by Stuart Hillmansen, Peter Amor, Rachel Fisher, Charles Calvert, and Alex Burrows
The UK has reduced its carbon emissions by 44% relative to levels recorded in 1990 with the transport sector acting as the largest emitter of Greenhouse Gases at 38%. Rail transport only contributes 2.5% of transport emissions, however rail must still decarbonise to achieve net-zero emissions by 2050.
Significant developments to decarbonising the rail industry include establishing a long-term rolling stock strategy to remove diesel-only trains from the GB rail network by 2040. However, for Heritage Rail where many trains are coal powered, how can they decarbonise? A simple option would be to stop steam trains from operating, but this would remove the excitement of watching a steam engine come to life and diminish the educational experiences that Heritage Rail offers.
At the University of Birmingham, we are exploring the decarbonisation of Heritage Rail, introducing hydrogen fuel to existing trains without reducing their historical value. This will inform policy for decarbonisation of Heritage Rail.
UK Progress on Transport Emissions
The UK has recently been commended by US climate change envoy John Kerry, for its progress on addressing the climate emergency, reducing its carbon emissions by 44% relative to levels in 1990, much quicker than other wealthy nations. The UK’s strategy has been to set a net-zero goal for 2050 to drive changes across all sectors to reduce emissions and decarbonise. So far much of the focus on reducing carbon emissions has been on roads, however the rise of electric vehicles will help address this, especially those that can be identified by a green-marked number plate. Cars, vans and HGVs are not an unjustified focus; the biggest contributor to UK carbon emissions is transport, and by far the biggest contributor to that is road transport.
Given that, you might wonder why we bother to look into rail decarbonisation, given that less than 2% of UK transport carbon emissions come from rail, making up just half a percent of total UK emissions. However, these numbers alone do not tell the full story; as the UK’s hundreds of diesel trains churned their way through 476 million litres of diesel last year, producing other emissions including small particles, and nitrogen and sulphur oxides, as they go. Diesel trains are not only noisy, smelly and generally unpleasant but they are also harmful as particulates and other emissions are known to have a negative impact on human health. This is a particular problem in enclosed train stations such as Birmingham New Street, where levels of these airborne pollutants can be very high. If we want to encourage people to use the railways, with the consequent reduction in congestion and emissions and improvement in quality of life, we therefore have a responsibility to reduce emissions.
Decarbonising GB Rail
Plans have already been made to start decarbonising the railways, such as the removal of all diesel-only trains from the national network by 2040. Significant progress has already been made, with the UK’s passenger rail CO2emissions falling considerably over the 2010s, despite an increase in passengers.
While positive progress is being made on the mainline network, there is one area of the railway which is going to be difficult to decarbonise; heritage railways. When the main attraction of a railway is coal-burning, steam-powered trains, it would seem there is little that can be done. Of course, we could ban steam-powered trains, but this would ruin the attraction of these railways, which are important for the tourism of the communities they serve and are an important steward of social and cultural history. Various coal alternatives have been tried, with varying degrees of success, but largely they have proved unsuitable. So how could heritage rail be brought into the age of low carbon, without reducing their appeal to enthusiasts around the world? One aspect of the heritage scene that could be explored is decarbonising heritage diesel trains, for which there are a number of possible solutions.
While it might be possible to run heritage diesel trains on biofuels, this is not as simple as it would at first appear. Firstly, these fuels are not a perfect solution; even though their production does take in carbon, they need to be transported to where they are used, and growing crops for biofuel can take up valuable land. Secondly, many older diesel engines may struggle to run well on modern biofuels, which may make this solution impractical. Another option is to replace the engine of a heritage diesel train with a system that produces fewer, or no, emissions. At first glance, this might not make sense for many diesel trains either; part of the attraction is the noise, the sights, and the sounds produced by these trains and the consequent feeling of nostalgia for by-gone times which these railways trade on.
It would be a mistake, however, to assume that all the trains on a heritage railway are there for public amusement. In order to marshall trains, move around old trains for maintenance, and keep the railway running smoothly, heritage railways require smaller locomotives called shunters. While these are often historic themselves (the most common type is the Class 08, dating from the 1950s), they are very seldom the main attraction.
