Carbon-efficient timetable optimization for urban railway systems considering wind power consumption

With the increasing application of urban railway systems around the world, their energy consumption has increased significantly and continuously over the past few decades, which causes large indirect carbon emission volume due to main electricity generation from conventional (fossil-fired) power plants. Penetration rate of the renewable energy generation, such as wind power and photovoltaic (PV), has been observed to increase in power systems in recent years, while the intermittency brought by natural weather conditions imposes difficulties on their utilization. Focusing on urban railway systems integrated with the electric power system with wind power generation, this paper proposes an optimization model to find its optimal timetable to minimize the carbon emissions resulting from its operation. Lanzhou Metro Line 1 is adopted as case study in the research, and the results show that the proposed method can locate the optimal timetable which reduces 2.17 t carbon emissions each day which is much lower than that of the original timetable. Furthermore, the analysis includes insightful comparisons and discussions between the optimal schedule and the original one, followed by the exploration of the difference between the carbon-efficient operation and energy-efficient operation.