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GREEN HYDROGEN Production of hydrogen via renewables-powered electrolysis could be an economical option along rail routes
ALTERNATIVE TRAVEL Hydrogen is also being tested within the aviation and shipping sectors where there are few other alternatives
KEY QUOTE Fuel cell hydrogen trains make economic sense above all when they are used on longer and non-electrified routes of over 100 kilometres
Hydrogen, a clean fuel at its point of use, has for many decades held tantalising promise for the decarbonisation of energy. But hydrogen does not occur naturally in its own right. It has to be produced from another state and is only as clean as the method used for that process. The financial and technical challenges of producing truly clean hydrogen, which can be done using electricity from a renewable source of energy, have until recently kept its promise out of reach. That is now changing.
Of all the much vaunted claims for the application of electrolytic hydrogen in the energy transition, two are now bearing up under close examination thanks to technology advances. The first is replacement of the vast quantities of “dirty hydrogen” used in petroleum refinement, metal treatment and fertiliser production, plus the potential replacement of fossil fuels used in industrial processes requiring extremely high temperatures. The second is to provide motive power for heavy commercial transport. The growing number of hydrogen powered trains in commercial use suggests they currently tick more boxes than hydrogen powered trucks employed in long distance road haulage.
Hydrogen trains have a bright future. They are already running in Britain and Germany and there are plans for more in Japan, Italy and elsewhere. Although railway electrification is the preferred option on a route to zero carbon, it is expensive. Case studies for Norway, the Netherlands, Britain and elsewhere suggest hydrogen can be an economic option. Battery powered trains are also being considered, but they tend to be outbid by hydrogen.
The environmental advantages of rail over road transport are clear. “High capacity urban rail requires, on average, less than a tenth of the energy needed per kilometre travelled compared with passenger cars,” states a joint International Energy Agency/International Union of Railways Report.
Work is underway to reduce the carbon footprint of all forms of transport, but the potential for trains to be zero carbon perhaps holds out most promise. The railways of Switzerland are almost zero carbon as the rail system is 100% electrified with around 98% of the electricity coming from carbon-free sources, hydro and nuclear.
Power systems the world over are aiming to reduce the carbon content of their electricity and railway owners are raising their electrification ambitions. Rail electrification, however, is costly and it may be difficult to justify the expense of installing the required infrastructure for lightly-used lines. Alternatives to electrification are flywheels, batteries and hydrogen fuel cells.
The first option is only suitable for short journeys, but the concept is proven and a prototype has been operating successfully for several years in the UK. The caveat is that the electricity source responsible for energising the flywheel should be carbon-free. The same caveat applies to the electricity used to generate hydrogen or to charge batteries, otherwise the transport is not carbon-free. Trains running on hydrogen appear to be an attractive option for several types of service and development of both battery and hydrogen trains is proceeding rapidly.
Direct rail electrification is a preferred option as railways move towards low carbon operations. The scope for electrification is considerable. Only about a quarter of the world’s railways are electrified (chart). The problem with electrification is its cost. The required catenary high-voltage cable infrastructure typically costs around €5 million per kilometre of double-track railway fully installed; some estimates are twice that, some less. Electrification of a single-track railway would cost less, but single-track lines invariably carry less traffic, making the economic case more difficult to justify.
If the line was lightly used and carried 20 trains a day (ten in each direction), each train would need to pay a fee of around €5500 solely to repay the investment. If the trains were full, that might translate to an acceptable premium per passenger, but not if they were lightly loaded. The picture changes if the line is busier, with 120 trains bringing the premium down to about €920 a train.
A lower cost electrification approach uses conductor rails adjacent to the running rails, but these have a number of limitations, including the issue of safety, and are only considered suitable for urban transport systems. High voltage systems, with the power delivered by overhead cables, is now the preferred option, worldwide, for all mainline railway systems. It is against this backdrop that numerous studies have been carried out recently to examine the viability of other potentially zero carbon propulsion modes.
Battery powered trains have been around for some time and have operated in Germany, New Zealand, Ireland and the UK. Their limitations were (and still are) their limited range and their extra weight. Until recently, the time needed to charge the batteries was a drawback, but the latest designs have provision for connecting to a medium (750 V) or high voltage (11 kV or above) power supply which enables faster charging. The principal advantage of trains running on battery power over electric or hydrogen trains is that they are cheaper.
