Ammonia-hydrogen propulsion system for carbon-free heavy-duty vehicles

Growing concerns about greenhouse gas (GHG) emissions are driving research into carbon-free propulsion systems. Heavy-duty long-haul transport faces challenges like rapid charging limitations and safety concerns. An innovative solution integrates an ammonia‑hydrogen engine with a range-extended electric powertrain, showing promise for eco-friendly vehicles. The integrated system produces onboard hydrogen, enhancing combustion performance of ammonia engine. Despite potential benefits, there are research gaps in dynamic system modeling and quantifying advantages in energy efficiency and carbon emissions. To this end, this study addresses these gaps by combining experimental data to create a zero-dimensional vehicle model, exploring optimal sizing and supervisory control system settings for an ammonia‑hydrogen-powered hybrid system in carbon-free heavy-duty vehicles. Dynamic analyses scrutinize the system's performance in energy consumption and carbon emissions during operation. Hydrogen from ammonia electrolysis sufficiently fuels the internal combustion engine, which the energy consumption of the ammonia‑hydrogen system competes with diesel vehicles only if the catalytic hydrogen production ratio is below 6.5%. At a 2.5% ratio, the system achieves 32.8% systematic energy efficiency, consuming 9.2% more energy than diesel hybrids but 5.1% less than conventional diesel vehicles. Ammonia‑hydrogen hybrids significantly outperform in greenhouse gas emissions, reducing well-to-wheel GHG emissions by 0.61 kg CO2-eq/km and 0.82 kg CO2-eq/km on average compared to diesel hybrids and conventional diesel vehicles, a 50.7% and 58.2% reduction, respectively.