Electromagnetic Energy Harvesting Systems in the Railway Environment: State of the Art and Proposal of a Novel Metamaterial Energy Harvester

In this paper, an overview on energy harvesting systems in the railway environment and recent advancements is presented. Energy harvesting systems in the railway environment vary from piezoelectric energy harvesters to electromagnetic energy harvesting systems (mostly mechanical vibrations to electric energy) which has been an interesting topic for researchers specially for applications to supply power to wireless sensor networks to insure safety on the railway track. Recently, experimental measurements have been observed for electromagnetic fields in the railway environment at a wideband range of frequency from 10 kHz to 1 GHz where unintentional signals or ambient energy has shown to exist in the railway infrastructure. The design of a high efficient and compact energy harvesting system has been considered. It is based on a metamaterial structure at a given frequency compatible for railway applications which is chosen at 350 MHz. The metamaterial design has shown good absorption at 350 MHz equal to 98% with a subwavelegth structure of λ/14 and thickness λ/100. Unlike metamaterial absorbers, the energy is dissipated through a via where 84% of the energy was delivered through a resistive load of 8.5 KΩ.