Preliminary design of an alternative energy storage system for a city car based on flywheel

Vehicle energy storage systems have a crucial impact on the spreading of hybrid and electric vehicles. Nowadays the most adopted solution is represented by batteries which suffer of ageing that reduces the battery capacity; moreover, the battery recycling at the end of its life is still a challenge and generate pollution. This paper presents a preliminary design of a kinetic energy storage system for city micro-car. The energy is stored by means of flywheel. First, an energetic model of the car powertrain including flywheel and bearings is proposed and used to evaluate the car energy requirement to accomplish its typical journey. Then, material, geometry and motor have been selected to fit all the vehicle space requirements. Then, analysis on the gyroscopic effects induced by the flywheel is shown when it is subjected to car chassis acceleration. Finally, preliminary considerations on bearing layout are drawn by comparing different bearings types.