Car movement patterns and the PHEV

Doctoral thesis, 2017

Roughly 30% of Sweden’s total greenhouse gas emissions originate from transport and a majority of them from cars. The plug-in hybrid electric vehicle (PHEV) avoids the range limitation of the fully electric vehicle while still allowing for a major share of the fuel to be replaced by electricity from the grid and can thereby reduce greenhouse gas emissions, local pollutants and energy security concerns. The expected share of electric driving for a given battery size is however dependent on the individual car’s movement. In this thesis, the potential to reduce fuel use in Swedish passenger car transport through an introduction of PHEVs is assessed by utilizing a comprehensive data set on Swedish car movements logged by GPS. In paper I, we analyze how individuality in movement patterns may affect optimal battery design, economic viability and potential for fuel substitution. Both optimal battery sizes and savings are found to vary substantially between drivers. Commuters are found to be among the first to reach viability for PHEVs. In paper II we analyze how different objectives can affect optimal battery range, viability, savings and share of electric driving. Our results suggest that different objectives among stakeholders could result in different optimal battery sizes and that a high share of PHEVs in a vehicle fleet is not enough to ensure a high share of electric driving. In paper III we evaluate the relative benefit of a PHEV in comparison to a BEV in a two-car household. The results suggest that the BEV in general is economically favored over the PHEV in two-car households if the vehicle usage is optimized within the household. The difference in potential share of electric driving between a PHEV and a BEV is in general small. In paper IV we analyze the potential for brake energy regeneration in Swedish driving conditions. We find that city drivers have the highest potential to regenerate energy per km of driving, but long distance drivers have the largest potential to regenerate energy on a yearly basis. Also, extra energy gains from higher regeneration power capacity were found to fall off quickly.