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STEEM - promoting energy savings for tramways

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 Alstom’s maximised energy efficiency tramway system (Système de Tramway à Efficacité Energétique Maximisé) has just been awarded a prize by France’s inter-ministerial programme for research and development into terrestrial transport systems (PREDIT) in the "Technologies for Energy and the Environment" category.

The STEEM project was developed in conjunction with the RATP and is based on an integrated energy storage solution. The system provides tramways with a high level of energy autonomy by enabling them to run without catenary power, be more effectively integrated into the urban environment and use less energy.

The solution was tested on one of the 21 Citadis tramsets over a period of more than a year, from May 2009 to September 2010. The test tramset autonomously covered a distance of approximately 300 metres between the stations of Porte d’Italie and Porte de Choisy on line T3 of the Paris tramway (Pont du Garigliano-Porte d’Ivry). During the tests, the tramset used an average of approximately 16% less energy.

How does it work?

In practical terms, supercapacitors are installed in a box on the roof of the tramset. These are used to store the energy generated by the tram when it brakes. They are also recharged when the tram stops at stations and its pantograph is raised, allowing the tram to be powered by the catenary. The supercapacitors store enough energy to make up for the lack of overhead catenaries between two stations, enabling the tramway to operate as normal.