Each mile in a hydrogen fuel-cell vehicle (FCEV) will require roughly twice as much energy as one powered by a battery, making them inevitably more expensive to run.
Yet while this fact has led some truck makers to largely steer clear of hydrogen, several major manufacturers — including Siemens, Toyota and Cummins — are building an even less efficient and more costly hydrogen solution for vehicles — the H2-powered internal combustion engine (ICE).
It begs the question: why?
The answer is, on the face of it, even more confusing — because logistics firms, which tend to operate on tight margins, are demanding the H2-ICE, even though it would seem to be the most expensive zero-emission transport option.
Jim Nebergall, head of Cummins’ H2-ICE programme, tells Hydrogen Insight that for a risk-averse industry like heavy trucking, which is reluctant to decarbonise at all, hydrogen engines offer a low-risk pathway to a carbon-free future — technology that is both more familiar than an electric drivetrain, and less capital intensive.
Freight companies would rather pay less upfront — even if it costs them money in the long run — as the “initial outlay of cash” for zero-emission vehicles is a “big deal”, he explains.
“Customers want to buy something that's low cost that they're familiar with. It's a baby step into a new technology.”
An H2-ICE truck is forecast to cost about 50% more than a diesel equivalent by 2027, Nebergall says, but an H2-FCEV truck would cost double that, while a BEV with the same 500-mile range would cost roughly 120% more than a diesel.
With such initial savings on the purchase price, it will take nearly half a new H2-ICE truck’s operational life — five to seven years — before the vehicle starts losing money compared to an FCEV equivalent, and even longer if the latter’s fuel cell needs to be replaced.
“Fuel cells have more heat generation, so they run hotter,” he explains. “You have to put more energy towards the cooling fans and they degrade over time. An engine doesn’t really age in efficiency, but a fuel cell will age and it won't be as efficient [at the end of its life compared to its beginning].”
In terms of operational performance, combustion engines also have the advantage of versatility over H2-FCEVs, the Cummins executive says, noting that the engine is less likely to be affected by dusty environments, or impurities in the hydrogen that would “poison” a fuel cell.
Trucking firms — such as US giant Werner Enterprises, which recently pre-ordered 500 of Cummins’ 15-litre H2 engines — are also enticed by the familiarity of an internal combustion engine, for which very little operator retraining is required.
“When they realise they have to move away from diesel to something, it's really a risk equation,” Neberfall says, noting that this attitude among potential customers prevails across the world.
“They want to de-risk that move. That's why the engine resonates with them because at least their technicians know how to work on it. It looks like an engine. It sounds like one. It fits in the truck. It’s just very familiar and the only thing they have to deal with is fuel.”
As truck operators opting for either H2 option would face upfront costs to fit specialist hydrogen storage tanks, sensors and non-sparking safety lights at their depots, adding expensive FCEVs on top of that capital investment is far from appealing.
“Service bays have to be retrofitted and upfitted to manage hydrogen indoors,” explains Nebergall. “That applies to both engines and fuel cells, and as we talk to customers, they like the idea that they can actually get started with hydrogen with the engine. We hear that a lot.”
This means that the flow of capex is steadier: invest in cheaper hydrogen ICE trucks and hydrogen infrastructure, and later — as the zero-emission vehicle market matures — invest in more efficient FCEVs.
Future obsolescence?
Cummins, which is also developing H2-FCEV and BEV powertrains, has no particular vested interest in any one technology succeeding over another, and Nebergall does not dispute the downsides of H2-ICE performance against its electric counterparts — freely admitting that BEVs clear the field in terms of tank-to-wheel efficiency, as well as operational and maintenance costs.
But it is worth noting that within five to seven years of Cummins’ H2-ICE engines hitting the market — the point at which the cost of H2-ICE trucks breaks even with FCEVs — technological advancements in BEVs could make both technologies obsolete.
Last month, Tesla completed delivery of its first electric truck to drinks giant Pepsi, which it claims can travel 500 miles (805km), fully laden, on one charge of its massive 1MWh battery.
And solid-state batteries are under development with possibly double the range of lithium-ion.
But Nebergall is more worried about the commercial vehicle sector trying to compete with the bigger battery car market for raw materials and losing out.
“I hope battery electric does as well as people want it to, because it is a great technology,” he says. “The commercial vehicles market is small [but] fuel cell [electric vehicles] need those same batteries just like battery electric does. As we really try to scale up the heavy-duty market, moving to battery electric will be a pretty big challenge.”
Access to charging infrastructure is also a major barrier for the uptake of BEVs in heavy trucking. Not only would it be technically difficult to enable multiple electric trucks to simultaneously fast-charge at the same location using renewable energy, but the time it would take to charge an electric truck might also be problematic for operators.
The matter is especially pertinent in North America, where truck drivers often cover vast distances without stopping.
In Europe, where road freight operation is regulated, and drivers are obligated to take a 45-minute break for every four-and-a-half hours at the wheel, electric trucks could be recharged during these stops.
However, the need to stop and recharge batteries could prevent the common practice of using two drivers to ensure the truck is continuously on the road.
Volumetric challenge
Nevertheless, the refuelling barrier is also a challenge for hydrogen vehicles, both in terms of availability and fuel costs.
