As the UK’s fleet of diesel trains nears retirement, manufacturers are pushing to replace them with environmentally-friendly alternatives, including battery-powered trains. Recent developments in battery technology have sparked interest, with companies like Hitachi and Siemens leading trials that could signal a new era for the UK’s rail network. Hitachi recently completed testing on a “tri-mode” train, which combines overhead electric power, a diesel generator, and a lithium battery, promising up to 50% fuel savings on non-electrified tracks. Siemens has also begun testing fully battery-powered trains and expects strong demand from UK operators such as ScotRail, Great Western Railway (GWR), and Transport for Wales.
Battery-powered trains could offer significant savings by eliminating the need for costly overhead electrification on unelectrified lines. For example, Network Rail estimates that electrifying a single kilometer of track costs between £1 million and £2.5 million. Hitachi’s trial trains can travel 70 kilometers (44 miles) solely on battery power, enough to run routes between electrified stretches, such as London to Oxford or Hull. However, routes like Crewe to Holyhead exceed current battery capabilities. Hitachi’s design can also recharge batteries on electrified tracks or during 10-15 minute stops, further increasing operational flexibility.
The push toward battery technology aligns with the government’s goal of achieving net-zero emissions by 2050, positioning hybrid trains as a stepping stone toward fully electric alternatives. Despite advancements, battery limitations remain. UK tracks with steep inclines, like the TransPennine routes, pose challenges due to higher energy demands, especially on longer journeys without electrification.
While battery technology offers environmental and cost-saving benefits, safety remains a concern. Hitachi’s trains use Nissan Leaf cells, which have a low incident rate, but damaged lithium batteries can experience “thermal runaway,” an uncontrollable heat surge that’s difficult to extinguish. Jon Simpson, a fire safety expert, notes that while lithium batteries are generally safe, fires can be challenging to manage in enclosed spaces like tunnels due to toxic fumes and limited water accessibility. Hitachi has addressed these concerns by equipping each cell with a heat shield to prevent fire spread and placing a cooling unit on the roof for temperature regulation. In addition, the company has designed software to monitor battery conditions continuously, and in severe cases, trains can use unaffected battery units or even be moved out of the way by another train.
Despite the complexities, manufacturers are optimistic. Hitachi’s UK and Ireland chief, Jim Brewin, states that as battery cells become lighter and more efficient, battery-powered trains will become increasingly viable. These ongoing innovations point toward a future in which fully electric trains could become the standard, reducing the UK’s reliance on diesel and advancing the sustainability of its rail network.
