Wireless Power Transmission Could Be Future of Electric Cars, Or Not

By · December 03, 2013

Qualcomm parking pad and vehicle receivers of different sizes

Qualcomm parking pad and vehicle receivers of different sizes.

The recent EVS27 conference in Barcelona was an opportunity to explore a technology which has made headlines, but still needs a lot more careful thought and education: wireless charging. AT EVS, two companies displayed wireless solutions, Qualcomm and Brusa, an American start-up and a Swiss company with decades of experience in EV engineering. I went to both booths.

Everybody talks about wireless charging but that's not even the right name for the technology. This is actually wireless power transmission (WPT) via a magnetic field between a transmitting coil on the garage floor and a receiving coil on the underside of the car. The charging process is distinct, and only begins after the coil in the car has transformed the energy it received in electricity.

The parking pad has to be quite big, and actually, the bigger the better because the device needs a degree of tolerance for misalignment. Brusa's parking pad was a bit larger and thicker than the one from Qualcomm. The Brusa unit had a tough industrial look, while the Qualcomm pad looked more like a home appliance. The American company obviously spent more time on design, and it also displayed a whole range of vehicle receivers. Size matters here: 3.3 kW; 6.6 kW and even up to 20 kW. A strong current can be sent via a magnetic field but it will need a larger receiving pad fitted to the car.

Brusa parking pad and vehicle receiver

Brusa parking pad and vehicle receiver

Since I have a cat, my first question was about safety. This is not going to fry the cat, right? Both representatives from Qualcomm and Brusa said it won't. Both systems have an obstacle detection device built-in, and it will instantly switch off the magnetic field if it sees something interfering.

Both companies did many tests, indoors as well as outdoors, and safety should not be an issue for the foreseeable future. WPT will remain an add-on technology. All EVs will keep on having a standard plug. This is somewhat like computers. Wireless Internet is everywhere nowadays, but most computers still have an Ethernet port just in case.

That means that WPT will make EVs more expensive. Then there's the garage equipment. When some people think a wallbox is expensive, a parking pad for WPT costs three to four times more. But the worst problem is efficiency.

Qualcomm parking pad

Qualcomm parking pad.

Electric vehicle fans are proud to say that an electric motor is much more efficient than an internal combustion engine. But WPT changes the efficiency equation.

Compared to a cable, WPT loses as much as 10 percent of the electricity it carries. In a Nissan LEAF, which uses 100 kWh per week, or 5,200 kWh per year, that's 520 kWh lost each year. The price of electricity varies a lot between regions, but to most people 520 kWh equals lunch money for several days.

So wireless power transmission may be more the future, because it's more convenient, but it's hard to think of a technology which makes EVs more expensive and less efficient as a progress. Ultimately, both Qualcomm and Brusa are clear-minded in the sense that they understand that WPT's success depends on who backs it. They're both waiting for a large car manufacturer to use the technology in a production model. EV fans will be waiting too, but not with as much attention as the wait for better batteries.


· · 19 weeks ago

apart from the price, efficiency was my second major concern but am (happily) surprised to see it looses only 10%, though I am suspicious of this figure.
My FIT EV gives me around 125 MPGe, so even if its 10% waste in transmission, i will still get around 110 MPGe, i would take it.

· · 19 weeks ago

"but it's hard to think of a technology which makes EVs more expensive and less efficient as a progress."

Perfect point....

We don't need another loss in the charging system.

10% loss is "ideal case". Nothing is ideal in the real world...

I will be happy to spend 5 seconds to plug in at home....

In bad weather, there are will be additional loss....

· · 19 weeks ago

This technology will likely find acceptance in specialty fleet applications, like car shares where users can not be counted on to plug in upon return.

Unlike public EVSE with a 25-30 foot cord, these charging units can not reach/serve 3-4
parking spaces.

· · 19 weeks ago

I think this is the future of EVs. Perhaps not this generation of WPT, or even the next, but, at some point, it will become as ubiquitous as wireless remotes for opening your car. People like convenience, and this is a convenience to the max.

WPT pads will be everywhere, works, malls, homes, etc. You just park and charge. You won't even have to think about it, or remember to charge your car, for that matter.

