HybridFlex train enters passenger service in the UK

By Mike Brezonick10 February 2022

A hybrid diesel-battery-electric train that reduces CO2 emissions by up to 25% has entered passenger service in the UK for the first time. The HybridFlex train is powered by two mtu Hybrid PowerPacks from

Rolls-Royce, and is operated by Chiltern Railways on the route between London Marylebone and Aylesbury.

HybridFlex train A HybridFlex train, powered by two mtu Hybrid PowerPacks, has gone into passenger service in the UK. (Photo: Rolls-Royce)

Together with the leasing company Porterbrook and Chiltern Railways, Rolls-Royce has converted a Class 168 DMU into the HybridFlex train. The partners are looking to prove that existing rail vehicles can be used in a climate-friendly way without the need to install complex and expensive new infrastructure.

It is also the first regular passenger operation with mtu Hybrid PowerPacks, of which 13 have already been ordered.

“It makes us proud to bring this groundbreaking propulsion solution, which we have continuously further developed over the past years, into regular service together with our partners,” said Lei Berners-Wu, vice president Global Industrial Business at the Rolls-Royce business unit Power Systems. “The immense CO2 savings based on existing and proven technologies are an important step on the road to climate neutrality, on which we are moving forward together with our customers in all applications.”

Rolls-Royce said its mtu Hybrid PowerPack combines the advantages of battery and diesel-powered trains. Trains with the technology can also be operated on non-electrified routes purely electrically and can operate emissions-free in urban areas or stations.

In pure electric operation, drive noise is reduced by about 75% (20 dB(A)), Rolls-Royce said. On the emissions side, the company said CO2 emissions are 25% lower than a conventional diesel drive. This is made possible, Rolls-Royce said, by the recuperation of braking energy, which is stored in mtu EnergyPack batteries.

In the HybridFlex trains, the batteries are mounted under the floor of the vehicle. A new type of driver assistance system, the mtu Intelligent Drive Manager, is also being used on this train for the first time. It is designed to ensure that the drive system automatically switches to all-electric operation in emissions- and noise-sensitive areas such as cities or train stations with no operator intervention.

“The mtu Hybrid PowerPack is an excellent example of how we are becoming a provider of integrated sustainable solutions with pioneering technologies,” said Berners-Wu.

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