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SwRI’S H2-ICE consortium demonstrates ultra-low emissions from hydrogen-fueled heavy-duty engine

Southwest Research Institute (SwRI) has successfully completed development of a hydrogen-fueled Class-8 demonstration vehicle, built as part of its industry-supported H2-ICE consortium. The central focus of the demonstration includes development of a Hydrogen Internal Combustion Engine (H2-ICE) that produces ultra-low NOx and CO2 emissions while still providing enough torque and power for most heavy-duty applications.

Launched in November 2022, the H2-ICE consortium gathered transportation industry leaders—including engine and truck manufacturers, fuels and lubricants providers, and Tier-I suppliers—with a unified vision of advancing sustainable mobility through innovative hydrogen engine technology. The consortium focused on demonstrating the potential for H2-ICE vehicles to complement other zero-emission vehicle technologies on the industry’s decarbonization roadmap.


To achieve the consortium’s goals, the engine needed to demonstrate industry leading NOx emissions in addition to the low CO2 emissions expected from hydrogen combustion. Despite a relatively short 18-month timeline, the SwRI team set an aggressive target of meeting the California Air Resource Board’s (CARB) Ultra-Low NOx designation of 0.02 g/hp-hr (grams per horsepower-hour).

SwRI converted an X15N natural gas engine provided by consortium member Cummins to run on port-injected hydrogen using components supplied by other consortium members.

The H2-ICE 370-horsepower engine produces 2,025 N·m of torque, which is considered ideal for most heavy-duty trucking applications. Engine efficiency is above 40%, peaking at 43%. Only trace amounts of carbon emissions have been measured in the exhaust, totaling about 1.5 grams of CO2 per horsepower-hour (g/hp-hr).

SwRI built on experience from previous heavy-duty low-NOx projects to develop a novel aftertreatment system specifically adapted to the hydrogen exhaust environment. Paired with the H2-ICE’s already low engine emissions, the addition of the aftertreatment system reduces NOx emissions to 0.008 with aged catalysts, well below the 2027 EPA limit of 0.035 g/hp-hr and an industry first.

The NOx emissions produced by the H2-ICE platform are already at or below the best numbers achieved in our previous diesel low-NOx programs. We anticipate the H2-ICE reaching near-zero tailpipe NOx emissions, with single digit mg/hp-hr levels under nearly all operating conditions. I am extremely proud of the team’s accomplishments and excited for the project’s future.

—SwRI Institute Engineer Chris Sharp, who led the aftertreatment calibration effort



However, hydrogen has a higher auto ignition temperature than diesel fuel,
so it can't be used directly in a diesel engine.

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