Passengers waiting for trains at stations between Harwich International and Manningtree in Essex have in recent weeks unwittingly played a role in an important project that could lead to the development of a cleaner, more efficient railway network.
Each weekday, an unremarkable-looking Class 379 Electrostar has shuttled between those destinations, but not always by using electric power from the overhead wires. Instead, for parts of the journey, the pantograph has been retracted and the train has been running on battery power supplied by two huge banks of cells positioned between the wheelsets of one carriage.
The Independently Powered Electric Multiple Uni (Ipemu) is the first battery-powered train to run on Britain’s rail network in more than half a century. Its use marks an important milestone in the project to demonstrate the viability of an eco-friendly battery-powered train.
Ultimately, Network Rail and its partners on the Ipemu project – including Bombardier, Abellio Greater Anglia and the Department for Transport – predict that, one day, batteries could be used to power fleets of new trains between electrified parts of the network and on branch routes where it would be too costly to install overhead lines.
“We’ve made terrific progress with this project so far and seeing the battery-powered train in timetabled service is a huge step forward,” says James Ambrose, Network Rail’s principal engineer on the Ipemu project: “The train has been running just as we would like it. We are using the five-week period to gather data on how it handles during passenger service – most travellers will recognise how quiet and smooth the ride is compared to a diesel train.
“We are always looking for ways to reduce the cost of running the railway and make it greener too. This project has the potential to contribute towards those goals.”
At the outset, Network Rail carried out a feasibility study that looked at a variety of technologies, including batteries, supercapacitors and hydrogen fuel cells, to progress the concept of an independently powered train. Battery technology was selected on the basis that it could, on paper, cope with the kinds of duty cycles encountered.
Six battery technologies were originally considered, and that was whittled down to three – lithium ferrous phosphate, hot sodium salt, and lithium titanate. “We discovered that two of the technologies didn’t meet our criteria,” says Ambrose. “Lithium titanate wasn’t sufficiently developed to be able to meet the safety requirements for the train.
“And with hot sodium salt, not enough thought had been given to the rafts that the batteries would sit in. For all the cells to fit, we would have had to reduce the number of batteries – and that would not have given us the duty cycle and power that we needed.”
Lithium ferrous phosphate was deemed ideal, and thought was then given to installing the technology on a train. Ambrose says: “The battery we actually went for had proven ability – it has been used on Segways, for military functions, and on London buses. It had pedigree behind it. We weren’t trying to create a new technology – we were trying to show that a proven technology was capable for use on a train.”
A Bombardier Class 379 Electrostar, a second-generation EMU, was chosen for Ipemu because it had the ability to use regeneration from the braking system. That would allow the train to harvest energy and re-route it back into the batteries.
Each cell is 3.2V and not much bigger than an AA battery. There are 300 cells in a single pod, which is about the same size as a car battery. There are 20 pods in a bank and there are two banks to make up a single raft, and six rafts in total.
“We had calculated that the trials would require a duty cycle of 50km on overhead, and 30km on battery power. For that we needed 560kWh of power,” he says. “That’s what the battery system was designed to achieve, with half of the energy used to run the route and half of it for heating, lighting and air conditioning.”
Once the battery cells were fitted on the train, testing was carried out on a section of track at Bombardier’s Litchurch Lane site in Derby, before moving on to the Old Dalby facility in Leicestershire for greater distances.
“To get the weight right for the train we had to take one traction package off to compensate for the weight of the batteries,” recalls Ambrose. “We had to prove that the train would still be capable of achieving the sorts of speeds that it was designed for, even with reduced traction package. The train was designed for 100mph, and during the Old Dalby trials we achieved that on both AC and on battery mode.”
The trials did throw up a few obstacles. With six banks of batteries fitted across two separate rafts, the partners found that the battery management system was struggling with balancing issues, often leading to the automatic shutting down of output from one of the rafts and relying on single operation.
“The battery management system wanted all the batteries to be at a certain state of charge,” he says. “If it wasn’t balancing, it would shut one raft down. We had to rewrite the software a few times to compensate and to widen the acceptable voltage bands. That was how we solved it. It was clear that we were trying to be too strict on some of our settings.”
Safeguards to prevent thermal runaway also had to be built in, says Ambrose. “We put stringent limits on the battery management system. If the batteries started to get near 60°C, then we wanted to know about it with an alarm. At 65°C we needed to know a bit more, and at 70°C we wanted it to shut down. We couldn’t take the risk of thermal runaway.
“Safety was high on our agenda, as we knew we had to get through the approvals process. We had to prove to the safety authorities that we had thought through all of these issues and mitigated against them.”
Then it was on to safety validation. The train operator had to be confident that its staff knew what to do in case of technical difficulty. Seemingly simple factors such as ensuring that all on-board employees knew how to isolate the battery should there be a problem had to be run through time and again. Also the emergency services had to be trained to deal with any situations.
For the trial itself, the train has been running between Harwich and Manningtree for five weeks, up until 12 February. Realtime data acquisition has been used to log performance, giving accurate insight into loading characteristics and the effect on the batteries.
“We are looking for a better understanding of range/durability,” says Ambrose. “Nobody has done a battery trial on the railway on this scale before. Everyone in the industry is asking how long will it be before you have to change the batteries?
“So, what we intend to do after the in-service trial is to fast-age the batteries that have been on the train, using lab testing to see what we can get out of them. Our target in terms of lifespan is five to seven years, which would tie-in with a normal heavy maintenance period on a train.”
In terms of how technology might develop to enable independent power on the railways, Ambrose thinks that a combination of batteries and supercapacitors might ultimately prove the ideal solution. “You could then harvest more of the regenerative power into your supercapacitors, which would give you that initial acceleration needed at stations, with the batteries then becoming the mainstay. You would extend your range by doing that.
“Technology moves on: we’ve seen supercapacitors used on trams for quite a while, so eventually it could be an area we move towards.”
Once the trial is completed, and the fast-age testing is done, the project partners will produce an industry model that will look at how battery power could be incorporated into the network. But a lot of other factors have to fall into place for that to happen, admits Ambrose. “It will be up to the Department for Transport to incorporate this sort of technology into franchise bids. Manufacturers need to come on board and say it’s a suitable technology that we can sell, and the rolling stock operating companies have to buy it.”
Wireless future: Use of batteries could remove the need for overhead electrification on some stretches of railway line
Spotlight on railway research
The IMechE is to hold a three-day conference on railway innovation.
The Stephenson Conference – Research for Railways – is an international event covering a wide range of research into railway infrastructure, rolling stock and control systems.
Keynote speakers include Richard Parry Jones, chairman, Network Rail; Dr Norimichi Kumagai from the Railway Technical Research Institute of Japan; and Keir Fitch, head of unit, Research and Innovative Transport Systems, DG Move - The European Commission.
The event will take place from 21-23 April at One Birdcage Walk in London. See
www.imeche.org/stephenson for more details.