GWR is trialling the UK’s first battery electric train, which it could one day roll out on branch lines in the Southwest, meeting the UK’s target to phase out diesel-only trains by 2040.

Much of the UK currently operates electric trains that take power from overhead lines on electrified routes. As I have written before, the Penzance to Paddington mainline missed out on electrification, and electrifying smaller branch lines is costly.

GWR have more branch lines than any other operator, however its battery-powered train will allow electric trains to operate across all the UK’s 2,000 miles of branch lines without electrification.

The challenge for battery-powered trains is the weight of the battery. GWR engineers have overcome this limitation by combining six small on-board battery packs with a larger trackside battery bank located next to a station.

When the train stops at the station, it uses fast-charging technology to charge the on-board batteries in just three and a half minutes – the time that trains across the UK rail network are scheduled to spend at a station.

So that charging does not impact the timetable, when the train comes into the station, it deploys two shoes that connect with a pair of power rails that run for a few metres located between the track’s running rails. For safety, they are not live until they make connection with the train.

To charge the train batteries in such a short space of time requires a large store of energy in the trackside battery bank. As charging the trackside battery is not time limited, it is trickle-charged to put less strain on the grid. It could therefore charge on renewable energy, such as an array of solar panels mounted on a canopy over the station car park or platforms.

The Penzance to Paddington mainline is only electrified from Reading, where trains switch from diesel operation to electric and speed up for the remaining miles into London. Trains that operate this route are bi-mode diesel-electric – the diesel powers a generator, which converts the energy into electricity to power an electric motor.

Technological advances are being made here too. Hitachi is developing a new bi-mode train at its factory in County Durham. The diesel generators are being swapped out for batteries, so the train can switch between taking power from overhead wires and battery operation.

The Hitachi train can run for 50 miles by battery on unelectrified stretches of track and, incidentally, uses the same battery cells as the Nissan Leaf car! The batteries can be recharged from the overhead power supply when the train is travelling on electrified track, or in 15 minutes when stationary.

The existing diesel-electric trains that operate on the Penzance to Paddington route could be retrofitted with these batteries and run with only small sections of electrified track to allow for recharging.

With modest investment, the Southwest could finally benefit from electrification – better air quality at stations and for people living close to the line, and trains that are quieter, faster and cleaner!