Induction will charge electric buses through their tires
Winduction, a spin-off from ETH Zurich, has developed an inductive charging system designed to power electric buses at stops through their wheels. This approach could allow smaller batteries to suffice, reducing both energy demands and operating costs. A pilot project is scheduled for 2028.
The three founders of Winduction (from left to right) in front of their electric bus: Laurin Schwitter, Sylvain Fricker, and Sonam Bhuka.
Image: Winduction
In inductive charging, Winduction relies not on a coil under the vehicle’s chassis but on the wheel. A charging plate is embedded in the road surface, while a second coil is located inside a specially designed bus tire. When the bus hovers above the plate, energy is transferred from the ground through the wheel to the vehicle’s battery via a magnetic field.
This approach aims to overcome a drawback of traditional inductive systems, where energy must be transferred across the distance between the road surface and the vehicle’s chassis, which can vary depending on the vehicle type. Winduction reduces this distance by integrating the coil on the vehicle side directly into the wheel. According to the ETH spin-off, the system achieves an efficiency of over 90 percent between the ground plate and the vehicle.
The technology is intended to enable electric buses to be recharged throughout the day with short stops at each station. This would allow the vehicles to use smaller batteries. According to Winduction, this would not only reduce purchase costs and vehicle weight but also allow for more space or payload capacity.
Inductive charging is also gaining importance in other applications these days. Honda is working together with Taisei and Taisei Rotec on a dynamic wireless power transfer system that supplies vehicles with electricity while they are in motion using coils embedded in the road. First demonstrations are planned for the 2027 Japanese fiscal year. The partners aim to test charging capacities of up to 150 kW for heavy commercial vehicles as well. In contrast, Winduction charges while stationary at stops and transfers energy through the wheel.
Winduction plans pilot operation starting in 2028
A technical challenge lies in the tires themselves. Conventional bus tires contain steel belts that react to magnetic fields and would convert part of the energy into heat. Therefore, Winduction is working with partners on a steel-free tire for the charging system. The higher cost of tires is expected to play only a minor role compared to the total lifecycle costs of a bus, according to the company.
Winduction is currently investigating with transportation companies what savings can actually be achieved. As an example, the company cites the route between Zurich Airport and Zurich Oerlikon. According to the startup’s calculations, charging stations would only be needed at two of the 24 stops there. Over a 16-hour operating day, the buses together would spend about three hours charging.
For comparison, Winduction points out that the electric buses currently in use on this route spend around five hours charging simultaneously at the depot at night. Charging during the day could, in the company’s view, not only enable smaller batteries but also reduce peak loads. Additionally, cheaper solar power could be utilized more extensively during the day in the future.
Backed by the Swiss Federal Office of Transport and the Swiss Climate Foundation, this ETH spin-off is currently building a testing infrastructure in Winterthur. A laboratory and a dedicated testing stop are planned to be established there. As the next step, Winduction aims to integrate all components in an industry-relevant format and construct a fully retrofitted electric bus.
A first pilot operation under real conditions is scheduled for 2028. The company says discussions are already underway with several Swiss transit operators, including potential use in the Zurich Airport area. This planned pilot project coincides with a growing fleet of electric buses in Zurich. The transit operator VBZ recently decided to acquire 20 more electric buses from Yutong and Daimler Buses, which are needed starting in mid-2027.
