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This was a miniature 10¼-inch gauge locomotive entered by the University of Birmingham. It had a 1.1kW fuel cell which continually charged a 4kW traction battery.
The aspiration that innovations trialled at the Railway Challenge would be seen on the mainline railway was realised in 2016 when Alstom unveiled its two-car Coradia iLint hydrogen train at the Innotrans trade fair. This train entered passenger service in Germany two years later.
Like the Railway Challenge locomotive, the iLint is a hydrogen/battery hybrid. Each car has a 225kW traction battery and 200kW fuel cell supplied from roof-mounted tanks which store 89kg of hydrogen at 350bar.
2050 target
The rail industry is currently developing a strategy for net-zero carbon rail traction by 2050. While this will require most lines to be electrified, where this is not feasible diesel trains will need to be replaced with alternative self-powered traction for which the only options are battery and hydrogen power.
As with road vehicles, energy density is a constraint for such alternative traction. Hydrogen, at 350bar, has one-seventh the energy density of diesel, and so is not suitable for high-speed or high-powered applications such as freight locomotives. However hydrogen trains do offer a reasonable range and performance. At 350bar, hydrogen has about twice the energy density of a modern battery pack. Hence battery traction is suitable for short-range services between recharging such as branch lines off electrified lines.
On the roads, the Committee on Climate Change (CCC) considers that hydrogen will be required for zero-carbon HGVs and buses. It estimates that, by 2050, the annual transport demand for hydrogen will be: HGVs – 22TWh, buses – 3TWh and trains – 0.3TWh.
Producing hydrogen
Currently almost all the world’s hydrogen is produced in large plants by reforming methane. This produces CO2 emissions that are around 80% of diesel fuel. As producing hydrogen by electrolysis is more expensive, the CCC report considers that the most cost-effective way of producing large amounts of hydrogen is by reforming with carbon capture and storage. However, producing hydrogen at large plants would require a distribution network.
The pilot scheme to operate a fleet of 10 buses in Aberdeen demonstrated the practicality of producing hydrogen on site. The scheme’s hydrogen plant consisted of three electrolysers (each the size of a 40ft container) with compressors, dispensers and storage tanks and required a 1MW electricity supply. This produced around 150kg of hydrogen per day to fuel the city’s hydrogen bus fleet. Trains require about 10 times more hydrogen than buses.
UK hydrogen trains
The University of Birmingham now has a full-sized hydrogen train in the form of Britain’s first mainline hydrogen train, Hydroflex, which is a joint development with Porterbrook leasing. However, this is purely a demonstrator vehicle.
Alstom unveiled its design for a UK hydrogen train in January 2019. This uses the company’s hydrogen technology within a converted surplus train. However, owing to the constrained UK loading gauge, hydrogen must be stored inside the train, which reduces available passenger space. It may be possible to produce a hydrogen train with tanks that do not encroach onto the passenger area.
Obtaining approval to operate a hydrogen train, with systems for which there are no standards, will be challenging. A further hurdle will be the financing of the hydrogen plant to fuel these trains. Hence it may be some years before UK passengers travel on hydrogen trains. Yet, if there is to be net-zero rail traction, these hurdles must be overcome.
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Content published by Professional Engineering does not necessarily represent the views of the Institution of Mechanical Engineers.