Alstom transfers tram power supply technology to buses

First SRS-powered bus in Malaga, Spain.

Technology that Alstom originally developed for trams in historic cities has now crossed over and is being used to recharge electric buses.

First used in 2003 on trams in Bordeaux, APS (Alimentation par Sol – or ground power) uses a powered metal strip that lies flush with the street surface between the two running rails, in the middle of the ‘four foot’ in railway parlance. The strip is divided up into short sections and only those sections covered by the tram body, and therefore protected from pedestrians, pets and other road users, are energised. Power is collected by a pickup shoe.

APS in use in Tours, France. The APS contact can be seen in between the tracks.

Not intended to replace overhead catenary, APS was used in historic city centres where the wires would be unsightly.  In outlying areas, the tram would deploy its pantograph and collect power from overhead wires in the conventional manner.

Following its successful introduction in Bordeaux, several other cities adopted the same system, including several in France and others worldwide, from Australia to Ecuador.


An SRS electric-bus charging station in Malaga.
The three conductors can be clearly seen –
necessary as there is no simple electrical return
as there is through the steel rails of a tramway.

In 2015, Alstom launched the SRS system (Système de Recharge statique par le sol – or static-based ground charging system), a derivative of APS which can be used to power both trams and electric buses.

The main difference is that the vehicle is not continuously powered by the in-road system but, instead, only connects at stops and charging points, when power storage devices such as batteries and supercapacitors are topped up.

The first application of SRS is as part of the PALOMA pilot project, currently underway in the southern Spanish city of Malaga. This sees a prototype of SRS for e-buses operating at a bus stop in front of the University of Malaga’s School of Industrial Engineering. It is equipped with a 200kW charger and is associated with a twelve-metre Linkker e-bus which is running on Bus Line 1, operated by EMT, the local transport operator.

Close-up of the SRS contact patch in Malaga, Spain.

PALOMA (Prototype for Alternative Operation of Mobility Assets) is a pilot project co–financed by the EU through the European Regional Development Fund and Spain’s CDTI (Centre for the Development of Industrial Technology). Alstom is leading a consortium with partners Endesa, a Spanish utilities provider, and Mansel, electrification contractor, and working with the support of the City of Malaga, transport operator EMT Malaga and the University of Malaga. The objective is to create the world’s first operating prototype of an automatic, ground-level, rapid-charging system for a 100 per cent electric bus.

Underneath a bus while charging, showing the three pickup shoes deployed down onto the contact strips.
Eric Marie, Alstom.

Eric Marie, Alstom’s vice president of systems and infrastructure, said: “This installation of SRS for e-buses in an important step for both Alstom and the city of Malaga, taking us a step further in the move towards fully sustainable urban mobility.

“We are proud of what has been achieved in collaboration with our consortium partners Endesa and Mansel, and, of course, the support of the City of Malaga and EMT Malaga, both of which are now pioneers.

“The project in Spain shows a way forward for the smooth operation of the enormous electric bus fleets we will see in coming years across Europe.”

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