Comparative global warming impact and NOX emissions of conventional and hydrogen automotive propulsion systems

Abstract

With the rise of cleaner technologies for transport and the emergence of H2 as a fuel, most of the emissions in the well-to-wheel process are shifting towards the energy carrier production (fuel or electricity). The objective of this study is to perform a simplified cradle-to-grave Life Cycle Assessment (LCA) that compares the greenhouse gases (GHG) and NOX emissions of H2, electric and conventional technologies for the automotive sector in Europe and to devise the optimum strategy of vehicle fleet renewal to reduce the emissions. In this study the effect of water as GHG was considered and, unless other studies, the current European energy mix and that meeting the objectives for 2050 were considered (while technology level was kept constant) since H2 from electrolysis and electric vehicles’ well-to-wheel emissions are sensitive to the energy mix. To estimate the emissions, the fuel, vehicle production and operation cycles were considered independently for each technology and then put together. For H2, the best production and distribution strategy was steam methane reforming (SMR) with CO2 sequestration for GHG-100 gases and without capturing CO2 for NOX, both with central plant production and tube trailer transport. Fuel cell vehicles (FCV) with optimum H2 production always produce the lowest GHG-100 emissions and slightly higher NOX than battery electric vehicles (BEV) in the EU 2050 scenario. In contrast, HICEV would need to reach a fuel consumption of around 30 kWh/100 km to be competitive in emissions against BEV, for that, direct injection (DI) combined with a range extender (REx) hybrid architecture is the recommended powerplant concept. Finally, the optimum strategy to reduce emissions that Europe could follow is presented for the short, mid and long term.