Application of hydraulic energy storage technology for urban rail transit systems

As the modern city arterial traffic, urban rail transit system has good effectiveness. It has regular starts and stops due to its specific operating conditions. A considerable amount of energy has been saved because kinetic energy can be recycled during braking and released when accelerating. This paper discussed the possibility of equipping the rail transit system with the hydraulic storage transmission. The proposed scheme was modeled in AMESim with dynamic analysis. According to the national standard, parameter matching was done. And based on the Beijing Subway Line 4, the prospects of proposed system was analyzed. Simulation results show that urban rail transit system using the hydraulic storage transmission meets the dynamic requirements of national standard. When braking, 36% of the kinetic energy can be converted to hydraulic energy and stored in the accumulator. However, the maximum value of energy recovery efficiency using electric motor is 30%. Also, the accumulator in the hydraulic storage system has the advantage of high power density, won´t cause voltage rise and won´t be affected by train schedule. Compared with the electric motor, using the hydraulic storage transmission system will save over a million dollars on Beijing Subway Line 4 per year, showing higher economic benefits and a promising prospect.