Energy-efficient train timetable optimization for conventional railways considering energy storage systems

To address the low utilization of regenerative braking energy and significant energy waste in conventional railway systems, this study aims to improve energy utilization efficiency by developing an energy-efficient timetable optimization framework incorporating energy storage systems. The proposed approach enables coordinated utilization of regenerative braking energy through both immediate and delayed mechanisms. Based on operational characteristics of conventional railways, an optimization model is formulated with the objective of maximizing total regenerative braking energy utilization. The decision variables include train departure intervals at the origin station and dwell times, subject to multiple constraints such as safety headway requirements, dynamic overtaking rules, and energy storage capacity limits. A simulated annealing-based solution algorithm is developed and validated through a case study of the Lanzhou-Wuwei section of the Lanxin railway. A test scenario involving 15 stations and 43 passenger and freight trains during a certain daytime period shows that the total regenerative energy utilization reaches 4 134.38 kWh, corresponding to a utilization rate of 56.28%. Sensitivity analysis is conducted to examine the effects of departure intervals, dwell times, storage capacity, train frequency, and the proportion of regenerative braking-capable locomotives on energy-saving performance. Results indicate that under high-density operation of regenerative braking-capable locomotives (approximately 58%), coordinated optimization of timetable parameters and storage capacity can achieve a maximum energy-saving rate of 86.33%. An economic evaluation based on net present value (NPV) method shows consistently positive returns on energy storage investment over a 10-year horizon. These findings demonstrate that integrating energy storage systems into timetable optimization not only enhances energy utilization efficiency but also yields significant economic benefits.