Can hydrogen keep the world moving?

Hydrogen has been hyped by some for years as a potential clean fuel for passenger cars, but has seen limited take-up. For other transport sectors, though, it could be a different story. Some experts still believe hydrogen could play a strong role for larger vehicles such as long-haul trucks, while many believe it holds the key to decarbonisation for aviation and shipping. Here, we take a look at the different prospects for hydrogen across the transport sector.

To some, hydrogen cars seemed like a perfect clean alternative to combustion-engine cars. They promised low or zero climate impact, no tailpipe pollution, long ranges, and short refuelling times. Despite years of hype, hydrogen fuel cell electric vehicles (FCEVs) have failed to gain ground.

“It does appear that the ship has sailed on [hydrogen fuel cell cars],” says Gniewomir Flis, a climate, energy, and hydrogen analyst at Agora Energiewende. “They just have been leapfrogged by battery electric cars.”

The two main reasons for this, he says, are a lack of refuelling infrastructure and the higher expense to run them compared to battery electrics: the lower efficiency of hydrogen vehicles translates into higher total cost of ownership.

According to the International Energy Agency (IEA), there were only 25,000 FCEVs on the road globally by the end of 2019, versus 7.2 million battery electric or hybrid cars. While this was double 2018 levels, they still represent just 0.5 per cent of new low-carbon vehicle sales. The world had only 470 hydrogen refuelling stations in 2019.

While companies such as Toyota, Hyundai and Honda continue to produce FCEVs and plan to expand, other firms have come down firmly against them. Last year, Volkswagen announced that “everything speaks in favour of the battery and practically nothing speaks in favour of hydrogen” when it comes to passenger cars.

The US has the world’s largest fleet of hydrogen vehicles, nearly all of them in California, the only state with a hydrogen fuelling station network. China, Japan and Korea also have significant and rising numbers. Sales in Europe fall far behind.

Sabrine Skiker from industry association Hydrogen Europe says Asiatic markets are still investing massively in these technologies. Japan, for example, is targeting 200,000 FCEVs by 2025. And FCEVs could offer advantages elsewhere in vehicle applications which need operational flexibility but refuel in a central location, such as taxis and buses, she says.

The story could change for FCEVs if a network of hydrogen was rolled out for other purposes, such as for domestic heating, says Oytun Babacan, a research fellow at Imperial College London. “Then hydrogen cars could be more favourable,” he says. “But it won’t be here soon.”

For energy-intensive applications like long-haul trucks, hydrogen may be the best option, says Babacan. Despite its lower efficiency, hydrogen could offer these large vehicles a lower weight load, increased range, and shorter fuelling times in comparison to battery electrics.

The race between the use of battery-electric and fuel-cell technologies in long-haul trucks “has not run yet”, says Geert De Cock, electricity and energy manager at non-profit Transport & Environment. “We need a strong regulatory push to get these zero-emission trucks on the road, then let the best technology win,” he says. California, for example, already has a zero-emissions mandate for trucks by 2035.

Hydrogen buses are another area where hydrogen fuel cells are competing. Supportive policies in China mean it now boasts some 4,300 fuel cell buses, 97 per cent of the global fleet. Korea has plans to produce 40,000 fuel cell buses by 2040.

Of course, widespread use of hydrogen as a low-carbon fuel would require a massive ramp up of cleaner production, since nearly all hydrogen is currently made from steam methane reforming.

Do green hydrogen trains make sense? Hydrogen trains are in their infancy but some people argue they could offer an alternative to the high cost of electrifying old diesel lines.

In 2018, the world’s first two fuel cell trains went into operation for an 18-month trial in Salzgitter, Germany.

The Coradia iLint passenger trains use flexible battery storage along with their fuel cells, can reach up to 140km/h and have a range of around 1,000km, similar to that of diesel trains.

Developer Alstom and its partners claim the project has proven that hydrogen propulsion is a reliable alternative to diesel-powered regional trains on lines which are not electrified. It is now working to roll out its train further afield, with a passenger service trial in Austria and the trains to be used in regular service in Germany from 2022.

The UK is also testing its own hydrogen-powered train. Mainline testing of the HydroFLEX train, a partnership between the University of Birmingham and train leasing company Porterbrook, began in 2020. By 2023, the technology will be available to retrofit current in-service diesel trains to hydrogen, according to the University of Birmingham.

Hydrogen trains are far from being rolled out more widely, says Agora Energiewende’s Flis. But Hydrogen Europe’s Skiker argues there is strong potential in this sector. “Half of the train lines in Europe are not electrified,” she says, “meaning that we have a potential for all those lines which are not electrified to use hydrogen instead.”

On the other hand, they would require the build-out of hydrogen refuelling stations, and add significant fuel and maintenance costs over a train’s lifetime compared to electrified lines.

“A hydrogen train eliminates the need to electrify the track, but at the cost of locking in forever an option that is more complex, higher maintenance and less than half the efficiency,” wrote Michael Liebrich, a senior contributor at BloombergNEF, in a blog last October.

The rollout of refuelling stations at train stations could be combined with other applications, Skiker of Hydrogen Europe argues: “You can imagine you have your hydrogen refuelling station for your train, but then actually, just outside of your train station, you have another nozzle being used for coaches, for example.”

