Waste energy analysis in hydrogen trains for increased system efficiency

Hydrogen trains are developed as part of a sustainable passenger rail transport. The overall efficiency of the vehicles is mainly influenced by the fuel cell efficiency of around 50 %. An efficiency increase is necessary for higher vehicle range and overall hydrogen cost reduction. Therefore, the presented paper deals with the research question, which technologies can be used to increase the efficiency in hydrogen trains. As waste energy potentials the waste heat of the fuel cell and the pressure reduction of the hydrogen between fuel cells and tanks are identified. These potentials can be exploited by absorption air conditioning, direct utilization of the waste heat to heat the cabin, hydrogen expansion engine and a hydrogen powered air conditioning (HyPAC) based on metal hydrides. To analyze these technologies, they were abstracted in simulation models. In the simulation models, measurement data from Talgo’s hydrogen train prototype TPH2 are used as input to calculate the effects of the different technologies in real driving cycles of the train. The comparison shows that the HyPAC is especially suitable to increase the efficiency in hydrogen trains because of a high technology readiness level and an additional cooling power which can be provided based on waste energy from pressure reduction. Overall, the application of the HyPAC can reduce the annual energy demand from a conventional heating, ventilation and air conditioning (HVAC) system by 25 %.