Abstract: A flywheel module has a flywheel as well as a speed transforming device which has a first in/output which is connected to the flywheel, and a second in/output which is coupled to a drive line of a vehicle. The speed transforming device has a bypass speed transforming device and a motor and/or generator. Energy can then be exchanged with the flywheel by suitably controlling the motor and/or generator. As a result of the delivery of a negative torque by the motor and/or generator, the flywheel accelerates and because of the delivery of a positive torque by the motor and/or generator the flywheel decelerates.