CO ₂ Well-to-Wheel Abatement with Plug-In Hybrid Electric Vehicles Running under Low Temperature Combustion Mode with Green Fuels

Plug-in Hybrid Electric Vehicles (PHEVs) can be considered as the most promising technology to achieve the European CO₂ targets together with a moderate infrastructure modification. However, the real benefits, in terms of CO₂ emissions, depend on a great extent on the energy source (fuel and electricity mix), user responsibility, and vehicle design. Moreover, the electrification of the powertrain does not reduce other emissions as NOx and particulate matter (mainly soot). In the last years, low temperature combustion (LTC) modes as the reactivity controlled compression ignition (RCCI) have shown to achieve ultra-low NOx and soot emissions simultaneously due to the use of two fuels with different reactivity together with high exhaust gas recirculation (EGR) rates. Therefore, the aim of this work is to assess, through numerical simulations fed with experimental results, the effects of different energy sources on the performance and emissions of a series RCCI PHEV. The dual-fuel engine was fueled with diesel as high reactivity fuel and bioethanol as low reactivity fuel. The powertrains are optimized to meet the European homologation legislation (WLTP) for PHEVs. The tailpipe emissions and fuel consumption of the series RCCI PHEV is analyzed and compared to the OEM no-hybrid passenger vehicle running under conventional diesel combustion and RCCI. A life-cycle analysis (LCA) is performed to evaluate the potential of the different energy sources to reduce the overall CO₂ emissions. Different electricity sources are investigated as well as different liquid fuels: e-diesel and bio-ethanol. The series RCCI PHEV technology achieved the tank-to-wheel 50 g/km CO₂ emissions target with medium battery size (13 kWh). In addition, thanks to the RCCI technology, the vehicle is able to meet the Euro 6 NOx and soot limits. The LCA shows that, depending on the fuel source, the total CO₂ reduction benefits variate. Also, the final use and the charging events of the series PHEV have a great impact in this sense.