Characteristics and assessment of the electricity consumption of metro systems: A case study of Tianjin, China

Owing to the complexity of metros, the energy consumption characteristics of metro systems exhibit variability and the energy-saving management of the systems encounters challenges. To encapsulate the essential characteristics of energy usage and to objectively assess the energy performance of metro systems, this study presents a generalized framework and applies it to a case study conducted in Tianjin. The study also employs correlation analysis to investigate the applicability of the indicators relevant to ridership. The results indicate that the monthly traction electricity consumption exhibits slight variation, while station electricity usage demonstrates substantial fluctuation with seasonal changes. For Tianjin Metro, the passenger factor hardly shows any effect on the electricity use of metro lines. The median value of traction electricity use is approximately 2.0 kWh/(car-km) and that of the average annual station electricity use of underground lines ranges from 95 to 155 kWh/m2. The emission from the traction sector is 12.2 kgCO2/(vehicle-km) and from the station sector is 118.6 kgCO2/m2. The study also identifies the energy-intensive lines of the Tianjin Metro and compares the energy utilization among various global metro systems. The authors hope that this study can help shed light on the assessment of the energy status of metro systems and serve as a source of information for other City-Metros to implement energy-saving management. In this study, a generalized framework is presented to evaluate the energy status of existing metro systems, and the characteristics of the monthly electricity consumption of the metro system are explored. Furthermore, the passenger volume-based evaluation indicator is proved unreliable and its reason is analyzed. The authors hope that this study will shed light on the assessment of the energy performance of metro systems and serve as a reference for other City-Metros to implement sustainable management.image