Electromobility: wireless charging – convenient and automatable Everyday test of inductive charging station in Braunschweig

Inductive wireless energy transfer is a future-proof way of charging electric vehicles, especially for applications in public spaces. A major advantage over wired charging is the convenience for the user and the ease with which it can be automated. Initially, this charging technology is likely to be used in inner-city fleet and taxi transport and in autonomous driving applications. Various projects and the publication of standards for inductive charging are currently raising public awareness of the technology.

Researchers in the LISA4CL joint project between Technische Universität Braunschweig and INTIS GmbH have developed a stationary inductive charging system for electric vehicles with a charging capacity of 22 kW. The necessary components have been successfully tested at TU Braunschweig’s Institute for Electrical Machines, Traction and Drives (IMAB) and the elenia Institute for High Voltage Technology and Power Systems. The charging technology was set up at the INTIS site in Lathen, Emsland, and a test vehicle was converted. Extensive tests of the system’s functionality and safety were then carried out together with Technische Universität Braunschweig. “The great potential for technical progress that results from cooperation between science and industry is well known and has been confirmed once again in the LISA4CL project,” says INTIS Managing Director Dr. Ralf Effenberger. The system was installed at the Automotive Research Centre Niedersachsen (NFF) in Braunschweig and handed over to the Facilities Management of Technische Universität Braunschweig for practical testing on the streets of Braunschweig.

Testing in everyday use

With the commissioning in Braunschweig, the LISA4CL project has moved into the inductive field test phase, in which the charging system developed so far will be tested in real everyday use. “The practical field test is a very important part of the project, as it allows us to test our technology in practice for its long-term function and benefits for the user,” says Professor Markus Henke, Director of the IMAB.

The technology: An inductive charging system consists of a road-side component and a vehicle-side component. Energy is transferred contactlessly from the road surface to the parked vehicle via an air gap using magnetic coils. Inside the vehicle, the electrical energy is transferred to the high-voltage battery via power electronic circuits.

High efficiency in wireless charging is a key factor for competitiveness compared to wired charging. With this in mind, the LISA4CL project paid particular attention to efficiency in the development and design of the system. “To achieve a high overall efficiency, both the individual components and the entire efficiency chain have to be optimised,” says Tim-Hendrik Dietrich, research associate at the Institute for Electrical Machines, Traction and Drives at TU Braunschweig. Furthermore, communication between the electric vehicle and the charging station is also crucial to the charging process. The realisation of the hardware and software for charging communication was therefore another focus of the development: “The implementation of the requirements of the technical standards now available for charging communication in inductive charging is a central building block for the implementation of the technology,” says Gian-Luca Di Modica, research associate at the elenia Institute at TU Braunschweig.

In particular, interoperability is required for implementation so that vehicles can charge at any inductive charging station, regardless of the manufacturer. To this end, standards and norms for inductive charging will be developed, defining the requirements for contactless energy transfer and communication between the vehicle and the charging station on the infrastructure side. The project will also support the standardisation of the 22 kW power class. “We will use our findings from the project to formulate recommendations and present them to international standardisation committees,” says Ralf Effenberger.

Implementation and objectives of the field test

The inductive charging system is being tested in practice in the day-to-day operations of TU Braunschweig’s Facilities Management team, even beyond the duration of the project. Relevant questions include the possible simplification of the operating process through the contactless charging technology or the effects on the range through so-called opportunity charging.

The effects on the power grid are also of interest, assuming that the number of charging points will increase significantly in the future. For this purpose, a grid analyser is integrated on the infrastructure side of the inductive charging system to record the energy consumption and performance of the system. The measuring device will also be used to measure power quality parameters in order to identify potential grid impacts.

Comparison of charging technologies

The evaluation of inductive charging technology, especially in comparison to conductive charging, plays a key role. With this in mind, a field test with a conductive charging infrastructure has already been carried out. Both the conductive charging points and the inductive charging station are connected to a central charging management system. The results of the inductive and conductive field tests will be used to compare the two charging technologies.

A further aim of the field test and its evaluation is to identify opportunities for optimising the inductive charging system as a result of its operation. The results will be used in the future development of contactless energy transfer systems.

Intelligent charging concepts

Another focus of the LISA4CL research project was the development of charging concepts for electric vehicles, in particular for fleet applications. The focus was on generation-orientated charging with renewable energy and grid-orientated charging depending on data about the current state of the electricity grid in order to reduce the impact on the grid. Real charging data and measurement data on grid quality from the conductive fleet field test have been incorporated into the development of the charging concepts. “Intelligent charging concepts play a key role in the mobility transition because they enable higher penetration rates of electric vehicles in grids without grid expansion and increase the carbon footprint of electric vehicles through the optimal integration of renewable energies,” says Professor Bernd Engel, Head of the elenia Institute at TU Braunschweig.

Project data:

The Federal Ministry for Digital and Transport Affairs (BMDV) funded the LISA4CL project for four years with around 1.6 million euros until March 2024. TU Braunschweig received over 1.3 million euros for the realisation of the project, split between the elenia Institute for High Voltage Technology and Power Systems and the Institute for Electrical Machines, Traction and Drives (IMAB). In addition to the project partner INTIS GmbH, Fairsenden, the Berlin Agency for Electromobility eMO and VW Nutzfahrzeuge were associated partners. The implementation of the funding guideline was coordinated by NOW GmbH (National Organisation Hydrogen and Fuel Cell Technology). The PTJ ( Projektträger Jülich) acted as project organiser.