Investigating the feasibility of braking energy utilisation on diesel electric locomotives for South African Railway Duty Cycles

Abstract

Five modes of transport exist on earth; 1) road, 2) sea, 3) rail, 4) air, and 5) pipeline. Railways have been used for centuries as a means of terrestrial bulk transportation due to its inherent low cost per tonne. Locomotives, the movers of trains, are often diesel powered with electric drive trains. This allows electric braking to be employed, getting rid of kinetic energy in the form of heat from high temperature, on-board resistor banks. This energy already exists on the locomotive as electrical energy, the main hurdle to find a concept that allows the on-board storage of this energy. The problem is identified as the need for a systematic method of predicting the energy savings of a locomotive with a regenerative braking energy storage system and determining the concepts feasibility. Aim is set to develop a tool that will allow simulation of a train of any configuration and load to be simulated on any route. Literature survey allows the understanding of the locomotive, energy storage systems and basic power control systems. It also allows selection of appropriate energy storage mediums for on-board usage. Subsequently, three methods are used to determine the energy consumption and braking energy on a train, per locomotive. Theoretical method is used for a first order understanding of calculated energy requirements. This is then compared to Data Analysis of a recorded data set of a trip from Phalaborwa to Richards Bay, the route in question. In this second method, the load on the energy storage system is calculated and limits imposed that prevent maximising of braking energy utilisation for a realistic understanding of possible energy savings. Thirdly, a fixed and dynamic train models are coded in MATLAB compatible software using numerical integration methods for solving multiple degree of freedom train systems. This final model allows full flexibility for optimization of the energy storage system to any parameters that are required. The results show that the dynamic train simulation model is the most accurate of the three methods when using a driver control Notches over distance corresponding to the recorded data set. Accuracies of in excess of 90% have been achieved. The concept proposed is a LiFePO4 battery energy storage system, with a bidirectional DC-DC converter for diesel electric locomotives. The feasibility of this concept in a train operating on a heavy haul route from Phalaborwa to Richards Bay is examined. Feasibility of this concept is concluded and recommendations made for future work to be conducted.