Electric cars are very much en vogue right now, as the world tries to clean up on emissions and transition to a more sustainable future. However, these vehicles require huge batteries as it is. For heavier-duty applications like trucks and trains, batteries simply won’t cut the mustard.
Normally, the solution for electrifying railways is to simply string up some wires and call it a day. China is trying an alternative solution, though, in the form of a hydrogen-powered train full of supercapacitors.
Hydrogen Rides The Rails
CRRC is a Chinese state-owned company in the rolling stock business. It’s at the forefront of rail projects in the country, and has invested heavily in conventional high-speed rail and even mag-lev technologies. It’s latest hydrogen-powered project isn’t built for speed, with a cited top speed of just 160 km/h, along with a range of 600 km on a full tank. That might not be quick by modern rail standards, but it’s enough to make it the fastest hydrogen-powered train in the world. It’s also equipped with self-technology for automatic operations without a driver or crew. The train operates as a four-car consist, and is charged with passenger duty.
The train relies on fuel cells to make electricity from its hydrogen fuel. Fuel cells are generally considered an emissions-neutral power source, as their sole output is water. Of course, sourcing hydrogen in a clean fashion can still be difficult, but fuel cells themselves don’t directly contribute harmful emissions to the atmosphere.
Notably, the train pairs the hydrogen fuel cells with a bank of supercapacitors. Fuel cells on their own are not great at responding to high instantaneous power demands. A design could obviously be built with a larger bank of fuel cells to serve peak power demands, but this would be expensive and inefficient.
Instead, supercapacitors are used as a power bank to cover off any spikes in power demand. The supercapacitors can be charged slowly over time by the fuel cells, and then deliver high power when it is needed most. The other benefit of adding supercapacitors is that they can store energy captured by regenerative braking. This can be particularly beneficial when a train is travelling down a long grade. That gravitational potential energy can be captured and stored as electrical energy for later use.
The CRRC effort compares ably with other hydrogen-powered rail projects overseas. German railways already operate a fleet of 14 Alstom trains on hydrogen fuel. The Alstom Coradia iLint passenger trains entered a pre-service trial back in 2018, and have since entered mainstream public service. They have a lower top speed, at just 140 km/h, though this is more than enough for the usual 80-120 km/h travel speeds on the EVB rail network. The German trains do offer longer range, with 64 on-board hydrogen tanks able to propel the trains up to 1,000 km. A single fill of the hydrogen tanks is enough for a full day’s service along typical routes. The new trains replaced a fleet of 15 diesel units, reportedly saving 1.6 million liters of diesel and 4,400 tonnes of CO2 annually. Alstom plans to ship more hydrogen train sets to other German cities, as well as France and Italy in future.
Research and development is also ongoing in the freight arena. An Australian project is exploring whether freight trains in remote mining areas could run on hydrogen instead of diesel. These long routes are unelectrified, and are currently plied by conventional diesel-powered locomotives. Freight trains tend to require much beefier locomotives, and so the challenge is somewhat greater than producing a hydrogen-powered passenger train. However, if this heavy haulage could run on hydrogen, there’s huge scope to cut emissions to a drastic degree.
Hydrogen fuel cells may seem like a curious choice for trains. Spending resources to create hydrogen, only to turn it back into electricity, is obviously less efficient than simply powering trains with electricity directly. The many overhead-wire and third-rail electric railways around the world indicate that this is a solved technology.
However, in certain circumstances, fuel cell trains do make sense. The trains can run on conventional, non-electrified railways in place of diesel trains, but without the usual greenhouse gas or particulate emissions. Employing a fuel-cell train eliminates the need to install overhead wires on many thousands of kilometers of track. This cuts up-front infrastructure expenditure. However, the trains do come with some expenses of their own. Maintenance of fuel cell trains is likely to be higher than that of conventional electric trains. There is also a need to establish hydrogen refuelling infrastructure along the train’s route. With a limited number of stops, it’s less onerous than providing hydrogen stations for road vehicles, but the infrastructure is still far from free. There’s also the need to provide hydrogen to the various refuelling stations throughout the network, whether via tanker trucks, tanker trains, or pipeline networks.
Fuel cell trains do offer a unique opportunity to cut emissions from railway transport. To achieve this properly, several factors must be considered. The trains should serve on routes currently inaccessible to regular electric trains, and must be fueled with hydrogen sourced as cleanly as possible. The entire supply chain of that hydrogen should also be taken into account, so as not to generate excessive emissions hauling it from production facilities to refueling stations. Costs should also be weighed up as to whether it would be cheaper, easier, and cleaner to simply install a caternary electric supply instead.