Electric multiple unit number 379 013 looks perfectly normal. It may be a tad cleaner than a few around the network and the interior is suspiciously immaculate. It may have a few more yellow-jacketed folk crawling over it on occasions. But otherwise, there’s nothing to differentiate it from any other of this rather handsome Electrostar class made by Bombardier.

The lights are bright. The doors open and close. In the brisk East Anglian air of mid-winter it is comfortingly warm inside with the gentle click of heaters and the background hum and hiss of air conditioning. It can be seen trundling up and down between Harwich and Manningtree as a perfectly normal train on a normal passenger train service. (And that’s Harwich as in ‘Harwich for the Continent’ proclaimed by the famous LNER holiday posters– leaving Frinton for the incontinent.)

To the fare-paying passenger there really isn’t anything out of the ordinary. It starts and stops normally. It makes EMU-type noises. It trundles effortlessly along at 60mph. Their journeys are uneventful.

But, having expended over a hundred words extolling its normality in an article which is meant to address railway engineering, there must be something odd about this train.

Added IP

The only clue that there is something unusual going on is the position of the pantograph. As the train goes on its daily routine, the pantograph is… down.

It’s an EMU, running under the wires and yet it is not connected to the overhead power supply – and there’s no third rail either!

There is another clue though and it doesn’t take a rocket scientist to work out what it means. Emblazoned on the sides of the unit are the words, “batteries included”. What else do you need? Perhaps we should have started there.

Yes, this is an EMU with added IP. It’s an IPEMU – Independently Powered EMU. And the independent power comes from eight tonnes of batteries positioned under the frame of the motor car. Unit 013 has been quietly running in passenger service since 12 January this year as part of proving trials to validate the whole principle of independent power using battery technology. So far it has proved itself to be eminently… ordinary.

Passenger expectations

The idea of sticking batteries in a train isn’t exactly new. London Underground uses battery locomotives. Battery trains were used in ammunition dumps to avoid the possibility of sparks. But none of the applications so far have addressed that minor issue of passenger comfort and passenger expectations in the twenty-first century. The punters want to be warm (or cool), they want good lighting, doors that open, toilets that flush, air-conditioning that works and they couldn’t care less what powers it all. The draw on power in a modern train is considerable and a class 379 EMU is one of the heavier users of power – hence its selection for the trial.

We’ll come on to the actual engineering in a moment, but it’s worth looking at why this train exists at all. Why bother? What’s the point?

Well, there is little point if all the train can do is sit in a station and spin its air-conditioning fans. It needs to do considerably more. The aim of the current exercise is to have a unit capable of sustaining all the hotel loads and to do a round trip of at least 30km without running out of puff.

With that sort of performance being a reality, a number of intriguing scenarios start to play out. Non-electrified branch lines linked to an electrified main line can benefit from electric stock and even from through services. Sections of non-electrified railway that link electrified lines can become part of new through services. Depots no longer need to be wired.

Unit maintenance can be carried out without the need for isolations or special overhead precautions. Routes which are prohibitively expensive to electrify because of infrastructure constraints can be partially electrified with the dead sections no longer an obstacle to electric trains.

Risks and gains mismatch

In the past, perhaps the easy solution – and indeed the only solution bearing in mind previous battery capabilities – was to build, run, maintain and fuel diesel units. But about 66% of diesel units are more than 20 years old which means that there is a bow wave effect for replacement. What to do? Build more diesel units? Or perhaps keep building electric units which have the capability of being modified to take an independent power source?

This whole exercise is not about a special build of special units. The exercise on the Harwich branch has involved an ordinary EMU – so ordinary that hardly a new hole has been drilled in it. As we’ll see in a moment, this has been more about ‘hole drilling not being permitted in someone else’s train’ rather than a desire not to drill. It’s been a good discipline though.

The current structure of the railways is not sympathetic to the development of an independently-powered train. After all, looking at who gains and who takes the risks reveals a complicated and awkward mismatch. The company that might gain from a new passenger flow will have a finite franchise length. The maker of batteries will need to spend a great deal on development work. A rolling stock manufacturer needs a firm contract. The testing of trains to full approval involves a huge number of interfaces.

