INTERVIEW | Why the world needs hydrogen combustion engines — even though they’re so inefficient
Risk-averse trucking companies prefer the lower upfront costs and familiarity of H2-engine vehicles, says Cummins executive Jim Nebergall
Hydrogen: hype, hope and the hard truths around its role in the energy transition
It begs the question: why?
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.”
“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].”
“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.”
“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?
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.
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.
“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.”
According to Nebergall, this could end up being the case in India, where Cummins is marketing all three zero-emissions drivetrains.
It could also reduce the country’s reliance on foreign countries for expertise, components and minerals for battery production, he adds.
Existing supply base
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.
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.”
(Copyright)Efficiency losses and NOx emissions
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.