Energy-efficient and reliable urban rail transit: A new framework incorporating underground energy storage systems

Within the transition process of urban rail transit systems, the challenges of high energy consumption, increasing carbon emissions, limited economic viability, and intricate risks emerge as significant hurdles. This paper proposes a novel energy utilization framework for the urban rail transit system that incorporates underground energy storage systems characterized by high resilience and low carbon. First, existing methods employed in urban rail transit are comprehensively reviewed. Then, a novel framework and strategic significance of the urban rail transit system incorporating underground energy storage systems are introduced. This integration effectively utilizes and manages diverse renewable energy sources and the available space resources. The viability is demonstrated through a case study by combining Nanjing metro. Finally, suggestions for research in pivotal areas are summarized.