What would be the options for decarbonising such a locomotive? If we were to take inspiration from the car industry, we could convert them using batteries. Although electric cars are increasingly becoming the norm, but batteries are not without their problems. The main issue is that the amount of energy that can be stored in a battery is limited and while no longer a problem for cars, trains are much bigger and heavier requiring more energy to keep going, particularly when shunting another train. In addition, the current diesel trains are expected to be in service for hours or even days at a time without refueling, and when they do refuel, this is expected to take a handful of minutes rather than the long durations typical for battery charging.
There is therefore a clear need for a technology which will provide more energy than a battery. One technology showing great promise is hydrogen, which when stored as a compressed gas, can store a lot more energy than a battery. This gas can be used in a fuel cell, which combines hydrogen with oxygen from the air. This reaction produces an electric current, which in turn can be used to drive the train. This is far more environmentally sound than a diesel engine as it produces no harmful emissions. While it is true that much hydrogen is produced from natural gas, hydrogen can also be produced by electrolysis of water; passing an electric current through it to split it into hydrogen and oxygen (an experiment many will have done in chemistry at school, albeit on a much smaller scale). If this electricity comes from renewable sources, it is possible to eliminate the use of fossil fuels entirely.
The first University of Birmingham foray into the sphere of hydrogen-powered trains was an entry to the Institute of Mechanical Engineering’s Railway Challenge, a competition for miniature locomotives entered by teams of young people. Subsequent years of the competition saw better and better entries from the University, culminating in Hydrogen Hero, which appeared not only in the competition but also at other events such as Rail Live and Modern Railways Rail Vehicles and Enhancements.
Further, in 2018 the University partnered with train leasing company Porterbrook to produce HydroFLEX, the UK’s first full-scale hydrogen-powered train. This project involved taking an old electric train and feeding it with electricity from a hybrid system containing both a hydrogen fuel cell and a battery. As the project progressed, it brought with it considerable experience of adapting advanced hydrogen technology to a practical railway context. This experience is very much transferable to a shunter on a heritage railway as many of these old locomotives are diesel electric, meaning that they have a diesel engine which drives a generator to produce electricity for the motors driving the train. It is entirely possible to replace this diesel engine with a hydrogen fuel cell system, to produce a modern zero-emission train engine inside a heritage shunter shell. Such an approach is not without challenges. While far better than batteries, hydrogen storage still takes up a lot more room inside the locomotive than the equivalent diesel tank; this must be factored into the design.
There are numerous other difficulties to be overcome; the controls of the locomotive, normally connected to a diesel engine, must be adapted to control a hydrogen fuel cell; the radiator and cooling must be changed; and the electronics of the fuel cell system must be adjusted to feed the existing locomotive. However, none of these challenges is insurmountable, and with HydroFLEX, the University has proven itself capable of overcoming them, working alongside a multitude of partners, suppliers and the wider railway industry. The sharing of such valuable experience with partners is also an ideal opportunity for up-skilling engineers across the rail industry as the widespread introduction of hydrogen-powered trains gets closer.
The advantages for a heritage railway of a hydrogen-powered shunter go beyond the reduction in carbon emissions. Such a conversion process would take a shunter out of service for a while, which presents an opportunity to overhaul the remaining components such as brakes, and to smarten up the bodywork with a fresh lick of paint. Further, the working environment on these upgraded hydrogen locomotives or HydroShunters can be cleaned up and vastly improved over the noisy, oily environment currently encountered. In addition, the HydroShunter would be unusual and interesting, potentially bringing in more visitors, while demonstrating clean, green rail initiatives and improve the wider public perception of emissions reductions and heritage railways. Following the impact of Covid-19 on heritage lines, bringing the railways back to life with a sustainable and modern twist may well improve revenues for the ailing sector.
While it is still challenging to envisage the decarbonisation of coal powered engines, the conversion of behind-the-scenes locomotives like shunters can provide many benefits both for heritage rail and for the rail industry as a whole.