The electrification of routes enables trains to be powered by energy from the national electricity grid. This is a good way to reduce the carbon dioxide emitted by rail transport. But this change will not completely decarbonise trains because the way energy is currently generated in the UK emits carbon dioxide. The good news is that the carbon intensity—the amount of carbon dioxide generated per unit of energy—has been decreasing in recent years and is forecast to continue doing so. However, for a variety of reasons, it’s not always possible to electrify rail routes. But, in essence this is due to the costs which are approximately £1.5m to £4m per single-track kilometre. 

Chart showing the historical and predicted future carbon intensity of UK electricity generation

Optimal Control: Decarbonising High-Speed Bi-Mode Trains chart showing grid intensity

Past intensity [1): from the series of annual Greenhouse gas reporting: conversion factors documents
BEIS Forecast [2]: from Updated Energy and Emissions Projections 2018, Department for Business, Energy & Industrial Strategy (BEIS)

Electrification also poses some technical challenges, for example, it can be difficult to install the overhead line equipment (OLE) required for electrification in old rail tunnels or under old bridges. There are a range of long-term solutions for these problems including battery trains, improved pantographs, and even hydrogen-powered trains. But in the near-term, a simpler solution has been devised. That is the bi-mode train which runs on electricity when it is available from the OLE and on diesel when it’s not.

Research led Loughborough University looked at ways to reduce the carbon dioxide produced by bi-mode trains. The team first developed a computer model of the train, in both modes, using computer modelling techniques that have already been applied in the aeronautic and automotive industries.

The team then used the model to investigate ways that the carbon dioxide produced by these trains could be reduced. When under OLE, there is little that can be done to reduce the volume of carbon dioxide a bi-mode trains produces. This is because the train is tied to the current carbon intensity of the grid. However, there are ways to reduce the total energy used, such as optimising the way energy is converted into power for the train. The research team has been developing a controller that can do this. 

The controller factors in the diesel engine, the generator and other power electronics components within the train and devises a set of inputs that minimise the total carbon dioxide emitted (while ensuring the train runs to schedule). This “intelligent controller” could reduce carbon dioxide output by up to 19%, reducing the carbon dioxide that enters the earth’s atmosphere and at the same time provide cost savings for train operators—a true win-win scenario.

The University of Loughborough is hosting a webinar, in association with RSSB, on 15 October (13:00 to 14:30) to discuss the latest research into decarbonisation in the UK. The event will focus on the bi-mode trains project and provide a unique opportunity to ask the project team and panellists questions about the future of rail decarbonisation in the UK. Register here

This project was funded through RSSB’s “Intelligent Power Solutions to Decarbonise the Railway” competition. The competition was launched in October 2018 and made £1m available to support the development of alternative, energy-efficient technologies for high-speed trains and freight trains, and innovative solutions for the provision, storage and distribution infrastructure of energy.