The future of transportation is electric, and hydrogen will be part of that future. But it's difficult to see a clear path to hydrogen-powered transportation. Too many variables still must fall into place before an accurate picture comes into view of the true cost of hydrogen and its practicality as a transportation energy source.
That's one of the central conclusions found in a wide-ranging guidance report on hydrogen fuel cell powered trucks just released by the North American Council for Freight Efficiency. The report, Making Sense of Heavy-Duty Hydrogen Fuel Tractors, highlights the challenges and benefits of making fuel-cell powered trucks competitive with battery-electric trucks as clean-energy alternatives to diesel.
The report outlines the present state of fuel cell technology and acknowledges they are a viable alternative to diesel and would compliment battery electric trucks in many applications. However, they are relatively new to trucking, and still need to be proven in different applications. NACFE warns that fleets thinking about fuel cell deployment will need to optimize the specifications for the intended application and be prepared to make adjustments along the way.
"While the technology is fairly mature, the application is fairly new, and there should be an expectation of a learning curve with any new technology," said report co-author and NACFE's director of emerging technologies, Rick Mihelic, in a call for trucking reporters about the report. "But that should not dissuade fleets from getting interested in it. Fleet feedback to OEMs is how products improve in our industry."
The bigger consideration at this point, even bigger than the truck or the specs, is the source of hydrogen to power the transition.
Hydrogen is produced from several sources, the most common being steam-methane reforming, which is known as black or gray hydrogen because of its high-carbon production process. Hydrogen is made from natural gas and is widely used in oil refining and fertilizer production. More than 95% of hydrogen production today comes from SMR processes. While it's usually produced onsite, NACFE says some of this source could be diverted to power fuel call vehicles.
There's blue hydrogen, too, which is made from gray hydrogen, but the carbon is sequestered or repurposed, making it a greener alternative than gray hydrogen.
As the chart below illustrates, there is a variety of hydrogen sources, defined by their production process and upstream carbon generation.
Little of today’s hydrogen production is used for transportation, but that will have to change as demand rises. NACFE says there's room for all these sources and that a portfolio solution to energy sourcing is needed, requiring a wide range of energy supply paths – even some the environmental purists may not be happy with.
"Purists pushing green hydrogen as a goal should accept that some compromise is needed to allow alternatives in the 'how' of getting to net-zero emissions," says the report. "Governments, advocacy groups, companies, fleets and the public need to come to agreement that either 'net zero' is the goal or 'zero' is the goal, because these are significantly different for hydrogen. Net zero allows for innovations in a number of energy streams to provide hydrogen in ways that do not let emissions into the environment. True-zero emissions, on the other hand, forces unrealistically rapid growth on solar, wind and hydro to carry the massive electrical load needed for a hydrogen future."
NACFE Executive Director Mike Roeth explained that it's the sources of hydrogen that will have the greatest impact on success of fuel cells. "It's about the creation and the distribution of the hydrogen and other factors around the availability of renewable energy."
The source of the hydrogen, in some cases, challenges the assumption that hydrogen is a zero-emissions energy source. Of course, the same can be said for battery-electric vehicles, in areas where the electric grid is still fossil-fuel based.
Green hydrogen, the most desirable form, is produced by electrolysis of water using energy from renewable sources. Producing hydrogen from renewable sources today remains quite costly, but it's improving, and the technology and its deployment are still relatively new.
Beyond the carbon content of the hydrogen source is the cost. Where industrial production exists, hydrogen could be relatively inexpensive. Producing hydrogen from renewable sources today, including the cost of the electrolyzers that actually separate hydrogen and oxygen from water, the compression of the gas, and the energy losses in the conversions from "well-to-wheel," can make green hydrogen pretty costly.
Patrick Molloy, a senior associate at Rocky Mountain Institute and a contributor to the NACFE guidance report, said the capital cost of the electroyzers that separate hydrogen and oxygen from water is declining and the machines are becoming more efficient, which will make available much larger volumes of renewable energy.
"We now have a pathway to green hydrogen," Molloy said. "We won't go from zero to 20 gigawatts of electrolyzers [overnight], but there are reasons to be optimistic and confident that we have a pathway to the transition."
