The aim of this work is to discuss the possibility to store energy on board electric vehicles by means of flywheels as alternative to common batteries. A detailed optimization of the power storage system for the mini-car Icar0 ZD-1 with a target autonomy of 50 km in urban context is carried out. A preliminary designed is then made considering the power consumption in urban context accounting for the full power-train energetic model. Material, geometry and motor have been selected to fit all the vehicle space requirements considering also that flywheels operate in vacuum environment. In particular, attention is focused on some critical aspects like the effect of vibrations transmitted to the flywheel. For this reason, induced gyroscopic effects are considered both in straight and during turns. Finally, a possible bearing configuration is presented.