Regenerative Braking Potential and Energy Simulations for a Plug-In Hybrid Electric Vehicle Under Real Driving Conditions

There are several possible configurations and technologies for the powertrains of electric and hybrid vehicles, but most of them will include advanced energy storage systems comprising batteries and ultra-capacitors. Thus, it will be of capital importance to evaluate the power and energy involved in braking and the fraction that has the possibility of being regenerated. The Series type Plug-in Hybrid Electric Vehicle (S-PHEV), with electric traction and a small Internal Combustion Engine ICE) powering a generator, is likely to become a configuration winner. The first part of this work describes the model used for the quantification of the energy flows of a vehicle, following a particular route. Normalised driving-cycles used in Europe and USA and real routes and traffic conditions were tested. The results show that, in severe urban driving-cycles, the braking energy can represent more than 70% of the required useful motor-energy. This figure is reduced to 40% in suburban routes and to a much lower 18% on motorway conditions. The second part of the work consists on the integration of the main energy components of an S-PHEV into the mathematical model. Their performance and capacity characteristics are described and some simulation results presented. In the case of suburban driving, 90% of the electrical motor-energy is supplied by the battery and ultra-capacitors and 10% by the auxiliary ICE generator, while on motorway these we got 65% and 35%, respectively. The simulations also indicate an electric consumption of 120 W.h/km for a small 1 ton car on a suburban route. This value increases by 11% in the absence of ultra-capacitors and a further 28% without regenerative braking.