The viability of commercial plug-in hybrid electric vehicles in different EU energy market scenarios

Abstract

Increasing global warming due to fossil fuel usage, increasing diesel price and efforts to improve urban air quality increase the need for new vehicle technologies. Hybrid electric vehicles have the potential to reduce fuel consumption and emissions related to engine combustion. In this thesis, a hybrid electric vehicle concept (HEV) is compared to a plug-in hybrid electric vehicle concept (PHEV) for a city bus application. The difference between a HEV and a PHEV is that the latter can be charged from the electricity grid. The purpose of the thesis is to evaluate impact on total life-cycle-cost and total emissions when a part of the traction power is provided by an electric motor instead of a diesel engine. Three scenarios regarding the EU energy market are established, reflecting present day and possible future developments until 2015. The scenarios are used to investigate the total life-cycle-cost and total emissions impact of different marginal electricity generation technologies and energy prices. Optimisation calculations of different powertrain configurations are carried out using the computer tool THEPS. Costs and emissions from vehicle operation and power plant electricity generation are then compiled. The results of the project indicate that it is possible to achieve diesel fuel savings between 14 and 57 % for a PHEV compared to a HEV. The extent of the savings depends on type and properties of powertrain components and length of the pure electric propulsion part of the vehicle drive cycle. Life cycle costs can potentially be decreased by 5 - 6 % and total CO2-emissions by 18 %. In order to decrease PHEV life cycle cost, a certain minimum fraction of propulsion in all-electric-drive mode is required. For the life cycle cost advantage compared to HEVs to increase further, the diesel price must be high and energy buffers’ (e.g. batteries) cycling sensitivity, energy density and cost must be improved. Emissions from vehicle operation are generally lower for PHEVs compared to HEVs, giving PHEVs potential to reduce local emissions. However, the type of marginal electricity generation technology used to provide the external electricity for buffer charging has significant impact on total emissions.