Not only are H2 filling stations currently few and far between outside a handful of select areas, but the volumetric energy density of liquefied hydrogen (at 8MJ per litre) is just 22% of that of diesel (36MJ/l) — and that of compressed H2 is even lower (just under 2MJ/litre at 300 bar and around 4 MJ/l at 750 bar).
This means that for a liquid hydrogen filling station to fuel the same number of vehicles as today’s diesel truck stops would require four to five times more deliveries per day in a standard-size tanker (and up to 18 times more for compressed H2). Along with the extra energy and storage infrastructure required to keep liquid hydrogen at cryogenic temperature of minus 253C, the costs are likely to mount up.
But Nebergall tells Hydrogen Insight that these calculations have already been factored into Cummins’ market analysis, which envisages hydrogen fuel costs of around $4-7/kg by 2030, which the company considers “practical” for market uptake.
He is nevertheless alive to the fact that H2-ICE is unlikely to see mass take-up without significant government support, noting that natural-gas engines never broke through into the commercial market because they, like hydrogen, are a premium product with an underdeveloped support infrastructure.
“You'll need [an economic] driver to really make hydrogen take off to more than 5-10% [market share],” Nebergall says. “The [$3/kg maximum US H2 production] tax credit on its own won't be enough. We need offsets for vehicle purchase prices in some way, shape or form.
“With the tax incentives on fuel, you might get the fuel to be the same price as diesel, but when your truck costs significantly more, then it doesn't matter that the fuel cost is the same. You have to get the vehicle cost down.”
But the case for H2-ICE trucks might be stronger in emerging economies, where a lack of available grid infrastructure in places of high demand could mute the uptake of more efficient commercial BEVs, he explains.
According to Nebergall, this could end up being the case in India, where Cummins is marketing all three zero-emissions drivetrains.
“In India, they don't have a very robust electrical grid infrastructure,” he tells Hydrogen Insight. “They're not going to upgrade the entire grid just to charge electric vehicles, so electric commercial vehicles don’t make a lot of sense. But they need something [to decarbonise] and hydrogen fuel is a great solution. As they've looked at the two [hydrogen] technologies, they really like the engine because it has low [upfront] cost.”
Manufacturing capability — and geopolitics — also play key roles in the business case for H2-ICE drivetrains in India’s heavy goods sector, says Nebergall, because hydrogen combustion engines can be manufactured locally in existing engine manufacturing facilities, cutting costs and saving factory jobs.
It could also reduce the country’s reliance on foreign countries for expertise, components and minerals for battery production, he adds.
Even so, H2-ICE was excluded from India’s recent package of support for hydrogen vehicles as part of its National Green Hydrogen Mission.
Existing supply base
Cummins intends to leverage its own existing factories for its H2-ICE roll out in the US, Europe, China, India and Canada, with only a few modifications to the production process.
In fact, the only major difference between Cummins’ hydrogen ICE and its equivalent diesel engine relates to the fuel delivery system as far as the cylinder head. Beyond that, the engine is exactly the same, Nebergall explains.
The only changes needed at the factories would be additional safety modifications to store H2 on site, and different fuel tanks.
This ability to use the sites and expertise already at Cummins’ disposal could go some way to explaining why the company has invested in this sector alongside its work in BEV and H2-FCEV drivetrains, despite the lack of certainty about what market share H2-ICE can expect in heavy-duty trucking.
But Nebergall insists that Cummins is simply opening a door for buyers who do not see decarbonisation as their core competence — and don’t have the cash to support it.
“Customers seem open to try new technology at small scale to educate themselves, but [they] appear to be risk-averse when it comes to purchasing new technology at scale to include in their mainstream fleet,” he says.
And he does not see any one technology as a silver bullet for zero-emissions heavy-duty trucking.
“Everybody wants to pick,” he says. “They’re like, ‘there must be one solution in the future and that must be the winner’. And everybody wants to know, ‘what's that thing, what's that winner?’”
“The way we see it is there won't be a single winning technology. We actually need a diverse array of technologies to meet all of our customer and application needs.”
The rate at which BEVs outstrip both H2-FCEVs and hydrogen combustion engines on efficiency is astronomical.
While a battery-powered truck delivers an average tank-to-wheel efficiency of 75-85%, hydrogen fuel cell trucks achieve just 50%, and hydrogen combustion engines are as low as 40-45% — similar to diesel, according to analysis from consultancy McKinsey.
Round-trip efficiency is even more devastating, especially if the operator is using green hydrogen: H2-FCEVs and H2 ICE require three to four times as much renewable energy to travel the same distance as a BEV.
But the efficiency handicap of hydrogen ICE versus hydrogen fuel cells is more complex. The McKinsey analysis also found that when heavy trucks operated at loads of more than 60%, hydrogen combustion engines actually became more efficient than either diesel or H2-FCEVs.
This means that for H2-ICE, like diesel, the most efficient operating mode is to downsize the engine and make it work harder, while for H2-FCEVs the opposite is true: the fuel cell needs to be oversized for the truck to maximise efficiency.
Operational mode also has a bearing on harmful emissions of nitrous oxides (NOx), which Cummins has edged down to almost zero in its heavy duty H2-combustion engine during steady-state operation — for example, when a truck is cruising along a motorway. This is far lower than could be expected from a diesel equivalent.
Residual NOx emissions in H2-ICE trucks would then be mopped up by the same after-treatment used by diesel trucks today, known as Selective Catalytic Reduction.