· · 19 weeks ago

I can't even be bothered to demolish Laurent, who waves his hand with unsourced claims about energy losses compared to wired transmission.
Suffice to say that Nissan, Qualcom and everyone else put extra losses at at most 2-3%.

The difference between me and Laurent is that I can back up what I say, and will be happy to do so if Laurent comes up with the basis for his claims.

Since he usually doesn't bother with evidence, I expect the typical grave like silence when he is asked to substantiate what he is on about.

· · 19 weeks ago

WPT is interesting especially for public parking places where it can prevent vandalism to the cables and outdoor where people don’t like to be under pouring water with a plug to connect. It can also be a good system simply to avoid forgetting to plug in.
Yield is a question of course but that is already good and improving, but beside wireless there can also be an as convenient contact based system like for a Roomba. Of course the contacts must be on a small bump to avoid water stagnation and there must be a security system based on high pressure contacts under the wheels or/and electronic check before the current can flow, but it is feasible too and a lot cheaper and 100 % efficient.

· · 19 weeks ago

Let's hope Qualcomm doesn't receive a government bailout when the market renders its opinion about the company's 'better mousetrap'. Responding to every dumb idea one encounters would be exhaustively futile. But like spreading public chargers at public expense everywhere - so EV advocates and vendors can mislead the public into believing EVs are 'just like' their old ICEs - that appears to be the marketing concept behind this product. (Actually it carries the deception to a whole new level, similar to trying to come up with a product that will condense gasoline from the atmosphere and teleport it into a gas tank.)

To get to the point, there are much simpler and probably less expensive technological solutions for prospective EV buyers with 'range anxiety' than trying to fill the world with 'free energy' ports (which definitely aren't free even if they aren't magnetic) - to whit, Volt-like range extenders. And this product really doesn't even seem to be about that - it appears to be aimed at drivers too lazy or absent-minded to even be bothered to take 3 seconds to plug in at the end of their driving day.

The bottom line here is: for drivers whose transportation requirements are not predictable enough to insure that the time and opportunity to charge within a safe range for their vehicles, EVs are NOT the answer. For those who regularly exceed the electric-only range of range-extended cars like the Volt, even they are not 'the answer'. (Hybrids are.) Trying to con buyers into believing there is or will be some technological fix for the present limitations of EVs will only result in disillusioned and antagonized customers.

The actual numbers who fit into this category are so small that it simply is not worth the costs - real and in 'marketing' expenses (of ubiquitous public charging station deployment) to attempt to placate their sometimes justified concerns about present EV technology.

· · 19 weeks ago

Well, I really think this is the future, and not just for lazy drivers, for anyone who thinks that wireless is the way to go. Wait, maybe the people who has a little remote with some buttons shoud take 3 seconds to use the key to close all doors, or perhaps this lazy people should actually turn on the whipers or lights instead of relying on the sensors, or why bother with automatic transmision when you can shift your gears right? what about phones or computers? wireless? why? can't you just wait till you get home or the office to hook up to a cable?, lazy, lazy guys...
WPT or inductive charging will make electric cars even more appealing to people, sure they will start with pricey cars and as an expensive option, but prices will go down and convenience will go up. In less than 1 year lots of people will have not just inductive charging tooth brushes or induction stove tops, but also phones, laptops, tablets...
I truly think this is the future, and if the first generation has 10% losses, the third will probably have less than 1%. The question here is not IF this technology will be mainstream, is WHEN it will be.

· · 19 weeks ago

There is nothing inherently wrong with inductance electric technology. I have one of those "single burner" induction cooktops, purchased for $69 at Target, and I think it's marvelous. It's a far more efficient way to boil water for my drip coffee or tea than to use a conventional electric hotplate or electric teakettle for the same purpose. One day, I'd like to get rid of the gas range and get a proper "four burner" induction unit installed into the kitchen countertop.

As for use in charging an EV, however, wireless inductance technology seems to be little more than a luxury gadget that is actually less electrically efficient (for now) than the simple plug-in cable alternative. Even if electrical efficiency comes up to match a cable connection, it's fair to assume that it will always be more expensive than a cabled EVSE.

