New technology will allow wireless charging of large electric vehicles such as ferries

Inductive charging is a type of wireless power transfer using electromagnetic induction to provide electricity to portable devices. Low power applications would include mobile phones and toothbrushes while high power charging generally refers to inductive charging of batteries at power levels above 1 kilowatt.

There are a variety of reasons why inductive charging has not been taken up in the field of transportation but manufacturers have been experimenting with the technology for years.

Professor Yujing Liu and the system that could charge high-power electric ferries and vehicles

Now, however, Researchers at Chalmers University of Technology in Sweden, have unveiled a new type of silicon carbide semiconductor and a newly developed copper wire which, between them, have suddenly made transmitting high power through air a realistic proposition.

The technology that has been developed in Sweden is not currently suitable for EVs because the charging cable is very heavy and unwieldy but it would be perfect for applications such as electric ferries, city buses or industrial electric vehicles.

Yujing Liu, Professor of Electric Power at the Department of Electrical Engineering at the University said: ‘You can have a system built into the wharf that charges the ferry at some stops while passengers get on and off. Automatic and completely independent of weather and wind, charging can take place 30-40 times per day.’

This breakthrough has been enabled by recent technological advances such as high-power semiconductors based on silicon carbide which have only been available for a few years and a new type of capacitor. 

Until now induction charging has been relatively inefficient but Yujing Liu says: ‘losses occur whether you use ordinary conductive [plug in] charging or charge using induction. The efficiency we’ve now achieved means that the losses in inductive charging can be almost as low as with a conductive system. The difference is so small as to be practically negligible. It’s about one or two per cent’.

Image: Chalmers University of Technology | Sandra Tavakoli