The Elizabeth Line adds 10% to London’s public transport capacity but what will it do for the environment and energy efficiency? Years of disruptive, noisy, energy guzzling and over-running construction may suggest not very much for some time into the future, but what the Crossrail Elizabeth Line delivers, right now, is the power of rail to provide a modern, reliable and convenient alternative to other transport modes.

As the public start using the service in large numbers, energy efficiency is the icing on the cake.

In its latest report on rail, published at the end of 2021, the International Energy Agency (IEA) reminds us that rail is one of the most energy efficient and least carbon-intensive forms of transport. While rail is responsible for 9% of passenger movements in the world it only accounts for 3% of transport energy use.

At a time of sky rocketing petrol and diesel prices for motorists, taking the train looks like a good bet and all the evidence is – strikes aside – that more people in the UK and elsewhere are thinking along these lines.

Developments in rail, from high-speed services to hydrogen-powered trains are big investments for any government. Modern trains are lighter, clean and indeed more energy efficient, although in the UK under 40% of the rail network has been electrified. Getting rid of diesel has been a slow process; that said, the UK looks positively sprightly on this front compared with the US and Canada where the vast majority of the rail network is still diesel.

The commitment, says Steven Hart, Lead Strategic Planner for the UK’s Network Rail, is to take as many emissions as possible out of the rail system. In the medium to long-term this is all about getting rid of diesel, with electricity taking over to provide a clean, low carbon alternative.

Energy efficiency back on the agenda  
While not being a new phenomenon – some of us can remember the 1980s – energy efficiency has taken on a new urgency in the face of rising fuel costs and growing concerns around energy security. At a recent global conference on energy efficiency organised by the IEA in Denmark, there were claims that a major push on energy efficiency starting now could save the equivalent to the current energy use of China by 2030.

‘Energy efficiency offers immediate opportunities to reduce energy costs and reduce energy reliance on imported fuels,’ agreed 24 participating countries in a statement at the end of the conference.

A modern rail service attracting large numbers of passengers undoubtedly has a part to play in this drive for greater energy efficiency. The Elizabeth Line, for example, which will eventually run for around 100 km from Reading to the west of London, to Shenfield in the east, is powered with the help of 1,500 km of cabling, stretching between two feeder stations at either end of the line.

Passengers taking comfort in the quality of their journey may also feel pleased that their trains are lighter than originally planned, making the all-electric service even more energy efficient.

The numbers tell the story. Weighing in at 319 tonnes, Elizabeth Line trains are well below the original spec of 350 tonnes max, which translates to 32 grammes of CO₂ per passenger km compared to 55 grammes.

On this basis alone, the world’s first fully digital railway can make its own contribution to energy efficiency and net zero. It can also play its part in London’s efforts to remain a revenue-generating, world class city with world class infrastructure, says Paul Hogg, UK Cities Director of the construction and engineering firm Arcadis.

‘For too long, Crossrail’s problems have choked the conversation on the need for Crossrail 2, the Bakerloo Line extension, the digital signalling upgrades to all London Underground lines and a whole host more,’ says Hogg. The line, he believes, has become a vocal champion for slick, energy efficient public transport and London will become a better global city for it.

What the Crossrail Elizabeth Line delivers, right now, is the power of rail to provide a modern, reliable and convenient alternative to other transport modes – energy efficiency is the icing on the cake.

High-speed future  
The same arguments can be applied to high-speed rail which is designed to connect cities and provide a cleaner, more energy efficient alternative to other modes of transport. HS2 in the UK and similar projects in other parts of the world demonstrate the huge investment involved in building new high-speed rail infrastructure – but the relentless pressure to move forward in this direction continues.

China is leading the way, closely followed by India, with state-of-the-art, high-speed trains like the Fuxing in China, boasting 12% lower air resistance and 17% of the energy consumption per 100 km of earlier models.

