific energy

The flywheel energy storage system is a way to meet the high-power energy storage and energy/power conversion needs. Moreover, the flywheel can effectively assist the hybrid drivetrain to meet the vehicle's large peak power requirements. For the automotive use of flywheels, it is particularly important to increase the moment of inertia of the flywheel as much as possible while keeping the overall mass increase low. In order to improve the specific energy of the system, a multi-stage flywheel rotor was designed. Consider a typical example here, such as I = 3, ε = 0.96, δ = 1.1 (i, ε, δ represent the speed ratio, mass ratio and radius ratio of the two-stage flywheel), where four groups of secondary flywheels are installed in a flywheel energy storage device. Without considering the mass of the second stage gear, the specific energy of the flywheel device was 6.19 times that of the original flywheel device. If the mass of the second stage gear was considered, the value was 5.80. Moreover, for certain ε and δ, the specific energy of the proposed system was related to the size of i.