Apparatuses, systems and methods are described for a flywheel system incorporating a rotor made from a high-strength material in an open-core flywheel architecture with a high-temperature superconductive (HTS) bearing technology to achieve the desired high energy density in the flywheel energy storage devices, to obtain superior results and performance, and that eliminates the material growth-matching problem and obviates radial growth and bending mode issues that otherwise occur at various high frequencies and speeds.