Optimization of cylindrical composite flywheel rotors for energy storage

The use of flywheel rotors for energy storage presents several advantages, including fast response time, high efficiency and long cycle lifetime. Also, the fact that the technology poses few environmental risks makes it an attractive solution for energy storage. However, widespread application of tailorable circumferentially wound composite flywheel rotors is hampered by the relatively low energy density that these rotors have been able to achieve. This contributes to high capital cost, which currently makes the flywheels prohibitively expensive for many applications. With the materials that are currently available, there seems to be ample room for improvement in the energy density achieved by composite flywheel rotors. To this aim, some of the design methods that have previously been proposed are herein studied, and our findings suggest that the manner in which the optimization problem is formulated is crucial to the design of high energy density flywheels. A new problem formulation is proposed, which is shown to lead to notable improvements in certain cases. By making use of the proposed problem formulation, flywheel rotors can be designed to consistently achieve high energy density relative to the materials that are made available. This can contribute towards lowering the cost of flywheel systems, and making flywheel energy storage viable for a wider range of applications.