Birmingham Centre for Railway Research and Education’s (BCRRE) research into the application of fuel cells and hydrogen in railway traction system design stretches back over the last decade and beyond. Hydrogen, in combination with a fuel cell, was identified by BCRRE and other researchers as a potential mobile fuel which would achieve combustion free autonomous capability in an effectively electric drive system. This solution would enable ‘emission free at the point of use’ vehicles to run on the non-electrified network.
Importantly, moving to a fuel cell system with a more direct conversion from chemical to electrical energy immediately opens up the opportunity to have higher efficiencies compared to combustion, and also solves the problem of combustion by-products such as NOx (nitrogen oxides).
BCRRE’s focus in this research was not to be an advocate of this technology, but rather to put the technology and its capability under deep scrutiny of the scientific method. Indeed, one of the seminal pieces of work, undertaken by Andreas Hoffrichter during his PhD at BCRRE, explored fully the role that hydrogen fuel cells could play in railways – where they may be suitable and, therefore, where they are not suitable.
Hydrogen, for example is not a solution which could, in the near term, be adapted for high-speed trains, or very long-range trains. These factors are explored further in the work BCRRE did through RSSB to support the industry’s decarbonisation task force.
Hydrogen education
BCRRE, as part of its education remit, aims to disseminate the findings of the research to foster widespread societal benefit. Hydrogen, as is often quoted, is the most abundant atom in the universe. Whilst this is an awe-inspiring fact, the problem is that, here on earth, pretty much all of it is bound up in molecules. Therefore, there is an energy cost associated with its production and, depending on exactly how the hydrogen is made, there can also be a CO2 cost.
In its work for the decarbonisation studies, BCRRE calculated the amount of CO2 per output kWh for hydrogen fuels. This ranges from something comparable to existing fuels to near-zero for hydrogen produced by renewable means.
Once hydrogen has been isolated as a gas, it has the following key properties which affect how the railway could use it. First, per kg of the gas, it has the potential to release approximately three times as much energy as the equivalent mass of fossil or liquid bio-fuel.
However, one kg of hydrogen, at standard temperature and pressure, takes up around 11 cubic metres, making for difficult storage. The state-of-the-art in storage for mobile applications is by compressing the gas to 350-700 bar and putting it inside carbon-fibre-reinforced storage tanks. This results in a system which can store more energy per kg than the best battery systems by quite some margin, but is not comparable to a simple diesel tank.
Calculations indicate that adequate range can be achieved for a tri-mode vehicle on representative routes with a daily refuelling assumption. This poses a problem for the railway industry looking for a like-for-like replacement of diesel fleets as they are often only pathed back to refuelling depots once every two or three days.
These challenges are currently being investigated by the team at BCRRE as part of the RSSB Intelligent Power Solutions to Decarbonise Rail programme of research.
Hydrogen innovation
Birmingham University’s sixth-scale demonstrator, the Hydrogen Hero, was one of the many highlights of last year’s Rail Live exhibition, where it had an audience with the Secretary of State for Transport, as well as other leading railway figures.
Around the time of the visit from the SoS, during a fortuitous conversation with the Porterbrook innovation team, BCRRE realised that it had the capability and expertise to rapidly upscale the demonstrator to mainline scale. This collaboration between BCRRE and Porterbrook was cemented at the signing of a memorandum of understanding at InnoTrans on 19 September.
Riding off the back of Porterbrook’s FLEX project, BCRRE realised that much of the engineering regarding conversion of an EMU into a train which can take any power source had been undertaken. Its engineering philosophy was to reuse much of this innovation and create a slim and elegant interface between the new fuel-cell/battery system and the existing train, without significant modifications to the driver’s desk or controls. Ultimately, the traction motors do not know what produces their traction current, the team just needed to create a modified traction-control interlocking system in order for the train to accept the fuel cell and battery power.
This modular approach could quite easily be translated to other rolling stock or new build. The intention for the initial prototype was to develop and build a system with enough power to operate the vehicle at low speed, in notches one and two. In the main, development followed established railway engineering practices although, for those areas where there are no railway precedents, then best practice from other sectors was followed and the team also engaged with both the ORR and RSSB.
The project kicked off in earnest in November 2018 and concept designs led to detailed design and manufacture. Orders were placed with key suppliers and an effective project management strategy was put in place to ensure the project remained on schedule. Static and dynamic testing is taking place in June and during this year’s Rail Live show, one year on from those initial discussions, a number of demonstration runs will enable delegates to witness the first ever UK mainline-scale railway vehicle being propelled by hydrogen.
As part of the approach in building a demonstrator vehicle, the fuel cell, battery, hydrogen storage tanks and other related equipment are being housed in the motor vehicle. This ‘lab in a train’ will enable the team to refine their traction system controllers in a suitable environment, and accelerate the engineering required to develop the traction system for full mainline application. There is still much work to do to get mainline ready, but the prototype demonstrator will accelerate the industry efforts and ensure railways meet future decarbonisation and air quality obligations.
The HydroFLEX team comprises lead partners BCRRE and Porterbrook Leasing Company, working with Ballard Power Systems Europe, Fuel Cell Systems , Luxfer Gas Cylinders, Denchi Power, Jeff Vehicles, DG8 Design & Engineering, Chrysalis Rail Services, Aura Graphics, SNC-Lavalin, DEU and Unipart.
