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Chinese Rail Operators Turning to Ultracapacitors to Improve Efficiency and Reduce Electricity Consumption

Chinese Rail Operators Turning to Ultracapacitors to Improve Efficiency and Reduce Electricity Consumption

| Alice Wu, Senior Manager, Business Development
In China, there are 14 cities with populations of over 10 million—never before has accessible and efficient public transportation been so critical. As the China railway system continues to experience increased ridership and longer hours of operation, the opportunity widens to employ ultracapacitor power systems for grid energy-efficiency and stabilization. Ultracapacitors can support grid efficiency by capturing excess braking energy and using that recycled energy to power the trains.

Approximately 80% of total energy consumed by trains is for traction. When a metro train engages in the braking action, the ultracapacitor system converts kinetic energy—energy that is typically lost in conventional friction-based braking systems—into stored electrical energy.

Unlike batteries, ultracapacitors rapidly charge and discharge, enabling them to capture and store more energy during each braking event. Battery-based systems have limited ability to absorb energy in the few seconds required to stop the metro train. During idle time, the ultracapacitors provide the stored energy back to the grid. In other words, the ultracapacitor-based system supports peak power back to the metro train at each starting.

Prior to 2000, there were only five metro lines operating in four major Chinese cities: Beijing, Shanghai, Taijin and Guangzhou. From 2000 to 2015, China’s metro line construction boomed to over 40 completed lines and more than 100 planned in 24 big cities. Based on the China National Transportation Report, there was a 25.56% compound annual growth rate (CAGR) of operating metro lines by kilometers in China from 2009 to 2014. In the next decade, this market is expected to continue to grow at a 20% CAGR based on current metro construction plans for major cities.

Over the next several years, significant growth is anticipated in both on-board and wayside deployment of capacitive energy storage to reduce the operating costs of China’s rapidly growing rail infrastructure.

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