When compared with batteries, hydrogen delivers a better range, lighter trains and takes up less volume on board. The weight of a battery powered train does not change during its journey, but the weight of a hydrogen powered train reduces, albeit slightly, as the journey progresses and the hydrogen store is depleted.
The economic advantages, but limited range, of battery electric trains means they are likely to be deployed mainly on branch lines, typically up to 100 kilometres in length, that are relatively lightly loaded. Hydrogen fuel cell trains are more versatile and in the UK a mixture of the two has been identified as the best option by Network Rail, the track operator.
In a report from September 2020, Traction Decarbonisation Network Strategy, the track operator identifies potential for another 11,700 track miles to be electrified directly, 900 track miles to be used by hydrogen powered trains and 400 track miles to be used by battery-driven trains. A further 400 track miles could possibly be used by hydrogen trains in cases where the economic preferences were less clear-cut. A “track mile” refers to the total length of the track, meaning that a ten kilometre double track section would have a track mileage of 20 kilometres.
Since the maximum range of battery powered trains is generally a little over 100 kilometres, it is unsurprising that a major 2019 study by the Hydrogen and Fuel Cells Joint Undertaking (FCJU) in Brussels, Study of the Use of Fuel Cells and Hydrogen in the Railways Environment, concluded: “Fuel cell hydrogen trains make economic sense above all when they are used on longer and non-electrified routes of over 100 kilometres.”
The principal disadvantages of hydrogen are its high fuel cost, the need to set up infrastructure to deliver the gas, and issues of safety raised by its volatility. Economic appraisals that include all the relevant costs associated with the fuel and its delivery can reveal when and if hydrogen trains can be competitive with other options, but the cost of gas explosions causing large scale damage to property and multiple injuries to people is harder to quantify.
The FCJU calculated the total costs of operating a number of routes and looked at both multiple unit trains (power unit and fuel on board the coaches) and the use of locomotive-hauled trains for longer routes. The comparative cost of the different propulsion technologies in three countries on the European continent was influenced by the length of the route and the cost of electricity in each country. The routes examined were the Montrejeau-Luchon 140 kilometre line in France, already partially electrified, a 165 kilometre stretch running from Aragon in Spain to across the border into France and a 300 kilometre line linking Groningen and Friesland in the Netherlands.
While diesel trains were cheapest in all three countries, hydrogen trains were the next cheapest in the Netherlands and Spain, but not in France where they were beaten by battery trains. Electrification was the most costly option in France and Spain, but on the longer Dutch route was cheaper than batteries (chart).
The French and Spanish routes are lightly used, but the Dutch route has a more intensive service (mostly hourly) and so it is perhaps not surprising that electrification emerges as the cheapest option, about 10% cheaper than using hydrogen trains. The Spanish route favours fuel cell trains at just over half the cost of electric trains. On the lightly-used French route, battery emerges as the cheapest option—about 10% cheaper than the hydrogen alternative.
The FCJU study also looked at the prospects for locomotive-hauled trains on longer routes in Estonia, Germany and Sweden. Route lengths varied between 210 and 720 kilometres. In each case diesel traction remained the cheapest option, but hydrogen was slightly cheaper than electrification for cross-border traffic between Russia and Estonia and it was significantly cheaper in the Swedish case (Kalmar-Linkoping).
Another study, the Techno-Economic Analysis of Freight Railway Electrification by Overhead Line, Hydrogen and Batteries, from 2020, examined the case for hydrogen trains for freight on two lines, one in Norway, the other in the United States. The Nordland line in Norway is 731 kilometre long and runs from Trondheim to Bodø in the far north with about 300 train movements. The US route, a 2883 kilometre stretch from Kansas City to Los Angeles, has about four times that number. The study concluded that fuel cell trains delivered the cheapest option on the Norwegian line, but not on the American line, where electrification came out as the cheaper option. The result again indicates that electrification demands a high intensity of services to enable the initial capital outlay to be recouped when spread over a large number of train movements. Even if the electricity used to charge batteries or generate hydrogen is not carbon-free, trains adopting either propulsion method are quieter than diesel trains and produce no harmful emissions along their routes.
