Vibration-Based Energy Harvesting Systems for On-Board Applications

Currently, the onboard applications of many electronic devices that could benefit rail operation are hindered by the lack of availability of electrical power in freight cars. Although the locomotives, of course, have available sources of power, the freight cars usually don’t have any. The systems presented in this paper are meant to provide a solution for distributed power in freight trains. Although ideas like Timken’s generator roller bearing or solar panels exist, the railroads have been slow in adopting them for different reasons, including cost, difficulty of implementation, or limited capabilities. The solutions presented in this paper are vibration-based electromechanical energy harvesting systems. With size and shape similar to conventional shock absorbers, these devices are designed to be placed in parallel with the suspension elements, possibility inside the coil spring, maximizing underutilized space. As the train goes down the track, the suspension will accommodate the imperfections and its relative displacement will be used as the input for the harvesting systems. The first prototype generation used a linear generator, with the advantage of no need for a mechanical transformation of the input. They have proven that they could work but present some limitations in terms of power and efficiency. The second generation of prototypes is built around a rotating generator. The linear input motion is transformed into rotation by a ball screw. The possibility of including a gearbox to increase the speed is the key to greatly improve performances. The latest built prototype has shown during lab tests that it is capable of providing up to 75W_RMS with displacements and velocities that resemble the relative motion across a vehicle suspension.