Cost optimization of hybrid composite flywheel rotors for energy storage

A novel approach to composite flywheel rotor design is proposed. Flywheel development has been dominated by mobile applications where minimizing mass is critical. This technology is also attractive for various industrial applications. For these stationary applications, the design is considerably cost-driven. Hence, the energy-per-cost ratio was used as the objective function. Based on an analytical approach for calculating stresses in multi-rim hybrid composite rotors, the nonlinear optimization problem was solved using a multi-strategy optimization scheme that combines an evolutionary algorithm with a nonlinear interior-point method. The problem was solved for a sample rotor with varying cost ratio of the rim materials. Instead of an optimal solution per cost ratio, only four optimal designs were obtained with a sharp transition between designs at specific cost ratios. This sharp transition is explained by the intricate interplay that exists between the objective function and the nonlinear constraints imposed by the applied failure criteria.