The role of hydrogen in transport

Last week I looked at the potential for using hydrogen in heating, something that still looks a way off. Hydrogen is having a more immediate impact in the transport sector. (See these earlier posts for why hydrogen is clean, provided you make it right) At present, the vast majority of transportation runs on oil. If we want to avoid climate breakdown, that has to change.

We can reduce demand and encourage more walking and cycling. We can electrify all kinds of things, from trains to buses to cars. But there are a few problem categories that need a different approach, such as planes and trucks.

One of the big problems with electric transport is the weight of batteries. Oil is very energy dense, which means you get a lot of miles out of a tank of petrol. Pound for pound, no battery comes close. That’s fine for smaller vehicles and shorter distances. It’s trickier for heavy vehicles hauling freight across a continent, as they’d have to haul the weight of their own batteries too. Planes and batteries are a non-starter: on current technology, the batteries to power a long-haul electric flight would make the plane too heavy to leave the ground, let alone carry passengers.

This is where hydrogen can help. It can store a large amount of energy in a small space. For a weight comparison, consider that every Tesla car has half a tonne of batteries to move. Toyota’s hydrogen powered family car, the Mirai, has a hydrogen fuel cell that weighs 56 kg. While it may be technically less efficient to make hydrogen than to store power directly in a battery, that weight advantage gives hydrogen some specific advantages.

So where exactly are we most likely to see hydrogen playing a role in zero-carbon transport? Let’s look at a few different categories to see where the possibilities lie.

Cars: First up, let’s start with the form of transport with the widest usage. Hydrogen fuel cell cars exist. They have done for a few years. Whether you can drive one yourself depends on refuelling points. In the UK, there hasn’t been a network to speak of and therefore there are very few hydrogen vehicles. They are more common in Japan and South Korea, both of which have targets to expand their use as a part of their low carbon strategies.

Why would you want a hydrogen car rather than a battery electric? Because the range is longer – the Toyota Mirai holds the record after being driven over 1000 kilometers on a single charge earlier this year. And when you do need a refill, it takes five minutes.

Public transport: Hydrogen cars might be rare on Britain’s roads generally, but it’s easier for fleets to use them. Taxi or bus companies can fit their own refill stations, and don’t need a national network to serve their city. London has had a few hydrogen taxis on the roads for a decade, and this year unveiled the world’s first hydrogen double-decker bus.

Heavy vehicles: Because of the lighter weight, hydrogen fuel cells are a good choice for trucks and vans. Like public transport fleets, companies can also run their own refill stations at their depots and don’t have to wait for a public network. Fuel cell vehicles can do longer distances than some of their electric equivalents, with Hyundai first onto the market with an HGV that will do 800 km. We’re also likely to see zero-carbon tractors and other farm machinery that runs on hydrogen, as well as rubbish trucks and construction vehicles. JCB launched a prototype hydrogen excavator in 2020, a world first. One category of vehicle commonly uses hydrogen already, and that’s fork-lift trucks.

Trains: Where there are overhead cables or pick-up rails, the battery weight problem doesn’t apply to trains. They can be electrified and draw the energy they need as they go. But electrifying an existing diesel line is very expensive, especially across long distances or challenging terrain. In some places, hydrogen is going to offer a compelling alternative. The first hydrogen trains debuted in Germany in 2018, and they will be replacing diesels on rural routes in greater numbers from 2022. The Hydroflex project in the UK has demonstrated that existing trains can be converted to hydrogen, which offers significant savings. This summer Indian Railways announced that it would trial hydrogen trains too.

Ships: Hydrogen for ships is an area of active research at the moment. It’s already practical for shorter distances. The first hydrogen ferry was delivered in Norway this summer, cutting the carbon emissions of the old ferry route by 95%. A small cargo ship is expected to launch in France this year and operate on the river Seine, and the first cruise ship in 2023 in Norway again. For larger ocean-going vessels, there are more complications. Storing enough hydrogen takes up a lot of space, and it has to be done safely. Some suggest that a more practical solution is to combine the hydrogen with nitrogen to make ammonia, which many ships could burn already with relatively minor adjustments to their engines. There’s further research to do before we see hydrogen make a serious dent in shipping emissions, but it’s an area to keep an eye on.

Planes: As a child, we used to fly to Madagascar with Aeroflot, on a Soviet airliner called a Tupolev 154. In 1988 one of these was adapted to fly on hydrogen and christened the Tupolev 155. It was announced at the time as a solution to both oil supply shortages and “an absolutely ecologically pure engine”. It flew over 100 times before the project was cancelled after the collapse of the Soviet Union, and nobody has built a hydrogen plane of that size since. But we know it can be done, whereas long-haul flights on battery power are impossible for the foreseeable future. It’s odd to think that we were closer to clean hydrogen airliners in 1988 than we are today, but history is wierd sometimes. There’s a huge amount of research going into this, a handful of very small prototypes, and Airbus plan on having hydrogen planes out by 2035.