Straße mit induktiver Lademöglichkeit
2023-06-30 publication

E-Mobility – Range: Infinity

Inductive charging promises to charge electric vehicles with no need for a pit stop. Time for a look at how and where in the world this promising technology is being tested – and how it could benefit not only motorists, but also the environment.

By Michael Neißendorfer

VDE dialog - Das Technologie-Magazin

It’s an enticing idea: driving all the way from Hamburg to Munich by electric vehicle without having to stop and recharge. And all without hundreds of kilos of battery in the vehicle floor. Many companies and research institutes around the world are working on the necessary technology: inductive charging via a magnetic field, which eliminates the need to hook up a charging cable. This opens up the exciting prospect of electric vehicles that can not only charge when stationary (like those already on the market), but while driving, as well. If enough roads were equipped with induction loops, such vehicles could in theory have infinite range.

Professor Nejila Parspour with team

Professor Nejila Parspour and her team at the University of Stuttgart have developed a highly efficient test section along the road. 90% of the energy used for inductive charging goes into powering the vehicle.

| Universität Stuttgart

Multiple projects have demonstrated the feasibility of this technology. Recently, a team from the Institute of Electrical Energy Conversion (IEW) at the University of Stuttgart opened a test track with what the researchers are calling the most efficient inductive charging system yet. They claim the system makes it possible to use 90% or more of the energy fed into the system to actually power vehicles, which easily puts it on par with conductive charging by cable. “This high level of efficiency is a milestone in inductive dynamic charging. We don’t know of any other system that’s similarly efficient,” says Professor Nejila Parspour, who is supervising the project together with Professor Krzysztof Rudion from the Institute of Power Transmission and High Voltage Technology (IEH) at the University of Stuttgart.

The test track on its campus in Vaihingen consists of 40 individual loop elements, each around half a meter square. The distance between the vehicle and loops is around 20 centimeters. The system automatically detects the vehicle’s position and energizes only the primary loops it is traveling over at a given time. This enables continuous charging at 10 kW, irrespective of the vehicle’s speed. One aim of the project’s research is now to further increase this charging performance.

Non-stop charging – no cables required

The powerful potential of inductive charging on the move is also being tested by the automaker Stellantis on its test track in northern Italy, which it has given the promising name “Arena del Futuro”. Having electrified a kilometer of asphalt on this “playground of the future,” the company's engineers are now testing inductive charging with various vehicles, including a spiffy Fiat 500e and a much larger electric bus from Iveco. Stellantis uses direct current (DC) to minimize conversion loss, along with aluminum loops, which are cheaper than the copper equivalent. The researchers report that the test track has already achieved charging outputs of up to 75 kW at a vehicle speed of 70 km/h. Stellantis emphasizes that its measurements of the magnetic field strength indicate “absolutely no adverse effect” on vehicle occupants or passersby.

Inductive charging offers several advantages. For one thing, charging a vehicle while it is on the move eliminates charging stops, which takes pressure off of charging stations – and there’s no need to untangle the cables in your trunk, either. Inductive charging solutions are also low-maintenance and safe from vandals. And there’s another big plus point: at some time in the future, if enough roads are equipped for charging on the go, electric car batteries could be up to 70% smaller than is currently the case according to a study by the Chalmers University of Technology in Sweden. This would greatly reduce the cost of electric vehicles and the amount of raw materials needed to make them.

A bird’s eye view of a bus driving along the circular track at the Arena del Futuro in northern Italy.

The “Arena del Futuro” in northern Italy has a 1,050-meter-long test track. Inductive charging technology is being trialled here on vehicles ranging from a Fiat 500 to an electric bus.

| Stellantis

In particular, inductive charging would benefit small shuttle buses and other autonomous vehicles by enabling them to operate around the clock without charging breaks. In the next step, Professor Parspour and her team at the University of Stuttgart want to try out the technology on an autonomous campus shuttle that is currently being programmed. The test track on the Vaihingen campus is to be upgraded to a “research road” for this purpose.

Another public test track for inductive vehicle charging is being built in northern Bavaria as part of the E|MPOWER project, whose partners include Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), Nuremberg Technical University, VIA IMC, Autobahn GmbH, Risomat and the Israeli company Electreon, which has been working on wireless charging for around ten years. The consortium plans to invest some €8 million in the project, which will involve electrifying a one-kilometer stretch of highway. “Building a test route enables us to try out the processes developed for automated manufacturing and integration into roads and to demonstrate that they work,” says Dr. Alexander Kühl from the Institute for Factory Automation and Production Systems (FAPS) at FAU.