The argument has been made that it will be more flexible in public installations, where L-2 (J1772, etc.) is now the norm. But think how easy it is to unplug the connector from one car and plug it in to the one next to - or across the parking median - from it. To "swap connectors" on a pavement-mounted induction plate, one needs to physically drive the charged vehicle out of the induction-equipped space and move the next vehicle in.

As for commercial applications (fleet vehicles, etc.,) true cable-connected quick charging makes far more sense. L-3 chargers are now available for under $10K and even the luxury homeowner might find it a glitzier way to impress their neighbors with a plug-in gadget that can charge their EV in less than an hour than a similarly priced wireless one that takes 6 hours or more to do the same thing.

· · 19 weeks ago

'it's fair to assume that it will always be more expensive than a cabled EVSE. '

Why? In detail, please.
Underground pads in public places do not suffer the wear and risk of vandalism that posts and cables do, and neither do you get wear on the cables.

As for the notion that they are an unnecessary luxury, we have been around the block on that before, and you have come up with no rebuttal to the fact that in cities is most of the world there is simply nowhere to put above ground chargers.
Not everywhere is middle America, which you seem to have some problems comprehending! :-)

· · 19 weeks ago

What is the efficiency of energy transfer compared with cable-connected charging?

The efficiency of Qualcomm Halo WEVC technology is comparable to conductive charging systems at similar power ratings. The industry target is for a commercial WEVC system to be 90% efficient and above. A very high quality conductive charging system could have efficiency figures in the mid-nineties due to losses in isolating and control circuitry, components, connectors and cabling. However, some conductive charging systems are reported to have losses around 15% or more. It is accurate to say that conductive charging will usually be 1 or 2% more efficient than wireless. As power increases say from 3.3kW to 6.6kW and up to 20kW the charging efficiency can increase since the standing losses are the same for all power levels. For example, the 7kW system on the Rolls Royce Phantom 102EX Experimental Electric Vehicle was shown to operate at over 90%.'


It would be nice if folk who write articles on technology would acquaint themselves with the basics of how it works.

So additional losses are of the order of 1-2%, not the 10% claimed.

· · 19 weeks ago

I have no problem comprehending what middle America is about, Davemart, even though I'm not really as intrinsically tied to that lifestyle as you allege me to be. I also know full and well how the British can sometimes stereotype us over here on the other side of The Pond as ostentatious and clueless as to how the rest of the world lives. That can certainly be true at times, but it's clueless at your end to pidgeonhole the other way around so broadly.

My mother, a British ex-pat, came over here in 1948 and lived out her life as if the rationing of the war years - an probably more tellingly, the immediate post-WWII years - never really stopped. Her level of frugality is something that I don't think most contemporary Europeans would fully appreciate, much less any American who didn't suffer through The Great Depression (as my father did.) Although I currently live in a 3 bedroom house, I also spent many of my early adult years in cramped apartments with street-only parking. I'm also aware of how people here in economic classes far below mine exist. Life in modern day America is no more like a 1950s TV episode of Ozzie & Harriette than does Downton Abbey represent the day to day existence in today's England.

Back to this wireless charging thing . . .

I think I've outlined in my previous post how an L-2 (no greater than 1 foot square, about 0.3 of a square meter to you) placed on a raised median with parking spaces on either side can accommodate any number of EVs. I see absolutely no advantage in a public EVSE installation that a collection of backtop-mounted induction pads could provide . . . other than vandals cutting cords (which will probably stop right after word gets out that one of the kids in the gang got fried with 240V of AC during the last EVSE raid.)

But I can envision one other disadvantage. Although I no longer live in a climate with harsh winters, I have "fond" memories of ice and snow buildup after a blizzard. Parking lots are routinely plowed in wholesale fashion, with large trucks scraping steel shovel blades against the parking surface. Anything that is protruding above the blacktop is almost instantly obliterated. Unless these induction pads are absolutely flush (and most I've seen are not,) they will be the first things to get torn to shreds and likely not repaired until the spring thaw.

The surface mount EVSE on the curb after a massive snow storm? Perhaps ice will have to chipped off of it after the snow is hand-shoveled away. But, if it was properly sealed from the elements to begin with, it will probably be still operating and far easier to repair in the dead of winter if it isn't.

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