Pollutant emissions analysis of three plug-in hybrid electric vehicles using different modes of operation and driving conditions

Abstract

To evaluate real-world energy consumption and tail-pipe emissions of current plug-in hybrid electric vehicles (PHEVs), we tested three PHEVs in different driving conditions. We considered measurements of emissions at different ambient temperatures and for various operating conditions regarding hybridization. The results show that the initial battery state-of-charge (SoC) determines the absolute CO2 emissions as CO2 emissions decrease with a higher proportion of electric driving. Therefore, the use of different hybrid driving strategies can have a strong influence on the overall fuel-saving potential. This does not apply to other pollutants such as NOx and particles, as the emission of these pollutants depends on the operating conditions of the internal combustion engine. RDE tests with a high proportion of electric driving show, in some cases, higher pollutant emissions than in tests with a low electric share. In general, the emission measurements done under real driving conditions show a higher variance compared to the test bench tests. In the case of PHEVs, this effect is further increased due to the different choice of driving modes and engine cold starts during electric driving. The variance of these parameters makes it difficult to estimate the emission benefits of PHEVs.