Evaluating a distributed regenerative braking system for freight trains

Abstract

This paper presents an investigation on a distributed regenerative braking system for freight trains. The system, which involves installing regenerative braking units on the bogies of freight rail wagons, is proposed in a patent by Transnet SOC Ltd. The system allows for numerous regenerative braking systems to be installed on a single freight train in a distributed manner, which collectively function together to perform regenerative braking on the train to reduce the energy consumption of the train. The proposed system would, if implemented successfully, alleviate challenges and limitations with current regenerative braking systems on diesel-powered freight trains. The goal of the investigation is to determine whether the system is both technically and economically feasible. The proposed regenerative braking system is conceptualized in this study by first establishing the requirements of the system from in-service train data, followed by the development of the subsystems and major components based on existing technology. A physical system simulation model is subsequently developed to establish the energy savings performance of the system concepts for typical freight train routes. The results show that energy savings of between 10% and 24% can be realized. This demonstrates the technical feasibility of the proposed system. Next, the proposed system and the candidate concepts are evaluated in economic terms by means of a cost–benefit analysis. The decision criteria calculated in the cost–benefit analysis provide unanimous results as to which of the candidate concepts are economically feasible. It is shown that four of the candidate concepts, all utilizing the same transmission topology incorporating a continuously variable transmission with different flywheel configurations, are economically feasible. It is therefore concluded that the results of the cost–benefit analysis indicated that the proposed distributed regenerative braking system for freight trains is economically feasible and could deliver favorable financial returns if pursued.