EV Charging Gets Moving with Inductive Dynamic Wireless Power Transfer
On a 1 km test track embedded with coils capable of 1 MW of power transfer, a team of engineering companies has demonstrated controlled inductive wireless charging of in-motion EVs using IoT and 5G communication.
Dynamic wireless power transfer (DWPT) is envisioned by some as a range anxiety killer. Through the method, which relies on either inductive or capacitive charging, backers believe that we can both expand the range of electric vehicles (EVs) and reduce the size and weight of the battery packs those vehicles must carry.
And they may be right. This month, a Fiat New 500 modified to include an Electreon wireless power receiver system was able to travel around an oval test track at highway speeds without depleting its battery’s stored energy.
Power Supply Via Roadway-embedded Coils
The Arena del Futuro (Arena of the Future) track was built by A35 Brebemi in Chiari, a small town in northern Italy about 70 km east of Milan. Construction began in November 2021 and involved embedding a series of coils in the roadbed.
Workers install inductive charging loops and electronics in the Arena del Futuro test track. Image used courtesy of Stellantis N.V.
These copper coils support inductive power transfer using magnetic fields. This is similar to the wireless power transfer used to charge many smartphones. The basic idea for dynamic wireless power transfer from the roadways up to moving vehicles is also being pursued by other teams, who are using capacitive rather than magnetic coupling for the power transfer.
For the Arena del Futuro, conductive loops were connected to the power distribution system with aluminum cables and then covered with four different types of asphalt. Aluminum cables were selected for power distribution to minimize total system cost; the differing asphalt chemistries were designed to test the performance impact of various road materials.
Laying the cable and connecting the inductive charging loops in the Arena del Futuro test track. Image used courtesy of Stellantis N.V.
The Arena del Futuro is powered by direct current (DC), with the goal being to minimize power losses and support those thinner, lower-cost aluminum cables. Using DC for power distribution may also support a more direct connection to renewable energy sources, such as solar, that output DC.
To demonstrate that the system could be retrofitted on existing roads quickly and with minimal disruption to local traffic, the roadway portion of the installation was completed in just two days.
DWPT — Safety Design Considerations
In discussing a similar test roadway program in Sweden dubbed Smartroad Gotland, the Electreon team explained the safety features of the system design. The tracks are controlled by Electreon’s cloud-based software, and energy transmission does not begin until a certified vehicle passes over a coil. So, a person or other vehicle passing over the coils will not be exposed to electromagnetic fields.
ABB control system installation at the Arena del Futuro test track. Image used courtesy of Stellantis N.V.
The vehicle recognition process is repeated as the vehicle passes over each subsequent coil. The coils can turn on and off in milliseconds, and magnetic fields inside the car reportedly have no impact on the driver or other passengers.
DWPT — Power Efficiency and System Features
Hard data on power transfer efficiency in these systems has not been made available, but project partner Stellantis reported that the efficiency is comparable to a typical fast-charging station.
At the Arena Del Futuro track, the Electreon power transfer system was demonstrated on a Stellantis passenger EV and an Iveco electric bus. As noted above, the Stellantis-modified Fiat New 500 was reported to operate at highway speeds without depleting its battery’s stored energy.
A Fiat 500 and Iveco bus powered by dynamic inductive wireless power transfer. Image used courtesy of Stellantis N.V.
Larger vehicles can use multiple receivers to increase power transfer.
The 12-meter long electric E-WAY bus from Iveco uses 3 receivers that each collect 25 kW for a total of 75 kW, a power transfer that allowed the bus to reach speeds of over 70 km/h; an electric airport shuttle at the Smartroad Gotland project also has 3 receivers supporting transfer of 75 kW; and a truck used at Smartroad Gotland has five receivers supporting a total of 125 kW.
But, as is commonly asked, how is this technology affected by snow and ice? After in-lab and real-world testing at the Smartroad Gotland roadway, the project reported that energy transfer is negatively impacted by neither.
Next Steps for Inductive Dynamic Wireless Power Transfer
Testing and research at the Arena del Futuro track will continue throughout 2022.
At Smartroad Gotland, Electreon aims to increase the energy transfer capacity of its receivers to approximately 30 kW, as well as to examine the next generation of its technology. In addition, the company has several other projects around the globe testing inductive DWPT, with more scheduled to come online soon.
While dynamic charging is perhaps more exciting, the technology involved here is also applicable to static applications like parking lots, taxi waiting areas, and bus loading zones.
Project partners envision that the integrated IoT and 5G communications will eventually provide more than just real-time system control. The system data could be used to monitor vehicle charging status, system health, and even to collect tolls for energy usage.
