In addition to building new zero-emission trucks, what if older diesel trucks were converted to hydrogen fuel-cell power? Two such initiatives were announced earlier this week.

Daimler Truck North America and diesel-engine manufacturer Cummins will update older Daimler-built Freightliner Cascadia semi trucks with Cummins-supplied fuel-cell powertrains, the two companies announced Wednesday.

The companies plan to have the first trucks ready by 2024. By then, Daimler also expects to have ramped up production of the battery-electric eCascadia, which was unveiled in production-ready form the same day as the fuel-cell announcement.

Startup Hyzon Motors is pitching its own fuel-cell conversion program as a way to get cleaner trucks on the road more quickly. The company said in a press release that, due to supply-chain issues, the current wait time for a new truck chassis is up to 16 months. Converting existing chassis provides a shortcut.

Hyzon plans to offer 110-kw and 200-kw fuel-cell stacks. It said examples of the latter will begin testing by the end of 2022, with a commercial launch after that. The stacks will be manufactured at Hyzon’s Illinois factory.

Other companies have expressed interest in building new fuel-cell trucks. In 2021, General Motors and Navistar announced plans to build 2,000 fuel-cell semis “in the near term.” Toyota and Kenworth have been demonstrating “Project Portal” prototypes in drayage service at the Ports of Los Angeles and Long Beach for a few years at this point.

Perhaps the most ambitious is the California Fuel Cell Partnership trade group, which plans to put 70,000 fuel-cell trucks on the road by 2035, supported by 200 newly-built hydrogen stations.

But while commercial trucks are seen as a more viable option for fuel cells than passenger cars at this point, it’s possible that even that window of opportunity is closing.

he moment for hydrogen fuel-cell passenger cars to play a major fuel in transportation has passed, and the window of opportunity is closing for heavy-duty trucks as well, according to a new study published as “comment” in Nature Electronics.

The study’s author, from Fraunhofer Institute for Systems and Innovation Research and claiming to be free of competing interests, argues that improvements to the range and charging capability of battery-electric vehicles have cancelled out the main selling points of fuel-cell vehicles—long range and quick refuelling times. Policymakers should now focus all efforts on promoting EVs, he argues.

EVs have already proliferated more quickly than fuel-cell vehicles, the study notes. At the beginning of 2021, there were about 25,000 fuel-cell passenger cars on the road, two models on sale (the Hyundai Nexo and Toyota Mirai), and about 540 hydrogen stations globally. In comparison, the study’s author predicts that by the beginning of 2022 there were likely about 15 million battery-electric and plug-in hybrid vehicles on the road.

Even in trucking, where the need for large battery packs has been a limiting factor, battery-electric vehicles outnumber fuel-cell vehicles, the study said. EV range may still be too limited for long-haul trucking, however, potentially providing a niche for fuel cells, according to the study.

Proposed megawatt charging systems could swing the advantage back to EVs, but it isn’t yet clear whether it will be less expensive than hydrogen, according to the study. The total cost of ownership will ultimately be the determining factor in whether fuel cells or batteries dominate in trucking, the study noted.

“Policymakers and industry need to decide quickly whether the fuel cell electric truck niche is large enough to sustain further hydrogen technology development, or whether it is time to cut their losses and to focus efforts elsewhere,” the paper concluded.

It’s not all bad news for hydrogen, though. The authors believe fuel cells could have a big future in aviation, shipping, and steel-making. Just not cars and trucks.

At least some automakers share that perspective. Volkswagen has laid out why fuel cells make no sense in cars. General Motors has closed the door on the tech in passenger vehicles, too, but sees it as a future tech for trucking and military uses. It’s also looking at hydrogen for portable generators and, ironically, EV fast charging.

Not every automaker is giving up on hydrogen fuel-cell cars. Kia and Hyundai both have fuel-cell tech in their roadmap, as does Toyota.

The California Energy Commission has also released a rosy projection—that fuel-cell tech is expected to reach price parity with gasoline by 2025. That’s based on the energy itself, not the vehicle tech or the cost of fuelling stations.