Dynamic Charging: Electric vehicle charging on the go

February 28, 2022

Where can I charge my electric vehicle?

It’s a question that many electric vehicle owners ask.

Range anxiety is a common concern for electric vehicle buyers. Drivers want to know how far they can go between charges, and how long the charge would take.

That’s where dynamic charging comes in. It’s wireless charging for moving electric vehicles, using the same principles that govern wireless charging for your smartphone. With dynamic charging, wires located under the road wirelessly transmit electric power to a receiver in the car, exploiting the principle of magnetic induction.

Dynamic charging differs from another kind of wireless charging, static charging, in one important way: dynamic charging implies that the vehicle is moving. With static charging, which is already occurring with modified vehicles, the vehicle parks on top of a charging pad, either in a public location or in the home.

Pilot projects are already underway in parts of the world. In Israel, wireless charging has been installed on a short loop bus route to test wireless charging. The state of Michigan in the US is gearing up to test a similar project.

The technology has also generated significant research interest, with engineers designing everything from the impacts of dynamic charging on electricity grids to payment models for the electricity consumed while driving.

IEEE Fellow Francisco de León, is a professor at New York University’s Tandon School of Engineering and a member of NYU’s Power Lab, where researchers have demonstrated a system capable of transmitting 50kW through an air gap of one foot with 91% efficiency.

He said that dynamic charging answers a simple question:

“Why would anyone want to stop to charge the car?”

Here, he answers questions about this promising technology.

What are some of the benefits of dynamic charging?

People are concerned about how long it takes to charge. The plugs for fast charging, the ones that charge in minutes or seconds, require large amounts of power, either high voltage, high current or both. Plug-in connectors will be very heavy, bulky and scary. Most people will not be able to handle them or would not feel comfortable.

Frequent charging on the road will also allow car makers to reduce the size of batteries, and therefore cut the cost of the car while elongating the lifespan of batteries themselves. Batteries are happier when they are not discharged deeply.

Is a road surface equipped for dynamic charging safe to walk on?

It’s the same principle that charges phones. Walking on the surface is safe as people don’t resonate with the coils. Magnetic debris may be a concern when a car is passing.

What kind of infrastructure is needed?

Short sections of the road need to be built (or retrofitted) to bury the cables under the asphalt (or a different material). Some research teams around the world are looking for better road surface materials suitable for wireless power transmission.

What’s the roadmap to adoption? Cars might not be built with this capability until there are roads to drive on.

All electric vehicles can be retrofitted with coils under the car to accommodate dynamic charging. Initially, dynamic charging would be additive to plug-in and cars would likely have both plugs and wireless charging capabilities.

What do you think would encourage dynamic charging?

All high-occupancy-vehicle lanes need to become EV lanes. In the end, it will be the cost of charging that is a deciding factor: at home vs on the road vs at work that will determine the winner.

Convenience will also play a factor, but mostly it will be the total cost. Home chargers are expensive. The faster the charger, the more expensive it becomes. But on-the-road charges inherently share the cost of the charger with many drivers.

If you want to learn more about design considerations for dynamic charging infrastructure, check out this article from IEEE Smart Grid.

ABOUT OUR AUTHOR
Francisco de León is an IEEE Fellow and is the editor-in-chief of IEEE Transactions on Power Delivery.