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Eric McDonald, Director, Testing & Infrastructure Development

This month, the state of Michigan announced its plans to install the country’s first mile of wireless electric vehicle (EV) charging road. Wireless charging makes it possible to charge EVs without the need to physically plug them into an electricity source. This charging method is known as inductive wireless EV charging.

There are two common types of charging—conductive and inductive charging. Most are likely aware of conductive charging, where electricity flows through conductors, like power cords. An EV charging station has a power cord, which is plugged into the EV, similar to a gasoline nozzle inserted in a gasoline-fueled vehicle. The electricity flows through the power cord to the EV battery.

Induction is not likely as familiar to most. You may be aware of wireless phone charging or an induction cooktop stove—both are examples of induction. Induction is achieved by the use of a metal coil with a magnet centered in the coil. Electricity is sent through the coil, resulting in a magnetic field of electricity from the charger to the item being charged (or cooked in).

The equipment (the phone, pan, or vehicle) need not be directly aligned with the charger. There must, however, be a transmitter (charger, stove) and a receiver (phone, pan, vehicle) made of specific metal components or there is no power flow. This is why a person may touch a wireless phone charger or an induction stovetop and not be burned or shocked.

For roadway inductive EV charging, the coil and magnet are embedded just below the pavement surface. The subsurface charger transmits the electricity via a magnetic field to a receiver on the bottom of the EV. The receiver accepts the electricity and moves it to the EV battery.

The receiver (vehicle) can move across a series of inductive chargers all while receiving electricity from those chargers. Thus, the vehicle can be in motion while receiving the charge. This is known as dynamic inductive wireless charging. The Michigan mile will feature dynamic inductive wireless charging with coils embedded in the travel lane, allowing for wireless charging while the vehicle is in motion. The mile will have static inductive wireless charging as well, with coils embedded in the parking lanes to provide wireless charging while the vehicle is stopped or parked.

This project will be important in advancing the state of EV charging in the United States. It will demonstrate wireless EV charging in a real-world environment and provide insight into development and installation of wireless charging infrastructure. With no requirement to manually handle power cords for charging, wireless charging will increase the potential to demonstrate fully autonomous vehicle technologies.

Figure 3: Photo credit electreon.com

Dynamic wireless charging can provide for increased driving range and therefore less range anxiety. Wireless EV charging projects also require cooperation in public-private partnerships, which can be used as a blueprint for future infrastructure investments. Please feel free to reach out to me via email at ericm@nextenergy.org.

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Join the discussion 2 Comments

  • Interested to know more details about this technology, solution and business model

  • David Anderson says:

    As a retired physicist, three issues come to mind:

    What is the efficiency of the energy transfer of these induction based charging systems as compared to conventional wire based systems?

    What is the cost of these roadway embedded systems compared to the alternatives?

    What is the cost of the vehicle’s induction equipment compared to the alternatives?

    I presume these systems will be more cost effective than ev charging using swappable batteries?

    I look forward to comments on this.

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