This year there have been two new battery train trials operating in the UK. Great Western Railway has been running a commuter train on a fast-charging battery on a branch line in Ealing, and Hitachi have just tested a hybrid inter-city diesel with an onboard battery. It’s part of global wave of interest in batteries on the railways, with new or retrofitted trains running in France, Japan, Germany and several other places.
There’s a good chance that it’s going to be an important technology. Trains that are all-electric can be run on renewable energy, and so electrifying railway lines is a way to cut emissions from diesel power. Lots of places have been electrifying their railway lines, India being the most ambitious and that deserves a separate post. But it can be expensive to upgrade older lines with overhead cables or powered rails, and passengers face months or years of disruption to services.
Lots of lines were electrified in the UK in the last century, and then there has been political wrangling over finishing the job. Big electrification schemes have been on again and off again like a faulty switch – announced, paused, unpaused again, and then cancelled. The projects that have been completed have been delayed and came in vastly over budget, discouraging politicians from green-lighting new ones.
Battery technology could provide a solution here. GWR’s current pilot has brought electric trains to a branch line that wouldn’t have been economical to electrify otherwise. They’ve done it by putting batteries on the train and then fitting rapid charge points at stations. The train pulls in and automatically lowers a ‘shoe’ onto a charging plate fitted between the rails. It can run all day on the rapid charges it picks up in the three minute stops at stations. Charging little and often keeps battery sizes down, reduces weight and makes the system more efficient.
Hitachi’s trial aims for something different, adding a battery to a diesel-electric hybrid. These trains already navigate the gaps in the network, using overhead wires when they are available and diesel elsewhere. Swapping one of the diesel engines for onboard batteries can do a few useful things. It can reduce fuel use by supporting the diesel engine on hills, and it enables regenerative braking. It also allows drivers to switch off the diesel on the way in and out of stations, coasting in on electric and reducing noise and air pollution. Overall the trial reduces diesel consumption by 35-50%, so it’s not a net zero technology at this point. It’s more of a bridge on the way to full electrification, getting significant carbon reductions on existing rolling stock.
We’ll be hearing a lot more about batteries on trains in the years to come, and then we won’t hear any more about it because it will be so normal. That will complete a transition that began over a hundred years ago, because there was considerable interest in battery electric trains at the turn of the 19th century. Accumulator railcars were running from the late 1800s in several countries. Thomas Edison was providing batteries for electric trains and trams in the US in 1911. As with his electric cars, they were ultimately overtaken by fossil fuels, which were too cheap to justify further research into battery technology. They hung on in a few places, including a solitary branch line in Scotland that ran battery railcars in the 1950s and 60s.
We’re in a different place today. Batteries are more advanced and there’s a huge wave of investment and innovation around energy storage and charging. Those old ideas are being revisited, alongside new ones such as direct solar-to-rail, single rail monocabs, or even retrofitted maglev. Zero carbon rail travel is on its way.
The Earthbound Report 
Where was the single rail line in Scotland? >
From Aberdeen to Ballater, until the line was discontinued. There’s a history of it here: https://www.railscot.co.uk/articles/Aberdeen_to_Ballater_by_BMU:_Notes_on_the_Battery_Railcar_Experiment/