Energy storage can be used to fill gaps when energy production systems of a variable or cyclical nature such as renewable energy sources are offline. This thesis research is the study of an energy storage device using high temperature superconducting windings. The device studied is designed to store mechanical and electrical energy. Mechanical energy is stored as inertia in the mass of the spinning rotor. This rotor inertial energy storage is very similar to the energy stored in a flywheel. Magnetic energy is stored in the motor's rotor windings and possibly in the field windings. Current flowing in these windings will create a magnetic field to store energy proportional to the current and number of turns in the coils and will also provide the impetus, in conjunction with pulses in the field coils, to spin the flywheel / rotor. The proposed device was studied to determine the amount of energy that can be stored and to estimate losses incurred to keep the mass of the rotor spinning and the losses resulting from operating the peripheral devices needed for operation. Feasibility and practicality were also examined for the proposed device.