The world’s first hydrogen-powered trains entered service in Germany in September 2018, with two pre-production two-car units, which have been operating in the north of the country on a route between Cuxhaven and Buxtehude ever since. The train is based on a design of diesel multiple unit that has been operating for several years. It has been re-engineered to accommodate the components necessary for it to run on hydrogen. The Coadia “iLint” has a 200 kW fuel cell and a 225 kW lithium-ion battery that stores surplus fuel cell energy and absorbs regenerative energy when braking. Roof tanks store 99 kilograms of hydrogen at a pressure of 350 bar. Alstom, the train manufacturer, claims the hydrogen train has a similar weight to the diesel version. The hydrogen consumption, at around 0.2 kg/km, is slightly less than that assumed in the FCJU study. The maximum speed is 140 km/h and the range is 600 kilometres.
Several regional rail operators in Germany have placed orders for the trains following the successful operation of the prototypes and the Dutch rail operator supervised an intensive test programme in spring 2020. The transport authority for the Frankfurt region has ordered 27 trains for delivery in 2022 and construction of a refuelling facility started in October 2020. A trial began in Austria in September 2020 that could lead to an order for further trains.
In Britain, the first mainline hydrogen train, Hydroflex, made its first demonstration trips between Long Marston and Evesham in central England in late September 2020. The venture belongs to rolling stock operator Porterbrook in conjunction with Birmingham university. The train has been converted from a four-car electric multiple unit. In a sign of developing competition in the market, Alstom has also announced its intention to convert another electric multiple unit for hydrogen operation.
Other manufacturers are also developing fuel cell trains and Swiss rolling stock manufacturer Stadler Rail will supply a Flirt train to the US in 2024 for operation in San Bernardino County, California. Further activity is reported in Japan and China.
Hydrogen fuel cells can also be used to propel ships, trucks and even aeroplanes with demonstrations of how to go about it at various stages. British company ZeroAvia claimed it completed the world’s first hydrogen fuel-cell-powered flight of a commercial grade aircraft in September 2020. The six-seater plane used for the flight is for the time being the largest hydrogen-powered aircraft in the world, says ZeroAvia. It completed a circuit around the aerodrome at Cranfield in England, where the company is based. The next step is a 400 kilometre flight to the island of Orkney off northern Scotland.
Anglo-French company Airbus is a hydrogen flight believer. “Hydrogen is one of the most promising zero-emission technologies to reduce aviation’s climate impact. This is why we consider hydrogen to be an important technology pathway to achieve our ambition of bringing a zero-emission commercial aircraft to market by 2035,” states the company.
The shipping industry lays claim to another “world first” for hydrogen in the shape of a ferry set to undergo testing at the European Marine Energy Centre in Scotland’s Orkney Islands. Initially, the ferry’s hydrogen fuel cells will power its auxiliary engines, but the aim is for it to run solely on hydrogen. The project has a strong claim to being truly green as its hydrogen is derived through electrolysis reliant on electricity supplied from a tidal power installation.
Fuel cell buses have been operating on the streets of London and other major cities for several years. Fuel cell cars are available, but they are expensive and unlikely to make much of an impact in the short to medium term. Among truck manufacturers, several big names are promoting fuel cell powered heavy commercial vehicles. A
hydrogen powered commercial truck built by Hyundai started hauling groceries in Switzerland in April 2020, the first of 1600 fuel cell electric trucks that the manufacturer plans to commission by 2025. Switzerland levies a tariff on heavy vehicles that corresponds to around €0.8/km. Green vehicles are exempt. As Switzerland’s electricity is 98% carbon free, its hydrogen trucks will have impeccable green credentials.
Most hydrogen today, however, is derived from non-renewable sources and even electrolytic hydrogen is reliant on electricity from grids that are still at least partially dependent on fossil fuel. Given that the production of hydrogen from renewables will always cost more than the renewables electricity used in the electrolysis process, clean hydrogen will always be more expensive than clean electricity.
As a result, truly carbon-free hydrogen, produced from renewable energy-powered electrolysis, is unlikely to contribute in any significant way to reducing emissions for many years yet. Should it eventually become a mainstream energy carrier alongside electricity, it will perhaps be the railways that demonstrated and spearheaded the hydrogen revolution.
TEXT David Milborrow PHOTO Johannes Hofman
David Milborrow is an energy economist with an extra-curricular interest in trains. Taking advantage of this fortuitous mix of expertise, FORESIGHT asked him to take a deep dive into hydrogen-powered trains and assess their commercial potential
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