Published on February 4th, 2012 | by Silvio Marcacci


Coming Soon: A Wireless EV Highway Charging System?

February 4th, 2012 by  

Stanford University researchers this week announced they have designed a road-based, high-efficiency wireless charging system for electric vehicles. In theory, the system could help create a network of all-electric highways that charge electric cars and trucks while they drive, reduce the need for point-specific charging infrastructure, and eliminate range anxiety.

The power transfer system is based on a technology called magnetic resonance coupling. This technology creates a magnetic field between the road and vehicle to transfer electric currents to the vehicle’s battery. Copper coils, placed under the road surface at regular intervals, are tuned to resonate at the same frequency. When an electric current is introduced, it creates a magnetic field between the coils that can then transfer energy to a receiving coil in passing electric vehicles.

Can it work?

While the theory may sound far-fetched, it was demonstrated in 2007 by researchers at the Massachusetts Institute of Technology (MIT) who used it to light a 60-watt bulb.  Energy was transferred between two coils six feet apart even when humans and other objects were in the way. That team of researchers created a spinoff company to use their technology to develop a stationary charging system that can wirelessly transfer electricity from transmitters to devices, including parked electric vehicles.

Inspired by the stationary charging breakthrough, the Stanford team were challenged to increase the amount of transmitted electricity to the level required to power a vehicle. They used mathematical simulations to prove that by bending the copper coils at a 90-degree angle and attaching them to a metal plate, up to 10 kilowatts of electricity can be transferred at a 97 percent efficiency rate.

Potential roadblocks

The charging system may theoretically work, but much more research and experimentation will be required to demonstrate the technology. Several challenges remain, such as ensuring the remaining 3 percent of electricity is lost as heat and not absorbed by humans as radiation, determining the optimal layout of road transmitters, and identifying how pavement and vehicle metal could reduce efficiency.

Even though the system could be years away from reality, the researchers think it could change the global ground transportation system. “You could potentially drive for an unlimited amount of time without having to recharge,” said Richard Sassoon, managing director of the Stanford Global Climate and Energy Project. “You could actually have more energy stored in your batter at the end of your trip than you started with.”

Source and image via Stanford University

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About the Author

Silvio is Principal at Marcacci Communications, a full-service clean energy and climate policy public relations company based in Oakland, CA.

  • Paul

    Messy thinking jr250, cars are faraday cages. a charger would have to be located outside the cage on the bottom of the car, and absorb the energy being conducted. charging would be tuned to take place about a foot from the road surface, the nearer the better actually. how does this cause problems for grandma’s pacemaker?

  • Inductive charging uses an electromagnetic field from a coil embedded in the ground to transfer charge to the battery pack of an electric vehicle. nductive charging would certainly leave homeowner’s garages free of cords.

  • keith poimboeuf

    We would also like to know how muck power Al Gore could save by putting Solar Panels on his home and what fuel Obama could save by staying at work and keeping his wife shopping for those stylish Walmart clothes, rather than burnign jet fuel for she & puppy since dogs can not fly in the same plane as their religion!! Thanks

    • Tom G.

      Hi Keith:
      A few years ago I remember that Al Gore was criticized big time for running around in his private jet talking about global warming while his home didn’t even have a single solar panel installed.

      I can’t remember the size of the solar system he finally installed but he did INSTALL something to get SOME of public off his back. I believe he also installed a Ground Source Heat Pump system which also helped reduce his homes energy consumption.

      However, he was still criticized for installing such a small solar system and some individuals commented it only provided a few percent of his electrical needs. It’s not that he couldn’t afford more solar, he just doesn’t see that as a priority I guess. You know how the old story goes – do as I say – not as I do.

      I will give him 10 points for trying but will subtract 100 for the way he lives. He is not someone I hold up as an example of a great American to my grandchildren.

    • Question

      What? Christianity doesn’t allow dogs to fly on the same plane? That’s really weird! I never knew that.Is it somewhere in Leviticus? Or in the New Testament? Help me out here!

  • Tom G.

    In about 4 or 5 years from now I will need a new car and it is my intention to purchase an ELECTRIC CAR. Not a parallel or series or range extending hybrid but a true all electric car. At my age I am getting really sick and tired of the gasoline, oil change, filter and tune-up routine. But wait, there is more to my story.

    I worked in the Quality Engineering field for over 25 years. In that field you deal with thousands of standards that result in things that work well and are uniform and consistent You know stuff like nuts, bolts, electrical power outlet voltages and even automotive car standards like tire sizes.

    THIS INDUCTIVE CHARGING STORY IS A BIG DEAL TO ME. We have men who are experts when is comes to automotive design and others who don’t know where to add oil to an engine. We have women who can build and race Indy cars and others who would never risk breaking a nail to plug in an electric car. For a smooth transition to a society built on electric vehicles we need to make the USE OF ELECTRIC vehicles as SIMPLE as possible. Inductive changing will be one of the MAJOR technologies that will allow that to happen.

    If I drive my electric car into my garage it should start charging WITHOUT me taking ANY action. If I can drive a gasoline powered car for a week or two without stopping for fuel, WHY would I even CONSIDER buying an electric car that I have to plug in every day? Why complicate my life further by trying to remember if I plugged in the car or not. What if I forgot and the next day I couldn’t take it to work. Nope – no electric car for me.

    If my wife goes to a grocery store shouldn’t she just be able to drive into a parking stall and have the vehicle start charging? If you think my wife is going to open the charging door on the car; drag out a dirty old charging cable and go plug it into some pedestal after having her nails done; you might want to reconsider your understanding of your significant other, LOL.

    We must STANDARDIZE inductive charging systems SOON for all vehicles sold in the U.S. It shouldn’t make any difference if I drive a Volt, Leaf, Cadillac or BMW; they should ALL have their inductive charging plates in the same location.

    That’s my story – what do you think?

  • Anonymous

    Wow. It’s like Standford was forced to spend their allocated funding dollars on something so they picked the first thing out of the bad ideas hat. 1. Unless you’re going to be driving for 12 hours on the highway, you batteries will not get charged as you are consuming most of the input power. 2. Say goodbye to all of your credit card magnetic strips. 3. Find an alternate route for Grandma or watch her pacemaker send her jolts a few times a second. 4. No more AM radio for you! 5. Find funding to destroy and rebuild all highways so 5% of existing vehicles can benefit… maybe. 6. Raise taxes on everyone so only those traveling on that part of the highway can benefit. Sign me up!

    • Question


      1) The point is really that highway driving won’t deplete your batteries. That will extend the range and mean time between recharging tremendously.

      2) In 10 years no one will pay by magnetic stripe credit card. We’ll all be using smart cards or smart phones to pay.

      3) It is a resonant charger. So unless your grandma has coils in her pacemaker of the same size and shape (about a foot?) she will be safe.

      4) Not a great loss.

      5) It isn’t clear that this would have to be done. You might do only one lane. And it isn’t clear how far spaced these might need to be.
      If one can transfer energy at high rate then one could pulse the energy to the car for temporary storage in a supercap (to be bled into the battery over time). This would mean a longer distance between installation.

      6) No, one could simply charge people driving electric cars… The cars would have a RFID chip and as they get charge they would get charged….

      So in the end not a crazy idea.. you just have to think it through…

  • Paul

    One of the most imprtant developments of this technology would be the potential to do away with onboard batteries altogether. lowering weight enormously and thus raising efficiency

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