Every once in a while, unfortunately more often than we would like to, we read about unfortunate accidents that take place at railway crossings at remote locations. These accidents most often happen due to lack of flashing lights and barriers to indicate that a train is arriving.
The main reason for not implementing these preventing measures is the difficulty in providing electricity at such places. Solar has been suggested a number of times as an option, however PV systems cannot guarantee constant supply of electricity all-day and all-night, every day and night. There are some technologies that can produce electricity from moving trains, like the Dutch Energy Train for example, but they are not applicable to rails that serve passenger trains.
A team of three young engineers at University of Nebraska-Lincoln took on the task to find alternative solutions. After lengthy research and tests, the students came up with five systems that can be used to harvest “free energy” from the rails.
The first system is designed to generate electricity via an inductive coil that is attached to the rail, above a permanent magnet, which has a radial magnetic field. As the train passes over it, the coil moves up and down through the magnetic field under the weight of the wagons. This in turn generates electricity.
The second system involves a strip of piezoelectric material, that is attached to the rail on its underside. Under the weight of the train, the rail flexes, putting mechanical strain on the material, which produces power.
Although these two systems generated enough electricity to power wireless sensors, they could not produce enough to meet the purpose of the study and power warning light systems. Therefore, the team had to find an alternative solution, and designed two additional systems (third and fourth).
The third one uses a ratcheting mechanism, which is attached to the rail and moved by its vertical flexion. This movement turns a gearbox, and drives an attached to the ties generator. The fourth system, is a type of hydraulic system, where a hydraulic cylinder and a motor are driven by the vertical deflection of the rail.
The team estimated that the second set of systems did generate sufficient amount of power, however they too had limitations. They both rely on flexion of the rails, which, unfortunately, cannot always be guaranteed, especially during winter, when cold temperatures stiffen the rails.
All this led to the development of the final fifth system. Here, a spring-loaded cam mechanism, attached to the rails, is pushed by each of the train wheels. Once a wheel passes, the spring is pushed back, and then again pushed forward by the next wheel. This oscillating motion is then used to drive an electricity generator, which produced the sufficient amount of electricity that the team was after.
Although only the fifth one was found suitable to power warning lights, the other four attempts were functional and did generate enough electricity that can be used for other purposes. Hopefully all five will find some real-life application soon.
All systems are thoroughly described in the paper recently published in the Journal of Rail and Rapid Transit.
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