Amid all the talk of rebuilt Pacers and Tube trains, it may have escaped people’s attention that another alternative to electrification or new-build diesel multiple units is available. What’s more, testing of this option has recently been completed.
The Independently Powered Electric Multiple Unit (IPEMU) is something that could appeal to operators on those occasions where DMUs could still be required.
The concept here is that electric multiple units are fitted with battery technology, enabling them to run under their own power away from overhead lines. And it certainly fuels the debate that is raging at the moment regarding the future for certain routes.
Could London Underground D78-Stock, rebuilt for heavy rail, be an option?
What about Pacers? They are seemingly detested by passengers, yet the belief that they could all be withdrawn by 2020 has potentially been blown out of the water by Porterbrook’s rebuilt ‘144’ (RAIL 768).
Some believe that new-build DMUs could be the answer. Rail Minister Claire Perry has actively called for that option, and manufacturers such as CAF and Hitachi have not ruled out building such fleets. The former delivered DMUs to Northern Ireland in 2011-2012, while the latter says its AT100 and AT200 concept trains could also include a diesel variant.
Meanwhile, the IPEMU has already undergone tests. The project started last year, using a converted Class 379, and involves Network Rail, the Rail Executive, FutureRailway, the Rail Safety and Standards Board (RSSB), Abellio Greater Anglia (AGA) and Bombardier. AGA operates the ‘379s’, while Bombardier built and maintains them.
A four-car electric multiple unit (379013) was selected last year and moved to Derby Litchurch Lane for modifications last May, before being taken to Old Dalby for testing.
Then, in January this year, it moved to Ilford, from where main line testing was conducted for one week (beginning January 5) on the Manningtree-Harwich Town branch. The following week it carried passengers, after which in-service testing continued until February 13. It was returned to Derby on February 17.
At an event held for VIPs on February 9, RSSB Director of Innovation David Clark said of the IPEMU: “It is a great example of cross-industry collaboration. The cost of a demonstrator was not feasible - it needed partnership, and that is what we got.
“This idea came from the Rail Technical Strategy, and there are opportunities to look at parts of the network that are not electrified.”
He expanded on that point by explaining the electrification schemes: “Only 60% of the network makes a business case for electrification. That means 40% needs an alternative.
“66% of DMUs are more than 20 years old. They need to be replaced, or we need to think of something different.” Clark said that the idea for the IPEMU came partly from the automotive industry.
NR Principal Engineer James Ambrose explains why a Class 379 was chosen. “We wanted a second-generation electric multiple unit. It had to have regenerative braking.
“The first to be fitted with that, I think, were the Class 323s. We needed a timetable and performance that matched it. The plans had to match something that was already ‘out there’. Later-built trains are power hungry, as they have power sockets and air-conditioning.
“A Class 379 was chosen as they are three to four years old. They are power hungry, and the thinking was that if it works on a Class 379 it should work anywhere.”
‘It’ is the battery technology. The Class 379 is fitted with 396 3.2 Volt cells, each the size of an AA battery. Twelve cells are connected in series, in a row (which equals 38.4V), and there are 33 rows connected in parallel to form a Volt Battery.
There are 20 of these 38.4V batteries, connected in series to form one Volt Pod (768V). Two pods are connected in parallel to form a Volt Module, of which there are three connected in parallel to form a Volt Battery Raft.
Two Battery Rafts are connected in parallel to the solebar of the Pantograph Trailer Standard Open (PTSO) vehicle on the ‘379’ (61913).
The Battery Rafts fitted to the Class 379 unit contain a battery box, isolation switch, power distribution control panel, battery charging inverter, and batteries and battery monitoring system, all mounted within a purpose-built rig.
Their creation follows the successful testing of several types of battery technologies, including Lithium Iron Magnesium and hot Sodium Nickel Salt. And Ambrose says that the rafts can be made bigger, if needed: “This is plug and play. There is no reason it could not go on other trains.”
Different battery technologies could also produce different results, he explains, with Lithium likely to be able to last up to 15 years.
However, he warns of possible problems: “Bigger batteries produce more heat. The raft is also eight tonnes, but with various trade-offs we made the vehicle five tonnes heavier . There are gains in going bigger, but you lose power.
