Detroit Tests Nation’s First Wireless EV Charging Road

A futuristic intercity roadway recently debuted in Detroit to charge EVs as they travel a quarter-mile stretch near Michigan Central Station. The first-in-the-nation pilot project uses wireless charging technology based on inductive coupling, where a receiver pad installed under the vehicle transfers electricity to the battery from copper coils embedded in the pavement. In addition to providing a dynamic top-up for EVs in motion, the system can deliver static charging for parked vehicles. 

 

Detroit’s new EV charging roadway under construction earlier this year. Images used courtesy of MichiganDOT

 

Inductive charging infrastructure can be found in Europe and other sites worldwide, but this is the first time it’s being deployed on a public road in the U.S. The road segment is a testing ground to fine-tune the technology, which should be publicly available in the next few years. Staff will use a receiver-equipped Ford E-Transit commercial van to evaluate its efficiency, operations, and potential long-term use cases, including public transit buses, shuttles, and last-mile delivery trucks. 

The project uses technology from Electreon, an Israeli company with dynamic and static charging systems installed on toll roads, highways, transportation routes, ports, and other sites worldwide. 

 

A demonstration of Detroit’s new EV charging roadway in action. Images used courtesy of MichiganDOT 

 

How Does Wireless Inductive Charging Work?

Like a wireless smartphone charging station or dock, Detroit’s electric road system uses magnetic resonance induction to couple the receivers installed under the EV’s chassis with the copper coils beneath the road’s surface. A roadside control unit manages electricity transfer via cloud-connected meters and real-time monitoring with a charging-as-a-service platform. Electreon’s power management units can charge up to 60 EVs simultaneously. 

In a dynamic charging scenario, an EV drives over the in-road coils to activate a signal in the secondary coils on the vehicle-mounted receiver. A magnetic field then transfers power wirelessly to the car’s battery. The system is only activated when a vehicle with the receiver passes over the coils. Electreon’s receivers can be installed under any EV, including passenger cars, vans, trucks, and transit buses.

The road’s charging segments can also transfer electricity to stationary vehicles in a parking lane. Electreon installed two static charging stations for EVs parked in front of Michigan Central Station. 

 

An electric truck receives a charge while driving over Electreon’s inductive charging system. Image used courtesy of Electreon

 

Flexibility is a significant benefit of inductive charging systems, as they overcome the limitations of conventional conductive charging using a plug or cable. While inductive charging is relatively new in the EV market, conductive vehicle charging has been implemented worldwide. However, such installations typically require an arm or pantograph mounted on the vehicle hooked up to a rail or cable, such as a connected rail system that charges buses overnight at a depot. 

Quick infrastructure deployment is another advantage of wireless charging systems. The Detroit project removed the existing top asphalt layer and laid 0.62 miles of rubber-coated copper coils 3.15 inches under the road surface. The space was then covered with asphalt and repaved within a few days. The project cost the Michigan Department of Transportation $1.9 million in state funds and $4 million from Electreon and project partners. 

 

Electreon’s Electric Road System and Wireless Charging Tech

Charging times depend on the battery’s size and the number of receivers. According to Electreon, each of its receivers for heavy-duty EVs can supply up to 25 kW to the battery. For light-duty passenger EVs, it provides 7 kW and 11 kW options. This is comparable with standard Level 2 equipment at public charging stations, with a typical power output of 7-19 kW. 

Electreon has tested the system at speeds up to 50 mph. In Sweden, a heavy-duty truck received a stable 100 kW of charging power while driving at 50 mph. The company maintains that charging efficiency is consistent regardless of speed. Higher-speed tests up to 74 mph are planned for 2023 and next year. 

The Detroit project marks Electreon’s entry into the U.S. market. Across Europe and in its home country of Israel, the company has deployed its electric road concept and wireless charging technologies to support several vehicle types, from electric buses with supercapacitor batteries to heavy-duty trucks with lithium-ion batteries. Its project portfolio includes a 0.62-mile static charging segment on a public road in Germany, a 0.7-mile toll road system for electric buses and passenger EVs in Italy, and a 1-mile roadway for electric trucks, buses, and heavy-duty vehicles in Sweden. 

Electreon worked with MAHLE, an automotive parts manufacturer, to formulate a charging methodology guiding the alignment of its interoperable charging system. SAE International recently selected the pair’s positioning method—the “Differential Inductive Positioning System” (DIPS)—as the global alignment methodology for the SAE J2954 standard. Under J2954, wireless power transfer enables automatic and highly efficient charging for up to 93% of EVs and plug-in hybrid vehicles. 

 

An overview of the DIPS technology for static charging in SAE J2954. Image used courtesy of MAHLE

An SAE task force surveyed original equipment manufacturers, Tier 1 suppliers, and wireless charging providers to determine a common alignment method for public ground-side infrastructure. The DIPS decision came after the team gathered feedback on minimum alignment methods, including fine alignment, pairing, and alignment check. The updated standard will be published in 2024.