Energy storage devices in electrified railway systems: A review

As a large energy consumer, the railway systems in many countries have been electrified gradually for the purposes of performance improvement and emission reduction. With the widespread utilization of energy-saving technologies such as regenerative braking techniques, and in support of the full electrification of railway systems in a wide range of application conditions, energy storage systems (ESSes) have come to play an essential role. In this paper, some recent developments in railway ESSes are reviewed and a comprehensive comparison is presented for various ESS technologies. The foremost functionalities of the railway ESSes are presented together with possible solutions proposed from the academic arena and current practice in the railway industry. In addition, the challenges and future trends of ESSes in the railway industry are briefly discussed.