Plug-in vs. Wireless Charging: Life Cycle Energy and Greenhouse Gas Emission Analysis of an Electric Bus System

摘要

Vehicle electrification through implementation of electric vehicles (EVs) withrechargeable batteries has the potential to significantly reduce the greenhouse gas emissionscompared to a fleet of internal combustion engine vehicles (ICEVs). Wireless charging, asopposed to plug-in charging, is an alternative charging method for electric vehicles (EVs) withrechargeable batteries and can be applicable to EVs with fixed routes, such as transit buses. Thisthesis study adds to the current research of EV wireless charging by utilizing the Life CycleAssessment (LCA) to provide a comprehensive framework for comparing the life cycle energydemand and greenhouse gas emissions associated with a stationary wireless charging all-electricbus system to a plug-in charging all-electric bus system. Life cycle inventory analysis of bothplug-in and wireless charging hardware was conducted, and battery downsizing, vehiclelightweighting and use-phase energy consumption are modeled. A bus system in Ann Arbor andYpsilanti area in Michigan is used as the basis for bus system modeling. Results show that thewirelessly charged battery can be downsized to 27-44% of a plug-in charged battery. Theassociated reduction of 12-16% in bus weight for the wireless buses can induce a reduction of5.4-7.0% in battery-to-wheel energy consumption. In the base case, the wireless charging systemis comparable to the plug-in charging system in terms of life cycle energy consumption andgreenhouse gas emissions. To further improve the energy and environmental performance of awireless charging electric bus system, it is important to focus on key parameters includingcarbon intensity of the electric grid and wireless charging efficiency. If the wireless chargingefficiency is improved to the same level as the assumed plug-in charging efficiency (90%), thewireless charging system would emit 6.3% less greenhouse gases than the plug-in chargingsystem.Keywords: Wireless charging; Plug-in charging; Life cycle assessment; Vehicle