Examination of the contributions of coasting and regenerative braking to the efficiency of electric rail vehicles

In this paper, the energy-saving strategies of coasting and regenerative braking are examined as it relates to electric passenger trains. Rail vehicles are generally not large consumers of energy, due to the small coefficient of friction at the steel-tosteel contact surface between the wheels and the running rails. However, a considerable amount of energy is required to accelerate a train from rest due to the high starting currents of electric motors and the large inertia to be overcome to set the train in motion. As the speed is increased, propulsion resistance increases exponentially, and so does the energy consumption rate, making energy efficiency improvement absolutely necessary for increasing the viability of rail operations. Coasting uses the momentum of the train to maintain motion with propulsion disabled. Regenerative braking captures and reuses the kinetic energy of the train on application of the brakes. These strategies are examined both individually and collectively to arrive at the most energy-efficient combination. A deterministic model is developed which calculates the speed and position of the train, and determines which deceleration method is more efficient, given the existing circumstances, so that energy efficiency is maximized.