What's Ahead for Hydrogen Combustion Applications?

As original equipment manufacturers (OEMs) continue to explore power alternatives amid the energy transition, one emerging solution is the use of hydrogen in internal combustion engines (H2-ICE) and its applications within the on- and off-highway markets.

“Combustion engine power remains the preferred choice for many leading OEMs, and this will likely continue to be the case for years to come as wider technologies and accompanying infrastructure grow,” said Jeremy Harsin, global director, Cummins Off-Highway Engine Business. “However, combustion technology is continuously evolving to meet new emissions regulations and achieve lower emissions, including the ability to use hydrogen as a fuel,” Harsin said.

According to Alan Schaffer, executive director of the Engine Technology Forum, the concept of hydrogen-fueled internal combustion engines are a key part of the energy future. “As we look at the energy future,” Schaffer said, “we see one of a great mix of fuels and technologies certainly more diversified than today, using electricity, hydrogen, biofuels and advanced internal combustion engines — those powered by gasoline, diesel, natural gas and propane. Those are tightly woven into the fabric of our global economy in many ways, in many different sectors, and today, we find ourselves in the midst of an energy transition.”

Schaffer and the Engine Technology Forum recently hosted “Exploring the Future for H2-ICE as a Decarbonization Strategy,” a webinar addressing the challenges that hydrogen technologies will need to overcome in the future. “On the one hand, we have an energy system that relies heavily on fossil fuels,” said Schaffer. “On the other hand, we are working toward a system of reduced carbon emissions and energy systems reliant wholly on renewable energy. Internal combustion engines uniquely have one foot in both of those worlds, and that is one of the incredible advantages I think we have going forward.”

On the engineering front, many see a blended future for off-highway mobile equipment power. According to Preston Oihus, product engineer, special technology, at Bosch Rexroth, “Mobile equipment in the future will have multiple fuel options and/or hybridized motion systems. Gasoline, hydrogen and other combustibles will continue to power primary power sources, but secondary sources will be powered by solar, wind, electrification, etc.,” said Oihus.

As Dr. Ameya Joshi of MobilityNotes and vice president of product at ClearFlame Engine Technologies has observed, “Almost all major manufacturers have some level of effort going on in hydrogen internal combustion engines at various stages of development,” noting several engines in development at this time are being designed for both on- and off-highway applications with a range of engine displacements.

One such example is from Cummins, introducing its next generation of versatile internal combustion engines that can run on low- and zero-carbon fuels like clean diesel, biofuels and hydrogen. According to the company, these engines are more efficient than previous generations, with reduced environmental impact. “The need to reduce greenhouse gas emissions (GHGs) from off-road machinery is driving interest among OEMs and end users in both hydrogen fueled engines and hydrogen fuel cells,” said Cummins’ Harsin. “Hydrogen fuel is a promising non-fossil fuel and provides a viable solution for reducing emissions. Used in either solution, it offers zero carbon capability when using green hydrogen produced using renewable energy.”

“The first thing that drives this industry is regulations and policies,” Joshi said. “Whether it’s reducing GHGs or reducing criteria pollutants, that is one of the key drivers for hydrogen use. The engine technology has advanced quite a bit, but there’s also a lot of work still being done on improving the efficiency of the hydrogen. Ice injection, fuel injection strategies are a critical part of this.”

In late 2023, Caterpillar announced the launch of a three-year program to demonstrate an advanced hydrogen-hybrid power solution built on its new Cat C13D engine platform. The program aims to have Caterpillar develop a transient-capable system for off-highway applications and demonstrate how state-of-the-art control systems and electric-hybrid components can help hydrogen-fueled engines meet or exceed the power density and transient performance of traditional diesel engines. With research planned to commence in 2024, the project is supported and partially funded by the U.S. Department of Energy’s (DOE) Vehicle Technologies Office (VTO) through the Office of Energy Efficiency and Renewable Energy (EERE). It is included among 45 projects across 18 states and Washington, D.C., receiving funding to advance research, development, demonstration and deployment in several areas critical to reducing GHG emissions in the transportation sector.

“Every off-highway application has its own unique duty cycles, life-cycle demands and performance expectations, and this complexity is driving the development of a wide range of power solutions for the energy transition,” said Steve Ferguson, senior vice president Caterpillar Industrial Power Systems. “One size does not fit all, which is why we’ve engineered flexibility into the C13D engine to serve as our platform of the future.”

Also represented in the Engine Technology Forum’s discussion was Ivan Tate, head of product engineering and Technical Center at FPT Industrial, who highlighted FPT’s commitment to maintaining diesel engine production while exploring alternative fuels like natural gas and hydrogen. “We’re committed to [maintaining diesel engine production], both from a vertically integrated point of view and from a market point of view,” he said. “We also keep a strong focus on alternative fuels that started 35 years ago with natural gas. We sell a full range of natural gas engines on-highway in Europe. This gives a second string to our engine development. It’s also very forward thinking from an off-highway point of view. H2-ICE is a natural step forward from the natural gas engine in particular, but certainly a very efficient way to have zero emissions at the tailpipe with any hydrogen and overall net-zero depending on the source.”

As is the case with other manufacturers in the same position, Tate said the company has also had to diversify increased investment in alternative parts of the vehicle that will support expansion. “We’re looking heavily into axles control systems, making batteries and researching the benefits and capabilities of fuel cells for our market”, said Tate. “In some regions, we are also looking at the practical applications of H2 across a number of highway applications. We’re running these engines. We want to get feedback servicing, life cycle, even operator experience. The only way we can do that is starting very early, building that convenience into that product.”

Cummins’ next-gen fuel agnostic B6.7 engine is designed to have hydrogen-fueled power capabilities. Part of Cummins’ HELM range, it maintains the familiarity of diesel technology without changing the structure of the engine block. Designed to use the same transmission, cooling and hydraulic systems as today’s modern diesel engines, it reduces complexity for equipment manufacturers and customers.

As the industry continues down the road toward a more sustainable future, it’s clear that OEMs are committed to finding the right fit. “For construction and aggregates, no single approach will effectively cut emissions and decarbonize the entire industry, due to varied duty cycle requirements and operational needs” said Cummins’ Harsin. “Any solution must balance productivity with reduced operating costs and reliability.” Harsin notes that as the off-highway industry evolves, so will combustion engine power to play a significant role.

As it stands, OEMs and industry partners continue to embrace fuel-flexible engines capable of operating on low and zero-carbon fuels like clean diesel, biofuels and hydrogen.