Alternative traction systems for passenger trains – Hybrid and Hydro FLEX

Relevant RTS critical priority(ies):
Low emissions

The rolling stock leasing company Porterbrook is investing in innovative retrofit projects to convert existing electric and diesel multiple units into hybrid trains, and reduce diesel train emissions.

Hybrid FLEX is a demonstrator battery-diesel train developed with Rolls-Royce and Chiltern Railways, with the old diesel engines replaced by a hybrid power pack. This could reduce fuel consumption and carbon dioxide by 25%, nitrogen oxides by over 70% and particulates by over 90%. Furthermore, the batteries permit silent and emissions-free arrival into and departure from stations to improve air quality.

Hybrid FLEX – GB’s first diesel-battery hybrid train

Hydro FLEX is a demonstrator hydrogen train converted from a redundant electric multiple unit by Porterbrook and the University of Birmingham. It is the first hydrogen train in GB – and the first retrofitted hydrogen train in the world – which also retains its equipment for working on DC third rail and AC overhead electrified lines. Porterbrook has invested £7m in the project, with hydrogen tanks, fuel cells and batteries installed on the train for an initial demonstration in 2019. Innovate UK subsequently funded mainline testing in 2020 and Hydro FLEX will be the centrepiece of an event at the UN Climate Change Conference of the Parties (COP26) in Glasgow in November 2021.