The Anonymous Widower

A High Speed Train With An IPEMU-Capability

Bombardier were reported by Ian Walmsley in the April 2016 Edition of Modern Railways, to be developing Aventra, with a 125 mph capability.

Bombardier have also told me, that all Aventras will be wired so they could be fitted with on-board energy storage.

I don’t know all the masses and speeds, but imagine if an Aventra with an IPEMU capability ran at high speed down an electrified main line and then with its on-board energy storage full to brimming, turned on to line with a reasonably high speed, where it might make a number of calls before returning.

A typical line could be London to Norwich via Cambridge, along the Breckland Line, which is not electrified from Ely to Trowse Junction south of Norwich. Parts have a 90 mph speed limit and I’m sure the speeds could be improved.

The train would need to use the energy storage, but this storage would be partially recharged every time the train stopped, by the regenerative braking of the train.

An interesting fact, is that the kinetic energy of a train is given by half the mass times the square of the speed. So if the train leaves the electrified section, as fast as is reasonably possible, it is carrying extra energy.

Because of the regenerative braking of Aventras and for that matter, Electrostars and some other trains. some of this energy can be recovered and stored in the on-board energy stoppage of an IPEMU, every time the train stops at a station

Intuition and many years of doing this sort of dynamic simulation, tells me, that the faster the train goes at the start, lengthens the range if on-board energy storage is available.

It is worth noting the energy levels involved. If you take the energy of a train travelling at 40 mph as one, the energy of a train travelling at 60 mph is 2.25 times as much and one travelling at 125 mph, a massive 9.76 times.

I think that other factors will also help.

  • A track built for speed.
  • Modern signalling.
  • An efficient train.
  • Low dwell-times in stops.
  • Advanced driving aids.
  • Good driving.

I suspect that Network Rail and Bombardier are doing extensive simulations of possible routes for trains with an IPEMU capability.

These calculations will probably show some routes are more suitable than others.

A route that could might be ideal, would be a branch where the line speed was high to a single station, so that by the use of the regenerative braking, the train could start the return journey with a high level of energy in the storage.

London to Norwich via Cambridge, is not a line to a single station, but both ends are electrified, so the trains will start the journey with full storage, probably losing a proportion of the energy at each stop.

I’d love to be doing those simulations. But it’s all physics that Isaac Newton would have understood.



April 23, 2016 - Posted by | Transport/Travel | , , , ,


  1. Yes the energy goes up with the square of the speed (E = 1/2mv**2), however the power required to maintain it depends on the rolling and air resistance of the train. The energy required to attain the speed depends on both factors (mass predominant), but much can be recovered every time the train stops and starts.

    These would be very useful for when there were OLE problems – the section could be isolated for repair and trains run on slow / diversionary lines while the problem was fixed. At the moment if there is break on ECML or WCML electric hauled trains queue up or worse diesel loco’s have to be sent out to tow in those stranded in the dead sections.

    Comment by Mark Clayton | April 24, 2016 | Reply

    • On the Aventra, Bombardier have paid special attention to the aerodynamics, rolling efficiency and secondary power consumption for lighting and air-conditioning. They’ve also designed the train for a short dwell time in stations.

      I think I read somewhere in a Network Rail document, that train recovery is important. But one of the other savings with the technology is reducing wiring in depots.

      Comment by AnonW | April 24, 2016 | Reply

  2. […] The Midland Main Line is being electrified and Ian Walmsley in Modern Railways has speculated that 125 mph Aventras could be used between London and Sheffield. I wrote about this in A High-Speed Train With An IPEMU-Capability. […]

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