Finding new ways Getting the world’s vehicles to work has always been a vital component of tackling the climate crisis. When it comes to small passenger vehicles, there is no doubt that the future lies in battery electric vehicles, not those powered by hydrogen fuel cells – the other viable alternative. However, as the size of the vehicle increases, hydrogen could become an increasingly attractive option. For buses, some argue that hydrogen power gives several major advantages over its battery-powered electric counterparts. Whichever one eventually becomes the main technology in buses could have an impact on other forms of transportation as well.
Hydrogen fuel cell and battery electric vehicles have similar propulsion systems. Both store energy to run an electric motor. However, in the latter, the energy stored in the form of hydrogen is converted into electricity by the fuel cell, rather than being stored in a rechargeable battery.
Electric vehicle sales reached 3 million in 2020, up 40 percent from 2019, with about 10 million electric vehicles now on the world’s roads. Hydrogen car registrations are still three times lower than this, and there are only 26,000 on the road globally, concentrated in three countries: Korea, the United States (largely California), and Japan. While there are still many hydrogen fuel cell cars available on the market, made by companies like Toyota and Hyundai, they tend to be more expensive than battery electric cars and can currently be difficult to refuel: hydrogen is expensive to buy, and there is a lot . There are fewer refueling stations than recharging points in most places.
But when it comes to larger vehicles, the picture isn’t entirely clear. As vehicles increase in size, it becomes more and more difficult to electrify them, with increasingly large batteries needed. For energy-intensive applications such as long-haul trucks, some experts say hydrogen may be the best option.
Buses fall somewhere between cars and trucks on this spectrum. “The big problem is the size of the buses,” says James Dixon, a researcher in modeling of energy and transportation systems at the University of Oxford. “Batteries have a relatively small energy density: the energy density is about 1/40 that of a liquid hydrocarbon fuel, such as gasoline or diesel.” Hydrogen also has a relatively low energy density (the amount of energy that can be stored per unit volume of mass or area) — about four to five times lower than petroleum fuels, but much higher than electric batteries, he adds.
China already has about 5,300 hydrogen fuel cell buses on its roads, the vast majority of the global fleet, but other countries are investing in the technology. Neil Collins, managing director of Northern Ireland-based bus maker Wrightbus, says his company is tech-neutral and manufactures battery-powered, electric and hydrogen fuel-cell buses. It feeds trip data from bus operator customers into a tool to model different driving cycles of its vehicles, to help them find the best technical solution for that specific route.
The advantages of hydrogen include shorter refueling times and an often larger tank range. Collins says hydrogen technology and infrastructure are more expensive, while it’s also likely that skills in the industry to use electric buses are higher than those of hydrogen. Dixon also notes that one concern about hydrogen has always been its safety. “It has a very wide range of flammability, and it’s hard to keep it in a pressurized container without leaking,” he says. “In terms of infrastructure, electricity is a lot easier, because you don’t need liquid fuel trucks.”
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