Numerical methodology for assessing greenhouse gas emissions in hydrogen-fueled internal combustion engines for road transport

Hydrogen-fueled internal combustion engines (ICEs) are one of the most promising solutions for decarbonizing road transport, mainly thanks to the possibility of converting modern engines for hydrogen operation with minor changes. This study evaluates the environmental impact of a hydrogen-powered light-duty vehicle through a bottom-up numerical methodology consisting of four steps: calibrating a predictive hydrogen (H 2 ) combustion model using single-cylinder engine simulations, optimizing via modeling the H 2 consumption and NO x emissions of a multi-cylinder SI engine, assessing the fuel consumed and pollutants emitted by a hydrogen-powered sport utility vehicle through real driving cycle simulations, and finally performing a well-to-wheel analysis using the vehicle consumption rate. Engine and vehicle simulation results show that optimizing air dilution for NO x control rather than fuel economy achieves near-zero NO x with a slight fuel penalty. The optimization focused on fuel economy leads to a 3.5 % fuel saving, while the optimization targeting NO x control results in a reduction of only 2.7 %. In exchange, NO x emissions are reduced by up to 97 %, reaching as low as 17 mg/km. Based on the well-to-wheel analysis results, it is concluded that H 2 -fueled ICE light-duty vehicles could exhibit a lower environmental impact than other existing technologies. Considering the two extreme scenarios proposed by the EU, a progressive reduction in equivalent CO 2 emissions can be observed from 2020 to 2050. Emissions decrease from values exceeding 20,000 kg CO 2 to nearly zero or even negative levels. • Well-to-wheel emissions of a hydrogen-fueled ICE passenger car were assessed. • A bottom-up numerical approach was used for the well-to-wheel analysis. • Optimizing λ prioritizing NOx control over fuel economy leads to near-zero NOx. • Negative well-to-wheel emission values in 2050 through H2-fueled ICE vehicles.