Ground-based electric charging – The Alstom SRS

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The electrification of public transport services is a significant step towards the decarbonisation of transport as a whole, and much progress has already been made. Many trams are electrified, and electric buses are increasingly making their way onto roads. As ever, there are challenges to be overcome in moving from fossil-fuel to electrically-powered vehicles, and the more large-scale the shift, the greater those challenges will be. One of these challenges is the implementation of an appropriate charging system. One of the more promising technologies being mooted as a possible solution is SRS ground-based charging technology from Alstom.

About the SRS Ground-Based Charging System

SRS won 1st prize at Transport Publics 2016’s Innovation Awards, in the category Energy – Environment. The new charging system is currently being considered primarily for trams – and indeed will be used by trams entering service on two lines in the French city of Nice over the next few years. However, the system could be useful for other vehicles as well and is being talked about as a charging solution for electric buses or electric trucks. It is a system designed to enable trams to make use of stored, onboard power rather than the usual catenaries. This dynamic charging, of course, is what would make it suitable for off-rail vehicles such as buses and trucks, but is no small advantage for trams too. It eliminates the need for installation and maintenance of power lines and reduces the visual impact of tram services on a city.

Video: Alstom’s SRS ground-based electric charging system, Source: Youtube

SRS is a static charging system which supplies power to vehicles through charging slots that can be installed in stations and at the terminals where the vehicle stops. Energy is picked up through collector shoes which make contact with ground-level conductors and stored through roof-mounted supercapacitors. It is a rapid charging system, allowing vehicles to collect and store meaningful amounts of power in the time they spend at a single stop and then travel without a direct power supply between stops.

Feasibility and Benefits

SRS is showing promise as both a feasible solution and one that offers no small portfolio of advantages. Charging facilities need only be installed at terminals and stations, which is a considerably lighter and potentially much cheaper solution than installing and maintaining power cables along full routes. It also adds a lot of flexibility, meaning the system developed for trams has the potential to be used for road-going vehicles with minimal specialist infrastructure.

One of the main advantages of Alstom’s system – which, the manufacturer is quick to point out, is entirely compatible with vehicles built by other companies – is its exceptional rapid-charging. It can take up and store meaningful amounts of power in just twenty seconds. This is what makes it theoretically quite reasonable for trams, buses, and trucks to recharge while they have stopped to pick up passengers or have to stop at a traffic light. This means that vehicles can operate more efficiently, not being taken out of service for dedicated charging time, and also reduces the size and weight of onboard energy storage solutions as it is not necessary for such a large charge to be held at any one time.

Naturally, the system also carries the benefits that are inherent to all electrified transport solutions; lower carbon emissions, more efficient operation, and the potential for carbon-free operation if the electricity originates from renewable sources.