Anthony J. Pennings, PhD


Wireless Charging Infrastructure for EVs: Snack and Sell?

Posted on | April 22, 2022 | No Comments

I recently chaired the defense of a PhD dissertation on patents for electric vehicle (EV) charging. Soonwoo (Daniel) Chang, with his advisor, Dr. Clovia Hamilton, did a great job mapping trends associated with the technology patents central to wireless electric charging, including resonant induction power transmission (RIPT).[1] The research got me interested in exploring more about the possibilities of wireless charging as part of my Automatrix series, especially since the US government is investing billions of dollars in developing electric charging infrastructure throughout the country.

This post discusses some of the issues related to wireless charging of EVs. Cars, but also buses, vans, and long-haul trucks are increasingly using electric batteries for locomotion instead of petroleum-fueled internal combustion engines (ICE). It suggests that wireless charging infrastructure be considered that can allow EVs to partially replenish their batteries (“snack”) and in some cases sell electricity back to the grid. Currently, not many EV original equipment manufacturers (OEMs) are designing their automobiles for wireless charging. Why not?

Most likely, OEMs are quite aware of what they need to succeed in the short term. Tesla, for example, has developed an EV charging infrastructure viable for personal autos using cables that plug into a vehicle. But we should also be wary of some of the limitations of plug-in chargers and prepare to build a more dynamic infrastructure that would allow charging in multiple locations and without getting out of the vehicle. These are some of my speculations, and they do not necessarily reflect the results of the soon-to-be Dr. Chang, whose research sparked a lot of my thinking.

You may have used wireless charging for your smartphone. It’s helpful to get a quick charge without dealing with plugs and wires. Inductive charging has some limitations though. While you can play music or a podcast, or talk over a speaker mic, it’s typically immobile. Your phone also needs to be very close to the charging device, its coils aligned properly, and it gets hot. It’s generally not that energy-efficient either, often losing more than 50% of its electricity while charging. With several devices connected in nearly every home, the losses can add up, putting strain on a community’s electrical grid.

In EV wireless charging, a receiver with a coiled wire is placed underneath the vehicle and connects to the battery. This “near field” charging requires that the vehicle be near a similar charging coil. The receiver needs to come near a charging plate on the ground to transmit the energy.

However, advances in magnetic resonance technologies have increased the distance and energy efficiencies involved in wireless charging of EVs. Power transfer is increased by electromagnetically tuning the devices to each other with a magnetic flux, allowing convenient replenishing of a vehicle’s battery. Electric devices generally have conductive wires in a coil shape that maintain stability for the instrument by resisting or storing the flow of current, initially. They are classified by the frequency of their current that flows through it that consists of direct current (DC), audio frequency (AF), and radio frequency (RF). These frequencies can be managed and directed to transfer power over a short distance to another electrical coil. They are not radio waves or emit ionizing radiation that have sufficient energy to detach electrons, so they appear to be relatively safe.

WiTricity for example, uses frequencies around 85 kHz to tune the two coils and expand the charging range from a few millimeters to tens of centimeters. The Massachusetts company has spearheaded the development of this technology and has opened up many possibilities, particularly its use in the public sphere. This may also include dynamic charging that allows a vehicle to charge while moving. See the below video about WiTricity:

It’s no secret that charging issues are a limiting factor for EV diffusion. Drivers of ICE vehicles have resigned themselves to getting out of their cars, organizing a payment, inserting the nozzle into the gas tank, and waiting patiently for a few minutes while the liquid hydrocarbons poured into their cars. Unfortunately, EV owners are still dealing with a lack of available charging locations as well as challenges with nozzle standards, payment systems, long lines, and lengthy charging periods. Currently, most EV owners in the US charge at home with L2 chargers that can readily be bought online or at a Home Depot. EV owners in urban areas need to find other locations, such as parking garages and may face fines for staying too long.

Standards both permit and restrict technological solutions. The Society of Automotive Engineers (SAE) published the J2954 standard in 2020 for wireless charging with three wireless charging levels — WPT1 (3.7 kW), WPT2 (7 kW), and WPT3 (11 kW) for transfer up to 10 inches. These generally may take up to three and a half hours to fully charge.[2]

Yes, these are not impressive numbers given the competition from high-end EV superchargers. Even the EVgo chargers at my local Walmart in Austin have several standards (J-1772, CHAdeMO, CCS/SAE) that charge from 14.4 – 50 kW.[1] Note that EVs have onboard chargers with varying acceptance rates (in kW) that convert AC electricity found in homes to the DC a car battery needs to store. A Chevy Volt with 3.3 kW acceptance will not charge as fast as a Telsa Model S with 10 kW no matter where it is plugged. Other factors include charging cables that can often be awkward to handle. The experimental charging “snake” that reaches out and automatically finds and connects to the auto’s electric nozzle doesn’t seem to be viable yet. So, charging is a limiting factor for EV adoption success.

The strategy behind wireless charging will probably focus more on what WiTricity has coined “power snacking” than full meals of electricity. Snacking is actually better for your battery as longevity improves if you don’t let the battery capacity run down to below 20% or recharge it to 100 percent. Keeping the electric ions in equilibrium across the battery reduces strain and increases the number of charge cycles before degrading occurs.