With the renewed focus on hydrogen, fuel cell trains are clearly sparking interest, but whether they will ever be rolled out on a wide basis remains to be seen.

Could hydrogen ships be the clean fuel of choice? 

Ships currently run on a variety of different types of fossil fuels, with the highly polluting heavy fuel oil (HFO) the most widely used.

There is widespread agreement that hydrogen, or another fuel made from hydrogen, will be the future clean fuel of choice for shipping.

“I think hydrogen is the molecule that will enable the decarbonisation of shipping,” says Flis. “Any larger cargo shipping or longer duration routes, that’s where hydrogen really has a chance to shine.”

Batteries may be a choice for short routes, which don’t need much range, he says, but this will only be a niche application due to their low energy density. Too many batteries are needed for long journeys, adding extensive weight and cost to the ship. Biofuels could play a small part, but sustainable production of these is limited and will be shared with other sectors.

Ammonia, which is made from hydrogen, is often considered the main contender against hydrogen. It is currently made via the energy intensive Haber-Bosch process, but could be made using fuel cells run on renewable electricity. Both would require retrofits on ships and each have advantages and disadvantages.

Ammonia is far easier to store and far more dense so takes up significantly less space on a ship. It is also highly toxic, corrosive, smelly (a potential problem for ports near cities) and likely to be more expensive to produce. Hydrogen is cheaper and has no toxicity, but is less dense and needs to be turned to liquid using cryogenic temperatures.

E-methanol, a synthetic fuel made from hydrogen, is also a contender, but would require a carbon-negative source of carbon – such as direct air capture – to make it carbon neutral, and would probably be yet more expensive.

The maritime industry has a goal to halve its greenhouse gas emissions on 2008 levels by 2050. There are few clear policies or measures in place to put it on this pathway, although the industry does have a wide range of pilot and demonstration projects.

Between them, biofuels, ammonia, and hydrogen could meet more than 80 per cent of shipping fuel needs by 2070, according to the IEA. A report from the International Council on Clean Transportation (ICCT) found that 99 per cent of voyages made along a China-US corridor could be powered by hydrogen with only minor changes to fuel capacity or operations.

Transport & Environment’s De Cock says green hydrogen is unlikely to be available in large quantities before 2030. Since there will be competing uses for this hydrogen, he adds, priority should be given to sectors with no alternatives available. “That’s aviation and shipping, essentially.”

It’s worth noting that there are a host of other technologies and measures – such as slow steaming or wind-assisted propulsion – that could make ships more fuel efficient in the first place.

Aviation, like shipping, is considered a ‘hard to decarbonise’ sector.

Hydrogen and hydrogen-derived fuels are also seen as the main offering to cut emissions. “We’re certain to see hydrogen play a meaningful, if not pivotal role in decarbonising aviation,” says Flis.

The aviation industry has an emissions problem and, increasingly, a PR problem. It needs to begin tackling its emissions but has limited options. The main international climate measure for aviation, CORSIA, only tackles emissions above 2019 levels, and is focused on offsets, which are far cheaper than alternative fuels.

Hydrogen planes are being developed by several companies. Airbus plans to launch a hydrogen combustion plane in 14 years, while last year British start-up ZeroAvia had its first test flight of a six-seater hydrogen fuel cell plane. However, these need an entire redesign of the plane, will have a limited size and range, and require a whole new distribution network of hydrogen in airports.

“Part of the problem [with hydrogen planes] is they have a big challenge on how to store the hydrogen on the planes securely, and whether you have sufficient space for it,” says Imperial College London’s Babacan. “The other problem is they’re worried about the propulsion technologies: if they’re reliable enough, if they are strong enough. So these are being tested.”

At least in the shorter term, another solution is needed to begin to replace kerosene. The main two options are kerosene biofuels and e-kerosene, a synthetic fuel made from hydrogen and carbon.

Both these can be blended together with fossil kerosene in today’s planes, with the ratio slowly increased over time. Both will cost several times more than current jet fuel, with e-kerosene expected to be especially expensive in the short term.

Norway already has a 0.5 per cent biofuel blending mandate, while Sweden is this year introducing a greenhouse gas reduction mandate for aviation fuel sold within its borders, starting at 0.8 per cent and gradually increasing to 27 per cent in 2030.

Kerosene biofuels are likely to play a role in the short term, but run into the same issues as for ships: there is limited supply of biofuels made from waste and residues, while crop-based biofuels, from sources such as palm oil, have a host of climate issues associated with them such as deforestation.

“Looking at all the options, we think that e-kerosene is really the way to go for the aviation sector,” says De Cock. “We cannot wait for hydrogen aircraft in 2035 to appear.”

Carbon-neutral e-kerosene production would require a clean source of hydrogen and removing carbon from the atmosphere to make the fuel. However, there is currently next to no e-kerosene production.

One issue with both e-kerosene and hydrogen, however, is that they are unlikely to get rid of the non-CO2 impacts of aviation, such as contrails caused by water vapour and particles. These emissions are poorly understood but thought to double or even triple the climate impacts of aviation.