Who is likely to take up the challenge and take the risks – in the off- chance that the idea is practical? After all, this isn’t part of a normal gentle evolutionary process often found in the development of a product. This is a step change – certainly for the railway industry.

Cross-industry collaboration

The whole exercise has been an example of macro cross-industry collaboration with rolling stock ownership, maintenance and operation all lying with separate companies.

It’s been where Future Rail, in a collaboration between Network Rail and RSSB, has been able to deliver the project by supporting the whole industry – both the supply chain and those that operate the trains on a daily basis.

_RHX2214 [online]

As David Clarke, director of innovation at the RSSB, puts it: “Research is relatively inexpensive, but the costs involved at the next stage of piloting and demonstration can be vast. And this is true in any industry. What we are about is de-risking innovation through demonstration.”

The trial running of the IPEMU in passenger service has been the culmination of a complex process coordinated by the project team which has representatives from Network Rail, RSSB, DfT, Bombardier, Valence, Abellio Greater Anglia and Future Rail.

After some initial work on the concept, vehicle performance simulations were commissioned along with battery performance design and testing in parallel with detailed stock conversion design. A Class 379 was selected as it was only four years old and already had dual-voltage capability. Network Rail let a contract to Bombardier for this part of the work along with the physical conversion which was followed by performance testing at Bombardier’s test track in Derby and then at Old Dalby.

Existing timetabling

The limitations have been formidable. The remit is to produce a train capable of delivering a passenger service to an existing timetable. This means that the range needs to be at least 50km (30 miles) travelling at speeds generally between 60mph and 100mph. The acceleration should emulate that of an existing DMU – something like 0.5m/s2 so that it can keep up with existing timetabling.

Incidentally, the acceleration of the Harwich EMU was certainly respectable although obviously fairly restrained for an EMU. The expectation from an EMU seems to be much greater than for a DMU. Diesel acceleration is accompanied with a great deal of noise and general fuss. Take away the noise, and diesel acceleration isn’t quite as impressive.

The duty cycle is pretty demanding too. 30km on batteries followed by 50km on OLE.

The achievements so far? James Ambrose, principal engineer working for Network Rail and the guy project managing the whole exercise, is upbeat: “The range has been 77km (48 miles). Speeds have been as-planned, as have all the other parameters, with the battery life still on- track to deliver five years – which ties in with the normal EMU heavy maintenance overhaul schedule.”

How many batteries?

Counter-intuitively, the batteries are not large. The basic building block is a 3.2V lithium ferrous phosphate cell manufactured by Valence. Each one is about 3” long. There are 12 cells connected in series to make a row. 33 rows are then connected in parallel to give a 38.4V battery. 20 batteries are connected in series in a pod to give 768V. Two pods are connected in parallel to make a 768V module and finally, three modules are connected in parallel in a 768V battery raft. Two of these rafts are slotted neatly under the frame of the motor coach in a space formerly occupied by auxiliary batteries, giving about 450 kW.hrs of capacity. Do the maths. There are an awful lot of batteries!

Why are the basic batteries so small? It’s all to do with heat dispersal. Too big a battery would lead to more heat being generated and the need to engineer a way of getting rid of it. This has weight and space implications – neither being available in the limited envelope of the train.

Free your mind…

Despite the doubts and doubters, despite the industry structure, it has been proved that independent power using batteries is a practical proposition. In March of this year the updated Route Utilisation Strategy will be published. It will acknowledge that IPEMUS could be used on some parts of the network, so avoiding costly electrification schemes and promoting new patterns of passenger services.

Free your mind of previous restraints.

Branch lines might need just 100 metres of electrification at the buffer stop ends to recharge batteries. Electrify just the heavy gradients. Through electric trains between Manchester and Cardiff – not impossible. Retain a core electrification unit that drip- feeds schemes piecemeal across the network instead of having peaks of expenditure followed by famine. The prospects are intriguing and, despite its seeming normality, the IPEMU is just the start…