Keeping our trains on track

4 min read

The UK rail industry is considering the options for alternative power technologies as itprepares to come under the environmental spotlight.

The railways have long enjoyed the image of a green mode of transport, particularly when compared to the environmental lobby’s nemesis, the petrol-guzzling car.

But last year this image was tarnished somewhat by research showing that on certain types of journey the amount of fuel used per passenger on trains is actually higher than if the same trip were made by road. No one with any sense would argue that regular train commuters should all jump into their cars, creating far more single-occupancy vehicle journeys and more pollution. But with car pollutant emissions decreasing each year, the train no longer appears the paragon of virtue it once was.

Trains are becoming heavier, with the latest vehicles produced for the UK weighing approximately twice the mass per passenger of those in Japan. EU emissions regulations for non-road vehicles will also begin to include new rail engines from 2011. These will set particulate limits at 0.025g/kWh by 2011, and limit NOx to 0.4g/kWh from 2014.

The UK rail industry is now funding trials of sulphur-free diesel to examine its impact on performance and engine life. This will reduce particulate emissions and allow further improvements through the use of aftertreatments. But, more fundamentally, the industry is beginning to investigate different technologies for powering trains in the future, and considering how these could be developed and tested.

As the lifetime of a train can be around 40 years, it is crucial the industry gets these decisions right, said Prof Rod Smith, head of mechanical engineering at Imperial College, speaking at a seminar, held this month in London, on future power technologies. ‘The technology window for the railways is long, and you have to live with that outdated technology. The automotive industry can renew itself every 10 years. So it beholds us to introduce absolutely the newest and best technology.’

At the seminar, held jointly by industry body the Railway Forum, the EPSRC-funded Rail Research UK (RRUK) and the Rail Safety and Standards Board, Smith and his colleagues from RRUK revealed the preliminary findings of a feasibility study into future power options, which is due to be completed next month.

Dr Rui Chen of the combustion and energy conversion group in the aeronautical and automotive engineering department at Loughborough University, outlined the potential technology steps the railways could take on the way to adopting hydrogen fuel.

These include immediate action to reduce diesel engine emissions such as using particulate filters, and short-term efforts to improve efficiency through recovering energy from braking for use initially for auxiliary power and later for propulsion. Fuel cells could then be introduced gradually into trains, possibly first as part of a hybrid system with a small diesel engine, to allow the technology to be proved before using it as the only power source. Lessons should be learnt from the car industry, he said.

‘I do believe the railway industry needs to look at the history, current development and future technologies of the automotive sector. The automotive industry has been continuously regulated for more than 30 years on pollution and fuel economy. In comparison, the railway industry has just begun to face this kind of challenge.’

The Rail Safety and Standards Board is also leading a three-month feasibility study into hydrogen fuel on the railways, being undertaken by AEA Technology.

With other transport sectors investing heavily in hydrogen R&D, the organisation was asked by industry to investigate the business case for moving to hydrogen fuel, the current status of research, and how the technology should be developed for the railways.

Jeff Allan, head of electrical systems engineering at RSSB, said progress towards the use of hydrogen by other transport, particularly cars, could leave the railways with little choice but to adopt the fuel.

‘Rail in the UK only accounts for six per cent of passenger kilometres, so it would be impractical if not impossible to go it alone from other forms of transport,’ he said.

This is likely to be particularly the case if the cost of carbon-based fuels spirals in future. But if fuel cells are to be used to power trains much development work remains to be done, according to Sujith Kollamthodi, principal consultant at AEA Technology Environment. At around 5,000 hours, the current operational lifetime of fuel cells is vastly inadequate for trains, and would account for around 10 years’ use at just one and a half hours per day, he said.

There are also question marks over the power density of fuel cells and the size of the resulting powertrain, which would be larger than the equivalent internal combustion engine, although research in these areas is likely to lead to improvements in the next 10 years. The UK rail industry could not realistically hope to develop the necessary hydrogen infrastructure on its own, and would need to seek support and research partners from across Europe.

Funding should be available under the EU’s Framework 7 programme to carry out vehicle demonstration projects, he said. But there may not be much of an appetite for collaboration on research into hydrogen trains in the rest of Europe, where electrification levels are far higher than in the UK, which has only 30 per cent of its routes electrified.

In France, where nuclear power accounts for around three-quarters of the electricity supply, the performance of the country’s electrified trains in terms of their overall carbon dioxide emissions is already ‘fantastic’, said Imperial College’s Smith. Indeed, many within the industry, including Smith, believe the UK could improve the environmental performance of its railways without the need to pursue future technologies such as fuel cells, by beginning a major electrification programme.

Once the initial cost of electrification was met, the industry could then benefit from the increasing use of renewable energy sources in the UK’s electricity supply, without further expenditure. But opinion is divided on electrification. Opponents claim it costs at least £500,000 a mile to electrify a section of track, while maintenance is 40 per cent higher than for nonelectrified lines. AC lines also look ugly, they argue.

Supporters claim electrification is often used in the UK as a euphemism for building a new section of railway, and the actual costs are tiny when compared with all the other work that tends to be carried out at the same time. Maintenance of electrified trains is cheaper, and they produce less noise, they claim.

One thing is certain, though: the rail industry is going to come under increasing pressure to clean up its act, as the environmental performance of other forms of transport continues to improve. But this will require a united effort, so the industry must reach an agreement on the best technology to pursue for producing emission-free trains. With new trains being introduced today likely to last another 40 years, this decision must be made soon.