In the UK, certainly, payback in terms of net gains in energy efficiency and carbon reduction can be a long time coming.

For all the arguments over cost and construction impacts, supporters of HS2 argue that the service will reduce the demand for air travel, road freight and car journeys, saving energy and taking hundreds of tonnes of carbon emissions out of the atmosphere. Once operational, it is claimed that the service can achieve just 8 grammes of carbon emissions per person per km, compared with 67 grammes of emissions from the same journey by car and 170 grammes by plane.

This seductive argument has to be set against the UK government’s own calculations which suggest that overall construction and operation of the HS2 route will result in 1.49mn tCO₂e, indicating that the route’s carbon emissions could exceed potential savings at a time when emissions need to be falling rapidly to reach net zero.

For politicians and grandstanding leaders, big infrastructure projects such as HS2 and Crossrail can be more attractive propositions than the grinding slog of electrifying existing services; but the simple truth is that we need both. According to Network Rail, the UK’s rail infrastructure owner, electric train journeys generate 25–35% less carbon per kilometre than those powered by diesel – and they are more energy efficient into the bargain.

The challenge for the future is how to turn clean, renewable energy into a reliable fuel for rail transport, particularly on lines where electrification isn’t economically viable.

Putting hydrogen into the mix  
One solution, perhaps inevitably, is seen as hydrogen and there are already pre-commercial demonstrations of hydrogen trains in China and other regions. In the UK, the Hydroflex train made the first ever hydrogen-powered journey, a 40-km round-trip through Warwickshire and Worcestershire. While hydrogen is expensive and still difficult to scale, it seems inevitable that it will play a part in the rail fuel mix of the future.

‘Having trains that can run on hydrogen power means they can run where there aren’t overhead wires and there isn’t electricity available, which means that we can run trains that emit zero emissions,’ says Helen Simpson, one of the chief engineers on the Hydroflex project. The train operates with a fuel cell which, in converting hydrogen and oxygen into electricity, drives its motors.

Another option in areas where electricity transmission is poor or non-existent are battery electric trains; the challenge being to get the right size, weight and storage capacity of batteries to make them commercially viable in this context. It’s a similar challenge to that faced by vehicle manufacturers, but on a larger scale.

More radical still, arguably, is the advent of rail technologies such as Hyperloop and Maglev, which are being promoted for their potential to deliver super-fast, clean and extremely energy efficient rail transport.

Hyperloop, which includes Virgin Hyperloop and Elon Musk among its proponents, puts the train in a raised and covered pod in order to remove both friction and resistance. Hyperloop transportation, which is currently being trialled in Holland, the US and elsewhere, is an evolution of Maglev (‘magnetic levitation’) which is already used for high-speed rail in a handful of countries, including Japan, China and South Korea.

Virgin Hyperloop test site 
Photo: Hyperloop

Interest in Hyperloop is growing because of its very high level of energy efficiency, the downside being the need to build an entirely new rail network – think HS2 on steroids.

Mix and match technology  
Whatever the next stage developments for the UK rail network, the government and the industry recognise that energy efficiency is back on the agenda. This is apparent in the drive towards lighter, more streamlined trains and in the continuing drive towards electrification – for efficiency and to attract a new generation of customers and passengers.

It is also a factor in the introduction of ‘bi-mode’ trains which benefit from new technology allowing them to be powered both by diesel motors and by overhead electric wires.

‘We certainly are seeing more units with that technology,’ says Mark Gaynor, Head of Rail Planning at the Rail Delivery Group. They include 500 Hitachi carriages, suitable for bi-mode trains, which are being delivered to Great Western Rail, with orders likely to follow in the UK as part of ‘mix and match’ efforts to modernise the network.  

The next step, adds Gaynor, could be ‘tri-mode’ trains equipped with batteries, diesel motors and roof-mounted pantographs for connection to overhead current. When it comes to accelerating towards a more energy efficient rail network I guess you just have to hedge your bets.