Highly efficient test track is only 20 meters long

The test track on the campus of the University of Stuttgart is just 20 meters long: e-vehicles can be inductively charged there while driving - with an enormous efficiency that has never been achieved before.

The test track was developed by a research team from the Institute for Electrical Energy Conversion (IEW) led by Professor Nejila Parspour as part of the MobiLab subproject »Research Road: Dynamic Charging and Secure Energy Supply«.

Charging while driving instead of long periods of standing by the cable: »Thanks to dynamic charging, we can increase the range of vehicles, reduce battery capacity and drastically cut the necessary charging time,« explains the professor.

Efficiencies of more than 90 percent

What is special about the test track at the University of Stuttgart is that efficiencies of more than 90 percent can be achieved. This makes the efficiency competitive with conductive charging using a cable. »With this high efficiency, we have reached a milestone in inductive dynamic charging. We don't know of any system that is similarly efficient,« says Parspour, who is overseeing the project together with Professor Krzysztof Rudion of the Institute for Energy Transmission and High Voltage Technology (IEH).

How does dynamic inductive charging work?

The test track on the Vaihingen campus consists of 40 individual coil elements with a footprint of 50 cm by 48 cm. The distance between the vehicle and the coils is 20 cm. The track automatically detects the position of the vehicle above the coil system and supplies only the relevant primary coils in the ground. Energy is transferred through magnetic coupling to the secondary coil in the vehicle.

The power transferred is proportional to the coil area on the secondary side. With the same footprint of 0.24 square meters, a power of 10 kW is continuously transmitted regardless of the vehicle speed. By comparison, a conventional power outlet provides 2.3 kW of continuous power to charge an e-car. Overall, the test track provides constant and uninterrupted power transmission while driving.

Numerous advantages for autonomous vehicles

Especially for autonomous vehicles such as shuttle vehicles, inductive charging routes offer significant advantages. For example, the vehicles could be in operation around the clock and without downtime while charging. In a next step, Parspour and her team therefore want to test the technology in the autonomously driving CampusShuttle of the University of Stuttgart, which is currently being taught. To this end, the test track is to be expanded into a research road on the Vaihingen campus.

As part of the inductive dynamic charging project, Parspour and her team want to further explore bidirectional charging. This would allow the vehicles to be used as energy buffers, for example. In addition, the scientists would like to further increase the power density, i.e. the energy transfer capacity per driving distance.

The MobiLab real laboratory

The test track for inductive and dynamic charging is a sub-project of the MobiLab real laboratory, whose goal is a car-free campus. In addition to the topic of inductive charging while driving, a team led by Professor Frank Allgöwer is developing an autonomously driving e-scooter and a research group led by Dr. Dan Greiner is conducting research on an autonomous CampusShuttle.