Ultracapacitors as sole energy storage device in hybrid electric cars?

New types of electric capacitors may provide, within several years, power capacitors which could be used as energy storage devices in serial hybrid electric car drives instead of a battery. This paper discusses how to determine the required size of such a capacitor used as the sole energy storage device. The performance requirements and parameters influencing the size of the capacitor are defined and a model of a hybrid car system is proposed to determine the size of the capacitor. Simulation results are presented to demonstrate the choices in selecting the capacitor size and to provide an estimate of the performance of a hybrid vehicle with capacitive energy storage.