Hybridisation of railcars for usage in non-electrified lines

Railcars for regional and local rail lines are powered by power units composed by an internal combustion engine coupled to a gearbox through the interposition of a hydraulic torque converter. Then, auxiliary loads are coupled to one mechanical flange, always through the interposition of hydraulic transmissions. Since these railcars are employed on short distances with frequent acceleration and braking phases, different levels of hybridisation may be considered, to achieve different benefits. First of all, converting mechanical auxiliary loads in electrical ones. Then, recovering part of the kinetic energy during braking. Finally, to allow entry, standstill and exit from stations in pure electric mode. This paper shows how to achieve these goals through different steps of hybridisation, by implementing different controls on several powertrain architectures. Additionally, different fuels were evaluated, i.e. Diesel or Liquefied Natural Gas (LNG). Different numerical models have been created, in order to analyse the different solutions. A preliminary cost-analysis for each one of the considered case studies has been performed.