Automakers are announcing plans to develop hydrogen-fuelled internal combustion engines (ICEs) for vehicles as an interim decarbonisation measure, given the time it will take to improve the economics of high-cost hydrogen fuel cell engines.

Indiana-based Cummins, a leading maker of diesel engines, revealed a plan in September to develop medium-duty 6.7-litre and heavy-duty 15-litre engines fuelled by hydrogen following preliminary testing over the summer.

British heavy machinery maker JCB is also researching hydrogen-fuelled ICE engines for its excavators and other vehicles, while Toyota is planning to launch hydrogen combustion versions of the Prius and Corolla by 2025. In support of this move, the Japanese auto-giant recently unveiled an experimental hydrogen-powered ICE Corolla racecar.

To better understand the advantages and disadvantages of hydrogen-fuelled ICE engines, Hydrogen Economist contacted Jon Mills, director of external communications at Cummins. He canvassed business and technical experts in the engine and new power divisions of the company to best answer our questions.

What are the major advantages of hydrogen-fuelled ICE engines over hydrogen fuel cell engines at the present time?

Cummins: We believe a range of alternative power solutions will be necessary to effectively help our customers transition to a carbon-neutral world in the coming years. The hydrogen engine may provide a more immediately affordable and adaptable solution in terms of vehicle installation, as it would allow OEMs to continue using familiar mechanical drivelines rather than converting entire fleets to battery electric or fuel cell electric all at once.

Will ICE engines require substantial modifications to run hydrogen instead?

Cummins: Converting current diesel or natural gas engine platforms to operate on hydrogen with substantial modifications is certainly possible, but our initial test work demonstrated that achieving the goal of zero CO₂ with current engines comes with a significant loss of performance and efficiency. To avoid that compromise, Cummins’s H2-ICE programme will be based on our next generation of gaseous-fuelled engine platforms designed from the outset with higher power density and without increasing weight or packaging space.

Assuming there are substantial modifications, what are they?

Cummins: Our hydrogen engine development programme will focus on a next generation fuel injection system—higher in-cylinder combustion efficiency, friction reduction and improved thermal management—to a degree not possible with today’s engine designs. 

Will these modifications add significant cost to hydrogen-fuelled ICE engines compared with diesel-powered engines?

Cummins: Technologies to achieve zero emissions currently come at a higher cost than a diesel engine. In terms of the hydrogen engine, that incremental cost is somewhat mitigated as it can be manufactured at existing engine facilities and is based on a proven platform and engine support network.

“We believe a range of alternative power solutions will be necessary to effectively help our customers transition” Cummins

In terms of operating cost, while hydrogen fuel costs remain elevated today, the number of renewable hydrogen production projects underway means we expect to see meaningful reductions in this price over time.

This will help us bring hydrogen down the cost curve, which is a critical component of achieving cost parity for both the hydrogen internal combustion engine and fuel cell powertrains, and for encouraging technology adoption.

What are the major disadvantages of hydrogen-fuelled ICE engines over hydrogen fuel cell engines at the present time?

Cummins: Hydrogen-fuelled ICE engines remove carbon emissions, but are not zero emission. The levels of NOx and particulate matter emitted from a hydrogen engine will be reduced below that of today’s most stringent regulations, but it is not zero. The end-goal is zero emissions which will only be achieved with battery electric or fuel cell electric, coupled with renewable energy sources. Our work to date also shows that fuel cell has a higher efficiency capability when compared with hydrogen ICE, and this will be important for fuel consumption and associated running costs.

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Author: Vincent Lauerman