How are trains reaching net zero?

According to the European Environmental Agency , “[t]rain travel remains overall the most environmentally friendly mode of motorised passenger transport in Europe,” but that doesn’t mean they don’t have an impact on global CO2 emissions.

We’ve recently discussed aviation transport and vehicles used in the mining sector, which both create a significant quantity of emissions but have a long way to go before becoming truly emission free.

Railway travel is completely different. Making up just 0.1% of emissions in Europe, per passenger, even transport via diesel-powered trains is still more ecologically sound than driving an EV car. But here in the UK, almost two-thirds (62%) of the almost 10,000?mi rail network operates on non-electrified track, consuming 103 million gallons (469 million litres) of diesel each year.

Green public transport is cheaper to run, which could be why so many governments are willing to make the initial investment into new technology, but we could very realistically see zero-emission railway transport in the very near future.

Fully electrified trains have been around since 1879, when German engineer, Werner von Seimens (yes, that Seimens), unveiled a train driven by a 2.2 kW motor capable of reaching a – not unimpressive – speed of 13km/h. Using an insulated third rail to supply its electricity with a contact roller, the train carried 90,000 passengers on a 300-metre-long circular track in its four months of operating.

But Seimens proved the technology could work and two years later in 1881, the world’s first electric tram line was opened in Lichterfelde near Berlin. Multiple electric trams were opened in the following decade, some of which are still around today , and the technology has only been improving since then.

Currently, there are multiple ways in which to approach low- and no-carbon railway vehicles, you might already be interacting with some of them on your daily commute!

Before we talk about low-carbon electric alternatives to diesel engines that are currently in use, let’s take a look at hybrid, electro-diesel trains. Utilising both a diesel engine which powers a generator that drives the trains motor and an electric supply which can then be used over electrified tracks. These are primarily used along railway lines where electrified rails aren’t consistently available. This means, similarly to a Plug-in Hybrid Electric Vehicle (PHEV), they can switch between electric and diesel power.

As we move away from diesel, outright removing or replacing these vehicles will be undeniably costly, but there is an alternative fuel that could help these trains run more efficiently – hydrogen.

Hydrogen Power

There are two primary methods for using Hydrogen to power vehicles, the first is to use a fuel cell directly generate electricity to power a motor, the second takes advantage of, hydrogen as a combustion fuel and can be used in very similar to diesel fuel by combusting it in a combustion engine. Hydrogen combustion engines are already being manufactured or made from existing petrol or diesel engines, the main difference from petrol or diesel combustion is just that hydrogen needs to use about two times the amount of air – meaning a bigger air chamber

We’re only starting to see these modifications be utilised, but in Ireland, Irish Rail have already trialled a modified diesel train so that it ran on hydrogen. The project cost €1.5 million with the goal of decarbonising the operations of Irish Rail’s diesel locomotives, and it’s costs like this that seem to be the biggest obstacle with modern hydrogen rollout.

In 2022, also looking to decarbonise and reduce the operating costs of its railways, Germany launched the world’s first hydrogen-powered train. Its development and implementation cost €85 million and just a year later, in 2023, the train made its last journey. Germany’s Ministry for Economic Affairs, Transport, Building and Digitisation decided to transition back to battery electric trains which are cheaper to operate.

Of course, the wider investment in BEV and battery technology when compared to hydrogen has meant that early investments into hydrogen technology fall to second place. Even as an alternative to bio-fuel, questions on hydrogen’s ability to keep up with current fuel demands will keep rising.

Germany backing out of its hydrogen strategy has yet to slow down other governments’ plans to move towards this fuel as a viable option. Italy have set aside €300 million to convert its diesel trains to hydrogen power and over in train-phobic USA, California have approved over two dozen hydrogen trains that are expected to be running by 2027.

If you’re interested in finding out more about hydrogen fuel’s efficacy in modern transport read our guide: Hydrogen: The Future of Fuel?

Fully Electric

Today, electricity reigns supreme, not just on the roads but on rail as well. Electrified railways combined with new battery technology and innovations like fast charging has meant that it’s becoming easier than ever to move over to electric.

Railway electrification has been a key strategy for transportation for well over a century, with the first electric locomotive used in the London underground making its first journey in 1890. Originally, steam locomotives had been used on the shallower tunnel lines, but the large amount of ventilation required made it near-impossible once deep-level tube lines were built.

There are three ways in which railway lines can operate utilising just electricity: Third Rails, Overhead Lines or solely relying battery technology.

Third Rails

These electric rails used a ‘Third rail’ (similarly to Werner von Seimens’ original concept) which gave power to a motor. These are commonly built from a specially conductive steel and are connected to the train using a conductive block called a “Shoegear” which glides over the third rail, keeping the electricity flowing into the train.

Third rails might seem simple, but they’re not without their faults. Firstly, having a highly electrified, thick metal rail easily accessible to anyone working or crossing over railway lines is an obvious hazard. And even with safety precautions, third rails use lower voltage, high current DC transmission which requires a consistent and frequent connection with substations.

On shorter lines, like the London Underground, this is okay, but for freight lines or railway lines that go through rural areas, having that consistent electrical supply is either incredibly expensive or a near impossibility.

Overhead Lines

The much more efficient option is AC-powered, high voltage, overhead lines, which are made up of one or more wires positioned above railway tracks. Trains attach to these using either a pantograph, bow collector or trolley pole ,which press against the underside of the lowest wire (called the contact wire). This allows current to flow through to the train or tram and back to the feeder station through the steel wheels on one or both running rails.

Where third rails are cheaper and simpler to install, the engineering costs of installing overhead lines is only one hurdle faced by electrification. The other is size – in regions like the UK, where rail lines have remained the same for centuries, many bridges and tunnels aren’t designed to support the height of overhead lines.

This hasn’t stopped overhead lines becoming a common site in most cities; for short distance, overground trams they are the best option. But they are also used across the world for intercity, regional transport.

Battery Electric

In recent years, passenger cars have taken full advantage of new battery technology, with some vehicles now boasting a range of over 400 miles. For trains, which have much more space than passenger cars, the two biggest challenges faced by adding batteries is weight and cost.

Battery weight has a huge impact on the range of a vehicle and it’s no different for trains, some of which are expected to travel hundreds of miles through completely unelectrified areas before they can stop and recharge. This might be why the world leader for battery electric trains is Japan, a country with easy access to electrical systems that allow for charging or refuelling and has the resources to invest in the infrastructure to support this type of train.

Similarly to Japan, here in the UK, we’ve even seen the introduction of battery electric trains across the Mersey/Liverpool area. The city centre’s Merseyrail Wirral line already used a third rail, but extending the outside of the city to its surrounding areas would have meant either implementing a third rail on pedestrian areas instead or allowing diesel engines (which operated on the surrounding lines) into the city’s underground.

The decision taken instead was to merge the two lines and replace the diesel-powered trains with battery electric. And it looks like battery electric will find its home in merging the lines between railways with third rails or overhead lines and ones traditionally using diesel trains.

Railway is the past, present and future of green transport, and there is still a lot of growing room for the industry. More governments are seeing trains powered by electricity as the cheaper (in the long run) and greener alternative to diesel power, but that initial investment is doing a lot to put off a speedy transition to fully green transport.

When it comes to hydrogen, while the fuel is continuing to gain popularity, without investment into its infrastructure, the cost of entry will be much greater than adding more existing electric railways to a city or country’s infrastructure.

If you’d like to read more on our electrifying series, click here to read about advancements in the mining industry.