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 NO_x 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 NO_x 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 NO_x 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-NO_x 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 NO_x emissions to 0.008 with aged catalysts, well below the 2027 EPA limit of 0.035 g/hp-hr and an industry first.

The NO_x emissions produced by the H₂-ICE platform are already at or below the best numbers achieved in our previous diesel low-NO_x programs. We anticipate the H₂-ICE reaching near-zero tailpipe NO_x 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