Comparative study of investment and efficiency to reduce energy consumption in traction power supply A present situation of regenerative energy utilization by energy storage system

Railway is widely recognized as eco-friendly transportation method. For example, in Japan, CO2 emission per person per 1km by railway is about 18g while it is 164g for car and 108g for air plane. On the other hand, the total amount of energy consumption for railway operation is not small and it is important to improve efficiency of energy utilization in traction power supply system more. As one of the most possible solutions to improve energy efficiency in traction power supply system, a regenerative utilization is expected and some energy storage systems have realized in d.c. traction power supply system in Japan. In this paper, some methods to make use of regenerative energy are compared not only in the effect but also in the cost. Other existing choices for eco-friendly energy utilization such as energy saving at station and renewable energy utilization are also compared. In conclusion, regenerative energy utilization by energy storage system has a large potential and will be a practical choice even from the viewpoint of return on investment in the near future.