Bavaria gets highway route for contactless charging of moving e-cars

Inductive charging of parked electric cars is state of the art and has been an option in some manufacturers' price lists for years. Making this possible while driving is an idea that has been the subject of increased investigation for around 16 years. It could help to alleviate the range problem of electric cars. A little over a year ago, our car expert Clemens Gleich asked himself: "It would be so nice if the electric car could draw power while driving on the highway, as long as the driver can keep going – without any limits on the battery. Where is the technology?" The federal government is now testing the charging of electric cars while driving on the A6 highway in Bavaria.

Charging coils under the asphalt

Autobahn GmbH and Friedrich-Alexander-Universität Erlangen-Nürnberg are officially starting research today on a one-kilometer test section between the Amberg-Sulzbach and Amberg-West exits. The charging coils are located under the asphalt, while the counterparts on the car transmit the current inductively to the charger and battery. The system comes from the market leader Electreon from Israel.

Inductive charging stations from this company are being planned, built or are already in operation in Israel, the USA, France, Italy and China, among others. In Germany, the Baden-Württemberg electricity supplier EnBW is already operating a much shorter inductive test track in Karlsruhe. According to Electreon, an inductively charged electric car has already driven almost 2000 kilometers in one go, which is considered a record to date. At the opening of the project, Bavaria's Science Minister Markus Blume (CSU) cited a seemingly extremely optimistic efficiency of "over 90 percent" and referred to "completely unimagined possibilities. Range problems are solved."

Overcoming distance

One technical problem is the distance between the coils. In the garage, a few millimeters are no problem. On the highway, however, the vehicle bounces, so the distance has to be measured in centimetres. However, this reduces the transmission efficiency. When the car is moving, the magnetic field must always be exactly under the moving vehicle. To achieve this, the coils are switched in sequence by a control system.

Electric cars can be retrofitted with a corresponding coil on the vehicle floor in order to be able to pick up the current from the coils in the road surface. Electreon installs the coils under the asphalt; the modules on the car have a transmission rate of up to 35 kW. One is enough for a car, trucks or buses get a multiple of this according to their power, typically three are sufficient. According to the company, the technology has been successfully tested at driving speeds of up to 80 kilometers. The company sees local public transport and haulage companies as the main target groups.

(fpi)