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First Heliox underground-chargers installed in Rotterdam

Underground installations in urban environments present engineers with a new challenge working with limited space and buried obstructions. Heliox engineers navigated the congested space underground Rotterdam for a charging infrastructure that respects the city landscape.


55 Buses 6 MW Rotterdam, Schiedam, Vlaardingen 8 Months
Roof-mounted pantograph


Rotterdam’s regional public transport operator, RET Rotterdam, was looking for a suitable charging infrastructure to electrify their bus fleet of 55 VDL Citea’s SLF-120. The sizeable project of 55 buses and 8 charging stations needed a charging solution that was unobtrusive, without distracting from the existing the public street furniture. Substantial adaptations would be required to the existing infrastructure, impacting daily operations as little as possible.


For unobtrusive charging, chargers were placed underground at Rotterdam CS. This solved the problem of keeping the chargers out of view but presented challenges when engineers were confronted with the existing thick maze of cables buried underground to serve the station and metro, restricting available space for installation. However, space was not the only challenge. Cooling systems were also installed to lower the heat generated by the chargers and maintain an optimum temperature. Installations were carried out at night to impact daily operations as little as possible. Masts holding the pantograph were specially designed to fit regular lamppost design, seamlessly aligning with the street view. In some cases, the distance between charger and masts was exceptional; in Vlaardingen West, a special cable path of 135 meters was designed and installed. All 55 buses are charged via pantograph, the so- called Bus-Up system. Two methods are used: depot charging at the Kleiweg in Rotterdam (thirty-two 2x30 kW Dynamic Charging chargers) and opportunity charging (sixteen 300 kW Charger) at different locations in the three cities. The project includes the first installation of the Heliox Dynamic; a charging solution that can switch from one to two buses for simultaneous charging. If one bus is being charged, it will be charged at the full power capacity of 60 kW. If two buses are connected, 30 kW will be transferred to both buses


Heliox is further pushing the limits of e-mobility to contribute to a sustainable future for next generations. The project demonstrates how Heliox provides flexibility within the specified parameters and where necessary, can respond with customized solutions. Maurice Unck, CEO of  RET adds, “This is RET’s first step towards a 100% zero-emission bus fleet in 2030. As a public transport company, we value taking responsibility in making our operations even more sustainable than it already is. Heliox proved to be an expert partner in this process.”    

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