The snacking can be done by a waiting taxi, a bus stopping for a queue of passengers, a quick stop at a convenience store, and perhaps EVs waiting at a red light. Shopping centers are likely to “capture” customers with charging stalls, especially if they can reduce costs by having micro-grids with solar panels on roofs.

Many countries have tested infrastructure for charging EVs in motion, although this will require substantially more investment. “Dynamic” wireless charging appears to be feasible but comes with high costs as it needs to be embedded in existing infrastructure such as bridges and highways.

The major issues for wireless charging are the infrastructure changes needed and the OEM buy-in. Wireless charging will require more planning and construction than the current charger station. They will also require monitoring and payment applications and systems. Most importantly, they will require electricity – and without significant capacity coming from renewable sources, the purpose will be mainly defeated. Vehicle manufacturers will need to include the wireless charging pads and ensure safety. On the positive side, they can use smaller batteries for many models as constant recharging will reduce range anxiety.

Wireless technologies have been successfully tested for “vehicle to grid” (V2G) transmission. This innovation means a car or truck can sell electricity back to the grid. These might be particularly useful for charging locations off the grid or places challenging to connect—for instance, charging pads at a red light. So we might see a “snack or sell” option in future cars. The prices are likely to vary by time, location, and charging speed, but this setup will present some arbitrage opportunities.

The arbitrage economics are based on ‘valley filling’ when EVs charge at low-demand hours, often overnight, and ‘peak shaving’ when an EV transmits stored energy back into the grid during high-demand hours. So, for example, a vehicle charging at home overnight with cheaper grid electricity or excess from solar panels can sell it on the way to work or at the office parking lot. You might not get rich, but considering the money currently spent on diesel or petrol, it could still help your wallet.

Effective infrastructure like highways or the Internet provides indirect network effects, allowing different entities to use the system and expanding that network’s possibilities. The Global Positioning System (GPS), for example, uses some 27 satellites that transmit pulsed time codes. These signals allowed multiple devices to be invented that triangulate and compute a latitude, longitude, and altitude position to provide different location services. In this case, an effective wireless charging infrastructure enables many different vehicles to use the electrical network. A lot of the wireless charging infrastructure will be done by corporate fleets like Amazon, Best Buy, and Schindler Elevator. Hopefully, the US Post Office will catch up.

However, the US government made a down payment on EV charging stations in the 2021 infrastructure bill. Legislation targeted $15 billion in the Infrastructure Investment and Jobs Act, for “a national network of electric vehicle (EV) chargers along highways and in rural and disadvantaged communities.” It was cut in half to $7.5 billion to provide much needed funding for electric bus fleets for schools and municipalities.[3] Should future infrastructure spending target wireless charging?

Once we move beyond the internal combustion engine (ICE) in vehicles, you will see a lot more flexibility in design of autos, buses, vans, trams, etc. They require fewer parts and are easier to construct. We see it on the lower end with electric bikes and even those controversial electric scooters. New forms of electric autonomous trolleys and vans are necessary to revive urban transportation in a quiet and sustainable way. All these changes in mobility will require changes in the electrical infrastructure.

The term “Smart Mobility” has emerged as an important sociological and technical construct. The city of Austin, Texas:

    Smart Mobility involves deploying new technology to move people and goods through the city in faster, safer, cleaner, more affordable and more equitable ways. Our mission is “to lead Austin toward its mobility future through meaningful innovation, collaboration, and education.”

Smart devices have expanded to smart vehicles. Autonomy is becoming prevalent and some cars and trucks offer full self-driving options (FSD), with or without a passenger. Wireless charging is central to this process. Auto-valet services, for example, will allow your car to drop you off and park itself, likely at a stall that can provide charging. Who is going to get out to plug it in?


[1] Gaining Competitive Advantage with a Performance-Oriented Assessment using Patent Mapping and Topic Trend Analysis: A Case for Comparing South Korea, United States and Europe’s EV Wireless Charging Patents. A 2022 PhD Dissertation by Soonwoo (Daniel) Chang for Stony Brook University in New York. He can be reached at

[2] A kWh is a 1,000 Watts of electricity. Named after James Watt, the inventor of the steam engine, a watt is the unit of electrical power equal to one ampere under the pressure of one volt. The time it takes to charge a car depends on both the car’s acceptance rate and the amount of electricity sent by the charging station. Volts x Amps – Wattage.

[3] Known officially as the Infrastructure Investment and Jobs Act, it authorized over half a trillion dollars in spending for airports, bridges, broadband, rail, roads, and water systems. It also included up to $108 billion in spending for public transportation such as rail as part of the largest federal investment in public transit in the nation’s history. Another $73 billion was for upgrades to the electrical grid to transmit higher loads while efficiently collecting and allocating energy.

Citation APA (7th Edition)

Pennings, A.J. (2022, Apr 22). Wireless Charging Infrastructure for EVs: Snack and Sell?



AnthonybwAnthony J. Pennings, PhD is a Professor at the Department of Technology and Society, State University of New York, Korea. Before joining SUNY, he taught at St. Edwards University in Austin, Texas. Originally from New York, he taught at Marist College and from 2002-2012 was on the faculty of New York University where he taught digital economics and information systems managementand. His first academic job was at Victoria University in New Zealand. He was also a Fellow at the East-West Center in Honolulu, Hawaii.


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