Lining up the Hydrogen Dominoes
The report makes effective use of a domino analogy to illustrate the complexity of the path to a hydrogen future. All the factors on the illustration are wild cards at present. Experts can speculate on the outcome, but until some of these factors solidify, it will be challenging to predict the eventual outcome.
Take the distribution network, for example. Fuel cell trucks will likely proliferate where hydrogen is readily available. It will be more expensive in areas where it has to be piped or trucked in. Predicting operating costs will be difficult until the price structure can be established and the saize of the market becomes evident.
Market penetration will depend on availability and pricing, but until those are known, it's difficult to predict the market potential. "As we have tried to show with the domino analogy, there are a lot of assumptions in every one of these business models," said Mihelic. "And they're not minor. You have to go deep into it."
Clearly, a lot still needs to happen before hydrogen becomes successful and a mainstream concern. Roeth said there are still many questions to be answered, and it may still be too early to expect reliable answers.
"There's much we still don't know," he said. "For instance, how much scale of hydrogen there is. Do industries and manufacturing move to hydrogen from other more carbon-intensive energies? Will trucking then be able to take advantage of that through the distribution network? How do we get the hydrogen to the pumps? And how will the cost of [future cost] of electricity impact hydrogen production and availability? You can't have just one or two of these dominoes fall; they all need to happen."
Fleet Concerns About Fuel-Cell Electric Trucks
While it almost seems like an afterthought, given everything that has to fall into place first, fleets will need to see the value in fuel cell electric trucks compared to battery electric trucks. The problem is, all we really know about then is what we've been told by the suppliers.
For instance, they are supposed to be lighter than battery electric truck, but how much lighter?
The full report includes a tare weight comparison of battery-electric and fuel-cell electric trucks. NACFE estimates that while current compressed natural gas trucks are roughly 1,500-2,000 pounds heavier than their diesel counterparts, because of the added weight of the storage tanks, plumbing, and increased frame length, minus the weight of the parts removed from emission systems.
Based on consultations with a variety of sources operating early prototype battery-electric trucks, they are about 7,000 to 10,000 lbs. heavier than diesel.
Fuel-cell tanks will be somewhat heavier than their CNG counterparts because they are designed for much higher operating pressure. NACFE expects production fuel-cell tractors to be 4,000-5,000 lbs. heavier than comparable diesel units.
The report also includes a comparison between a diesel and fuel cell truck, with a theoretical specification (produced by Ballard) matching the range of NACFE’s Run on Less Regional diesel demonstration fleet trucks.
“Using an estimated specific density of 36kg tank weight per 1 kg of hydrogen yielded a tank weight of 3910kg (8,600 lbs.)” The net weight impact was estimated by Ballard “to weigh 7,750 lbs. (3,520kg) more than a diesel truck.”
Based on those assumptions, both observed and theoretical, the weight differential between and full battery electric and fuel cell electric isn't that great. However, as the report notes, "Purpose-built tractor designs may find further ways to optimize for weight, and technology improvements on fuel cells likely will improve efficiencies and allow smaller tank sizes over time."
There's not a lot of certainty there upon which to start spec'ing a fleet of tractors, which speaks to one of the final major points of the report: Fleets will have some difficult decisions to make when considering low-carbon alternatives to diesel.
"It's going to be very important for fleets to really focus on the optimization of the specifications of these trucks, such as how much battery or how much fuel cell in addition to current considerations like 6x4 or 6x2, for example," Roeth said. "Those considerations will still exist in the electric truck world."
Despite all the recent talk about fuel-cell being a viable alternative to battery electric trucks, there are only a handful operating in North America today. That means getting a real-world perspective on this alternative energy source is difficult. And that makes it hard for fleets to start building business cases and planning for eventual adoption.
Likewise, sources of hydrogen have never before been tapped to provide fuel for transportation. That demand will open new markets for hydrogen suppliers and will drive innovation, which inevitably leads to greater efficiency and lower cost.
These are early days for hydrogen, and as NACFE's Making Sense of Heavy-Duty Hydrogen Fuel Tractors report makes abundantly clear, there's more we don't know about than what we can be certain of. It's really complicated.