Over the past few years, truck and engine makers have generated a lot of buzz around developing zero-emission drivetrains to help meet climate and sustainability goals. Traditional OEMs and tech start-ups, at home and abroad, now offer battery-electric powertrains to provide commercial fleets with viable alternatives to diesel- and gasoline-powered trucks, and many have hydrogen-fuel-cell-electric powertrains in the works as well.
The tried-and-true internal combustion engine has been largely absent from the conversation. Some truck makers announced they were shifting their research and development investments away from ICEs to focus on ZEVs. If ICEs were mentioned at all, it was usually to point out diesel and gasoline engines would remain important in trucking for many years during a gradual transition to zero emissions.
This year, however, brought a renewed focus on internal combustion designs that run on lower carbon alternative fuels. Fleets worried about the viability of battery or fuel cell technology will have more clean-burning options to power their trucks in the near future.
A Fuel-Agnostic Future
Let’s go back a decade to when natural gas engines were the darling of “green” trucking. Cummins and Westport Fuel Systems in 2001 created a joint venture to research, develop and manufacture natural gas engines for trucking applications. The two companies shared research and development on the engines. But the basic business arrangement was for Westport to supply the upper engine fuel management technology, the “head” of the engine, while Cummins supplied the lower “block” portion of the engine.
The resulting Cummins-Westport engines ran reasonably well in many fleet applications, although there was a noticeable drop-off in range and power compared to diesels. This was mainly due to the lower British Thermal Unit content in compressed or liquified natural gas. BTUs are essentially a way of measure the energy (or power) content present in a fuel. Diesel fuel has a higher BTU content than almost any other type of vehicle fuel on the planet, meaning essentially that a smaller amount of the fuel can produce more energy that can be converted to torque, horsepower and vehicle range.
But those were only first-generation natural gas engines. Something much more important was going on during development, according to Puneet Jhawar, the general manager of Cummins’ global natural gas business.
“We now have more than 30 years’ experience researching natural gas engines,” he says. “During that time, we learned a lot about how the engine head manages these very complex and different thermal environments to better control and optimize the combustion event for many different types of alternative fuels — not just natural gas.”
Cummins and Westport dissolved their joint venture last year. Moving forward, Cummins said it would concentrate on the development of natural gas and other alternative fuel engines. Earlier this year it announced it was developing a new line of “fuel-agnostic” engines.
Meanwhile, Westport turned its attention to developing a hydrogen high-pressure direct injection system that will allow engines to burn liquid hydrogen with a small amount of diesel used as a pilot fuel to initiate combustion.
Suddenly, several different types of greener alternative fuels are on the table for use in trucks. And thanks to new, advanced engine head and fuel injector technologies, they will perform as well as diesel in terms of torque and horsepower, although range limitations may remain an issue.
“Cummins’ new fuel-agnostic platform features a series of engine versions that are derived from a common base engine,” Jhawar says. “Which means they have a high degree of parts commonality. Below the head gasket of each engine will have largely similar components and above the head gasket will have different components for different fuel types. This allows for scale in manufacturing not previously possible for these newer fuel types.”
In addition to natural gas and hydrogen, Cummins new engine platform will also offer propane and gasoline versions of engines for medium-duty vehicles.
Furthermore, Jhawar adds, natural gas and hydrogen engines are two key technologies that Cummins believes have the capacity to power the transportation sector with lower and zero carbon fuels. Even better, he notes, new ICE engines and fuels hold promise for trucking because of their low costs, comparable performance to legacy diesel engines, and environmental benefits.
Transformation, Not Disruption
The upshot of all of this, according to Julie Blumreiter, chief technology officer and co-founder of ClearFlame Engine Technologies, is that base diesel engine technology can be configured to run on any reasonable alternative fuel, and still behave like a diesel truck.
“We suddenly don’t have to worry about charging times for batteries,” she explains. “We don’t have to worry about the practicality or weight considerations of specialized fuel tanks or large battery packs. We have diesel performance on demand, with no range or weight penalty. So, what we really have here is a transition for fleets to new fuels using proven ICE technology, instead of a disruption where they have to move to entirely new types of powertrain technologies.”
While natural-gas fueling infrastructure is plentiful compared to electric and hydrogen, it is still not at diesel levels, says Thomas Healy, CEO and founder of Hyliion, which makes a hybrid electric-and-natural-gas powertrain.
“Fleets will need to think about what piece of their operation is best suited for natural gas and evaluate the infrastructure needs from there,” Healy says. “It is important to keep in mind, though, that fleets have numerous high-quality natural gas fuel providers that are ready to assist them with this task. Getting fueling infrastructure behind the fence is much easier and quicker with natural gas than other alternatives.”
ClearFlame CEO and co-founder B.J. Johnson agrees that infrastructure issues will persist for a long time, limiting the ready availability of some fuel types. That’s why ClearFlame has opted to focus its engine technology on ethanol, a clean, alternative fuel with a well-established national support infrastructure already in place.
“Ethanol is the only alternative fuel that is currently at scale with a national infrastructure on par with gasoline and diesel,” he says.
New propulsion systems aimed at boosting truck performance while reducing emissions will still likely transform ICE-powered trucks of the future, Healy says.
Hyllion, which has been working on hybrid drive systems with several OEMs, including Daimler Truck North America, recently inked a deal with Cummins to optimize its natural gas engine as the generator for the Hypertruck ERX powertrain.
The Hyliion Hypertruck ERX is an electric range extender semi-truck powertrain solution using onboard power generation to recharge the batteries. The system offers 75 miles of electric range to qualify for credits under the California Air Resource Board’s upcoming ZEV mandates and can achieve up to 1,000 miles of full range through the generator. Cummins’ ISX12N will be optimized with the Hyliion Hypertruck ERX so it can use the existing 700 natural gas stations across North America for refueling.
“Obviously, we believe that hybrid powertrains are a great way for fleets to help address the needs of shippers and regulators today, without waiting for the infrastructure of tomorrow,” Healy says. “When paired with ICEs, particularly those running renewable fuels like [renewable natural gas], these systems can deliver very similar (or greater, in some instances) emission reductions without radically changing the operational model of the fleet or imposing significant fleet or society-level infrastructure investments that total in the hundreds of billions of dollars.”
At the same time, technologies are being developed —such as cylinder deactivation and the opposed-piston concept — to make ICEs run more efficiently, burning less fuel and cutting carbon emissions.
The new future of ICEs has just begun to dawn. There will likely be additional technology breakthroughs to come that will further solidify the role ICEs will play in trucking’s future. But, as Mark Twain once quipped, reports of the ICE’s pending demise have clearly been exaggerated.