Could hydrogen trains be the future of rail?

29th October 2018 | Commercial Energy

With increasing concerns about climate change and harm from diesel emissions, greener transport is now a political imperative. In February the transport minister Jo Johnson called on the rail industry to provide a vision of how it will decarbonise. He stated that he wished to see “all diesel-only trains off the track by 2040” and viewed “alternative-fuel trains powered entirely by hydrogen” as a prize on the horizon. But, seven months previously, transport secretary Chris Grayling announced the cancellation of three electrification schemes, necessitating extra diesel trains. The week beforehand, Grayling stated that the government intended to halt petrol and diesel car production by 2040.

Notwithstanding these apparent contradictions, Johnson is right to stress the need to decarbonised the rail industry. Although trains offer great environmental benefits, the industry cannot rest on its laurels.

Hydrogen trains

A train’s power ranges from 450kW for a two-coach local train to 6mW for a 125mph 11-coach electric inter-city train. The respective power-to-weight ratios of these trains are 5.7 and 10.5kW per tonne. Commuter trains do not necessarily travel at high speed but required high power for the acceleration needed to operate a passenger service with frequent stops to an acceptable timetable. An electric multiple (EMU) typically has twice the acceleration of a diesel multiple unit.

A UK diesel freight locomotive of typically 2,500kW might haul a train of 2,000 tonnes. Freight services, and depots, also require shunting locomotives to marshal trains. These need a high tractive effort to move heavy loads but only operate at high speeds so require a low-powered engine of, say, 250kW.

As of March 2017, Britain had 14,000 rail passenger vehicles, of which 72% were electric trains and the rest self-powered. There are also 800 freight locomotives, of which 16% are electric. In addition, there are 180 shunters.

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