Investigation of Inductive Charging Systems
Electro mobility is becoming increasingly popular. The ultimate break through depends to a significant degree on the available charging infrastructure. While the network of conductive charging stations (energy transfer to the vehicle through wires) is increasing, inductive charging (contactless energy transfer) is still in its infancy. Inductive charging includes three different scenarios. Firstly, «static charging», where the vehicle remains parked over an extended period of time and the driver typically leaves the vehicle. Secondly, «stationary charging», with a duration of a few minutes, where the driver routinely remains in the vehicle. Finally, «dynamic charging», where the vehicle is charged while moving. The required infrastructure differs significantly in each case.
Generally very limited publicly accessible data is available concerning efficiency and standby losses of inductive charging systems. Only a few products are commercially available and relevant standards for such systems are still under development. More information is available for inductive chargers intended for «heavy duty vehicles» such as city buses, as more systems are already in operation. City buses tend to have similar shapes and chargers can be optimized for a specific fleet within a limited geographical range.
A basic conclusion from this investigation is that the standby losses of an inductive charger differ only marginally compared to those of conductive charging. The power conversion efficiency (grid to battery) tends to be slightly lower for inductive systems. A highly efficient operation of a wireless charging system is technically possible, but the proper alignment of the vehicle with respect to the transmitter coil has a significant impact on the efficiency.
Projeckt Partner: Swiss Federal Office of Energy