A historical review of developments in self-powered electric rail vehicles from 1835 to the present

Electrically-powered rail vehicles that do not make use of overhead or rail-based electrical supplies have a remarkably long history. This is often forgotten in discussions of recent developments in this field. Since the very first demonstrations of electric motors for rail traction in 1835, there has been interest in electrochemical methods for providing electrical power. This grew steadily in the second half of the nineteenth century, but by the start of the twentieth century, the success of railway electrification schemes based on overhead catenary or third-rail systems meant that electrification based on stored electrical energy was largely confined to secondary routes. These were lines where electrification schemes based on externally generated power and overhead wire or third rail supplies were deemed unaffordable. Lightweight battery rail vehicles were used extensively in Germany in the second half of the twentieth century, mainly on those secondary routes. In the early twenty-first century, battery developments greatly improved the possible performance in terms of weight, range and cost. Other factors, such as reliability and safety, also improved, leading to a renewed interest in this technology for railway traction applications. That was becoming important for rolling-stock manufacturers and rail operators in meeting government-imposed targets for rail decarbonisation. The report reviews the history of self-powered electrical rail vehicles in general and discusses how battery and fuel-cell technologies have been applied to rail transport. It includes information about present-day developments and trends that may be important for the future, such as the use of supercapacitors and the introduction of discontinuous electrification schemes, where only some sections of a route are electrified, and trains are equipped with batteries or other forms of energy storage to allow them to traverse the unelectrified sections. It includes a discussion of some important research activities that may lead to new developments.