The possibility for energy regeneration by electrification in Swedish car driving

Paper in proceeding, 2014

The ability to regenerate energy when braking is a valuable advantage of hybrid and fully electric vehicles. How much energy that can be regenerated depends mainly on the car driving and the capacity of the driveline. Detailed studies of possibilities for brake energy regeneration in real world driving are needed to better understand the potential gains of car-electrification since test cycles do not take individual driving or elevation into account. This study has analysed the potential for regeneration in Swedish car driving by applying a model for a normalized vehicle to a highly detailed and representative data set of individual car movements for privately driven cars in Sweden. The share of energy at the wheels used for braking was found to range from 12% to 63%, with an average of 30%. Engine braking could however reduce the amount of recoverable energy to about 16%. On average 42% and 89% of the potentially regenerable energy is available below 10 and 40 kW, respectively. Drivers with lower average speed have in general a higher share of the energy at the wheels potentially available for regeneration. This is however not an important factor to determine the total yearly energy/cost savings. Instead the yearly mileage is shown to be a more relevant indicator on total energy savings from regeneration. The results are compared to the NEDC and WLTP test cycles.