Project Profile: HybridFLEX Battery-Diesel Train

The HybridFLEX project is a landmark UK initiative demonstrating the successful retrofitting of legacy diesel multiple units (DMUs) with an advanced battery-diesel hybrid propulsion system. This profile details the technical specifications and strategic implications of converting Class 168 and Class 170 ‘Turbostar’ trains for reduced emissions and enhanced operational efficiency on non-electrified routes.

Technical Specifications

The core of the HybridFLEX project is the retrofitting of existing diesel multiple units with the Rolls-Royce mtu Hybrid PowerPack. This modular system integrates an EU Stage V compliant low-emission diesel engine with an electric motor/generator and an mtu EnergyPack battery system. The conversion enables dual-mode operation: the train can run on diesel power for inter-city sections and switch to zero-emission, near-silent battery power when entering and leaving stations or operating in environmentally sensitive urban areas.

A key technical feature is the system’s ability to capture and store kinetic energy through regenerative braking. This recuperated energy, which would otherwise be lost as heat, is stored in the battery pack and redeployed to assist with acceleration, reducing the load on the diesel engine. This process contributes to a projected fuel consumption and CO₂ emissions reduction of up to 25%. Further environmental performance gains include a 70% reduction in nitrous oxide (NOx) and a 90% reduction in particulate matter. The system integration, managed by Ricardo, involved complex mechanical, electrical, and control system engineering to ensure seamless functionality and compliance with rigorous UK rail safety standards.

Key Takeaways

• Viable Decarbonisation Pathway: The project validates hybrid conversion as a rapid and cost-effective strategy to decarbonise a significant portion of the UK’s legacy diesel fleet, bridging the gap to full electrification or hydrogen power.
• Model for Collaborative Innovation: The successful partnership between rolling stock owner (Porterbrook), technology supplier (Rolls-Royce), and integration specialist (Ricardo) provides a blueprint for accelerating complex engineering projects in the rail sector.
• Tangible Performance & Efficiency Gains: Beyond emissions reduction, the hybrid system delivers significant operational benefits, including improved acceleration for reduced journey times, lower noise pollution in stations (up to 75% reduction), and decreased maintenance costs due to reduced wear on mechanical brakes.

Frequently Asked Questions (FAQ)

What is the HybridFLEX train?
The HybridFLEX train is a converted Class 168 or 170 ‘Turbostar’ diesel train that has been retrofitted with a Rolls-Royce mtu hybrid battery-diesel system. This advanced system reduces CO₂ emissions by up to 25% and significantly cuts noise and air pollutants, allowing the train to operate on pure battery power in sensitive areas like stations.

Who is building the HybridFLEX train?
The HybridFLEX conversion is a collaborative project. It is led by the rolling stock owner Porterbrook, the core hybrid technology is provided by Rolls-Royce, and the complex system integration and certification is managed by the engineering consultancy Ricardo.