Battery only electric traction for freight trains - A technical and operational assessment

The rail transport industry has been required to engage with the world effort to reduce the climate effects, as well as the reduction of criteria pollutant and noise emissions, which strongly affects the populations nearby the rail infrastructure. Electric powertrains have been widely used by railways, with its inherent efficiency and cleanliness. However, the required infrastructure has restricted its use to medium to large density traffic corridors, given the large infrastructure and maintenance costs involved. Light to medium loaded rail stretches and large freight rail corridors, running in rural areas, have adopted the diesel-electric powertrain approach, that relies on an onboard diesel generator, with the inherent environmental negative effects, especially to the rail nearby communities. In this context, alternative traction technologies, such as Hybrid-Electric Rail, Hydrogen Fuel Cell Rail and Battery Only Electric Rail, have been considered by the rail industry as potential alternatives. The BOER route, due to the recent battery technology breakthroughs (associated with performance improvements and reduced costs) is set as a promising alternative and has a potential do be used as a decarbonization strategy for both passenger and freight rail systems at low to medium density traffic lines. Nevertheless, the BOER technology sets great challenges, given the high energy and power required by rail vehicles, as well as the harsh rail operational environment, with huge effects on the performance, charging infrastructure requirements, fleet availability, costs, as well as the environmental sustainability associated with the mining and disposal of materials required by the battery chemistries. This paper presents, based on the state of the art available technical literature, an unbiased review of the BOER technology and an assessment of its potential for the freight rail industry, highlighting the associated technical, operational and environmental challenges.