Performance analysis of hybrid energy storage in different driving cycles

Electric Vehicles (EVs) are the best alternative to deal with fossil fuel and air pollution crisis. These vehicles have an electrical propulsion system which is connected to an Energy Storage System (ESS). Internal combustion engine propulsion system (parallel hybrid EV), engine-generator (series hybrid EV), or fuel cell system (fuel cell hybrid EV) may also exist in an EV. High performance ESS is needed as a result of electric power requirement. The batteries, conventional ESS, have high energy and low power specifications for use in EVs. Another candidate for EV´s ESS is ultra-capacitor (UC). The ultra-capacitors have very low energy and high power specifications. In recent years, some designs have been proposed to combine batteries and ultra-capacitors to develop a hybrid energy storage system (HESS) with high energy and high power specifications. In this kind of ESS, the power fluctuation of the battery is reduced and the life of the battery is increased. In this study, the behavior of a heavy duty EV with an ESS is compared with a HESS one. This comparison is done in 5 different driving cycles which have different level of aggressiveness. The results show that the vehicle performance, the energy saving characteristics and the battery life criteria improvement values are related to the aggressiveness characteristics of driving cycles.