He adds: “There’s a desire for more electrification, but it is not viable to electrify all of the railway, so is there another answer?
“Low bridges, for example, are very expensive to wire due to the infrastructure. Trains may be able to coast, but a train could ‘sit down’ . Long-distance Independent Power could help, but the big win could be ‘gaps’ such as travelling from east to west across a line that is not electrified.”
Ambrose believes that there are plenty of benefits to the project: “There are reduced rolling stock costs, it will be a far better way than relying on fossil fuel for power, and there are reduced electrification costs.”
He says that passengers should also find their ticket prices cheaper, as a result of other costs being reduced and not being passed on to the fare box.
“Diversionary routes could be opened up, too,” he notes. “There would be increased availability, and an IPEMU would be greener, cleaner, smoother and quicker than a DMU.”
Network Rail is due to issue a strategy document in late March regarding electrification. At the February 9 event, it was made clear that IPEMU would feature. Says Ambrose: “It will consider the conversion of DC to AC power, and also IP fleets.”
He tells RAIL that 31 different bids were received after the contract to convert an EMU was put out to open tender. Bombardier won that deal.
But it wasn’t just about the train, as Ambrose explains: “We had to get all the data for the train and its power demand. Batteries had to be tested in a laboratory environment. Performance testing using 379013 was carried out at Litchurch Lane, where it ran at speeds of up to 20mph on a mile-long test track. From there it was taken to Old Dalby, where it could run at speeds up to 100mph.
In the cab, it was essential that the driver didn’t see much change. Ambrose explains: “We didn’t want the driver to see anything different. It was a dual-voltage train, and instead of AC/DC it is AC/IP. It doesn’t look any different.”
Four AGA drivers are trained to drive it. All are based at Colchester, and they visited Old Dalby for training and testing. They first had to learn Class 379s on the West Anglia Main Line, as the EMUs do not run on the Great Eastern Main Line.
The route chosen was the Harwich Town-Manningtree branch. Ambrose explains why the route was selected over the Marks Tey-Sudbury line (which isn’t electrified) and the Southminster route.
“There would be little disruption to passengers and it is electrified, so if there was a problem the pantograph could be raised. The journey is a 50-minute round trip.
“We looked at an 11-mile battery run and actually have built confidence. We know it will do round trips.”
He acknowledges that problems have still been encountered: “We had problems with the Volt balance on the rafts. But even performing with only one raft, it performed the same as the targets we wanted.”
Ambrose says of the IPEMU: “We have developed it. We have proved it. It gives us IPEMU, and from that we need to develop the strategy to look at where it could be used. The Department for Transport is keenly interested in this being used for future franchises.”
Performance-wise, acceleration is 0.5 metres per second, the equivalent of a Class 153 single-car diesel multiple unit. Ambrose points out that these figures are the basics for the IPEMU and what it has been tasked with doing. He says it has met the design criteria for a Class 379, which can do 0-60mph in 51 seconds.
Costs have been mentioned, but not specific figures. Production costs for an IPEMU against an MTU power pack were deemed to be more expensive, but this was defended because the ‘upstream’ costs over the lifetime of a train would be cheaper on an IPEMU than a DMU.
Feasibility studies have also been carried out on converting older EMUs to IPEMU, which would require the trains to be fitted with new traction packs. With plans to do this on Class 317s and ‘321s’, and with work under way to do so to Class 455s, Bombardier has carried out a feasibility study into converting a ‘317’, although physical conversions have not been done.
NR does admit, however: “Any future IPEMU would most likely be designed as a new train and not an adapted unit, to minimise energy consumption. But this project will also provide useful information for retro-fit.”
Per Allmer, head of Western Europe, Middle East and Africa region at Bombardier Transportation, says: “The IPEMU demonstrates what battery technology offers the rail industry. Following extensive design and testing work, the train has now successfully begun a trial passenger service, proving the viability of the concept.
“It’s a technology we can incorporate into future new-build trains, such as our Aventra platform, and retro-fit into existing modern rail vehicles, adding value to existing fleets.”
Whatever happens, the IPEMU offers another alternative for the railway to consider, when examining how to solve the issues of capacity and electrification.
- This feature was published in RAIL 769 on March 4 2015