Research: Energy Storage Systems for Regenerative Braking

The study builds on the previous COMET study on Energy Efficiency, which was conducted last year as metros experienced increasing energy costs driven up by the conflict in Ukraine. This study examined how members use recovered braking energy and reviewed the extent and use of energy storage systems amongst members, particularly to increase the efficiency of regenerative braking.

The data shows that the average share of traction energy obtained from regenerative braking is 27% across members, however there are notable differences between fleets and technologies. Key findings of the study cover areas of energy storage systems, relevant technologies, and benefits of using energy storage systems. The report includes several mini-case studies of metros who currently have or are in the advanced stages of implementation of energy storage systems for regenerative braking. These include examples from Washington WMATA, Ottawa OC Transpo, Seoul Metro, and Tokyo Metro.