The new HybridFLEX train will deliver emission-free battery operation. Credit: Chiltern Railways.
The HybridFLEX train combines diesel and electric power for enhanced acceleration capabilities. Credit: Ricardo.
The green HybridFLEX train is the UK’s first hybrid-powered passenger train. Credit: Chiltern Railways.

The HybridFLEX train is the UK’s first hybrid-powered passenger train unveiled by Chiltern Railways, a train operating company.

The hybrid battery-diesel train is developed by UK-based rolling stock leasing company Porterbrook in collaboration with engineering firm Rolls-Royce. Launched in July 2021, the new state-of-the-art trains are scheduled to begin full-scale passenger operations in September 2021.

HybridFLEX is the latest member of Porterbrook’s portfolio of alternative traction systems designed to help the UK’s railway system in its efforts to achieve net-zero emissions by 2050.

The new trains will aid Chiltern to decarbonise its railway network and improve the passenger experience through fleet modernisation.

HybridFLEX development history

Porterbrook and Rolls-Royce signed an agreement to convert Class 168 and Class 170 ‘Turbostar’ diesel multiple units (DMUs) from diesel-only to hybrid-electric operation at the InnoTrans rail transport industry trade fair in Germany in 2018.

Rolls-Royce agreed to provide hybrid systems for installation on two test trains for a six-month testing period. The agreement covers the initial delivery of two mtu Hybrid PowerPacks based on type 6H 1800 engines.

The train is being tested at the Ecclesborne Valley Railway in Wirksworth, Derbyshire. It carried passengers for the first time between Marylebone and Bicester Village in July 2021.

HybridFLEX features

The HybridFLEX project involved the installation of a Rolls Royce mtu hybrid drive system to a multiple diesel unit, resulting in a vehicle that can run on both battery and diesel power with seamless transition between the two modes.

The hybrid drives are expected to reduce maintenance costs over the lifespan of the vehicle due to decreased wear and tear of components such as brake pads and discs.

The HybridFLEX is a converted Turbostar DMU that was previously powered by a conventional MTU drive system.

The train is installed with a diesel engine compliant with EU Stage V emissions standards, an electric motor, and an mtu EnergyPack battery system that is designed to store the energy recovered during braking.

HybridFLEX benefits

The HybridFLEX trains are expected to make rail travel more environment-friendly, improve air quality, and reduce noise at stations and other sensitive locations.

The train’s emission-free battery operation will reduce CO₂ emissions and fuel usage by 25%, noise emissions in stations by 75%, nitrous oxide (NOx) emissions by 70%, and particulate emissions by 90%.

Furthermore, the train units will reduce travel time and increase route capacity through improved acceleration capabilities.

MTU Hybrid PowerPack details

The MTU Hybrid PowerPack is a high-tech environment-friendly drive system that combines the benefits of diesel and battery-powered trains. It is a more sustainable and cost-effective alternative to conventional drive systems.

The Hybrid PowerPack originated from the proven and successful mtu underfloor drives. MTU, a Rolls-Royce brand, upgraded and outfitted the mtu PowerPack with hybrid technology.

The mtu hybrid drive comprises a modular kit that includes a range of drive components and can be configured to meet the specifications of the customer.

The Rolls Royce mtu hybrid drive provides the flexibility to be incorporated in new diesel hybrid vehicles or retrofitted into existing vehicles.

Contractors involved

UK-based critical rail systems supplier Ricardo was contracted to provide engineering support for the integration of the hybrid powerpack’s mechanical, electrical, and controls systems in 2019.

The company engaged its Automotive and Industrial division staff and rolling stock experts to deliver the contract. It also performed activities related to certification and approvals.