Electrifying a kilometer overnight

The system is to have a charging output of up to 70 kW. Electreon’s modular technology will be installed along the kilometer of highway by removing a layer of asphalt. The whole process, including resurfacing, will take just one night. Autobahn GmbH plans to assign the project a lane that already needs resurfacing work – an example of the synergies that will help to make the project highly cost-efficient. From mid-2025, drivers with compatible vehicles will be able to try out the innovative charging technology for themselves.

On such a short stretch, however, the boost it will provide to their batteries will be modest. At highway speeds, 70 kW of charging output over a distance of one kilometer equates to around half a kilowatt of charging. This suggests that when installing induction loops, priority should be given to road sections where there are frequent jams and slow-moving traffic. These will often be in urban areas, where residents without their own private charging points at home will no doubt welcome inductive charging with open arms. Parspour highlights another benefit of wireless charging in cities: “Unlike charging stations, inductive systems don’t take up any space, so they can be more easily integrated into urban infrastructure.”

Still too expensive

One question that still needs to be answered is whether the inductive technology makes financial sense or charging cables will remain the more cost-efficient solution. According to the energy supplier EnBW (a participant in the ELINA research project investigating the use of dynamic charging infrastructure in public transportation in Balingen), comparing the costs of inductive and conductive systems is difficult because neither dynamic nor static inductive charging systems are currently being built on an industrial scale. This is one of the questions the ELINA project is seeking to answer as it investigates the technology’s potential.

Inductive charging coils

Induction loops for wireless charging are embedded in the roadway.


Here, EnBW is weighing the costs of contactless charging technology against its many upsides. Smaller battery sizes could be a major factor on the cost side; after all, the cost of its battery makes up around 30 to 40% of a vehicle’s total price depending on the model, meaning it can run well into the five digits. Smaller, more lightweight batteries would also cut electric cars’ power consumption, while electrified roads could reduce battery wear and increase their useful life. Unlike other solutions, such as the overhead contact lines currently being trialled to power electric trucks, inductive charging infrastructure could be used by all manner of automobiles, from small cars to large commercial vehicles. These savings have the potential to offset any additional costs of the system itself.

Resource-efficient charging with magnetized concrete

For her part, Parspour believes that stationary inductive and conductive charging systems currently have similar costs and that the additional expenditure for on-the-move charging will be limited. She anticipates extra costs of around 10% for a new road and sees a great deal of potential to cut this down to 3 to 5% through mass production.

One interesting idea to cut costs and increase efficiency is to use special magnetizable concrete. This solution is being worked on by Magment, a company based in Oberhaching (near Munich). The material needed to build such a road surface is cheaply available in the form of ferrites – metallic materials such as oxides of iron, nickel and zinc, which have a very high reject rate (7%) in production. Each year, some 500,000 tons of rejected ferrite materials are crushed into aggregate and used in road building. Ferrites make concrete more stable and durable, which is a positive side-effect on busy roads. By adding electric coils and optimizing the material’s composition, Magment has created a magnetizable concrete that can be used to charge electric vehicles. Another advantage of the system is that the ferrite particles in the concrete reduce the amount of material needed for the electric coils, making this a more resource-efficient design than other solutions.

Wireless charging under real-world conditions

Using the example of a forklift, founder Mauricio Esguerra explains what makes inductive charging so appealing from a cost perspective: around €7,000 in savings, which are possible thanks to a significant reduction in the required battery size. This is almost enough to cover the installation of an induction system, meaning that the solution nearly pays for itself right at the outset.

Magnetizable concrete is already in use. In the US, for example, several kilometers of Magment’s dynamic inductive charging technology have already been installed. And in Germany, electric scooters can often be found charging as they wait for their next rider at docking stations, many of which use Magment’s system.

Anyone who wants to see the new technology for themselves will have the chance at this year’s regional garden show in Balingen, an hour’s drive south of Stuttgart. Here, dynamic wireless-charging technology is being tested in practice for the first time in Germany as a way to power a shuttle bus. The project partners – Electreon, EnBW, the Karlsruhe Institute of Technology (KIT) and Stadtwerke Balingen – have installed a 400-meter-long electric road system (ERS) under the asphalt on Wilhelmstrasse. Inductive charging points for stationary charging are also planned at each end of the route. The electric bus is being provided as part of the ELINA research project. In a second step, the researchers want to install induction loops on other routes and a stationary inductive charging point at a bus depot, thus extending the project to regular bus traffic.

While the public is set to encounter the technology more often, widespread implementation and that non-stop trip from Hamburg to Munich are likely still a long way off. Until then, charging stops will remain an opportunity for travelers to stretch their legs, enjoy some fresh air and recharge their own batteries.

Michael Neißendorfer is a freelance journalist in Munich who specializes in sustainable mobility and electric vehicles.