Climate change and environmental sustainability have attracted significant worldwide public attention in the past decade. The value of the widespread utilization of green energy has become increasingly prominent. As one of the largest energy users, transportation has been shifting towards electrification, since electrical energy offers several environmental benefits due to the substantial uptake of green energies in electric power structures. Electrified railway structures not only reduce carbon dioxide emissions, but also enhance the performance of the vehicles. Currently, there is a increasing benefit in developing the energy efficiency of railway vehicles; in particular, braking energy recovery has drawn substantial attention. Due to the extensive utilization of regenerative braking technologies, electric railway vehicles can transform the kinetic energy (in the braking phase) into electric energy for the use of energy reuse.
Technology improvement has been promoted aiming for an environment-friendly traction power supply system for railways. Between other things, a static energy storage system using lithium-ion batteries for hybrid cars has been put into practical use since 2007. This method momentarily stores renewing power generated from a train when it is stopped and the power can be applied for energy saving, procedures in opposition to regeneration cancelled and compensation for a voltage drop. The application design for a stationary energy storage system (SESS) has been prevalent in recent years. The application of the SESS at railway companies can promote to the reduction in the global warming gas emissions.
HITACHI is developing railway systems that use storage battery control technology to save energy and reduce carbon dioxide (CO2) emissions. The first application for onboard storage batteries came with the commercialization of series hybrid drive systems that reduced the fuel consumption of diesel trains on non-electrified railway lines. While collecting field data, Hitachi has also developed an efficient regeneration system to improve energy efficiency on trains and has verified its effectiveness through operational trials.
An example of the new advances in the industry in this concept can be found in the Toshiba Lithium-ion battery, SCiB™, ABB’s lithium-ion on-board energy storage system and Alstom who offers Mitrac traction battery is used for the first train fleet in passenger service.
Focus even forward, the opportunity of rail traction may lie in solid state battery technology, which reduces the need for a liquid electrolyte. In theory, this could have double the capacity of a Li-ion cell, whilst at the same time improving safety further. Research is continuing, and we could see solid state batteries established within the market by 2030.
Fixed electrification infrastructure not only comes at a financial cost, but also involves power to build and sustain, which in turn produces greenhouse emissions. With laws and budgets becoming more rigorous, especially considering any new responsibilities resulting from Climate Change Conference (COP26), we may very soon start seeing better adoption of battery-powered traction as a more cost-effective and green solution.
